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Guest Message by DevFuse

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what to go by for checking blow by!

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3 replies to this topic

#1 mickytrus


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  • northeast

Posted 13 March 2004 - 12:22 PM

I got a subie loyale with a head gasket oil leak....
about 160k..... I am gonna pull it today..... and regasket
the motor........ I am little concerned about blow by.....
(compression getting past the rings and into crankcase).
which can cause excess pressure and give you gasket leaks..
I know that these motors are prone to leaking... and Initially
with the help of the forum and people being helpful.... I am gonna
just regasket the motor........
Here is the deal........ I got this thing running... right now as
we type here....... I just figured let me pull the oil cap off while
it is running.... And what I found is excess pressure coming
out at the oil fill cap....... I put my hand on it and it is quite abit
of pressure... I checked on my other subie.... there is pressure there too but, not as much(this one has 215K and leaks like a pig...(ifpigs can leak?).. So I am concerned............ how much pressure should the be at the oil fill cap........ I know from
past experience with other motors..... there shouldn't be any......
NOw keep in mind that this pup here has a bad head gasket....
but I don't think it is leaking compression... I didn't do a compression test.............
How should I go about testing this motor for blow by.....
any one know....... I do have an engine compression tester......
Can some one out there help me asess this motor..........
I don't want to regasket it and find it has blow by.......
I will get it rebuilt if need be.......... or rebuild it myself............
thanks, Micky

#2 gmcfan


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Posted 13 March 2004 - 12:59 PM

A blown head gasket won't cause blow by into the crankcase. Blow by is a natural thing with an internal cumbustion engine, the rings can't seal 100% otherwise, engine makers wouldn't have invented road draft tubes, and eventually, PCV valves to help vent gasses and lower pollution coming out of the engine.

Check your PCV valves, they could be plugged, causing excessive pressure in the crankcase.

#3 mickytrus


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Posted 13 March 2004 - 03:20 PM

yeah that makes sense......... I'lll check the
pcv.......... so your car has 173,000 on it
and going strong?????.................................
pcv could very well be clogged...........
What is the general consensus out there...
for longevity of these motors..............
I'm gonna have the motor out anyway..........
should I do a ring job and a valve grind??????
Should I consider doing this while the motor is
out or should I slap it together with nice
new OEM gaskets I have coming from www.1stsubaruparts.com.
I am just looking for some insight here...........
reassurance I guess.......
Should I go and do a compression test.....
just for the "smell of it".
What should the compression in these pups be???

#4 Myxalplyx


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Posted 13 March 2004 - 03:56 PM

Is there a situation where you can get so much blowby into the cam housing that it would be too much for the PCV valve to handle?

I asked because I had a new PCV valve installed late last year and my oil dipstick tries to come out during full throttle. It wasn't a Subaru make PCV valve. I changed to a Subaru PCV valve and it is still doing it. The two vacuum hoses seem fine and they aren't that old (Still soft to the touch). The camshaft housing was recently put back together so no pluggage there. I'm lost!

Don't mean to hijack or ride this thread but I've been dealing with this for quite some time now. It's starting to get annoying.

I'd do a compression test just for reassurance that your compression is ok and rull it out in case anything may point to it.

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