Huge Boost Leaks :eek:

[Ryan86]

My car's been down recently because of a burnt clutch, so I've been trying to fix all my leaks... wow, I never knew there were this many!

I've already replaced the BISS O-Ring and cap, and the injector insulators. I thought that would have fixed it....nope.

Today I finally got a real compressor and pumped it up to 20psi. Results? In 10-15 seconds it'd drop to zero from both the turbo inlet and throttle body elbow. The o-rings inside the throttle body seem to be leaking...those are going to be a pita to fix. And then there's some air comin out between the screw threads of the nipple on the compressor housing. I've tightened it more, but that didn't help. Teflon tape? Or what?


Annnd...the worst of it all... I can hear a howling sound when I take off the oil cap. I turned the engine over a bit and tried the test again...still heard the same howling noise. I'm guessing this is bad. What exactly would need to be fixed? Is it still drivable?

Also, a little random, but could these boost leaks be why my Greddy Type-S makes such a short note and won't flutter no matter how tight it's set? Every ther one I've ever heard makes a 'tune', while mines just a very quick psht.

 

[RamenPride]

Annnd...the worst of it all... I can hear a howling sound when I take off the oil cap. I turned the engine over a bit and tried the test again...still heard the same howling noise. I'm guessing this is bad. What exactly would need to be fixed? Is it still drivable?

probably just a leaking PCV

 

[guitarXgeek]

About the air hissing out of the oil cap.. try and do the boost leak test when the motor is fully warmed up. This way the rings will be better sealed and most likely the air won't be hissing out of the oil cap cause the rings should be sealed (assuming they are still in good condition). Just a thought..

 

[Ryan86]

Engine was warmed up...kept burning myself too .

I ordered a new OEM PCV valve today. Hopefully that was the problem..

 

[steel_3d]

Just remove the pvc valve from the valve cover and keep it attached to the hose to the intake mani. Then do the test. If the pcv's not leaking that way, it's good.

 

[Stapl3]

Screw buying another one for it to go bad and be a mystery leak. I ditched a 16g because my new PCV valve just couldn't be bad already. Sure as shit...

Just cut the rubber line between the pcv valve and the intake manifold. Put a plug in both hose ends.

Done. Forever.

 

[Ryan86]

New PCV valve.. still air leaking into the valve cover Not as much though...

What else could it be? And how would I go about testing it?

 

[Stapl3]

When testing, take the vacuum line off the pcv valve and put a plug (bolt) in it. If the air is still leaking, still don't worry. It's probably because the motor is cold and the rings aren't expanded fully.

On my old DSM, I would just cap that PCV valve off and the nipple on the side of the valve cover. I was more concerned with leaks I could fix easily.

 

[oldman]

Just cut the rubber line between the pcv valve and the intake manifold. Put a plug in both hose ends.

I have seen many of your posts and you seem to be fairly knowledgeable about DSMs but the above statement is just plain wrong. Do you understand the purpose of a pcv valve?

 

[DSMJim]

Screw buying another one for it to go bad and be a mystery leak. I ditched a 16g because my new PCV valve just couldn't be bad already. Sure as shit...

Just cut the rubber line between the pcv valve and the intake manifold. Put a plug in both hose ends.

Done. Forever.

This will work for a very short period of time.

Crank case pressure is releived though the PCV valve (positive crankcase ventelation) and if you plug it up, pressure will build and eventually find somewhere else to go. What will happen generally is your dipstick will pop out all the time and the pressure will be relived though there. Most people know about the dipstick problem on T/E/L cars so they have pinched the dipstick tube to fix it. What happens then is pressure is still there with nowhere to go. Guess what the next tube off the pan is? Oil return from your turbo. Except here the tube does not extend higher than the motor so it's going to push oil around.

Next the motor will try and push oil up your return tube against the feeds pressure which it will eventually overcome and the oil will squeeze out your turbos seals into either the intake or exahust. If it goes out your exhaust eventually you will think you blew your motor from all the smokeing and if enough oil gets in there it will completly coat your exhaust and muffler inside in oil. I have seen this happen on a talon personally that come into the shop. If it's out the intake then it will buil up into the cooler and eventually make its way into the engine. Oil in the combustion chamber is a really bad thing. On a high HP motor it promotes detonation or poor combustion and a whole host of probems which eventually blow up the motor.

All from plugging your PCV, sounds fun huh?

 

[oldman]

Good post Jim, I figure you now have plenty of time to make long quality posts , welcome back.

To add to what Jim posted. You also have to worry about other seals that are associated with the crank case as well, oil rings, valve seals, VC gasket and pulley seals. Never plug up the pcv, either relace it with a non-leaking OEM unit or at least VTA, with the pcv hollowed out or replace with a straight fitting, preferably to a catch can.

 

[Stapl3]

Jim, the line going from the side of the valve cover to the intake pipe will release the pressure that would be in the crankcase and won't be a boost leak as it's metered air going back into the turbo.

If your motor is leaking like this due to blow by or whatever and you're running that valve cover line to the street or through a breaher cap, you're going to have a boost leak. Same goes for having a gutted PCV and running it to a breather cap or catch can like oldman is suggesting. Atleast one of those two needs to go back to the intake pipe if you're in this situation.

I feel PVC valves just cause problems and think it's best to eliminate them. I wen't through 4 of them in half a year. I just capped both ends (intake manifold and pcv) and was done with that crap forever.

Bottom of post 8, I was just talking about fully capping off the valve cover nipple during testing. During testing, the nipple of the side of the valve cover was capped and I removed my dipstick and put my thumb over that to keep the air from coming out. I was testing for leaks in my vacuum lines, TB, turbo, intercooler piping, etc. I knew the leaks in the motor were there, and they weren't going to get fixed, so I just worked around them.

