Can you tell if your HG is blown?

[Rob]

Howzit Guys,

While inspecting my coolant level on Sunday, I notice to what looks like, dirt or rust in the coolant expansion tank. Could be oil. So I thought maybe the HG is blown. However I checked the oil cap on the engine block, no white stuff there at all. She doesn't smoke at all, no white smoke, no smell. So I'm guessing that because the engine stood still for nine months and again for a month last month, so could be rust or something. I'm going to completly drain the whole cooling system, bleed and refill. Will do more checks then.

How else can I tell if the HG is blown? Oh and I don't see any leaks around the HG or any oil dripping anywhere. All seems fine. Only thing that has made me ask this question and suspect the HG is gone is the coolant colour.

Also when I filled it up on Sunday to the COOL Mark on the expansion take it still gave me a coolant low warning. Check it again today and she's back down to the bottom of the tank, very low. How is this possible?

Thanks guys!

Oh, if you're all sick to death about hearing about my poor, sick E34, don't worry about this problem just yet. I'm going to focus on the power issue first get engine power back then tackel everything else.



Thank you.

Rob.

[cschollum]

well you say its loosing water, that could be a sign of a blown gasket, however rusty water would be quite normal in a 1990 engine, a few flushes should cure that for a while

i would fill it up again, then monitor the operating temperature on a normal drive, make sure it doesnt go over half way on the guage, then reasses the water level when you get back after its cooled - if its lost more and youre sure there are no leaks, then I would suspect head gasket

[Rob]

Damn, I really hope not. Will get the system flushed and re checked. By the way is the HG hard to replace?

Oh and it lost water when I didn't even drive it at all. just ran the engine, It over heats while idleing!

[cschollum]

i wouldnt bother flushing it, untill you have established if the gasket has gone, 1 it will be a waste of time and 2 in the process of bleeding the system you may further damage the head

id see what others have to say at this point, the m20 engine is quite trigger happy in blowing gaskets, it certainly seems like that is the issue, overheating and loosing coolent.

the gasket isnt that difficult but it is to do right, depends on your experience and you must get the belt and tensioner back on correctly or it will smash the valves - plus the head nmay be warped and require skimming - as I say it depends on what your experience is

when you say it overheated while idling, how long did it idle for?

[Rob]

Idling for about 30 mins then will start to get hot. No the car has always had a overheating problem. My old man had the car before me and said its always got hot only when standing still really.

[cschollum]

you should never let the car idle for that long, really doesnt do it any good, plus you have no rush of air running past the radiator

take it for a run with a full coolent level and see how it behaves, keep an eye on the temperature and check level when cooled back down

but never idle for so long

[Rob]

See I have to wait for my pump to come next week, before I can take her out. But I don't think the HG is gone as the motor was recently re done. After a cam belt snapped.

[schematic]

You can get a pressure check done to check for leaks also another check would be a compression check on engine but you need the proper gauges should not cost too much to have tested

Howzit Guys,

While inspecting my coolant level on Sunday, I notice to what looks like, dirt or rust in the coolant expansion tank. Could be oil. So I thought maybe the HG is blown. However I checked the oil cap on the engine block, no white stuff there at all. She doesn't smoke at all, no white smoke, no smell. So I'm guessing that because the engine stood still for nine months and again for a month last month, so could be rust or something. I'm going to completly drain the whole cooling system, bleed and refill. Will do more checks then.

How else can I tell if the HG is blown? Oh and I don't see any leaks around the HG or any oil dripping anywhere. All seems fine. Only thing that has made me ask this question and suspect the HG is gone is the coolant colour.

Also when I filled it up on Sunday to the COOL Mark on the expansion take it still gave me a coolant low warning. Check it again today and she's back down to the bottom of the tank, very low. How is this possible?

Thanks guys!

Oh, if you're all sick to death about hearing about my poor, sick E34, don't worry about this problem just yet. I'm going to focus on the power issue first get engine power back then tackel everything else.



Thank you.

Rob.

[joshua43214]

I would respectively like to make a few corrections. You should be able to safely idle the car for days with no ill effects concerning the heating, this is harder on the catalyst than any other part. There is a huge difference between runing hot and over heating, please don't confuse them and interchange the words. Running hot is whenthe gauge goes high on the gauge, overheating is when the coolent become hot enough to boil and the gauge goes into the red. ALL cars will run slightly hotter if left to idle, this is normal and is not a concern. If your car overheats at idle and not while cruising, you probably have a fan issue ie. loose belt, bad clutch, cloged radiator fins etc. If you have a overheat problem at all speeds, you probably have a waterflow problem ie. bad T-stat,cloged radiator etc.

If the car runs hot at idle and not at cruise, once again its probably an airflow probem, but could be a waterflow problem as well. If it runs hot at all speeds, it is also still probably a waterflow problem, but a bad radiator can cause this too.

Bleeding the system will absolutley no effect on the head, you simply can not do more damage to the engine bleeding it.

Please give us a proper description;
How high does the gauge get?
What is your ambient temp?
How long does it take to get there?(short time=waterflow)
Does the fan clutch engage?(air flow)
Does the aux fan come on?(air flow)
Does it cool back down when driven?(air and water flow)
Does it cool back down when idle is raised slightly?(water flow)
Does it cool back down when idle is raised to 1500rpm?(air and water flow)

Answer all of these questions to yourself, then ask yourself what the common demoninator is. Diagnosing most cooling sustem problems is straightforward, but people seem to think its voodoo. I see people toss parts at cars with overheating problems almost as much as they toss parts at cars for driveability issues.

Report back with your findings, don't use words like "overheat" unless the car is going into the red. it just raises red flags with people and you will get flooded with guesses about the cuprit.

Here is how the cooling system works;
As the car heats up, the water absorbs the heat from the engine and is circulated through the engine. When the water gets hot enough, the T-stat opens, and allows cold water from the radiator to enter the engine, this cool charge of water will then close the T-stat. The water then transfers its heat to the radiator allowing it to radiate off, while the water in the engine heats up again. This process is repeated until an equilibrium is established, this equilibrium is dependant on ambient temp. In very cold weather, the T-stat will just open and close as described above until the car is turned off. In warmer weather, the radiator will not be able to shed heat fast enough to keep up with the engine. At this point the T-stat will remain open(or partly open) constantly alowing a constant enchange of heat from the engine to water to radiator. The hot air coming ouf of the radiator is drawn accross the fan, when the thermocouple get hot enough, the fan clutch will engage, increaseing the air flow through the radiator and increasing its efficiency. In very hot ambient temps, the air flow at idle will be insufficient to maintain safe temps and a safety circuit will cut in causing the auxiliary fan to start. This fan will then bring the temp down to a safe level and then turn off.

If every thing is working properly, you the car will idle at a safe temp for as long as you like. This maybe about 3/4 gauge in very hot areas as the car cycles the aux fan on and off. So if its 105 degrees out and the gauge goes up to 3/4 or even higher when left to idle, but does not go into the red, its working as intended. Higher temps do mean increased pressure, so this can be hard on older weaker systems.

[Tiger]

Simple CO test will determine if you got blown headgasket. Mechanic should have this tool.

Check for coolant leak... like at your thermostat housing... heater core, etc. DO a pressure test and you should be able to find the leak.