Gonna reach out to the mighty Sigforum brain trust for some advice. Pretty sure I have a head gasket replacement in my future, but figure I'd ask for any other thoughts.

I have a project car I bought a few weeks ago, and have been tinkering with it. Knew going in I'd have some work to do, so no big deal. Haven't driven it outside the original test drive, and up and down the driveway (about 150 yards).

Car: '95 Cutlass Supreme w/approx 82K on it. Has a GM LQ1 in it, which is a 3.4L DOHC 24v V6 (not the 3.4 OHV used in later year GM cars). Not the most user friendly motor GM ever put out.

Issue: Blows white smoke, coolant smell under hood (and some smoke, which I can't track down), idles smooth but some hesitation when reveving it up. No check engine light.

Work done to it: I've replaced the lower intake manifold gaskets (twice), as well as various other things (upper radiator hose, heater hose, coolant change, standard tune up stuff, ect).

Did a coolant pressure check @15 PSI: Went down to ~4 PSI in about an hour. I can't seem to find what is in spec, and what is out of spec, but IMO it should hold pressure longer than that.

Put in some dye, and found a leak (upper radiator hose) and fixed that. Still loses pressure.

No milky oil.

Diagnosis: Best guess at this point, is it needs a head gasket (or two), but I'm looking for some advice, or something else that I might check before I do the head gaskets. Being a DOHC engine, it is a bit more involved than an OHV engine, especially with the timing belt.

With ~82K on it, it really shouldn't need new head gaskets, but at 25 years old, who knows (especially not knowing what maintenance was done before). GM started using Dexcool in '95, which can cause premature head gasket failure (I've heard)

Take it to a place with an emissions analyzer...a sniffer. You can open the coolant reservoir/overflow tank and stick in the sniffer in (not in the coolant, just in the air space in the reservoir). If you have a blown head gasket you should see exhaust gasses register on the analyzer.

So, is it losing coolant as a result of all this?
If so, then the head gasket(s) is the obvious answer.

Get yourself one of these, or something similar.



The blue fluid will turn a greenish-yellow color if there are combustion gases present in the coolant. As bad as this one sounds, you might not even need the aspirator bulb.

quote:

Has a GM LQ1 in it, which is a 3.4L DOHC 24v V6 (not the 3.4 OHV used in later year GM cars). Not the most user friendly motor GM ever put out.

This may be the understatement of the year.

Those intakes are a pain, takes a little practice to get perfect, and can cause your symptoms if not done right. If you think they are not the problem, you can do further diagnostics.

I'd pull all your plugs, pressurize the cooling system until it bleeds down, and then see if you are getting coolant in any of the cylinders. Use a bore-scope if you can, or have someone roll it over while you watch for coolant to shoot out a plug hole. Plan on how to catch up to a pint of coolant if it fills a cylinder and you have good cranking speed, and don't put your eyes in the way. Had an engine take out a fluorescent light over a workbench with a 1/2 inch stream of coolant doing this before.

If you have leakdown tester or similar setup you can put pressure in the cylinders at TDC, valves closed. I use a compression tester hose with the valve stem removed, and a valve connected to shop air. Leave the coolant pressure cap off and gradually put pressure into the cylinder while watching and listing for bubbles in the cooling system. Be careful, if not at TDC engine can turn over, keep hands and tools clear of belts and sprockets.

Only thing I can add is that those cars required timing belt changes at certain mileages. And if I remember correctly those are interference engines, could get real ugly real quick if a belt fails.

You may want to start by taking off the rad. cap and looking for bubbles. Not very high tech but cheap!

Jim

If it’s blowing white smoke out the exhaust after the engine is up to operating temperature for several minutes that is a head gasket. This should not be confused with the typical condensation that has to burn off inside the exhaust when the engine is cold or in really cold temperatures.

Sounds like a head gasket. A leak down test will tell for sure. A test kit can be bought at Harbor Freight pretty cheap. Found the following with an online search.


Cylinder Leakage Test

Perform a cylinder leakage test by injecting regulated shop air into the cylinder head's spark plug hole, then visually searching and listening for a leak. The valves, rings, and head gasket seal the combustion chamber. The intake valve leads to the intake manifold, and the exhaust valve leads to the exhaust tailpipe. The piston rings lead to the crankcase and the PCV valve in the valve cover. The head gasket between the head and the block seals the cylinder and the engine's cooling system.
Cylinder leakage test.

By introducing compressed air into the combustion chamber through the spark plug hole, we're able to listen and see any air escaping through one of these areas.

If the intake valve were not seating correctly, air would escape past the valve and into the intake manifold. Air heard at the throttle plate indicates a faulty intake valve at that particular cylinder as the problem. If air is heard escaping through the tailpipe, the exhaust valve is defective, probably burned. If air is escaping through the PCV outlet, the piston rings are faulty. If air bubbles appear from the radiator neck the head gasket (most likely), the cylinder head, or the block's deck are at fault. Always refer to the manufacturer's specifications before performing any automotive test.

You need to look at the economics of doing major repairs on a 25 year old car that was known to be a "potato chip" from the get go.