Hope this clears up what I was saying.

 

[oldman]

If your motor is leaking like this due to blow by or whatever and you're running that valve cover line to the street or through a breaher cap, you're going to have a boost leak. Same goes for having a gutted PCV and running it to a breather cap or catch can like oldman is suggesting. Atleast one of those two needs to go back to the intake pipe if you're in this situation.

Blow by is not the same as a boost leak in that you're losing metered air because fuel has already been added. The reason and the only reason the breather is routed back to the intake pipe and pcv back to the intake manifold is to achieve the most efficient crankcase ventilation, a pull from the intake pipe under boost and a pull from the manifold under vacuum. The reason and only reason that both are routed to a catch can or VTA is to keep oil out of the intake, not as good as the stock routes but it's the next best thing. With that said, under no circumstances do you ever want to plug up the crankcase side of the pcv especially if you already know you have heavy blow by.

I'm just talking about fully capping off the valve cover nipple during testing. During testing, the nipple of the side of the valve cover was capped and I removed my dipstick and put my thumb over that to keep the air from coming out. I was testing for leaks in my vacuum lines, TB, turbo, intercooler piping, etc. I knew the leaks in the motor were there, and they weren't going to get fixed, so I just worked around them

Not a good thing to do especially during a pressure test when you're pushing 20psi. If you don't have plans to fix your ring problems that is fine as most of us are poor and bounded by financial situations, just don't compound the problem by plugging up the pcv.

 

[Stapl3]

Fair enough, run both back to the intake pipe with a fuel filter in the middle of the line acting as a "breather cap".

Either way, the air that's coming out the valve cover from either hole is metered at one point and time like any air that enters the engine properly. It's a boost leak, plain and simple. If it can't be fixed properly, it has to be routed back to the intake system.

 

[oldman]

Either way, the air that's coming out the valve cover from either hole is metered at one point and time like any air that enters the engine properly. It's a boost leak, plain and simple. If it can't be fixed properly, it has to be routed back to the intake system.

I will try and explain this again. Blow by (bad rings) is not a boost leak because it's a piston ring leak during the compression stroke and you're losing air fuel mixture, not just metered air so you don't need to recirculate it like a BOV where fuel has not been mixed yet. Blow by happens anytime the car is turned on, even at idle when you're in vacuum. When you get into boost, the situation gets worse due to two things.

1. You're compressing already compressed air therefore there is more air to blow through the ring.

2. Higher rpm = more compression stroke = more blow by.

Remember when the car is running, all the valves are opening and closing really fast unlike during a static pressure test when they are stationary. In fact, during a compression stroke (when blow by happens), the intake valves are closed further suggesting that blow by <> boost leak. Hope I made it clear.

 

[Stapl3]

If it's after the injectors, it doesn't need to be recirculated because X air already got Y fuel. Got it.

 

[DSMJim]

Fair enough, run both back to the intake pipe with a fuel filter in the middle of the line acting as a "breather cap".

Either way, the air that's coming out the valve cover from either hole is metered at one point and time like any air that enters the engine properly. It's a boost leak, plain and simple. If it can't be fixed properly, it has to be routed back to the intake system.

It's a small enough amount of air that it doesn't need to be metered. In a stock configuration the PCV and breather (two lines from the valve cover) go to the intake AFTER the MAF. If you look inside the maf it lets a particular amount of air in unmetered which it is tuned for. The amount of air going in from the crankcase will not make any difference. A boost leak is a leak in the pipes between the turbocharger where it's pressurized and the head where the intake manifold attaches. A small amount of air Naturally passes the rings (blow by) so this is not a boost leak, this a natural function of the motor.

A PCV valve on a properly working motor is to relieve the pressure inside the crankcase that is built up from a very small amount of gas-air mixture that leaks out of the combustion chamber past the rings literally into the bottom end where the rotating assembly is. This pressure builds up though the entire long block (bottom end and head) as air can pass through the oil chambers that run down from the head to the block to the pan.

This air is basically exhaust gas that is trapped in the bottom end. It MUST be relieved somewhere. The function of the PCV is to relieve this "exhaust" air from the bottom end/head so it doesn't build up and eventually blow the dip stick out or blow the head gasket or something eventually would pop with enough pressure. They take it from the head as their is less oil in the head than there is in the block. The reason they put it to the intake and not just out to the atmosphere is two fold.

1) When the intake is sucking on the PCV it relieves this pressure. This actually makes HP (see a Dry Sump Oil system for more info on this) because its taking away the pressure from the engine so all the rotating parts move easier without pressure on them. Even venting the PCV to the atmosphere causes a small HP loss (read: Small) because the engine is not longer having the gasses vacuumed by the intake.

2) The "exhaust" air in the crankcase is "dirty" and can't just be released to the atmosphere as it's basically just raw exhaust so it's a pollution concern. So having the intake pull the air from the crank case allows it to be burnt in the combustion chamber and out the exhaust system to the catalytic converter so it's released to the atmosphere like normal exhaust gases in the most efficient manner thats friendly to the environment.

 

[oldman]

If it's after the injectors, it doesn't need to be recirculated because X air already got Y fuel. Got it.

With just one exception, intake valve seal leaks. With multi port fuel injection systems, like the one in our car, only fires during the intake stroke of the piston when the intake valves are open. This means although valve seals (located at the intake ports of the head where the valve guides are) are after the injectors, a valve seal leak into the crankcase would mean that you're losing metered air most of the time and air fuel mixture only when the injectors are open. In any case, the solution should be replacing the seals rather than trying to reroute it back to intake which is just a bandaid if it would even work at all.