QuestionQUESTION: I'm working on a volvo 960 engine assembly with constant dense white smoke coming out of the tailpipe. The car came to us with rough idle, not overheating and we found the number 4 compression was much lower than the others'.( One of two exhaust valves was damaged with a hole.) As the car has done 320,000 km and the car owner asked us to assemble the engine.
We replaced the piston rings, valve seals, cylinder gasket and other seals...We also did the cleaning and the 12 air intake ducts holes of cylinder head. When we first put the engine back and started it. Immediately we found constant dense white smoke coming out of the tailpipe and a few later the engine became running rough.
We thought and checked a lots. We decided to remove and disasseble the engine again to check and try to find the possible causes. We found out that the exhaust pipes of the cylinder head were wet with oil as we didn't use the special liquid sealing compound between the upper cylinder head and lower cylinder head. We only checked one of the cylinder bores which is fine by using a special measure tool. The piston rings and pistons are correct size.
Second time we reassembled the engine with all necessary steps we did except one thing which is when we installed the cylinder head, I followed the 1st and 2nd stages, and the 3 stage was 90 Nm. Was I right? It says the 3 stage is 130 degree. I am afraid to break any cylinder head bolt as I did once.
After everything was done, we run the engine. In the first few minutes it run fine without any dense white smoke. And then it cames back again but much much less. We let the engine idle for 5 hours and there is still much less constant white smoke, but much more when accelerating. The engine runs very smooth this time, no check engine light on, no trouble codes, the O2 sensor readings are 0 and 1 voltage up and down. ETC reading is 93 degree with AC on.
Is there something wrong I have missed?
I look forwards to hearing from you. Many thanks.
Yours faithfully
Tony
TAIWAN
ANSWER: Tony, sounds like you did everything right. stage 3 at 90 is acceptable. Did you check for a crack in the cylinder head? Roger
---------- FOLLOW-UP ----------
QUESTION: Dear Roger, thanks so much again. I didn't check for any crack in the cylinder head as I mentioned that the volvo 960 came to us with the normal operating temperature. So we ruled out the possible crack problem. Besides, the exhaust manifolds were so oily inside the 6 pipes after we FIRST assembled the engine and run it.
If there is a crack in the cylinder head, after the warm-up, especially the white smoke is coming out. And then we shut off the engine, removed the connecter between exhaust manifolds and the catalytic converter. We also removed the two exhaust manifolds from the cylinder head. We found no oil in these pipes and the exhaust parts of cylinder head. We run the engine without exhasut manifolds, there is still no white smoke coming out whenever the engine is cold, hot or accelerating --- we did this test only for 30 seconds at 1500 rpm when the engine was hot enough. Do you think it was enough?
But we did found some oily liquid in the Catalytic converter and the rest of two mufflers, which means the oily liquid must have gone there after the first time we assembled and run the engine. We tried to clean the three parts and let them dry in the sun, which seems it won't work much better.
Now I am wondering how long it takes to burn oil left side the catalytic converter and mufflers when the engine is idling.
Or do I have to remove the cylinder head and send it for any crack check, which we can amke sure if the cylinder head is OK or not? Because there is white smoke when accelerating but unplug the CO test hole there is no white smoke coming out of the CO test hole.
I look forwards to hearing from you again. Many thanks.
Yours faithfully
Tony
TAIWAN
AnswerTony, It does take a while to blow out all that oily stuff from the exhaust. You should have sent out the head for cracks anyway. The 960 is known for bad heads. Usually its between cylinders 2 and 3. I probably would drive it for 2 weeks before taking it apart again. Roger
