Head gasket replacement options

[Rus]

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]

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....

[Rus]

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?

[gale]

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

[Rus]

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]

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

[Rus]

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]

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]

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]

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