Loosing Coolant - Head Gasket?

[Hallmark]

This is my '95 525 that has 203K miles on it. About a month ago I started loosing coolant and after checking it all out realized the water pump was beginnng to rattle. I replaced the pump and the rattle went away, but the coolant kept disappearing. I've been having to top off the coolant after 60-80 miles of driving but the car has never overheated (even before the water pump was replaced).

Yesterday I determined to get to the bottom of the mysterious disappearing coolant. I topped off the radiator and started it up. I let it reach operating temp and then spent 20 minutes crawling around the engine bay looking for leaks, but found nothing. Finally I went to the back of the car and stuck my hand behind the exhaust. There was a noticable amount of steam coming out of the tailpipe. The engine runs fine when warm but does have a little "morning sickness" when it is first started up (lasts less than a minute).

I'm guessing it's a leaky head gasket. There's no water in the oil or visa versa. Anything else I should check before I commit to tearing it apart? Is there any other work I should take care of if I take it down to that level?

Thanks guys,

[Martin in Bellevue]

I'd check the hoses & coolant line fittings for leaks first. Is there no coolant residue at any of the hose ends or along radiator sides? The cap may be relieving coolant pressure too soon also; new caps are cheap. You could pull the spark plugs & look for the steam-cleaned plug. A borrowed boroscope might help isolate the cylinder that is getting steam-cleaned.

[Hallmark]

I replaced all the hoses about 65K miles ago. I was hoping for a wet area under the radiator since this is easy to replace and I figure its about due anyway. I haven't pulled the plugs, but this seems like a good idea. Where would one find a boroscope to borrow?

Thanks for the ideas.


I'd check the hoses & coolant line fittings for leaks first. Is there no coolant residue at any of the hose ends or along radiator sides? The cap may be relieving coolant pressure too soon also; new caps are cheap. You could pull the spark plugs & look for the steam-cleaned plug. A borrowed boroscope might help isolate the cylinder that is getting steam-cleaned.

[ryan roopnarine]

what i'd do if i were you would be to get the suspect car up to operating temps (normal driving will suffice), park the car up, and check the "hardness" of the top radiator to thermostat housing hose every hour. the only way anyone knew that my HG was gone was because the hoses were unusually hard during running, and they would hold that hardness overnight. my cooling system will "hiss" when you take the cap off after resting overnight, but the hose will be soft before you do so. this is one way...

[Alan_525i]

This sounds exactly like my problem this past summer. Kept having to top off the coolant. Never found any mixing or external leaks. Finally, after 4 or 5 months of this it started to appear in the oil.

[Hallmark]

what i'd do if i were you would be to get the suspect car up to operating temps (normal driving will suffice), park the car up, and check the "hardness" of the top radiator to thermostat housing hose every hour. the only way anyone knew that my HG was gone was because the hoses were unusually hard during running, and they would hold that hardness overnight. my cooling system will "hiss" when you take the cap off after resting overnight, but the hose will be soft before you do so. this is one way...
:)

[Hallmark]

Was there anything more serious?

This sounds exactly like my problem this past summer. Kept having to top off the coolant. Never found any mixing or external leaks. Finally, after 4 or 5 months of this it started to appear in the oil.

[Gene in NC]

Hold Kleenex at tail pipe after cold start has flushed out condensation. If smoke is oil or no smoke paper will hold. If steam paper will wet and tear. Not high tech but works.

Has Throttle Housing Heater Plate been replaced? If not, do it anyway. All m20s go bad and then drip coolant down on the chassis to engine wiring connector which corrodes the connections and cause HAVOC. Very slowdrip may go on for a long time before it is really noticeable. Fitting is high on engine so leak doesn't usually show over night.

[Hallmark]

?

Hold Kleenex at tail pipe after cold start has flushed out condensation. If smoke is oil or no smoke paper will hold. If steam paper will wet and tear. Not high tech but works.

Has Throttle Housing Heater Plate been replaced? If not, do it anyway. All m20s go bad and then drip coolant down on the chassis to engine wiring connector which corrodes the connections and cause HAVOC. Very slowdrip may go on for a long time before it is really noticeable. Fitting is high on engine so leak doesn't usually show over night.

[Alan_525i]

Was there anything more serious?

Nothing really more serious, however, when taking off the head you may notice other things that are worth doing while its off. If you really want to keep costs down and feel lucky, pull off the head, don't even look at it slap on a new gasket and head bolts and you're done. Many people have done gone this route. I'm more of a belt AND suspenders kind of guy so i rebuilt the head top to bottom.

[Don]

This will cost a little but usually gives an answer. Take it to a radiator shop and have them check for combustion particulate in the cooling system. If you do then there is communication between the cooling system and the combustion "system".

Don

[Hallmark]

Combustion particulate in the coolant confirms our findings...book 'em Dano!


This will cost a little but usually gives an answer. Take it to a radiator shop and have them check for combustion particulate in the cooling system. If you do then there is communication between the cooling system and the combustion "system".

Don

[ryan roopnarine]

the combustion "particle" thing that it think you speak of is really just a reaction of any present exhaust gases. this didn't work for me, it really depends on how your gasket fails. one of the reasons i don't think this method works well is that you have to do it when cold...ie, the exhaust gases can be vented when opening the rad cold, and if its not severe enough, the gases aren't present in enough quantity to change the color of the testing chemical until the car is hot enough, at which point....the coolant would be spewing out of the radiator bottle....

[Gene in NC]

Don't know bout m50 but Throttle Housing Heater Plate should be there. Thought major diff between m20 amd m50 was dual cams. Engine wiring harness connector should be in same place, below throttle housing and on side of engine just above oil pan.