View Full Version : Head gasket replacement options
Hello everyone!
First, a little background on the situation:
My car recently began accumulating pressure in the cooling system, which led to a couple of leaks showing up. Initially I thought it was a clog in the expansion tank neck hole where the small hose from the radiator connects. Since the last time the system was serviced was about two years ago, I went ahead and replaced the thermostat, radiator cap, expansion tank, radiator hoses, and the radiator to expansion tank hose. New coolant was used (BMW Blue). This all happened about two weeks ago.
When I checked the fluids yesterday, I found that there was once again pressure in the cooling system after a complete cool down. I believe that my headgasket must be leaking some combustion gases into the cooling system and causing this condition. This brings me to my primary question of how to go about replacing the head gasket.
It must be noted that the head that is currently on the engine has one spark plug that is stuck due to a mis-threaded plug sometime in the engine's history. Thus, the threads would need repair.
So my options are as follows:
1) Replace the head gasket and have the current head inspected, cleaned, and repaired. The engine has about 126K miles on it, so the head isn't high mileage. Engine doesn't use oil or coolant and has not been overheated while in my possession.
2) Obtain another head and prepare it for replacement so as to minimize down time.
Option 1) is likely cheaper but more time consuming, while option 2 is a bit more expensive, but would basically be a straight swap. My concern with option 2 is that the head I obtain may not be in the best of condition and thus would require a lot more work than the current head which is known not to leak oil or have been overheated.
I'm leaning toward option 2 only because of less down time during the gasket replacement, but please lend me your opinion regarding anything that I'm missing in this picture.
Scott C
09-09-2007, 03:23 PM
Hello everyone!
First, a little background on the situation:
My car recently began accumulating pressure in the cooling system, which led to a couple of leaks showing up. Initially I thought it was a clog in the expansion tank neck hole where the small hose from the radiator connects. Since the last time the system was serviced was about two years ago, I went ahead and replaced the thermostat, radiator cap, expansion tank, radiator hoses, and the radiator to expansion tank hose. New coolant was used (BMW Blue). This all happened about two weeks ago.
When I checked the fluids yesterday, I found that there was once again pressure in the cooling system after a complete cool down. I believe that my headgasket must be leaking some combustion gases into the cooling system and causing this condition. This brings me to my primary question of how to go about replacing the head gasket.
It must be noted that the head that is currently on the engine has one spark plug that is stuck due to a mis-threaded plug sometime in the engine's history. Thus, the threads would need repair.
So my options are as follows:
1) Replace the head gasket and have the current head inspected, cleaned, and repaired. The engine has about 126K miles on it, so the head isn't high mileage. Engine doesn't use oil or coolant and has not been overheated while in my possession.
2) Obtain another head and prepare it for replacement so as to minimize down time.
Option 1) is likely cheaper but more time consuming, while option 2 is a bit more expensive, but would basically be a straight swap. My concern with option 2 is that the head I obtain may not be in the best of condition and thus would require a lot more work than the current head which is known not to leak oil or have been overheated.
I'm leaning toward option 2 only because of less down time during the gasket replacement, but please lend me your opinion regarding anything that I'm missing in this picture.
There are places that have "rebuilt" heads for roughly $1K, I almost went down that path....
There are places that have "rebuilt" heads for roughly $1K, I almost went down that path....
I'm aware of such remanufacturing outfits, but for that price I think I'd be willing to live without my car for a little while. What I'm considering is purchasing a used head and then having a local machine shop inspect, mill (if required), and recondition the head. I've never dealt with a machine shop, however, so perhaps I'm over-reacting when it comes to the time it takes to recondition a head? I'm also a bit weary of the spark-plug thread repair that will need to be done on the current head on the car. Somehow, I would feel better having a head that didn't have a heli-coil installed.
What path did you choose in the end?
