points for figuring it out so quickly. that plenum? is something else

 

Thanks to this thread, and having to deal with multiple vacuum leaks and check valve issues recently, I've gotten pretty good at setting up the compressor and fittings for a boost leak test.

I find that having that along with an automotive stethoscope makes the job that much easier. Having an inspection camera really helps as well in the tight confines of this engine bay.

 

It sucks the pictures have disappeared

 

I see the OP pictures still

 

I found a boost leak coming out of the second port inside the intake plenum, right after the MAF. If you stick your hand in there you can actually plug the hole with your fingers and feel the air escaping. In other words the leak is coming through the oil tank. So, off I went and replaced the intermediate piece as described by Earl. The thing is after replacing the part, I still get a leak through the second port. The pressure bleeds down from 20 psi down to 7.5 psi in 60 seconds. If I rotate the engine the leak down rate slows down to 10.5 psi from 20 psi in 60 seconds. It looks to me as if the air leak is coming through the engine and back into the oil tank via the bottom end? I can't seem to see any check valve that would be part of that pathway. Does any body have any pointers? All the usual culprits seem to fine. Venturi tube, check valve # 16.
Thanks.

 

Not sure I can help, but what happens when you take the oil cap off? Does it leak worse??

 

You have 6 cylinders in there that dont seal 100% perfectly. You will get a pressure drop if your timing a set static pressure drop. To do a Boost leak test you apply a constant pressure say for eg 20 psi using a pressure regulator and find any leaks to atmosphere. Your not interested in pressure drop rather where the air is pissing out the pipes/crack or holes. Any other air hissing or escaping requires your engineering skills built up over time to determine if its a problem or just natural leakage.
If you think air is passing the rings into the block too quickly then you need to do a proper cylinder leak down test pressurising from the spark plug on the power cylinder cycle. ie both valves closed. Then your testing any pressure drop through the valves, head gasket and rings.
Frank

 

Frank,

your explanation makes sense. I think I fixated too much on the 60 seconds at 20 psi part. The leakage is not linear. It will move down from 20 to 15 and then hang with the needle not moving and it will start going down again. The pressure will drop from 10 down to 5psi in 60 seconds and it can hoover around the 5 psi mark for another minute or so. It sounds as if the "system" can't really take 20 psi and hold it there. The good thing is no other leaks!

I did remove the oil cap because I could feel air escaping. I cleaned the O'ring and put it back on. No more air. I may want to figure out how to do a leak down the next time I change spark plugs.

Thanks.

 

If you do it from the lower boost hoses you will not get blow by via the oil cap. I make the boost leak testers for that.
Here is a link to some good info on my blog with video

 

I have this very kit from you Mark, good bit of stuff worth having

 

How often is it nesessary to completely drop the motor to find a leak? I had two shops that have smoke tested it tell me they could not find it without dropping the motor.

 

Well,

there goes my answer as to why I am getting blow by through the oil tank. I am capping the compressor side to the turbos when pressurising the system. I suppose it means that air enters the oil return lines via the center section of the turbos and ends up in the oil tank and eventually in the intake manifold. Next time I'll do it from the lower intercooler hoses.

Thanks for the heads up Marksi.

 

The answer is never lol
Usually clients get to me when it's too late. I offer all This support for free with my tuning and include the tester but more importantly prevent you from paying a shop $1200 to drop a motor to fix a leak lol. I can't be fooled.
Some sell tunes, I tune cars but more importantly I make sure your car is 100%. A simple vscu line off your fpr can cause a dangerous lean condition.
A pressure test will find it. Data logs , which I make you do , will find it.
Don't believe a $600 OTC tune , some eBay turbos will get you 700 hp like a many believe. That's a long process and 8 out of 10 cars have leaks all over. A simple dv swap in most cases created leaks- human error. That's when you get the torque exceeded limit error code. Take that to a Indy shop and they are replacing mafs and o2s then drop the motor lol. Smh.

 

I found a significant boost leak with Markski's kit. A boost hose had half popped out of the intercooler and it wouldn't hold pressure. Took the rear bumper off and managed to fix the problem. Car runs heaps better now.

 

Nice that's what it's about.