1985 745t m46

I've been experiencing a wet spot around my filler cap recently and have been trying to track down the cause. My first step was to just replace the filler cap gasket, but this didn't eliminate the wet spot (came back after a long drive and yes, the cap is really tight).

Today I replaced my oil separator as a second step (much easier than I thought with the downhose wide at the top to prevent it from slipping into the pan). However, after I got the separator out I found the old one was completely unobstucted (even blew through it to check and found NO resistance). Probably should have simply blown through the top hose at the manifold to check before replacing it, but the part was cheap online and the new part can't hurt the situation... hopefully.

Anyway, I haven't driven the car with the new separator yet, but since the old one was unobstructed I'm thinking my problem must be something else. What other problem besides a worn o-ring on the cap and clogged separator (and hoses, all unobstructed on mine) could lead to excess crankcase pressure? I'm assuming the one hose I couln't check (down hose into pan from separator) is unobstructed as well since any blockage would have backed up into teh separator and been readily apparent when I removed it.

I've had the tappets adjusted, and this wet spot has resurfaced both before and after the adjustement. I have noticeable valve slap, but my reading leads me to conclude that is common on the b230 engine. My ponderings:

1) Would a blown/broken ring cause this problem? Wouldn't I notice more serious issues if this were the case?

2) Would a faulty knock sensor retarding timing and increasing temperature cause the problem? I've had a cherry exhaust manifold after some short but hilly drives and have been thinking of testing/replacing the sensor.

3) Would a faulty CBV (comp. bypass valve) cause pressure in the crankcase and engine to increase and lead to positive pressure at the filler cap (instead of the correct negative pressure)?

So far I've replaced the aformentioned O-ring and separator, along with the vacuum hoses from the manifold to the dash, manifold to the CBV, and boost gauge split to the boost cut-off under the dash.

Any help is greatly appreciated, just don't have the knowledge or experience to track this sucker down. Really annoying since I just had the front seals replaced less than a month ago... I can only imagine what that pressure is doing to my nice new seals, argh!

thanks,
rt

RT, a compression test will tell you if it is blow by of the rings.

I had a compression test done before I put my second turbo unit on, but that was about 50k miles ago, so I guess it's possible one or more rings have gone since then. Damn it, it's only at 215k miles.

Okay, so what can I expect assuming the rings on one or more of teh pistons are bad? Slow degradation and eventual full seize or is this the kind of thing that leads the engine to just rip itself apart eventually?

I guess I'm just wondering how long I can drive the car before I have to scrap it. I'd rather keep it, but it is an '85 and I don't think an engine rebuild is really wortn the money (although all the cash I've put in lately to get it in good shape suddenly becomes pointless).

I'll probably have another compression test done when I take it in to change the oil next.

-rt

When I would pull the oil fill cap on my B230FT with major wear on the cylinder walls (.040" taper) it would spray oil out on idle. After I resleeved it (only way to save a block with that much wear) it did not spray oil at idle. Conclusion: excessive blowby=oil spray or no blowby=no oil spray.
Have you done a compression test both wet and dry? Do you have any other oil leaks?
Also on diesels we used to see worn turbos create crankcase pressure, have no idea if that's a possibility on Volvos. On the diesels we could run a manometer on the engine and disconnect the turbo drain line to see if values returned to normal, would not be easy on a Volvo,though.

Not sure how scientific it is, but I had a very similar problem and did the same things as you are doing now. Then I took the car to the shop and they pulled the oil dipstick out and you could see the gases coming out, then they unpluged the hose from the flametrap and pluged the dipstick tube with the finger - the flow of gases increased from the flametrap hose and when they pluged the hose, the gases were flowing more from the dipstick tube.....took 5 minutes to do, teh guy said that it is an "excesive blowby" caused most likely by blown piston rings - In my case it was not worth it to try to open the engine and disgnose it more. The car was old and I got rid of it....