Despite the one sparkplug thread issue, with only 126k on your original head, I would choose it over a rebuilt one of questionable history. Repairing the thread is no big deal. I would live with whatever downtime and let a machine shop inspect & repair your existing head.
just my $ .02
Despite the one sparkplug thread issue, with only 126k on your original head, I would choose it over a rebuilt one of questionable history. Repairing the thread is no big deal. I would live with whatever downtime and let a machine shop inspect & repair your existing head.
just my $ .02
Gale,
If I were to use my current head, to what extent would you consider servicing it? Basic hot tank, inspection, and new valve guide seals (these would be included in the head gasket kit)? Also, as far as headgaskets go, would it be better to purchase an OEM set, or are aftermarket sets sold by autohausaz and BMA high enough in quality?
winfred
09-09-2007, 08:00 PM
id helicoil the plug (if needed) check it for straight and stick it right back on if it was in my hands, you can usually see the bad spot in the gasket where the seep is, m30s typically leak at the right rear corner due to a slight defect in the gasket
id helicoil the plug (if needed) check it for straight and stick it right back on if it was in my hands, you can usually see the bad spot in the gasket where the seep is, m30s typically leak at the right rear corner due to a slight defect in the gasket
I guess I'll stick with the current head then. I'd still have to find a machine shop that can accurately check the head surface and install the helicoil. Since a head gasket kit includes the valve guide seals, would you recommend having the shop replace those as well? As a final check before I start gathering parts for the change, is there any other reason why a cooling system would accumulate pressure over a relatively long period of time (~ 1 week)? This began happening toward the end of July and has persisted. Can head gasket leaks be that small?
Bin_jammin
09-09-2007, 09:32 PM
I don't get it, your system is holding pressure and you think it's a bad thing? It's supposed to do that. If you're not overheating, you're not leaking anything, and you're not using any fluids, I think you're barking up the wrong tree, try just driving it and don't worry about it.
winfred
09-09-2007, 09:38 PM
they can be fairly small leaks, valve seals wouldn't hurt, if you have a air compressor you can pressurize the cylinders with a compression tester with the valve removed, fill the cooling system to the top and watch as you air up each cylinder for the coolant to rise, you will need to turn the engine over to get the pressure to hold in each cylinder
Robin-535im
09-09-2007, 09:50 PM
Gale,
If I were to use my current head, to what extent would you consider servicing it? Basic hot tank, inspection, and new valve guide seals (these would be included in the head gasket kit)? Also, as far as headgaskets go, would it be better to purchase an OEM set, or are aftermarket sets sold by autohausaz and BMA high enough in quality?
Hi Rus,
I recently went through an m30 head rebuild - I can turn a wrench but had never done a HG before so this might be of some help.
1) Find a good head rebuilder that has experience with BMWs. Call the dealer, call the local top-notch indy's, call machine shops, try to get someone who has at least a good reputation for building good heads, and if you can, a BMW-specific guy... but I'd choose the former over the latter.
2) I see two routes: complete rebuild or just fix the HG and put it back on, like Winfred said. I didn't see much middle ground, and the first option is a $2000 task once all is said an done, the second option maybe $200. If there are no other problems and you aren't *looking* for a reason to hot-rod the head, (and there is nothing damaged inside) then just bolting it back in after you're sure it's flat is a fine idea IMHO, and it's cheap. Machine shop can spec it out and see what needs to be cut off to flatten it.
3) if you rebuild the whole thing, inspect the guides to see if they need replacing, and if so, be sure your machine shop knows how to do it right. I found a couple that were a bit more heavy handed than I was comfortable with, and at last found a shop that understood finesse. All the suppliers we tried wanted to sell us e28 guides, which are not the same as the e34 guides.
4) The HG kit should have everything you need to do the whole head remove/install, (gaskets, valve guide seals, compression washers for the banjo bolts, fuel injector o-rings, valve cover gasket) so hold off on buying all that extra stuff until you're sure it's not in your HG kit. I bought a Victor Reinz (SP?) kit and it seemed fine, though others probably have much more to say about gasket choice.
HTH!
- Robin
I don't get it, your system is holding pressure and you think it's a bad thing? It's supposed to do that. If you're not overheating, you're not leaking anything, and you're not using any fluids, I think you're barking up the wrong tree, try just driving it and don't worry about it.
I'm not worried that I have no leaks or that my system is holding pressure. I'm worried about the fact that my system builds up STATIC pressure over a certain period of time. This effectively creates a gas pocket in the thermostat area and expels fluid into the expansion tank. If left unattended, the system eventually builds enough pressure and a leak develops. That's what prompted me to start looking at the cooling system after using the car for two years with zero issues and no unexplained pressure being present in a completely cold system.
they can be fairly small leaks, valve seals wouldn't hurt, if you have a air compressor you can pressurize the cylinders with a compression tester with the valve removed, fill the cooling system to the top and watch as you air up each cylinder for the coolant to rise, you will need to turn the engine over to get the pressure to hold in each cylinder
I have an air compressor, but no compression tester. Thank you for the tip though. Would you happen to know of any reputable machine shops in the New Orleans area?
