Boost leak around intake manifold, please help

[GreddyMR2]

Hi there,

I took a car to a tuner and before mapping he did a boost leak test and we found some leaking point around silicons, tightened them, but there is still a huge amount of air coming from around intake manifold. We can't feel the air with hand, but it's clearly heard. We still did not check from under the car.

I am using Cometic gaskets (they ar thin paper gaskets) and because we are going to take intake manifold off, I've ordered OEM gaskets. Are Cometic gaskets such a crap? Should OEM gaskets solve this boost leak?

Now when we fill the system (blowing from the air filter location) with air, pressure drops from 0,5bar to 0,2bar very fast and then it takes some seconds to drop to 0.

What else should I check or do when we will be changing gaskets?

Thanks!

[jimGTS]

sure its not coming from the ISCV (idle speed control valve)?

these leak a little out of the factory. theres not alot you can so about it.
(as its a metal on metal contact)

[Peter Gidden]

I presume you've removed the inlet cam to do the tests?

[GreddyMR2]

We checked the ISCV, it has a very small leak, but definitely it's not the main leak.

Peter, no, it was not removed. I also think that all intake valves must be closed doing this test, but the tuner thinks different. He said he did a lot of tests like this and normaly all cars hold around 0.5bar.

[Peter Gidden]

Peter, no, it was not removed. I also think that all intake valves must be closed doing this test, but the tuner thinks different. He said he did a lot of tests like this and normaly all cars hold around 0.5bar.

IMHO pointless doing a pressure test with valves opening and closing. How is he developing 7psi of pressure without the valves closed?

[GreddyMR2]

Peter, no, it was not removed. I also think that all intake valves must be closed doing this test, but the tuner thinks different. He said he did a lot of tests like this and normaly all cars hold around 0.5bar.

IMHO pointless doing a pressure test with valves opening and closing. How is he developing 7psi of pressure without the valves closed?

Tuner told that inlet valves are open, then exhaust valves are closed and other way around. There is a very small time when all valves are open and we turned a couple of times with started not to have this situation.

Also, I suppose that if the system is not leaky then the sound of air would appear somewhere in exhaust. Now it's heard around intake manifold.

And everywhere I read about boost leak test - nobody takes cam off. Also checked some videos and I see like pressure is holding without cam's off. I definitely have a huge leak

[ashley]

Unless you camshafts are running overlap, which I think yours are? In which case you will struggle to find a reliable crank position where the engine is air-tight, and even if you do- you end up performing a leak down test as the air leaks past the piston rings.

Still- if you can hear air leaking past the inlet manifold it does sound like a serious leak, assuming that what you are hearing is not air leaking past the inlet valves themselves.

Would be worth putting soapy water around the edges of the manifold, then you should be able to see the leak as it starts to bubble

[jimGTS]

yeh soapy water around the injectors and mani will hopefully reveal something

[GreddyMR2]

yeh soapy water around the injectors and mani will hopefully reveal something

I hope so... We put some water on the top of injectors, looks like they are tight. Last chance that the leak is somewhere from under the manifold. Maybe even the vacuum canister. We'll see it next monday or tuesday. And yes, I will have to make sure the valves are closed. I need to get engine at TDC, right?

I ordered oem intake manifold gaskets anyway, because probably they are better than cometic paper ones.

Unless you camshafts are running overlap, which I think yours are?

Why do you think they are overlap? I am using 3SGE cams.

The strange thing is that even I have a huge boost leak, the car runs quite good. Or I don't know how it should really run...

[ashley]

I think the 3SGE camshafts do have overlap in them don't they? I can't remember (bin a while since I researched them), but I'm sure someone helpful on here can confirm...it's really really common, especially on NAs.

[GreddyMR2]

Little update. We found a leak!
Air was going through the 2 T-VIS o-rings that were very old.

Now it holds 0.6-0.7bar when it was ~0.2bar before.

At the same time we had to remove t-vis, because we didn't have those orings. We just put bolts in those empty spaces and anbolted t-vis flaps. Now I need to find a proper t-vis eliminating plate and fit it.

At least we can map the car now