Potentially blown head gasket? (Page 1/4)
1985 Fiero GT MAY 19, 01:29 PM
So, I was driving home from church today to notice my temperature was higher then normal, checked my coolant level and it was empty, with very little in the loop still, got home without any overheating, tried to figure out where my leak is, couldn't find any leaks at all, so for no reason, I checked my oil dipstick.

What I found wasn't comforting. Showed well overfull, with it being a milky color, not as bad as some I've seen online etc. but seems to be coolant in the oil. I have no oil in the little remaining coolant, both in the radiator and the thermostat housing, my oil fill cap is globby/yellowish, and had water condensate on it.





What are your thoughts, head gasket? Or is there somewhere else that oil and coolant can mix together, causing this. It is strange there's no oil in the coolant, it's basically a one way leak, only coolant into the oil. Do you think the rest of my engine is still ok, as it ran maybe 30 minutes with the oil like that (not super bad, but obviously not as good as straight oil) I didn't let it overheat, no strange noises, etc.
olejoedad MAY 19, 03:56 PM
Have you recently changed the water pump?
1985 Fiero GT MAY 19, 03:56 PM

quote
Originally posted by olejoedad:

Have you recently changed the water pump?



No, I haven't.
Patrick MAY 19, 07:14 PM

quote
Originally posted by 1985 Fiero GT:

It is strange there's no oil in the coolant, it's basically a one way leak, only coolant into the oil.



I would hazard to guess that wherever this cross-contamination took place, that the coolant pressure (when hot) was greater than the oil pressure at that location.


quote
Originally posted by 1985 Fiero GT:

What are your thoughts, head gasket? Or is there somewhere else that oil and coolant can mix together, causing this.



Years ago, I was prepared to pull the heads on my Z28 Camaro due to coolant getting into one combustion chamber. I lucked out and discovered that there was a slight break in the intake to head(s) gasket that was allowing coolant to enter one of the intake runners. In your case, it's possible that an intake manifold gasket leak has allowed coolant to enter the crankcase.


quote
Originally posted by 1985 Fiero GT:

Do you think the rest of my engine is still ok, as it ran maybe 30 minutes with the oil like that (not super bad, but obviously not as good as straight oil).



I've seen images of crank bearings being damaged due to coolant circulating in the crankcase. No idea though how long it might've taken to damage them.
1985 Fiero GT MAY 19, 07:49 PM

quote
Originally posted by Patrick:

I would hazard to guess that wherever this cross-contamination took place, that the coolant pressure (when hot) was greater than the oil pressure at that location.



Yeah, that's what I was thinking to.


quote
Originally posted by Patrick:

Years ago, I was prepared to pull the heads on my Z28 Camaro due to coolant getting into one combustion chamber. I lucked out and discovered that there was a slight break in the intake to head(s) gasket that was allowing coolant to enter one of the intake runners. In your case, it's possible that an intake manifold gasket leak has allowed coolant to enter the crankcase.



Yeah in some more research, it seems it might be an intake gasket or perhaps something in the water pump/timing cover area, no weird smoke or smells, regular power when it was running, which would seem to indicate there's no cylinder head gasket leak.


quote
Originally posted by Patrick:

I've seen images of crank bearings being damaged due to coolant circulating in the crankcase. No idea though how long it might've taken to damage them.



Yeah I know, I hope it wasn't too long. Is there any estimation on how much overfilled it is with the coolant/oil mixture, I would assume there would be some linear 5 liters per inch of dipstick or something, but there's definitely a lot of coolant in there.

I obviously am not putting fresh oil in until I have fixed the leak, would it be smart to drain the oil/coolant mixture, and leave the engine dry for however long it takes to fix this, or should I leave the oil/coolant mixture in for now?
theogre MAY 19, 08:40 PM
Yes, bad head gasket can to above...
Iffy head, block & more can cause bad head gasket.

Lower Intake manifold &/or gaskets to heads can fail causing same problem.
Yes, iffy WP & Timing cover do that w/ V6. Many replace the pump & do something wrong & then leak coolant inside, outside of engine or both.