And Robin,
Thank you for your write up. That definitely put the options in perspective. I don't really see much reason to do a full rebuild on the current head since it shows no signs of leaking oil past the valve guides or any other issue.
Thanks again for the responses. If anyone can recommend a good machine shop in my area (New Orleans, LA), I'd appreciate it.
Bin_jammin
09-10-2007, 02:29 AM
I'm not worried that I have no leaks or that my system is holding pressure. I'm worried about the fact that my system builds up STATIC pressure over a certain period of time. This effectively creates a gas pocket in the thermostat area and expels fluid into the expansion tank. If left unattended, the system eventually builds enough pressure and a leak develops. That's what prompted me to start looking at the cooling system after using the car for two years with zero issues and no unexplained pressure being present in a completely cold system.
I think you're visualizing how the cooling system on a car works, but you're doing it incorrectly. A cooling system is a closed system, it should never develop an air pocket. There should never be enough of a coolant loss for you to ever be able to notice it, even water evaporating should re-condense inside the expansion tank. If you have an air pocket developing inside the system, it's because you have a leak, it's either allowing water to leak out, or air to leak in.
If you have pressure in the tank, there's no reason to believe it's because of an air bubble in any specific part of the system, least of all in the thermostat area, because that's going to be a very high flow area. The higher the flow, the lower the pressure, this would effectively eliminate an air pocket there.
To make it perfectly clear, If you DID have an air bubble developing in any specific area of the engine, you would blow a head gasket. Any spot that has trapped air means a spot that doesn't have water flowing, and that would rapidly equate to a spot that would not have heat removed and transfered to the atmosphere via the radiator.
I imagine you're hearing a hissing sound when you're opening your coolant tank cap. This could either be explained by the fact that you have even 1/2psi left in the system, which is practically nothing worth of pressure, but the car ought to hold that for hours and hours, or it's vacuum, which the car ought to hold for longer. You'd have vacuum because when the coolant heats up it expands, as it cools it contracts. Cool and contract enough, and it will crate vacuum inside the system, perfectly normal operation. Holding either vacuum or pressure means you have no leaks anywhere, if you had even a small leak it would bleed that pressure (positive or negative) off a lot faster than what you're describing.
Lastly, since you mention this is a new behavior, perhaps you had a leak previously, and enough crap built up in your system to plug it, allowing you to hold pressure now? What color is your coolant?
X2. You can do the Heli-coil yourself. Since you state it wasn't overheated then your head is probably straight and can be bolted back without machining. New bolts, proper torque procedure etc. You'll be fine.
A different head will be an unknown, why gamble?
Bin_jammin,
I know that the system is a closed system. This is exactly why I am worried about the appearance of gas or air (I doubt its air) in the system. I've checked for leaks. I've replaced any hoses that showed evidence of leaking and they are now bone-dry. I also bled the system and made sure to drill the breather hole in the thermostat to facilitate proper bleeding. I see no way whatsoever for air to get into the system through a leak (which I have yet to find, and I look on a regular basis at every hose in the engine bay).
I agree that the system holds vacuum/residual pressure after cool down. It has done this on a regular basis for two years and I was not worried by it, since it is normal. What I'm describing is positive pressure. I can feel that the system is pressurized when cold because the hoses are firm, and when I open the expansion tank cap, its not a mild hiss as you'd expect from minor vacuum build up. I get a very prominent sound of substantial pressure being bled off. That is NOT normal. That much pressure cannot and will not build up from air getting in through a small leak.
Also, if you read my first post, I stated that the coolant is new BMW Blue. I've never used anything else in the system, but when I got the car two years ago, it had green coolant. I serviced the system with all new hoses, thermostat, and new blue coolant (flushed system with water....water was crystal clear).
Lastly, I know there is extra gas in the system because I can bleed it off using the thermostat bleeder. If I shut the engine off and let it cool for a little bit, I can open the bleeder and some sort of gas gets expelled. No, its not my coolant boiling. This is done at a temperature below coolant boiling point and only with partial pressure in the system. After I do this, the coolant level in the reservoir tank goes back to normal mark (when system completely cools down). Given about a week's time, I once again get the system pressurized when cold and coolant level in tank through the roof.
