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Excessive crank case pressure even after PCV replacement

Moyni

Moyni

Active member
Joined
Apr 1, 2019
Location
"Race City, USA" - Mooresville, NC
Pretty much as the title states. My barnfind 87 740 with a B230F is still pushing out past the oil cap and keeps blowing out the crank seal even after 3 attempts with different brands. Even went as far as pulling the crank cover and pressing the gasket in that way and then sliding it over the crank to make sure it wasnt pinched. The oil cap I had to buy one of those heavy duty ones and bend the tabs on my oil cap to keep it from leaking. I did the PCV and all the hoses except for the one that goes down into the block since I have heard it can break and then you need to drop the pan.

Whats the likelyhood that the tube is blocked up into the crank case? Car seems to run fine otherwise, doesnt smoke or have any sort of oil consumption by my front crank and rear main seals are definitely dripping at this point.
 
I had the same issue after servicing my high miles classic wagon. So I got an oil fill cap from a 70 B20 get the hose, too. Then I T'd it into the hose from the breather box to the intake pipe. Problem solved made it to 445k miles with that one. There is an old thread from me with some pictures.
 
dl242gt said:
I had the same issue after servicing my high miles classic wagon. So I got an oil fill cap from a 70 B20 get the hose, too. Then I T'd it into the hose from the breather box to the intake pipe. Problem solved made it to 445k miles with that one. There is an old thread from me with some pictures.
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I have a spare metal cap I could sacrifice to a drill bit and bulkhead AN fitting... hmmm
 
Putting on a tighter cap may only make things worse. You can verify crankcase pressure using the latex glove test over the filler neck. It should suck down (early engines) or at least remain flat (later engines). If it puckers then you've got excess crankcase pressure. New seals on the front risks blowing out the rear main seal as the next weakest place in the system.

Did you remove and clean or replace the oil separator box on the block? They can eventually get caked inside. The little plastic tube below it in the crankcase can occasionally get blocked if the engine is badly neglected. It's an elbow and you can try carefully reaming it with a wire. They get brittle so reaming them with a tool or trying to remove them for inspection/cleaning can easily break a chunk off that falls down into the crankcase. Make sure the small PCV hose brass fittings on the throttle body are clear. You should occasionally remove them and clean the holes in the throat with a wire or undersized drill bit.
 
945T said:
Putting on a tighter cap may only make things worse. You can verify crankcase pressure using the latex glove test over the filler neck. It should suck down (early engines) or at least remain flat (later engines). If it puckers then you've got excess crankcase pressure. New seals on the front risks blowing out the rear main seal as the next weakest place in the system.

Did you remove and clean or replace the oil separator box on the block? They can eventually get caked inside. The little plastic tube below it in the crankcase can occasionally get blocked if the engine is badly neglected. It's an elbow and you can try carefully reaming it with a wire. They get brittle so reaming them with a tool or trying to remove them for inspection/cleaning can easily break a chunk off that falls down into the crankcase. Make sure the small PCV hose brass fittings on the throttle body are clear. You should occasionally remove them and clean the holes in the throat with a wire or undersized drill bit.
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PCV box and all hoses were done a few months ago, car only gets like 100-200 miles a month on it right now.

Compression was good when I first got the car and was trying to get it running. Engine only has 160k on it, no other running issues noticable. I probably still have the original compression test pics

20240918_173735.jpg 20240918_175045.jpg
20240918_174126.jpg20240918_173735.jpg

I have a sneaking suspicion its the tube down into the crank case. This car did sit for ~15 year so some stuff is worse off than other parts. I might try to get the box off and run a boroscope down in there or even a pipe cleaner and see if that helps
 
plumb the vented b20 cap and send it. vent the fuel pump cover plate and I bet you get another 100k miles from that worn down redblock
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Moyni said:
I guess I could always run one now and see the results
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Good idea.
It's possible it went up after running regularly again, but it's an easy check before spending more on it.
120 is about 30% lower (at least) than is should be.
 
alschnertz said:
Good idea.
It's possible it went up after running regularly again, but it's an easy check before spending more on it.
120 is about 30% lower (at least) than is should be.
Click to expand...

Didnt do a glove test but just put my hand over the oil cap hole and could physically feel vacuum (not pressure out) so maybe I am just real shit at installing gaskets? Who knows, it doesnt seem to have a drop at the bottom of the cover now so I will just keep an eye on it. Point still stands that the engine needs a reseal for sure
 
Moyni said:
Didnt do a glove test but just put my hand over the oil cap hole and could physically feel vacuum (not pressure out) so maybe I am just real shit at installing gaskets? Who knows, it doesnt seem to have a drop at the bottom of the cover now so I will just keep an eye on it. Point still stands that the engine needs a reseal for sure
Click to expand...
vent it anyway. and if you want to be super shade tree add 2 stroke oil to the fuel. go less than 1% ratio. it will lube the engine and artificially bring up the compression
 
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