Crank case pressure issues

[V8chevette]

Hi all,

I'm having some trouble with my 3.9 RV8, took the car out for a spin at weekend got home and found that oil has been pumping out of the engine around the sump gasket and the back end of the inlet manifold gasket there was also oil around the base of the distributor.

I'm presuming this is down to to much crankcase pressure, i have a PCV valve on the left hand rocker cover which breaths in to the edelbrock air filter and a small breather filter on the right hand rocker cover.

I've also noticed gases pumping out of the dip stick hole.

So does anyone have an idea what could be causing this? could it be worn piston rings or worse?

Or is there an easy way to reduce the pressure?

Thanks in advance

[Bobbybedtime]

Hi,
I had exactly the same problem last year, after a bit of research it pointed to the head gasket (s) leaking. I has oil around the top of the distributer and around the valley gasket at the bell housing. My car had been stood for many years and I was in the process of getting it back on the road.
Apparently gas gets pushed out into the valley, then into the timimg chain area where it pressurises the timing chain cover then typically leaks by the distrbuter. Other places would be crankshaft oil seal. The older 14 bolt heads with tin gaskets are prone to this failure. When I pulled mine apart it appears both gaskets were blowing. I'll try and attach some pictures.
I've just finished putting mine together with composite head gaskets ... which is possibly where all I've written looses credibility because I'm not conviced I'ved cured the problem. Put a new cam in mine so just today ran it in a 2500rpm and it seems I have oil coming from the valley gasket at the bell housing. I could just be paranoid and it may just be a normal leak.
I did notice oil bubling out of one of the rocker cover screws tonight, I'll be following this thread with interest. I may well do a compression test to see If I've got problems in that area.
Regards,
BBT.

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[V8chevette]

Yep that is identical to my problem.

I'll be doing a compression test tonight so i shall post the results up, if you could post some pictures that would be great

Cheers Jonathan

[DaveEFI]

Hi all,

I'm having some trouble with my 3.9 RV8, took the car out for a spin at weekend got home and found that oil has been pumping out of the engine around the sump gasket and the back end of the inlet manifold gasket there was also oil around the base of the distributor.

I'm presuming this is down to to much crankcase pressure, i have a PCV valve on the left hand rocker cover which breaths in to the edelbrock air filter and a small breather filter on the right hand rocker cover.

I've also noticed gases pumping out of the dip stick hole.

So does anyone have an idea what could be causing this? could it be worn piston rings or worse?

Or is there an easy way to reduce the pressure?

Thanks in advance

They will push oil out if the crankcase gets pressurized. Have you got a flame trap screwed into the front of the OS rocker cover which the breather pipe attaches to? If so, this can get blocked. In the worst case, you might have to use a blowlamp to clean it - after removing obviously.

On some EFI models, the passage in the plenum can get blocked too - so check this on your air filter, and the valve and hoses.

The air intake to the crankcase is at the back of the NS rocker - this has a very small hole, about 1mm, so check that is clear too with a bit of wire.

[Darkspeed]

Had similar issues with a car I bought - turned out that the dipsticks who had serviced the car for the owner over filled the engine with oil and the crank was literally swimming in oil. - Enough to bow the valley gasket such was the pressure.

Two factors - 1. Some muppet had rounded off the sump plug so could not drain the oil but figured lets just pour in new oil anyway - 2. The oil dipstick was loose in the block leading to it being 1/2 further up than it should have been.

Not only was it well above the level anyway - but when the dipstick was pushed fully home it was over an 1- 1/2 above max. - Drained out over a gallon of oil after filing new flats on the sump plug.

Upside is that I got a car with suspected blown engine - oil was pumping out of everywhere + over and around bellhousing onto exhausts - got the car dirt cheap and turned out to be a good motor

Andrew

[DEVONMAN]

Hi V8Chevette.
If I understand you correctly you say you have a PCV valve breathing into the air cleaner. This would be incorrect as to work properly the valve needs to be connected to a manifold vacuum point on the engine side of the butterfly. If the PCV valve is connected to the air cleaner then the valve is actually partially blocking the flow.
As others have suggested, you may well have a blowby problem but it would be worth sorting the PCV first.
Regards Denis

[V8chevette]

Hi V8Chevette.
If I understand you correctly you say you have a PCV valve breathing into the air cleaner. This would be incorrect as to work properly the valve needs to be connected to a manifold vacuum point on the engine side of the butterfly. If the PCV valve is connected to the air cleaner then the valve is actually partially blocking the flow.
As others have suggested, you may well have a blowby problem but it would be worth sorting the PCV first.
Regards Denis

Yes that’s what i did after chatting to a friend of mine i have realized it's wrong, the problem is i don't have a vacuum point on the carb or manifold so i'll have to fettle something.

I'll keep you posted

[V8chevette]

Right the plot thickens

I have plumbed the breathers correctly now and the oil sill refuses to stay in the engine

So i did a compression test and out of the eight cylinders i could only get to six of them as 7 and 8 are tucked under the bulkhead.

But the six i did check all gave a reading of around 150psi the lowest being 148psi the highest 155psi so all seems well on those cylinders.

Next i found an old mechanical oil pressure gauge and lobbed that on, it read 40psi at tick over and 100psi when revved a tad high, so i borrowed another gauge off a mate and that reads 20psi at tick over and 80psi when revved still way to high

So i'm thinking to much oil pressure now, i stripped the oil pump down and the pressure relief valve was not stuck so gave everything a good clean and put it back together with no change

Any suggestions what could cause high oil pressure?

I will add that the oil pump base i'm using is an original Buick item not Rover.

[spend]

Soounds simply like the spring in the PRV is too strong to me.

Unless oil is leaking from gaskets where oil pressure is present, I can't see why the extra pressure would cause leaks though?

[kstrutt1]

The high oil pressure can only really be a faulty relief valve or a blockage in one of the passages which return the oil to the sump, have you tried another pump?

[Bobbybedtime]

Hi,
Got mine sorted out last week. Pretty simple in the end.
There is a breather which goes from one rocker cover to the plenum.
Its attached to the plenum via a pipe which it pushes over. The pipe has a hole @ about 09:00 which lines up with the hole in the plenum.
My metal pipe was loose, as I pulled off the breather from the rocker and rotated it up the holes lined up, I then blew through thinking it was clear. When I rotated the breather down the pipe rotated out of alignment and blocked the hole.
As soon as I realised this and lined it up properly i have absolutely no crankcase pressure.
Regards,
BBT.