Leak down test - breather valve leak?

[adam g]

In order to try and diagnose a misfire I carried out a leak down test this weekend. I pumped air in at the intercooler inlet and blocked the breather outlet from the cam cover - and nothing else.

This resulted (from circa 2psi up) in a significant leak coming from the black dome shaped pressure regulator valve that comes off the crankcase. Having since read up on the breather system operation I conclude that this should never be under pressure anyway and only is so due to me having blocked the cam breather. However, I still found it surprising that pressure should build here so quickly as surely it has to leak passed the piston rings to get this far, unless there is another problem.

So, either my rings are shot or the ball bearing PCV is leaking and letting pressure through from the manifold, correct?

[mike74]

I feel your pain having just replaced said breather last week. When pressuring the system, I heard bubbling coming from the sump which others suggested could be that valve. The valve itself is only 6 pounds but its a right b!tch to get at. I changed mine and my everlasting 00561 code and reluctance to boost went away

[adam g]

I feel your pain having just replaced said breather last week. When pressuring the system, I heard bubbling coming from the sump which others suggested could be that valve. The valve itself is only 6 pounds but its a right b!tch to get at. I changed mine and my everlasting 00561 code and reluctance to boost went away

I was going to remove it to test it last night but as you say , it's not in the most accessible place and the factory crimp clips look like a pain to remove. I might do another test and listen for the sump bubbling first.

While inspecting the valve I noticed a wiring harness trapped between a metal pipe on the breather system and my power steering reservoir, it had worn through two layers of insulation through to bear wire. Its the harness that carries the signal to my coil packs so I think Ive found the misfire. It might not be the only problem though so will still check the valve.

[mike74]

Being honest, if you're at the stage of removing the valve to inspect it you'd be as well replacing it for all the cost that's involved. I found that its possible to manoeuver a pair of pincers underneath the inlet manifold/throttle body to cut through the uppermost clip on the tee assembly (the one that fits onto a small hose which connects to underside of inlet). I used the 90° portion on a scriber to pick the lower most clip open. Then its just a case of unplugging the blue multi-plug connector for the charcoal canister and wiggling the whole tee assembly out to the left of the throttle body & then upwards.
Be prepared for much frustration, profanities & skinned knuckles!
This is the valve that I bought, got it delivered within a couple of days
http://www.ebay.co.uk/itm/2520344901...%3AMEBIDX%3AIT

[Rusty]

Block the breather off at the inlet hose and pressure test from there. The breather system is not designed to be under more than a little pressure, although it should be in good order and be able to take a little pressure, du to it being after the MAF, so any leaks will result in minor changes to the amount of air in the system.

Generally, 20+ year old rubber hose and plastic, spending their lives covered in oil and being heated and cooled by up to 100degC aren't going to be in good order, so ditch the lot and replace it all either with OE or with a custom setup

[adam g]

Being honest, if you're at the stage of removing the valve to inspect it you'd be as well replacing it for all the cost that's involved. I found that its possible to manoeuver a pair of pincers underneath the inlet manifold/throttle body to cut through the uppermost clip on the tee assembly (the one that fits onto a small hose which connects to underside of inlet). I used the 90° portion on a scriber to pick the lower most clip open. Then its just a case of unplugging the blue multi-plug connector for the charcoal canister and wiggling the whole tee assembly out to the left of the throttle body & then upwards.
Be prepared for much frustration, profanities & skinned knuckles!
This is the valve that I bought, got it delivered within a couple of days
http://www.ebay.co.uk/itm/2520344901...%3AMEBIDX%3AIT

Thanks for the link my new one arrived yesterday. My old one had the smallest leak. Not enough to affect performance but as you say, for the price and hassle it's worth changing anyway. The new one takes a bit more pressure to open but hopefully that's because it's new rather than poor quality.

[newsh]

That small valve has to deal with boost pressure as well as vacuum so a small leak will affect the running a lot. The bigger valve in the system down by the crankcase outlet should also be in good order but will not affect running as much as it only deals with vacuum, however a decent leak anwhere in the PCV system will cause unmetered air to enter the inlet and therefore lean running.