1998 V70 high crankcase pressure episodes

[erikv11]

What can cause intermittent (like once every few weeks) high crankcase pressure?

- 98 V70 GLT
- 220k factory engine
- even compression 175 psi across the board (warm, dry, WOT numbers)
- turbo is a 15g with 180k (but the same problem happened with the factory 13g)
- factory GLT ECU
- factory exhaust
- complete PCV done, including the port into the oil pan and the PTC, etc
- clean and clear turbo oil return line

Episode 1, early Dec: car is running perfectly fine, then it suddenly blurts oil out the filler cap and blows out both rear cam seals (all 4 cam seals are new SKF, installed by me). Codes for misfires only.

I clean it up, re-seat the cam seals, it runs great. I suspect the 13g leaking oil internally is the problem, so I swap in a 15g. Still runs great. PCV is working great no smoke out the dipstick and it sucks in a glove on the filler neck. I drive 2500 miles over the holidays, hassle-free, top of the engine is bone dry, Oil consumption is low, about 1/2 quart over 2500 miles. Some oil out the bottom of the intercooler.

Episode 2, last night: the same thing happens, oil out the filler cap and both rear cam seals popped. Clean up oil, replace cam seals, check compression, check PCV, everything looks fine. Like last time, there are only codes for misfires.

What could be causing this? How can I troubleshoot it?

More history: when I got the car in August, the PCV was probably original, it was completely plugged at the block. The car was smoking out the tailpipe when letting off the throttle, burning oil, presumably blowing oil through the turbo due to clogged PCV. It was also oozing oil everywhere out the valve cover, the PO's mechanic had sealed it with RTV. I fixed the PCV and the cover, new cam seals, tune-up, then all was fine until the problem mentioned above.

The one thing I've noticed that could provide a clue is, this car intermittently has a very slight stumble, almost like a bad MAF, but never throws a code with it. The MAF is a low mileage Bosch that worked fine in my NA. It did this stumble with the 13g and still does with the 15g although it is much less often and less severe now, almost not noticeable. I don't think it is the MAF, it is something else.

Guesses:
- Clogging cat or exhaust? But runs fine in between.
- Too much oil getting through the 15g turbo and the 13g? Seems unlikely I know. This 15g has slight shaft play, but I've never used it before, it came with my R with blown engine and that engine was abused before I got it. PO ran it low on oil and tore up the bottom end.

I could use some help, any ideas?

[jimmy57]

I have seen backfires do this. When cranking it over or just as it hits when cranking, is there any indications of a cough or a sudden shake? Not all backfires are violent and loud.
Excess crankcase pressure usually pushes one seal out and then pressure is released. Backfires can push out a few in one instant.

[erikv11]

I haven't noticed anything like that at startup, but I will pay more attention to it. When it is so cold like it is now in winter, startup is usually not super smooth anyway.

But that occasional "stumble" I mentioned, I wonder if those are small backfires while going down the road.

So that could be a timing problem? I checked the timing when I replaced all four cam seals in August. I thought is was maybe off by one tooth, so I spent a lot of time on it when putting it back together it should be good. This was my first experience with the mechanical style tensioner, I should note it was not properly locked when I got in there.

Or somehow running a little rich, without throwing any codes for it?

[jimmy57]

Are the distributor cap and plug wires in good shape?

It couldn't be rich without lots of issues. Just short of impossible to have both be bad with biased signalling offset in the same way so the diagnostics doesn't pick it up. Lean is what usually causes backfires if it is mixture related.

[erikv11]

The cap and wires are new, Bosch and Bougicord, so unless I got a bad part they should be in good shape.

Plugs are Autolite coppers with 5k now, they were newish when I got the car so I left them in. They looked normal when I pulled them last night for compression.

I do have a new set of Volvo plugs sitting in the garage, I could put those in?

[erikv11]

Update, opinions encouraged:

Episode 3: The morning after the episode 2 cleanup, the same thing happens 5 minutes after startup. So maybe not so intermittent now. Smoke dumping out the exhaust, cam seals blown. I have to leave town for work so the car sits in the garage for 3 weeks. While sitting it drains like 8 ounces of oil out the intercooler weep hole.

Today I pull the bottom hose at the intercooler and drain another 4 ounces of oil, so there was like a cup and a half in there. Run the car, there is slight crankcase pressure even with the cam seals still blown out, a glove on the oil filler hole stands up slightly. I pull apart the PCV and it is essentially bone dry, as is the fresh air intake side of the turbo. All plugs are clean gray-brown except #5 has a little black on one side. Compression is 175 across the board. PCV lines are open (I did not check the drain into the block) and the cold side of the turbo is very clean, hardly any oil at all.

I could use any insight/opinions, especially if they suggest troubleshooting. Why is there so much oil in the turbo side of the intake and why are the cam seals blowing out?

Ideas so far:
(1) Stuck piston ring. I think the clean plugs and good compression argue against that?
(2) Clogged PCV, like from an intermittent kink etc. I think the bone dry PCV rules this out? the oil is getting in on the other side of the turbo.
(3) Backfires. Seems like this is still possible. I put in new plugs today but I did not put the car back together yet. Wires, cap, rotor are new.
(4) Oil is spewing into the turbo due to a bad internal seal, and being dumped into the intercooler. But then why do the cam seals blow out, but the plugs look clean? Or is it the little bit of black on #5 plug?

[abscate]

Are the MAFs for a turbo and NA the same ? That surprises me.

[Ben850]

I was thinking a burnt exhaust valve, but you had mentioned the compression was consistent across the board.
An intermittent sticking/bent valve?

Just a thought.

It is an issue I would not want to deal with, so please update when you figure this one out Erik.

I'll trade you a "J" relay for the answer.

[erikv11]

Are the MAFs for a turbo and NA the same ? That surprises me.

Yep, 95-98 MAFs are all the same, turbo and non-turbo. Some of the 94s use it, too.

[erikv11]

... I'll trade you a "J" relay for the answer.

Sure, I owe you four answers!