Hello,

I have oil and thick puffy smoke coming out of my exhaust system... Heads were changed a little over a year and a half ago and the car has been running fine ever since with no issues. I recently got the compressor replaced and started using the a/c. Then the car randomly overheated around 6 months later. I shut the engine off and released the pressure from the radiator and couldn't find any leaks. It started up fine and ran good for about a week afterwards...

I put it in the shop when I got back home (from out of town) (The car sat up for around a week at the airport) before all of the chaos started just for a checkup. Thinking that the water pump circulation levels were low. The upper rad hose that goes to the thermostat would get warm. The lower side hose and tank would always stay empty and cool. The mechanic told me it was running fine and it was just low on fluid... Me being the person I am. I go change the pump,thermostat, & cap.. Total of around 70 bucks and 2 days off an on worth of work, no big deal.

So today I start it up... it cranks fine idling smooth. First time I'd started it all day... texas weather is around 55 degrees. I go less than .5 of a mile and it kills on me. Won't turn over without serious amounts of gas being applied to the pedal too. I get it started back up and moving.. Pull over to the parking lot and there's the gas/oil/antifreeze I guess mixing in the heads causing this HUGE ass cloud of smoke immediately upon start up... The car idles really low at around 400RPM and sounds like it's missing. But it doesn't kill. I let it sit for around 45 minutes.. I get a tow home. Engines cooled down by then. I start it up... No problems with cranking it now, but the thick ass smoke cloud returns...

I know something is mixing in the head and probably getting to the plugs which is why it's blowing out of the exhaust. I need an expert decision on whether or not to keep throwing money into this abyss though.

Only reason why I have this car is because it's my deceased brothers.. It's a project car to me. Fiberglassing a/b pillars, door panels, customer interior etc... I have quite a bit of money tied up into it to keep it running and looking good. I just need to know if it's worth fixing... OR if the mechanic that fixed it the first time even did what he was suppose to do correctly. My cost for new heads would be around 1100, the car has a hair over 143,000 miles on it...


In need of serious advice please anyone!

Thank you for your time.

Also... Is it worth doing a rebuild on these engines? Or would someone just recommend a swap?

The overheating could have been caused by a stuck thermostat (been there), and if it got really hot, it may have cracked a head, causing coolant leaks into the combustion chamber(s), or warped a head, causing a gasket leak. You might pull a few spark plugs, and look for one that's cleaned off by coolant.

I figured that... I was reading the haynes manual and I did a test. The top hose that connects to the stat housing is warm. The lower hose was like the car hadn't warmed up at all. After a 40 mile freeway drive at 80mph... I can get the work done fairly cheap... It's frustrating to do repetitive work though.

I pulled the dip stick and there is antifreeze mixing with oil. No milky antifreeze though... Is there any possibility it could be an intake manifold gasket?

First of all. You need to buy a Cadillac Factory Service manual for the DeVille. Those 'repair' manuals are a waste of money. ebay has FSMs for the '94 DeVille at lower pricing than the OEM publisher HELM, although Helm still has brand-new ones available for $105(manual #GMP94EK). A man who does his own work needs the FSM. Best tool you can have and will pay for itself almost immediately.

Second: Pull and read the plugs. They can tell you a lot. I'd do a compression test and an air-leak test to determine the health of the engines' lungs. Head gasket problem/valve train problem/head-bolt problem/head problem. AF in the oil isn't good.

Have you checked for trouble codes? The Onboard Diagnostic system is always the place to start looking for clues in the detective story of 'WTHs wrong with my car'.

Good folks on the forum and more help will be offered I'm sure.

Anti freeze in the oil is almost a sure sign that the HG has failed.

No codes at all, Outside of of A012, which is an issue with the ACP Panel which needs to be replaced.

I am going to pull the plugs on Sunday after letting the car sit for a few days and see what the deal is. I know for a fact last time when this happened (before I had owned the car) they ran K&W in it and it sealed up the engine pretty good... It wasn't running hot or anything, no loss of power, great gas mileage, no idle issues either... Only reason I got the heads fixed was to run the a/c eventually, especially since I was driving it on more of a regular basis and the Texas weather tends to get to you after a while in the summer.

I'll definitely look into the FSM... I intend on keeping the car forever in my mind... if I can keep it running that long. (damn sentimental value) So it'll definitely be a good investment.

I thank you for all of your help and input, It's definitely appreciated.

A cool lower hose with a warm upper hose is most likely a plugged radiator. Pull it and have it checked for proper flow. A "thickass" cloud of smoke is oil, a "thickass" cloud of steam is coolant. Steam disapates quickly in the air, oil smoke lingers around the car. Oil? coming out the exhaust is most likely black residue from carbon within the exhaust system dripping from the tailpipe and is a normal by product of a car with a cat converter. If coolant is mixing with the oil, it could be the engine oil cooler within the radiator and not the engine at all. A good radiator shop can do a test to verify hydrocarbons in the coolant which would be present if the head gasket or intake gaskets have failed.