Mysterious Boost Leak Under Intake Manifold
#20
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i would check your injector orings on the intake manifold. sometimes they sound like a leak inside the valve cover. if your intake manfiold has been off that gasket is also a possbility. if it truly is inside the valve cover, it could be valve stem seals. of the PCV valve is stuck open and boost pressure is getting into the crankcase. headgasket isn't a possibility for the leak because it is not pressurized with intake air anywhere (unless you have bad compression on a cylinder, then its time to pull the head). if you have positive crank pressure, it will blow out through the vent from the valve cover to the intake, not through the headgasket.
#21
i would check your injector orings on the intake manifold. sometimes they sound like a leak inside the valve cover. if your intake manfiold has been off that gasket is also a possbility. if it truly is inside the valve cover, it could be valve stem seals. of the PCV valve is stuck open and boost pressure is getting into the crankcase. headgasket isn't a possibility for the leak because it is not pressurized with intake air anywhere (unless you have bad compression on a cylinder, then its time to pull the head). if you have positive crank pressure, it will blow out through the vent from the valve cover to the intake, not through the headgasket.
Yea, I checked them when I first came accross this issue. The only thing I can think of is that the motor was cold the last time I did the leak test. maybe this is why air was getting past some of the seals.
I replaced the PCV valve not too long ago, so I would be hesitatnt to think it was that. Although it very well could be.
I do believe, after doing several tests to about 15psi, I had a couple of drips on oil on the ground as I have the one pvc connection which normally goes to the intake disconnected for the test.
I was actually planning on pulling the head this weekend, and replacing the headgasket. Should I pull the valve cover before hand and see if there are any other issues I can see before I pull the head on the weekend, and am stuck on ordering parts?
Thanks for the help on this,
#22
i would check your injector orings on the intake manifold. sometimes they sound like a leak inside the valve cover. if your intake manfiold has been off that gasket is also a possbility. if it truly is inside the valve cover, it could be valve stem seals. of the PCV valve is stuck open and boost pressure is getting into the crankcase. headgasket isn't a possibility for the leak because it is not pressurized with intake air anywhere (unless you have bad compression on a cylinder, then its time to pull the head). if you have positive crank pressure, it will blow out through the vent from the valve cover to the intake, not through the headgasket.
- The intake manifold has never been off
- I will install a new pcv valve tonight when I get home
- I will also check the injector O rings again, but I highly doubt they are the cause as I have checked them serveral times. They are seated correctly, and I have even sprayed them with soapy water during the test.
I'm just trying to avoid having to pull things apart more than once.
Say, go to replace the headgasket, and put it all back together, and find out the valve stem seals are bad...
#23
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when you have a throttlebody leak, the hissing is obvious. when you move the throttle cable, the sound changes, but it is still the throttlebody seals... hopefully you didn't think the sound goes away when moving the cable.
#24
On the contrary, the sound only becomes apparent with I move the throttle cable...
I tried to see if I could hear the leaking air when not moving the cable, but its dead silent. I only hear the leak once the cable is moved.
Maybe this is all related to doing th boost leak test on the car while it isnt fully warm?
#25
So I just got home, and didnt have time to stop by autozone and pickup a compression tester, so I will have to test that tommorow night.
But, I did another test right after I just drove 30 minutes, and the car was still hot/warm. Same issue, sounds like it is coming from inside the valve cover. Sounds like cylinder 3 (closest to battery).
Definatly not coming from the injector o rings. I did not pick up a pcv valve either, so hard to say about that, but it is not more than 2 years old.
I will report back tommorow after the compression test and new pcv valve replacement. Although I know the compression test will be low in cylinder 3-4, given I know I have a head gasket leak.
Although, I logged a 2-4 gear pull tonight at about 25 lbs, no traction in 2nd gear, and third was clean with no timming pull nor knock. Very rich afr's though, 10.1's on the wideband.
But, I did another test right after I just drove 30 minutes, and the car was still hot/warm. Same issue, sounds like it is coming from inside the valve cover. Sounds like cylinder 3 (closest to battery).
Definatly not coming from the injector o rings. I did not pick up a pcv valve either, so hard to say about that, but it is not more than 2 years old.
I will report back tommorow after the compression test and new pcv valve replacement. Although I know the compression test will be low in cylinder 3-4, given I know I have a head gasket leak.
Although, I logged a 2-4 gear pull tonight at about 25 lbs, no traction in 2nd gear, and third was clean with no timming pull nor knock. Very rich afr's though, 10.1's on the wideband.
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