2001 JDM newage STI, 60k miles, modded to 340/340 (Andy F remap)

Within a couple of hours of buying the above car, an oil leak occurred which turned out to be the front crankshaft oil seal. This seal was replaced and car ran like a dream and very quick.

After around 40 miles of the seal being replaced, the leak developed again. The car was returned to the mechanic, who replaced the same oil seal. The explanation given for it going again, was that there could be excess pressure building up inside the engine causing the seal to blow. Engine breather pipes have been checked already.

Question
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What can cause this build up of pressure and how can we check if there is excess pressure?

Thanks

 

Normally caused by ring blowby - have a Compression Test and a Cylinder Leakdown test done - this will pinpoint where the problem is.

Mick

 

my front crank seal went, the one in the oil pump, but i drove mine for about 5 miles before i knew, and i had to rebuild due to bearings being dry, yours is a different problem if it blows a new seal, all the best, phil.

 

haven't you posted this thread before???

same answer as last time, in that it is quite likely to be the oil pump pressure relief valve jammed causing v.high oil pressure

IMO ring blow-by would not be enough to blow the crank oil out unless incorrectly fitted

alyn

 

The car had blown 1 seal before I posted the thread. Since then the car has been back for a 2nd seal so that's why I have re-posted but with new info.

The fault you describe is certainly feasable. Thanks for your input. Is there a simple way to test this valve or is it a case of stripping off the cambelt cover and removing the oil pump.

 

Are you seeing high oil pressure readings? i would say until the problem is corrected do not drive the car. Covers\Timing belt off to get the oil pump out and check its condition. I had some right fun getting the crankshaft pulley off Subaru special tool

 

There is no oil pressure gauge fitted. How can the pressure be tested without a gauge?
Thanks

 

When the oil filler cap is removed, there is quite a throb of air that can be felt coming from the filler neck. Is this right?

 

It needs a gauge to be tested. Take it to a specialist that can diagnose the problem and take your next step from there. If your self sufficent then carry out some tests yourself. Good luck

 

Compression Test and a Cylinder Leakdown test done showing no problems and engine actually running very healthy.

#stockcar
It is looking more like the oil pump pressure releif valve as you suggest.
Can this PRV be checked or is it crankcase off again to get to the pump?

 

if you remove the front covers & crank pulley then you can get to the large allen bolt cover of the pressure valve........
alyn

 

jee's bob,he's not having much luck with that car is he..hope he gets it sorted without the need of spending big bucks

 

It's possibly something or nothing.......maybe the seal has been put in incorrectly?

 

hmmmm, strange one that...

 

At least the Compression and Leak Down tests came back ok indicating that the pistons/rings/bores/head gaskets are in good order.
Its un-usual for the PRV in the pump to stick in the shut position and give excessive oil pressure - they normally stick in the "relief" position and the oil pressure drops to the point of starvation to the mains and then the big ends.
IMHO,i would remove the pump to check the back plate screws are tight as when they work loose,the oil leaking internally on the pump will tend to push the seal outwards.
While the pump is off,you can remove the PRV(10mm Allen Key) and check to see if it is jammed in the bore of the pump or if it is scored.
The OEM Subaru oil seals are cheap enough and you can make sure its fitted correctly with the pump off the engine.

Mick

 

Thanks for that.

Forgot to say, the PCV valve was changed today also which could have been an issue?