Pull the spark plugs look in w/ cheap bore scope to see any piston got coolant wash is easy first step. For that matter, Just pulling the plugs may show similar coolant washing.
Then fill coolant system w/ water then pressure test that looking for possible leak(s). https://www.fiero.nl/forum/Forum2/HTML/145505.html Coolant Pressure Testing for Fiero.

may need to take valve cover(s) off then look in oil drain holes while pressure test the coolant.

Example: If engine got way hot... may have warp/crack head(s) etc & just replacing the gasket won't last if does Fail very fast like seconds to days.

------------------
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1985 Fiero GT MAY 19, 08:59 PM

quote
Originally posted by theogre:

Yes, bad head gasket can to above...
Iffy head, block & more can cause bad head gasket.

Lower Intake manifold &/or gaskets to heads can fail causing same problem.
Yes, iffy WP & Timing cover do that w/ V6. Many replace the pump & do something wrong & then leak coolant inside, outside of engine or both.

Pull the spark plugs look in w/ cheap bore scope to see any piston got coolant wash is easy first step. For that matter, Just pulling the plugs may show similar coolant washing.
Then fill coolant system w/ water then pressure test that looking for possible leak(s).

may need to take valve cover(s) off then look in oil drain holes while pressure test the coolant.

Example: If engine got way hot... may have warp/crack head(s) etc & just replacing the gasket won't last if does Fail very fast like seconds to days.




I will pull the spark plugs tomorrow and see what they look like, don't have a bore scope, but I know exactly how my plugs should look (checked them a week or so ago haha).
My engine definitely didn't get a chance to get hot, temp gauge is normally at 1/4, noticed on the way home it was at 1/2 (105 c), went to 3/4 at 60km/h, 1/2 at 80km/h, and accelerating, decelerating, or swerving all momentarily brought down coolant temp (sloshed the little remaining coolant around?). I pulled over within 15 minutes, added 3/4 liter of coolant I had, let it cool for 45 minutes, drove the last 15 minutes home, gauge never hit full, temp light never came on, engine bay temp was normal, and the engine didn't overheat.

Another interesting thing is it sucked the coolant reservoir dry, so the system was not under any pressure, and coolant was actively being pumped into the engine oil and sucked from the reservoir.
theogre MAY 19, 09:11 PM
The Gauge & ECM sensors will lie when have low coolant in the engine because where installed on V6.
The heads Will get way hot driving "only" 15 minutes w/o proper coolant flowing thru them.

That's Even when you don't "boil over" puking coolant on the ground.
jelly2m8 MAY 20, 12:30 AM
I will give Huge props to you for being vigilant on checking the dipstick, something I am bad about on my own vehicles ( whole other story, not Fiero...)

Reading the replies above, We all know some disassembly is in order. A compression check may, and I say may point towards a head gasket, But could be either of the above, intake gaskets, Timing chain gasket etc

Time for some evasive surgery. You know it has to come apart, start with the intake and work deeper if it seems it needs to.

Generally the coolant pressure will be like ~ 16 PSI, that should be less than a high mile 2.8's oil pressure, so here is where you have to thing, what and where is over powering the other.

[This message has been edited by jelly2m8 (edited 05-20-2024).]

1985 Fiero GT MAY 20, 12:37 AM

quote
Originally posted by jelly2m8:

I will give Huge props to you for being vigilant on checking the dipstick, something I am bad about on my own vehicles ( whole other story, not Fiero...)

Reading the replies above, We all know some disassembly is in order. A compression check may, and I say may point towards a head gasket, But could be either of the above, intake gaskets, Timing chain gasket etc

Time for some evasive surgery. You know it has to come apart, start with the intake and work deeper if it seems it needs to.

Generally the coolant pressure will be like ~ 16 PSI, that should be less than a high mile 2.8's oil pressure.




Yeah, I don't know why I checked the dipstick, but it was good that I did, and yeah my oil pressure is definitely higher then normal coolant pressure, which would seem to indicate that it is dumping coolant into an oil return/open area in the engine, like the timing chain or camshaft areas.