760 Crankcase Pressure

Hi all! First time post, forgive me if I do something out of the usual format.

About 4 weeks ago I scored my dream car, a 1990 760 Turbo Wagon. I got it cheap because the previous owner did not want to fix the "rear main seal" leak that his mechanic told him about. Turns out theres no real main seal leak but the oil separator was previously loved. By previously loved I mean slapped on with a healthy heaping of RTV and no o-ring. After using some elite detective skills I discovered that it was also broken in half. Cool! Easy fix right? Wrong.

Since replacing the separator and flame trap hose a few minor issues have shown up that makes me think I have a larger issue. Turbo Inlet hose (coming from air box ->turbo) tore at the pcv solenoid elbow thingy. Replaced. Drove for 2 days, lost power at 50 mph. It was good for about 2500 rpm or 40mph on a flat road, black smoke, would hear an air leak if I tried to go above that. Found hose from intercooler to throttle to be ripped. Creating a work around until part comes in.

Is this a case of 28 year old hoses being shocked by spirited driving (previous owner was 85, drove around town) or should I be looking for some other signs of poor crank case pressure? Or something else? May-hap a saboteur!

additional notes:

-engine running, oil cap off, oil spray/gargling went away after oil separator replaced.
-valve cover nuts were barely even hand tight, replaced valve cover gasket about 20 minutes ago to be safe
-inline fuel pump positive post legit just fell off when I made eye contact with it, shotty wiring. since rewired, ordered new cradle and pump. fuel filter has become one with banjo bolt on fuel rail side.
-nothing else seems to be disconnected, no damaged wires in engine bay.
-turbo looks suspiciously wet, cant confirm if PCV issue or seal issue.

Thanks for reading the wall of text.

You didn't write how many miles the engine has done. That would be a good indicator. Did any maintenance records come with the car?

A car that has been owner by an 85y old driver will probably not have been driven very hard and most likely only short distances without the engine getting up to operating temperature. This can sludge up the engine. Sludge can get the piston rings stuck causing blowby.

it's an old car, hoses and belts can be OK if the car is never driven in boost /high rev mode. But once you do boost the engine hoses may let go. And belts may snap at high revs. I consider that to be a neglected maintenance issue.
As for the blowby, maybe do the jiggle test? Have the engine running and the oil cap loosly laying on the valve cover opening. It is supposed to stay on the opening, idealy the cap should be sucked on to the valve cover. The more blowby, the more the cap will jiggle. If the engine has badly worn rings the cap may even be pushed completely off the valve cover.
A little wiggling is acceptable.

Other then that, just do a full 'stage 0' on the car. After that it's a question of staying on top of regular maintenance.

Oh I completely forgot about that sorry. It's sitting at 206,000. While we are on the subject the water pump does look new, but it has a failing seal I've noticed and I am consuming a small amount of coolant to either that leak or head gasket. sticker on timing belt cover is blank, lol. The oil cap does not dance when rested on the cover (I did this while I had the car running, before breaking the pump), but its the updated plastic cap which iirc do not wiggle test as well. I replaced the gasket on it for good measure. I did change the spark plugs today, because it was running so rich I figured I fouled them up pretty good; cyls 2,3 & 4 were dry fouled. cyl 1 has yellowish deposits on it. compression is good.

I would include in the stage zero replacing most every rubber hose both large and small. If any of the air handling hoses look oily and wet they should be replaced. Typical is the ones from the turbo to the intercooler. The short coupler from the intercooler to the cold side pipe. Another one that gets nasty is the turbo inlet hose which gets the pcv gook dumped into it from the oil separator box.

What do you mean by dry fouled spark plugs? Be sure to set the gap on new plugs.

dl242gt said:

I would include in the stage zero replacing most every rubber hose both large and small. If any of the air handling hoses look oily and wet they should be replaced. Typical is the ones from the turbo to the intercooler. The short coupler from the intercooler to the cold side pipe. Another one that gets nasty is the turbo inlet hose which gets the pcv gook dumped into it from the oil separator box.

What do you mean by dry fouled spark plugs? Be sure to set the gap on new plugs.

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I am replacing all previously untouched air hoses this weekend with pie cut welded pipes, wasn't my first choice but this car is my daily and I need to move fast. I have replaced the inlet hose already and the pcv hose going to the "flametrap" elbow. I blew into the turbo side PCV going towards separator with cap off, no restriction there. As a correction to my previous comment about the plastic oil cap: since getting the car running again (replaced fuel pump that I broke) I have done the wiggle test with the cap again. It dances like crazy. Top end noise is noticeably worse since all above stated repairs. Using a screwdriver as an ear on the valve cover I have pinpointed the noise to the center of the camshaft/respective valve, it sounds like a valve adjustment issue objectively but the fact that it is so variable with the repairs so far leads me to believe that it is not; I am aware that as things heat up valve noise can change. Starting to think that I'm going to have to take the head off and get a look at the rings. Spark plugs were dry fouled from previous air hose failures, unmetered air going into turbo, ran rich as hell, fouled the plugs. Plugs are gapped at .26, no ignition issues.

I will certainly follow the advice of the both of you and will finish the stage 0.

Sounds to me like the motor mounts are wasted. I'm sure that all of the hoses/rubber is old and weak, but the motor mounts are always particularly suspect as the rubber degrades just as bad.

quillc said:

Sounds to me like the motor mounts are wasted. I'm sure that all of the hoses/rubber is old and weak, but the motor mounts are always particularly suspect as the rubber degrades just as bad.

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engine doesn't move too much on start up, does not shake at idle. not entirely convinced motor mounts would have anything to do with this issue.

Even if the mounts look good. Volvo planned on some engine movement and the air hose system accounts for engine movement. If you don't and make the hoses too rigid it will pull hoses off things like the turbo outlet.

Just keep making things good as stock. Service the neglected stuff and you'll get it sorted out.

If you do a bit of research NAPA has listings for hoses of varying size and angle.

dl242gt said:

Even if the mounts look good. Volvo planned on some engine movement and the air hose system accounts for engine movement. If you don't and make the hoses too rigid it will pull hoses off things like the turbo outlet.

Just keep making things good as stock. Service the neglected stuff and you'll get it sorted out.

Click to expand...

Noted for sure! Decided to take a very close look at everything today while doing intake manifold gasket, man those carbon filter lines going to the intake are soo close to being dust. Throttle body needs some serious love as well, lots of deposit inside of it. Everything must go! Haha.



the saga continues

thank you all for the continued replies.