Thank you for your input, but I'm still quite convinced that my headgasket is heading south since I've already redone most of the hoses and made sure the system wasn't leaking anywhere. To verify, I'll try to get an adapter for my air compressor and pressurize the cylinders to see if any of them cause the coolant level to rise.
Ross,
Would checking the head for straightness require a special rule? I've seen machinists use a very large metal one to check for straightness, but I'm not sure where I can obtain this. From reading it seems like a rather expensive tool.
Scott C
09-10-2007, 07:55 PM
I'm aware of such remanufacturing outfits, but for that price I think I'd be willing to live without my car for a little while. What I'm considering is purchasing a used head and then having a local machine shop inspect, mill (if required), and recondition the head. I've never dealt with a machine shop, however, so perhaps I'm over-reacting when it comes to the time it takes to recondition a head? I'm also a bit weary of the spark-plug thread repair that will need to be done on the current head on the car. Somehow, I would feel better having a head that didn't have a heli-coil installed.
What path did you choose in the end?
I decided to use my own head and rather than commit to $1K, take it as it came (A real man :) ). I took winfred's advice and inspected the areas likely to crack, verified straightness (finding a straightedge was a challenge, i borrowed one from work) and bolted it back together. It was not so much fun to be honest but I have a Vanos M50. I would likely never do this job again!
Scott
Thanks Scott, I figured the straight edge won't be a simple one to find. I looked at the inspection procedure in the BMW repair manual and here's a quote from it: "Check levelness with a standard steel ruler, grinding the cylinder head sealing surface if necessary". Perhaps one of the mechanic gurus can shed some light on this terminology. Obtaining a standard steel ruler is much easier than getting a precision-cut tolerance-certified straight edge.
Scott C
09-10-2007, 08:47 PM
Thanks Scott, I figured the straight edge won't be a simple one to find. I looked at the inspection procedure in the BMW repair manual and here's a quote from it: "Check levelness with a standard steel ruler, grinding the cylinder head sealing surface if necessary". Perhaps one of the mechanic gurus can shed some light on this terminology. Obtaining a standard steel ruler is much easier than getting a precision-cut tolerance-certified straight edge.
If your car hasn't overheated, I would think that there is a good chance your components are straight, but you never know until you get it apart. Part of my problem was that this car is my daily driver and well, it really sucked having to drive my other car for weeks (other car was in major overhaul mode).
Most importantly, take your time on this, plan on taking digital pictures of every little thing, label every connector - be careful, some of the connectors have gaskets that can fall out. On mine, there were plastic timing chain guides that I read about and sure enough, they could be broken in 1 sec if care was not taken removing or installing the head. I also had a lot of puckering when turning the engine manually prior to starting because I wasn't quite sure if everything was perfectly lined up - when in fact it was.
The straight edge I had was a 24", ground to .001" if I remember correctly. I treated that thing like gold.
Here is one of the places I found a head at...
http://www.cylinder-heads.com/products.cfm?startrow=1&brandid=33&catid=27
Don't forget (on M50 anyway) to replace your head bolts...
Scott
If your car hasn't overheated, I would think that there is a good chance your components are straight, but you never know until you get it apart. Part of my problem was that this car is my daily driver and well, it really sucked having to drive my other car for weeks (other car was in major overhaul mode).
Most importantly, take your time on this, plan on taking digital pictures of every little thing, label every connector - be careful, some of the connectors have gaskets that can fall out. On mine, there were plastic timing chain guides that I read about and sure enough, they could be broken in 1 sec if care was not taken removing or installing the head. I also had a lot of puckering when turning the engine manually prior to starting because I wasn't quite sure if everything was perfectly lined up - when in fact it was.
The straight edge I had was a 24", ground to .001" if I remember correctly. I treated that thing like gold.
Here is one of the places I found a head at...
http://www.cylinder-heads.com/products.cfm?startrow=1&brandid=33&catid=27
Don't forget (on M50 anyway) to replace your head bolts...
Scott
Yes, the head bolts are on my shopping list. I've also read the warnings about the chain tensioner piece on the M30 and hopefully I will not damage it. I can't seem to find a source for these precision straight edges...even online. :(
I can't seem to find a source for these precision straight edges...
http://www.sjdiscounttools.com/measurement-tools-specialty-measurement-straight-edge.html
Ouch! those things aren't cheap.
