I have a 1991 with the 305 tbi(with 221,000 miles) that burns coolant. I searched throught the forum and the internet, but i couldn't find a person with a problem like mine.

Here's what it does, when i start it up there is no white smoke whatsoever, but after running for maybe 10 minutes it will start smoking white smoke with a sweet smell to it, it is definatly not just condensation in the exhaust system, as it will continue to smoke for as long as it's on. Normally i'd just assume it was a head gasket or cracked head, but there was no coolant in the oil (atleast that i could recognize), i checked all the cylinders for compression, and the biggest drop below the average was 5 or so psi. Also, i had started it and drove it up and down the road, and then i shut it off for over a week, when i came back, i took off the radiator cap and it still had pressure in the system. I had changed the spark plugs and none of them looked like they had excessive deposits or excessively clean. The engine purrs like a kitten with no misfires, and it has a normal amount of power.

I replaced the manifold gasket in hopes that it would fix the leak, but to no avail.

Could the residual pressure in the cooling sytem be from the cylinders compressing air into the system? Is there some other way for the coolant to enter the cylinders or exhaust system that i'm missing? Am I in denial about the head gasket or head?

Thanks

 

You need to confirm that coolant is indeed getting into the combustion chamber(s).

There is a test kit that is simple to use. It detects combustion gasses in the coolant. You might be able to rent one of these testers. You'll probably have to buy the test fluid, though.

Example:

http://www.tooltopia.com/lisle-75500...oWvJOYpp_w_wcB

Edit: Coolant can get into the combustion chamber(s) through a crack in the cylinder head.

 

I have the manifold off, because I was going to just go ahead and replace the head gaskets, so I cant really do that test - i probably should have thought of that before i took it apart.

This just occurred to me, is it possible for there to be a crack somewhere in either the head or the block that opens up when the engine warms up thus explaining why it does not smoke right away.

 

Did you check the water pump? A few weeks ago, I had the odor and my radiator was always short coolant but never showed leaks on the ground. I brought it to a radiator shop and the owner had me idle it for ten minutes. Afterwards, we saw coolant dripping from a little valve looking thing at the bottom of the water pump. Once the water pump was replaced, no more problems.

 

I put head gaskets in there and put it all back together and it still smokes (steam), its definatly still burning coolant, the exhaust will make your eyes water.
Weird thing was was that when I took the heads off, none of the cylinders had any evidence that would tell me that they where burning coolant, no rust, no deterioration, no nothing(except coolant in the cylinders from when I took the heads off). The only evidence of deterioration was on the intake around the coolant crossover ports, also there was light rust on the heads in the same place. Heads where true at the combustion chambers and intakes and I saw no evidence of cracks anywhere in the combustion chambers (no money to magnaflux so i used a magnifying glass). Could it be leaking there at the intake? What are some indicators of either a cracked head vs intake leak? There's no vacuum in the crankcase. No one lends a combustion leak checker around here, so I'll have to buy one and I wanna make sure there's nothing I'm missing.

 

hey 1991camaro1996, did u figure it out?

i'm investigating white smoke on revving too (91 rs 305 tbi) and had pretty much teh same symptoms:

- puff of white smoke on revving (as if showing off, idle and small revs were symptomless)
- coolant looks clear / greenish (not brown)
- coolant reserve is a bit low and i now have to add back to the cold fill line between diagnoses
- no bubbles in dipstick

tests:
just did a combustion leak test (the one with the color changing fluid) but my fluid stayed blue. i did a compression check too and changed the spark plugs, but i got 150 dry on all cylinders, except #7 and #8 were at 120 dry 150 wet. i've read that's supposed to mean worn piston rings. could also be that my battery was a bit weak for those cylinders but a friend said he saw the pressure build stepwise (e.g. 90-120-150ish) on #7. spark plugs looked okish (some a little oily with carbon deposits, other a bit white like the "too hot" picture in the haynes manual)

i had been noticing a wet spot on the manifold between the throttle body and the driver side valve cover, but i had assumed it was condensation or something else, but it came back after wiping it down and now i think its coolant bubbling up through the intake gasket. Actually, im hoping that is all it is and nothing more

i did a coolant pressure test and found two tiny leaks on clamps on the main radiator hoses. i bet if i patch those up i'll see/hear the internal leak better? i hope im not just pumping coolant into where it shouldn't go

my rad cap only holds 7psi (not 16). i got a new one but haven't put it on yet

after i put new spark plugs in and hooked everything back up and started it and let it idle for a bit before shutting it down. i shined a flashlight thru the oil fill hole and i think i can see a tiny puddle of coolant right by the rocker arms the engine did sound noisier but i cant put my finger on the type of noise, im imagining the coolant is diluting the oil and failing to lubricate properly but i dont have a good ear for this stuff. it could be the new check valve i put on the vacuum coming off the back of the intake manifold. it snapped when i was fixing a melted connector and the replacement rattles when you shake it

 

Regarding the wet spot under the intake... Your coolant hose might just be leaking from the thermostat housing when it's warm and gets pressure.

 

FWIW when we replaced head gasket that dumped coolant into the exhaust, they would steam out the tailpipe for 20 minutes or so, while the water burned off.

 

This is a possibility, but I've never seen a clear dribble or trail from the hose to the wet spot. When I pressure tested the coolant system and found the two tiny leaks, it didn't look like the coolant dripped/flowed in that direction. I think it may be coming up through one of the holes there.

I hope my story is similar to: https://www.thirdgen.org/forums/tech...ld-gasket.html with a happy ending

My to-do list for the weekend:

- walk of shame back to oreillys/autozone to rent the pressure tester again
- double check the leaks I had found previously (I had tightened the clamps).
- duct tape / quick emergency repair, and pressurize for a few hours (I want to make sure I find other leaks, especially internal ones). I'd do this overnight, but I don't have a garage and don't want to risk neighborhood pets or kids licking any leaked coolant.
- take out all the spark plugs (goddamit, it took me three days just to get the old ones out for the compression test). Loosely tape paper towels over the plug holes and crank her over to see if any coolant gets fired out of the holes.

---

shameful questions i kno im an idiot:

- do u think its plausible old coolant (eg 4-6yrs without a flush) is eating away at the gaskets? should i throw out old unused coolant thats been sitting in a bottle too?
- should i drain whatever coolant i have asap after i do the pressure test? id have to buy all the stuff to flush it out and recycle it. im going to take the car to a mechanic either next week or in the next 3 weeks to get it fixed and inspected. can it wait that much longer to get a proper flush?

 

how is the EGR set up on those engines? I had a pontiac sunfire that had a similar problem and when I was changing the head I found the gasket at the EGR housing was bad and alowed coolant right into the exaust

 

dunno... but the first time i smogged the car after i bought it, it failed because of high nox. egr replacement has kept them super low, but it could be failing again

no coolant sprayed out after pressurizing for 4+ hrs and cranking. the old leaks were in fact fixed by tightening the clamps. but i did find a new leak tho so maybe the test isnt definitive. i pumped back up to pressure and cranked a few more times but i didnt wait more than a few minutes.

the leak was right where NCC-2569 said it would be. its audible and you can see itty bitty bubbles of coolant that dribble towards the passenger side, so the 'wet-spot' remains a mystery. maybe its an old oil spill i havent been able to wipe away and the light just hits it weird right there. i cant tell what im looking at (another reason to keep the engine bay clean).

now im thinking my oil burns white and i have blowby from clogged oil passages / pcv. not looking forward to taking off the valve covers

i should have just taken everything apart last week. but i didnt want to throw parts at it and hope it would work because i thought i was going to get over my head anyways