White smoke means either coolant or trans fluid.
You mentioned a leaking hose which could explain smell under hood.
Trans vacuum modulater could be bad allowing trans fluid to be sucked into system.
If exhaust smells like coolant then it probably is coolant. Might try disconnecting vacuum line to trans and see if smoke clears up. Should clear up in just a few minutes if that is the problem.

Disclaimer: I worked on cars mainly from 50s, 60's & early 70s so a 95 might be a bit different.

quote:

Originally posted by 1967Goat:
Take it to a place with an emissions analyzer...a sniffer. You can open the coolant reservoir/overflow tank and stick in the sniffer in (not in the coolant, just in the air space in the reservoir). If you have a blown head gasket you should see exhaust gasses register on the analyzer.

This ^^^^

That block tester crap is hit or miss, and I used it plenty of times. Once we got our emissions test machine we could find a head gasket leak in seconds. Just make sure the car is warmed up/operating temperature.

But here is the issue, it may not show up on that test, normally if you leaking exhaust gas into the rad you will also get a pretty quick overheating problem, which you dont seem to have.

quote:

Originally posted by VictimNoMore:
So, is it losing coolant as a result of all this?
If so, then the head gasket(s) is the obvious answer.

Not sure. I pulled off the upper intake half a dozen times, and it looses a bit of coolant each time, hard to keep track if it is losing coolant on a regular basis or not.

quote:

Originally posted by egregore:
Get yourself one of these, or something similar.

The blue fluid will turn a greenish-yellow color if there are combustion gases present in the coolant. As bad as this one sounds, you might not even need the aspirator bulb.

Good advice, thanks! Tried one today and the fluid stayed blue the whole time.

quote:

Originally posted by dynorat:
Those intakes are a pain, takes a little practice to get perfect, and can cause your symptoms if not done right. If you think they are not the problem, you can do further diagnostics.

If you have leakdown tester or similar setup you can put pressure in the cylinders at TDC, valves closed. I use a compression tester hose with the valve stem removed, and a valve connected to shop air. Leave the coolant pressure cap off and gradually put pressure into the cylinder while watching and listing for bubbles in the cooling system. Be careful, if not at TDC engine can turn over, keep hands and tools clear of belts and sprockets.

Yes, they are. I think a leak down test is my next step.

quote:

Originally posted by Pal:
You may want to start by taking off the rad. cap and looking for bubbles. Not very high tech but cheap!

Jim

No bubbles.

quote:

Originally posted by 21bubba:
You need to look at the economics of doing major repairs on a 25 year old car that was known to be a "potato chip" from the get go.

No, no I don’t. It is a project car, and economics have nothing to do with diagnosing a head gasket. The expense associated with the head gasket repair (if it needs one) isn’t that big of a deal to me.

quote:

Originally posted by gjgalligan:
White smoke means either coolant or trans fluid.
You mentioned a leaking hose which could explain smell under hood.
Trans vacuum modulater could be bad allowing trans fluid to be sucked into system.
If exhaust smells like coolant then it probably is coolant. Might try disconnecting vacuum line to trans and see if smoke clears up. Should clear up in just a few minutes if that is the problem.

Disclaimer: I worked on cars mainly from 50s, 60's & early 70s so a 95 might be a bit different.

Not sure how the Cutlass is set up, but I’ll look into it!

quote:

Originally posted by Southflorida-law:

quote:

Originally posted by 1967Goat:
Take it to a place with an emissions analyzer...a sniffer. You can open the coolant reservoir/overflow tank and stick in the sniffer in (not in the coolant, just in the air space in the reservoir). If you have a blown head gasket you should see exhaust gasses register on the analyzer.

This ^^^^

That block tester crap is hit or miss, and I used it plenty of times. Once we got our emissions test machine we could find a head gasket leak in seconds. Just make sure the car is warmed up/operating temperature.

But here is the issue, it may not show up on that test, normally if you leaking exhaust gas into the rad you will also get a pretty quick overheating problem, which you dont seem to have.

I’ll look into this one, don’t go any emissions analyzers around here, but I’ll look.



And the coolant combustion gas test was a negative. Well, that's good and bad news. Good news if it isn't a head gasket, bad news if it is a false negative. In addition, guess I need to start looking for the next thing.

If memory is correct on the 3.4X there is a small coolant hose about the size of a fuel line that serves as a throttle body heater. Make sure that the gasket between the intake and the throttle body is good and there are no intake manifold leaks either from bad gaskets or corrosion from incorrect coolant.

1995 is the first year of Dexcool, we had a lot of coolant related problems in the subsequent years not limited to failing gaskets, sludge in cooling systems. Corrosion is always in the back of my mind, a lot of strange failures at least to me over the years.

With the coolant odor and white smoke on startup I'm suspecting intake or throttle body related internal leak. We did not see many of those with head gasket leaks in their era but that was a long time ago, time and miles does change things.

quote:

Originally posted by 21bubba:
You need to look at the economics of doing major repairs on a 25 year old car that was known to be a "potato chip" from the get go.

Yes, one of the engines on my "do not even think about buying" list