I've bought from SJ Tools before, decent outfit.
mamilapon
09-10-2007, 10:49 PM
There's a product that you can put in your coolant to check whether its mixed with combustion gases or not. I'd do that first.
Bin_jammin
09-10-2007, 10:57 PM
Yes, the head bolts are on my shopping list. I've also read the warnings about the chain tensioner piece on the M30 and hopefully I will not damage it. I can't seem to find a source for these precision straight edges...even online. :(
Any competent machine shop will be able to make you a calibrated straight-edge, for pretty short money. After all, if you're qualified to machine aluminum, you're probably qualified to cut some steel. Make a nice case for the edge, you don't want to be dropping or dinging it.
Another thing, when you've got the head off, clean it until it's bare metal. I've always used a right angle grinder with an aluminum cleaning cookie on it. You don't want to get fooled into thinking your head is warped by having anything left on it at all. Don't assume that because you've scraped it it's straight, it you can see the outline of the old gasket, there's probably too much left behind.
Get a nice set of feeler gauges for checking warpage, and get a nice set of ANGLED feeler gauges for later on when you're adjusting the valves. The exhaust manifolds are a piece of cake, put them on when the head's in the car. The intake manifold is going to be tougher, put it on outside the car, and install it with the head, getting to the underside nuts can be a trial. Don't bother pulling the starter, just take the leads off.
It's really a simple job on the m30, it's very hard to goof up.
Any competent machine shop will be able to make you a calibrated straight-edge, for pretty short money. After all, if you're qualified to machine aluminum, you're probably qualified to cut some steel. Make a nice case for the edge, you don't want to be dropping or dinging it.
Another thing, when you've got the head off, clean it until it's bare metal. I've always used a right angle grinder with an aluminum cleaning cookie on it. You don't want to get fooled into thinking your head is warped by having anything left on it at all. Don't assume that because you've scraped it it's straight, it you can see the outline of the old gasket, there's probably too much left behind.
Get a nice set of feeler gauges for checking warpage, and get a nice set of ANGLED feeler gauges for later on when you're adjusting the valves. The exhaust manifolds are a piece of cake, put them on when the head's in the car. The intake manifold is going to be tougher, put it on outside the car, and install it with the head, getting to the underside nuts can be a trial. Don't bother pulling the starter, just take the leads off.
It's really a simple job on the m30, it's very hard to goof up.
Thanks for tips :) I've got a couple of sets of feeler gauges, both straight and angled. I haven't had any time yet to explore the machine shops in my area, but I'll definitely give them a go first before dumping 65-100 bucks on a straight edge.
Would anyone know who makes this chemical that can test for combustion gases (CO2) in the coolant? I've found a Snap-On kit, but it costs nearly 70 dollars and is obviously meant and sized for shop use. I wouldn't have a use for 16 oz of fluid after one test :(
Would anyone know who makes this chemical that can test for combustion gases (CO2) in the coolant?
SJ Tools (no affiliation) sells a kit for $25
http://www.sjdiscounttools.com/lis75500.html
Robin-535im
09-11-2007, 10:30 PM
Thanks for tips :) I've got a couple of sets of feeler gauges, both straight and angled. I haven't had any time yet to explore the machine shops in my area, but I'll definitely give them a go first before dumping 65-100 bucks on a straight edge.
Personally... I wouldn't bother checking it myself as you could probably have a machine shop put it up on a machine bed and have it indicated out with a dial indicator on a CNC machine. So if you spend the $$ for the straight edge, either a) you think it's bad and take it in to the shop, where they go ahead and re-measure it before skimming it, or b) you think it's okay and if you're like me... still take it in to the shop to have them double check! :)
For $100 bucks you might get it checked AND cleaned up at a good shop.
SJ Tools (no affiliation) sells a kit for $25
http://www.sjdiscounttools.com/lis75500.html
Thank you gale! Just placed my order there. Let's hope the analyzer will help me reach some sort of diagnosis.
And Robin,
You are probably right. Knowing my anal self, I'd probably end up bringing the head to a pro anyway.
Thanks again guys, I'll keep this thread updated as I try to solve this.
Bin_jammin
09-12-2007, 07:13 PM
SJ Tools (no affiliation) sells a kit for $25
http://www.sjdiscounttools.com/lis75500.html
I don't know if you know any of your local shops, but I've got a sniffer here, and we don't charge more than $40 or so to sniff coolant for HC, might be time to hit up your locals.
