BLT leaking air out of valve cover

[PrimerPLus]

I went to do a Boost leak test and I pressurized the system to 20psi and I hear air coming out of the valve cover from the hose that goes back into the intake. If I put my finger over it, it builds pressure and a woosh sounds comes out of it when I let go. This seems to be my only leak, if it is a leak. I am not sure if it is supposed to do that.

I think this might be a bad PCV valve?

Here is a picture of the hose I am talking about.

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[nickk90]

Could be PCV valve or air passing buy the shaft seals in the turbo. Pull the PCV out and put you finger over it. If that isnt whats leaking bypass the turbo on your boost leak test and if it stops then its just the shafts seals letting air past.

 

[PrimerPLus]

Will do. Thanks for quick reply.

Ok I went and unscrewed the pcv valve from the valve cover and pressurized it to 10psi and no air coming out of the valve but there is still air coming out of the hose. If I put my finger over the hose hole and the pcv valve hole and then remove my finger there is a Whoosh sound still.

 

[Firsts tuner]

Shaft seals. Mine does the same thing. I forgot to uncap the pcv hose and that other vent. After running for about a minute I smelled oil. Apparently I built up enough crankcase pressure to push the oil past the seal and send it into the exhaust. Oops.

 

[96awd16g]

IMO it's more likely that your valve seals are leaking and venting the pressure into the valve cover, whole lot more likely than turbo seals.

 

[Colt4G63 also]

It's normal for some air to leak past the piston rings, and into the crankcase. That's why it's reccommended to do your BLT on a warm engine.

Ps. Don't block that off with your fingers anymore unless you want to blow out an oil seal.

 

[nickk90]

Try bypassing the turbo in your test and see if it stops. If it does then you have nothing to worry about. If it doesn't you may need valve stem seals.
I put my money of the shaft seals though and its normal for them to let air pass under boost leak test.

 

[PieEyedPiper]

Lots of opinions; here's mine.

Do it warm and eliminate the turbo from the equation. Put the tester on your ic inlet and let 'er rip.. Err.. fill.
I also agree, if you're building pressure in the cc "oldman" will come out of retirement and annihilate you and your engine.

 

[PrimerPLus]

I will be sure to do the BLT without connecting it to the turbo.
Would it be best to use the TB elbow or the Intercooler for bypassing turbo?

 

[PieEyedPiper]

I use the ic to include as much of the system as possible, like the bov. Testing at the tb is fine but now you won't know if your bov flange is sealed tight.

 

[Black'95]

Every time I do a BLT, I have air in the crankcase: Air will leak past the rings (even new good ones!) all day long, and air will get past the turbo oil seal (even good seals!).

Forget that junk PCV valve and get one of these: Boomba Racing, Inc. :: Check Valve


Best thing I ever did!

 

[PrimerPLus]

I have not got a check valve yet but do you think that is the cause of this?
IMG 08041 - YouTube

IMO it's more likely that your valve seals are leaking and venting the pressure into the valve cover, whole lot more likely than turbo seals.

Is this an issue that I should be worried about or can I just go on with not worrying about it?

 

[undefined0000]

I have not got a check valve yet but do you think that is the cause of this?
IMG 08041 - YouTube



Is this an issue that I should be worried about or can I just go on with not worrying about it?

Holy crap. How much PSI was that? And is that on a cold motor. did you read everything above?

 

[PrimerPLus]

I put in 25psi, as that is what I am tuned at.

No not a cold motor I just turned it off after letting it idle for about 15mins.

 

[BogusSVO]

Any blue smoke while the engine is running?

Doubt it is valve stem seals, for them to pass that much air, the seal would have to be gone, and a good chance the guides too.

Think about the clearance between the guide and the valve stem.

It will be common for some air to make past the rings, into the crank case, then flow up the oil return passages.

Another thing to keep in mind is what cylinder is on what stroke.
There is a small point that all 4 valves will be open in the same cylinder, this is overlap.
it is at the end of the exhaust stroke, going into the intake stroke.
That is why the gauge dropped pressure so quickly.

Personally, I would stop with a BLT, and do a leak down test.

 

[Calan]

Any blue smork while the engine is running?

Agreed.

Green smork is at least manageable, but the blue smork is bad news.


*****

OP - You probably have some valves open.... and I agree on the leak-down test.

 

[PrimerPLus]

No blue smoke, I am going to replace that PVC valve and I will do a leak down test. I did a compression test and I got 174-175-175-174

When I get results from leak down test I will report back.

 

[PrimerPLus]

I did my Leak down test today. Here are the results.
This was done on a cold engine. I can not start it until my fuel pump arrives.
Results:

Cylinder #1 : 35%
Cylinder #2 : 30%
Cylinder #3 : 30%
Cylinder #4 : 35%

Air is leaking out of Dip stick and Oil fill cap.

Now I have to stay that the harbor freight leak down tester is not the most accurate
But I feel it was close enough. According to Calan's tech writeup, I think I have the following issues.

Whistling or hissing out of the PCV valve, oil filler cap hole, or dipstick tube - Worn piston rings or cylinder wall.

I don't know if 30-35% is major issue. Will I be fine to drive it with my mods/boost etc. Or should I park it and not touch it until I can fix the rings?

 

[sciondan]

Probably ok to drive as long as your not blowing the dipstick out under boost. You having any issues besides some excess crank case pressure?

 

[PrimerPLus]

No actually it runs and pulls really well .

 

[9D9X]

Hope to find out about this too. My car has always done this, and my car runs and drives great no smoke either. O yea forgot to say my car has no pcv valve I have the JM race manifold.