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boost leak ?

4doorboost

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Joined
Aug 19, 2008
Messages
208
Location
Westlake Village, Cali
sp ive been trying to boost leak with no luck, i get air coming out of the exhaust and out of the oil cap(its off) so i have a new motor, she doesnt smoke at all, evo111gt 16g. i blocked off the egr, got a new pcv, and am putting my motor at 30 degrees and still i can only build around 10psi. why would there be air coming out from the oil cap. my rings should be fine, as they only have 10k on them, the turbo is pretty new, no smoke out of the exhaust, im thinin the valves are overlapping? maybe valve seals? but would it run fine if the seals were bad? maybe turbo seals? any help appreciated i havent done a compression test but the motor runs strong and doesnt smoke at all
thanks
 

Quoting 4doorboost:
Alright, I've been trying to perform a boost leak test on my car with no luck. I have air coming out of the exhaust and out of the oil cap, it's off. I have acquired a new motor, one that doesn't smoke to my knowledge, with what I belive to be an EVO 3 16G.

I blocked off the EGR, replaced the PCV valve with a new one, and I am putting my motor at 30 degrees. However, I still can only build around 10psi.

Why would there be air coming out from the oil cap? My rings should be fine, as they only have 10k on them. The turbo is rather new, and no smoke is coming out of the exhaust. I'm thinking the valves are possibly overlapping? Possibly the valve seals? However, it would it run fine if the seals were bad, correct? Could it be the turbo seals?

I haven't yet done a compression test, however, the motor runs strong and does not smoke at all.

Thanks in advance for any help guys.



There we go, with the first issue taken care of we can now answer your question.

If you have air coming from your oil cap you may be getting blow by, your piston rings may be no good. Your motor does not have to smoke to have fucked up compression, so do a compression test. Also, make sure all your vacuum lines are hooked up where they should be.

EDIT: Are you saying that you are running your motor without your oil cap?
 
Last edited by a moderator:

4doorboost

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Aug 19, 2008
Messages
208
Location
Westlake Village, Cali
i just had the motor rebuilt, all new fully forged aluminum. i dont see why the rings would be bad, i was maybe thinking intake valve seals, because turbo seals would smoke...
 

SouthCaliVR4

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Joined
Jul 31, 2010
Messages
984
Location
North county San Diego
Quoting 4doorboost:
sp ive been trying to boost leak with no luck, i get air coming out of the exhaust and out of the oil cap(its off) so i have a new motor, she doesnt smoke at all, evo111gt 16g. i blocked off the egr, got a new pcv, and am putting my motor at 30 degrees and still i can only build around 10psi. why would there be air coming out from the oil cap. my rings should be fine, as they only have 10k on them, the turbo is pretty new, no smoke out of the exhaust, im thinin the valves are overlapping? maybe valve seals? but would it run fine if the seals were bad? maybe turbo seals? any help appreciated i havent done a compression test but the motor runs strong and doesnt smoke at all
thanks



I would try rotating the motor as I ran the test & looking for a point that losses less through the valve train. No, valve seals would have nothing to do with it. Test run on a hot motor or a cold one? where are you tapping in as a start point the mas or the turbo?
 

Not necessarily, I have had bad seals on two previous turbos and they just had oil in them but did not smoke. Your wastegate actuator may be stuck open. Your rings may not be bad, they may of been installed improperly.
 

4doorboost

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Aug 19, 2008
Messages
208
Location
Westlake Village, Cali
i do the leak test at the thrittle body to eliminate the turbo, im going to rotate the motor tomorrow and see i do have cams so the valves maybe be getting stuck open. i hope not my motor was built by a shop so that would be a bummer, i guess i have to do a compression test and see
 

nickbuilt

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Feb 17, 2010
Messages
474
Location
queens, ny
Do you have the hose that runs from the passengers side of the valve cover to the intake pipe disconnected? Because many people have capped the turbo by removing the filter and pumped air thru the intake pipe right into the valve cover!

-nick
 

Quoting 4doorboost:
i do the leak test at the thrittle body to eliminate the turbo, im going to rotate the motor tomorrow and see i do have cams so the valves maybe be getting stuck open. i hope not my motor was built by a shop so that would be a bummer, i guess i have to do a compression test and see



You do a leak test at the throttle body? What's the point of a boost leak test if you skip the piping. Do your test at the turbo. But if you have a boost leak your car won't stop building boost at 10 psi it will have trouble even getting to ten. Check your timing too, your timing may of jumped or may not have your marks lined up.
 

4doorboost

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Aug 19, 2008
Messages
208
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Westlake Village, Cali
yeah i doit in sections the throttle body tells me the shaft and injector seals things like that and i can do it at the turbo aswell. i def have a boost leak cause i can hear it and my wideband says i do.
 

4doorboost

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Aug 19, 2008
Messages
208
Location
Westlake Village, Cali
did a boost leak just now and my oil is bubbling pretty bad and i had a lot of air coming out of the oil cap and the vent hose on the side, i tested from the turbo.. so does this mean my rings? im going to do a comression test later but i hope my motor didnt tank after 10k it runs and idles fine feels strong but odviously there is a problem. cold it be the head? i reused it when i built the bottom end
 

SouthCaliVR4

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Jul 31, 2010
Messages
984
Location
North county San Diego
Don't use a boost leak to determine ring condition. do a compression test & a leak-down test. see what you're actually are dealing with.
 

donkeylips

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Joined
Jun 18, 2009
Messages
552
Location
Rochester, NY
^^^this. A recently built motor should be even more suspect. First get your compression test numbers, and if they're low find out if it's the rings, intake valves, exhaust valves, or HG.
 

Heres what you need for a leak down test. I have this one and it works good.

click

Harbor frieght has a leak down tester for 30 bucks cheaper.

click
 
Last edited by a moderator:

Quoting 4doorboost:
did a boost leak just now and my oil is bubbling pretty bad and i had a lot of air coming out of the oil cap and the vent hose on the side, i tested from the turbo.. so does this mean my rings? im going to do a comression test later but i hope my motor didnt tank after 10k it runs and idles fine feels strong but odviously there is a problem. cold it be the head? i reused it when i built the bottom end

\


Take your valve cover off, check to see if there is anything out of place, i.e. lash adjusters laying out, rockers out of place.
 

4doorboost

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Joined
Aug 19, 2008
Messages
208
Location
Westlake Village, Cali
i just got a compression tester and im gunna do a test tonight. i just went outside and had my buddy rev the engine and when you rev the engine up it actually smokes a little right when you let off, its white smoke and not a lot. i also dont run a cat. could it be that i didnt break in the car properly and the rings didnt seat properly, ill post my compression #'s tonight but im thinkin rings.. is it hard to re ring pistons? and what would a shop charge to do this
 

4doorboost

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Aug 19, 2008
Messages
208
Location
Westlake Village, Cali
i just did a compression test and she shot 160 155 155 153 ish, thats good correct? that was on a warm motor. the thing is that the first crank was a little low thenit built up to 160 so does that mean my rings r bad, im comfused
 

MitsuDriver274

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Joined
Jan 20, 2004
Messages
319
Location
Bellingham, WA
Is your watergate operating properly? And bov?

And are you doing your leak down test with the piston at tdc? I'm interested why you would have it set at 30?
 
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