I don't know if you know any of your local shops, but I've got a sniffer here, and we don't charge more than $40 or so to sniff coolant for HC, might be time to hit up your locals.
I don't know of any local shop that I'd let within a mile of my car.
Bin_jammin
09-12-2007, 08:55 PM
I don't know of any local shop that I'd let within a mile of my car.
Dude, I've been a mechanic for a long time, and I totally agree with you. If it helps, there's not much they could do to your car while sniffing the coolant, as the only two things they need to touch would be the hood and the coolant tank cap.
Dude, I've been a mechanic for a long time, and I totally agree with you. If it helps, there's not much they could do to your car while sniffing the coolant, as the only two things they need to touch would be the hood and the coolant tank cap.
Well, I'd rather not give them the chance to screw up. As an example, I had new tires mounted and balanced at a shop not too long ago. Naturally I decided to be normal and bring the wheels while they were still attached to a car (not doing that again). This was the first time my car ever entered a shop of any sort after getting a complete repaint. Two years without a single ding or scuff...only to have one of the grease monkeys set some of his crap down on my trunk and then move it. Presto...we've got a scuff mark on a perfect paint job. Naturally I'll never set foot in that establishment again. Unfortunately, the general work ethic and standards in my area seem to be much lower than in other places I've lived. The best service I've gotten around here was from smaller businesses where the owner actually cared about his customer. BTW, after my car was scratched, I also had to clean the driver's interior area from the same grease monkey. In the long run, it comes down to what the business owner/operator enforces in his shop.
P.S.: My other motive for not letting a shop sniff my coolant is that I want to see how this procedure works. I guess that's the curious engineer in me :)
Bin_jammin
09-12-2007, 11:01 PM
Well, I'd rather not give them the chance to screw up. As an example, I had new tires mounted and balanced at a shop not too long ago. Naturally I decided to be normal and bring the wheels while they were still attached to a car (not doing that again). This was the first time my car ever entered a shop of any sort after getting a complete repaint. Two years without a single ding or scuff...only to have one of the grease monkeys set some of his crap down on my trunk and then move it. Presto...we've got a scuff mark on a perfect paint job. Naturally I'll never set foot in that establishment again. Unfortunately, the general work ethic and standards in my area seem to be much lower than in other places I've lived. The best service I've gotten around here was from smaller businesses where the owner actually cared about his customer. BTW, after my car was scratched, I also had to clean the driver's interior area from the same grease monkey. In the long run, it comes down to what the business owner/operator enforces in his shop.
P.S.: My other motive for not letting a shop sniff my coolant is that I want to see how this procedure works. I guess that's the curious engineer in me :)
Too bad you're not closer to New England, if you can push your car up here I'll be happy to let you watch, you may be disappointed though, it's really not exciting:
Open expansion tank
Start car and warm to operating temp
Attach sniffer to scan tool, set tool to sniffer mode, purge lines on sniffer etc...
put sniffer end to coolant tank opening
Let sniffer sniff
Read sniffer and check that HC is stable at 3ppm or lower
Charge customer for test
Update on the situation:
As I mentioned previously, I ordered the coolant testing kit and received it this week. Today I finally had a chance to perform the test as per the kit instructions. The test fluid showed no presence of combustion gases in the coolant. Now I am quite puzzled since it seems that the head gasket is now out of the question. Could the coolant be causing this issue? When I recently changed the hoses and thermostat I only drained the radiator. I did not drain the block, so only about 1/2 of the old coolant was replaced. After that procedure, the pressure accumulation didn't stop, but it was no longer as severe as before I performed the work. So could it be the coolant that has degraded? Before I replaced hoses and thermostat I tried to bleed the system and found that the coolant in the expansion tank actually boiled a few minutes after the car warmed up to operating temp. Today this did not happen (1/2 new coolant?). What exactly happens when coolant starts to break down?
Edit: Looked up some MSDS info on ehtylene glycol and found that it can produce CO and CO2 at its decomposition temperature of 413 degrees C. This obviously is not relevant in a car engine. What is of interest is that ethylene glycol is not very compatible with acids or bases. Thus, the pH of the coolant mixture may have an adverse effect on ethylene glycol. I guess I'm looking at a full drain, flush, and refill of the system as the next step.
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