About 4k miles ago I had rear and front engine seals replaced at a volvo mechanic. Right after that I replaced (myself) everything related to PCV, which by the way was not clogged. The reason to replace PCV was that I noticed oil was disapperaing at a fast pace after the rear and front seal replacement. Before the replacement, I was losing about a quart every 2000 miles. Now I am loosing a quart for every thank of gas (about 300 miles)The car does not smoke, there are absolutely no leaks in engine. Oil is not going into coolant either. So my guess is that oil is going into intake. There is no smoke out of dipstick.

I suspect two things and want you guys opinion as you are much more knowledgeable than I am:

1- The valve seals may have gone bad ( more likely)

2- When front seal was replaced, they did something wrong with oil pump and its relief valve ( less likely)

The car is a 1994 850 NA, 180K miles. Engine runs smoothly, power is OK and mileage is around 23 miles per gallon mostly city driving short trips.

Thanks for your help.

Icelandic

Probably valve seals/guides. Pull your plugs and check for copious amounts of black soot. Use a flashlight and take a look at the top of the pistons, they should also be black if you are burning that much oil. Plus the exhaust should smell like oil.

Klaus
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Please answer, we need to know if the advice is good or bad. The 164 has a new home, all I am left with are 2 turbos :)

Klaus, that is the case. Spark plugs look blackish. Piston tops look black and soothy. Exhaust smells different than it did in the past.

Now, what is involved in repairing valve seals and guides? I Assume it takes a complete engine head tear down correct?

Icelandic

I haven't needed to do this yet, but I believe that the seals can be replaced by just removing the valve cover, not the entire head. Remember, there is no gasket, just sealant to put the valve cover back on.

I wonder if you could be sucking in oil through the intake manifold somehow. You could check the lines at the vacuum tree and other lines into the manifold. I doubt this is the case, but better to look know than later.

Klaus
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Please answer, we need to know if the advice is good or bad. The 164 has a new home, all I am left with are 2 turbos :)

Thanks for your input Klaus. I make it a point to clean throttle body and all the vacumm lines every 10k miles. Whenever I do it, I always find considerable amounts of oil in the plastic curved pipe between the air cleaner flex hose and the TB. In my opinion, the PCV in our cars have a design flaw that causes too much oil to go into the intake in the form of vapor. I think that the pipe going from the oil separator to the intake should be routed in such a way that its temperature would make the oil to condense and flow back to the oil separator. Perhaps some kind of cooler should be incorporated in the system.

I will look for someone to do the valve seal work for me. It is beyond my mechanical abilities to tackle this job succesfully.

Icelandic

Re-check all of the PCV hoses you replaced. Make sure none of them have a kink in them or are pinched. It is possible that the vacuum pressure routed through just one line causes too much draw on another? Just fishing. It doesn't make sense to suddenly have high oil consumption unless one of the valve guides just rotted away.

Klaus
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Please answer, we need to know if the advice is good or bad. The 164 has a new home, all I am left with are 2 turbos :)

I have the same problem with my 94 turbo wagon, have for some time. Replacing the oil seperator, and hoses helped for a short time. I also have oil leaking from the fill port (have replaced seal) and dip stick. Valve seals are the only cause I know of. I plan to flush the system with parts cleaner, to eliminate clogged oil return ports, then replace valve seals and guides.

Securt, thanks for your input. Before doing anything to the engine, I decided to run auto-rx and see if it helps in anything. I am now about 400 miles into the cleaning cycle, but I doubt it will correct the problem.

In order to replace the valve seals, does the engine head have to be taken apart or just valve cover?

Thanks,

Icelandic

1 - verify by removing the oil filler cap when engine is idling hot that there isn't excessive crankcase pressure - due to a clog in oil separator, etc.

2 - lift off the upper timing belt cover and see if everything in there is dry.

3 - do you smell oil near the engine?

KSG,

There isn´t any noticeable crankcase pressure. As a matter of fact, at hot idle there is a light suction both at dipstick and oil filler. Like I said on my post everything related to PCV has been replaced, and engine block ports where oil separatot attaches were cleaned during replacement.

I have already checked the camshaft seals. Every thing is dry and clean. no signs of oil leaks anywhere in the engine. No funny smells either.

Icelandic