gsrboi80

iTrader: (38)

I always leak test off the turbo. Never put a car to TDC to do a Leak Test. I simply plug off the line going to my catch can from the side of the VC when doing a test.

Can pressure tests 30 psi no problem except those stupid TB shaft seals that are leaking again. 3rd set

mega-z

iTrader: (13)

Would u think that some of the valves are not closing all the way? or is that even possible?

TTP Engineering

iTrader: (465)

it is normal.

fre

iTrader: (4)

I would assume you mean the driver side port where it recircs into the intake on stock vehicles, which means that is a normal place for air to escape. That makes sense, seeing they put the valve from the crankcase there in the first place. They expect some leaking into the crankcase then.

I didn't even notice it until I fixed all my other boost leaks, which makes sense, because it was the hardest one to hear.

I am still curious as to where the air leaks by though (pistons or turbo bearing). Or maybe something I am not thinking about. I need to look at that rear recirc valve again and see how it is plumbed.

mega-z

iTrader: (13)

o i c. So when the car is not on tdc air can flow through?

fre

iTrader: (4)

No, it doesn't matter where your engine is, because you will either have the intake or exhaust valves closed. You will never have both open at the same time, so you should always have a seal.

If the intake valves are open and exhaust closed, the air will get into the combustion chamber but can't get out. On the other hand, if the intake valves are closed and exhaust valves open the air can't get into the combustion chamber at all.

gsrboi80

iTrader: (38)

gsrboi80

iTrader: (38)

Yes sir I have it out to a catch can then back to the intake I just plug one of the hoses when leak testing. I still retain the stock PCV system on the back of the VC.

Ted B

iTrader: (6)

At TDC where the piston is on the tail end of the exhaust stroke and at the beginning of the intake stroke, both intake and exhaust valves are open.

Ted B

iTrader: (6)

Mega-z's situation is one that is disturbing.

A pressure test of the intake system revealed pressure making its way into the valve cover. A faulty PCV was initially suspected, but it checked out ok.

Next, a leakdown test was conducted for each cylinder. 1, 3, and 4 checked out fine. With 2, pressurizing the cylinder resulted in pressure under the valve cover.

Normally, this is a textbook case of a ring seal issue. And while that can't be ruled out, there do not seem to be any other obvious telltale indicators (e.g. oil consumption), although he's just gotten things running again after dealing with a headgasket sealing issue that resulted in two blown water pump pressure caps.

Given occam's razor and the fact that there are four oil drainback passages immediately adjacent to cylinder 2, coupled with the fact that he just replaced the headgasket, my initial suspicion is that the head seal is compromised, allowing communication between 2 and an oil drainback passage. It's impossible to know one way or another at this point, but this is my hunch.

Anyone is welcomed to comment.

BluEVOIX

iTrader: (69)

How much air is actually leaking from your valve cover?

I've done a boost leak check as well.

1st. I tested the intercooler pipings. Unpluged the upper pipe to the TB and plugged it. Next I ran the boost leak checker to the turbo inlet and pressurized it. Held the boost, no leaks.

2nd I plugged the upper pipe back to the Throttle body and checked for leaks. Air would slightly leak out of the valve cover pcv's. (I have unpluged the pcv system & checkvalve and am running vent-to atmosphere)

If I'm not mistaken air leaking out of the valve cover slightly is completely normal because pressure does leak around the pistons and down to the crankcase. Then from the crankcase it follows through to the valve cover and out the pcv's.

BTW, I did not set it to TDC. Just turned off the motor and ran the boost leak check. Also I have compression tested my motor and it all checked out good.

Ted B

iTrader: (6)

Enough air is coming from the valve cover to generate some pressure. The air leak inside the engine that is pressurizing the cover is audible.

This was detected through a boost leak check, and isolated to #2 through a leakdown test with the engine warm. It is not normal.

Liqquid

It can be the turbo if the seals or thrust washers are bad... boost pressure gets into the center section and pressurizes the crank case causing air to try to escape from wherever it can. Namely, that port you are referring to that normally is recirculated into the intake pipe. One condition that may be noticeable when driving is when you build up some boost and then let off the gas, you will see some light colored smoke come from the exhaust... but only when letting off after boosting.

This condition can happen if a turbo becomes oil starved due to engine failure and the seals are damaged.

Ted B

iTrader: (6)

Right, but a leakdown test takes the turbo and entire intake system out of the loop.

Liqquid

yes, did not read your last post till I posted mine... figured i'd leave it though just for the benefit of those doing searches for information in the future. (in case they do not see a leakdown issue)