Volvo: 850 T5 Smoking Exhaust, 850 t5, head gasket

Question
QUESTION: Hello, I have an 850 T5. It smokes, especially at idle. Smoke smells oily and somtimes a tad like coolant. 250,000 mi. Original turbo. Gas mileage is normal. Power is normal. I had a Volvo mechanic tell me to replace the turbo, but I want to make sure the turbo is the culprit prior to replacing it. He did not run OBD II or examine the car. How can I diagnose this and what else could the smoke be caused by? Thanks!

ANSWER: Ed,
If you are burning oil then possibly turbo, valve guide seals, rings most generally are the cause. Cylinder leakage will help eliminate the rings. There is no test for the turbo or the valve guide seals. Just trial and error or just a good "gut" feeling. The OBD will not verify any oil burning problems. If you have coolant that is being burnt you then have a possible head gasket of crack in the head.

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QUESTION: Thanks for your informative response!  To follow up: can you give me a range of what this type of work would cost labor-wise? I can get a rebuilt turbo for $695, but I imagine it is difficult to install.

I checked the spark plugs for oil or deposit. They are clean (not oily and no black deposits). Does that rule out anything? Thanks again!

Answer
Ed,
The only real way to see if valve guides are leaking is to pull the intake and look at the intake valve to see if there is oil laying on the valves. Now that might not be 100% either, as only a small amount of oil would have to leak in to cause some smoking. The plugs could be buring off the oil that is left and not showing signs. If the compression is good and there is not any low cylinders, and the cylinder leakage test does not show any leakage, the plugs are clean a good gut feeling would be turbo. It is not that easy to tell what is the cause of burning oil without renewing or repairing some known causes. You can not check the turbo seals they just need to be replaced.