Boost leak when testing at tb elbow.

johnwohl · 01-10-2006, 02:07 AM

Hi all. I started boost leak testing today at the throttle body elbow and I'm already having troubles. It seems I can only hold about 3-5 psi!

I verified that my tester assembly is airtight and it is not leaking at the throttle body elbow. I am using the tester from boostpro.net to do the testing. I am using a pretty good electric compressor to provide the air. I shut my engine off normally and it is not TDC if that matters.

I found that I was getting quite a bit of air coming out of my valve cover vent so i capped that off. The first problem I ran into was obvious. The throttle body gaskets (elbow to tb and tb to intake mani) were leaking so I replaced those. Great, those no longer leak.

Now though I can still only hold about 3-5 psi. I can't hear any air escaping anywhere. I listened to the exhaust pipe too and can't hear any noise.

I checked my PCV valve and it rattles around good and I can barely eek out a little air through it blowing as hard as I can, I didn't use the compressor because I didn't know if I would break it or something. I did go to advance auto and get some new pcv valves (3 actually) but they were all pretty pathetic and I could blow quite a bit though them.

I am wondering now if the pcv valve might be the problem and how I could verify that. Maybe also a valve is open or something letting air escape? I don't know and I'm finding this frustrating. On another note, the car feels fine and pulls ok but I do spike a bit. Any ideas are appreciated. I tried to proofread but the spellcheck doesn't work on my browser for some reason so please excuse any errors.

steve · 01-10-2006, 05:49 AM

Quote:

Originally Posted by johnwohl

I checked my PCV valve and it rattles around good and I can barely eek out a little air through it blowing as hard as I can, I didn't use the compressor because I didn't know if I would break it or something. I did go to advance auto and get some new pcv valves (3 actually) but they were all pretty pathetic and I could blow quite a bit though them.

I am wondering now if the pcv valve might be the problem and how I could verify that. Maybe also a valve is open or something letting air escape? I don't know and I'm finding this frustrating.

Don't worry about damaging the PCV, under boost you going to be hitting it wil your max boost pressure. If you can blow into it and have it leak you know that it's trash. If it leaks at all when you put the compressor set to your boost pressure from the barbed end to the threaded end then it going to when it's in the car.

You may have better luck with an OEM valve from the dealer. Most of these valves go into various N/T cars where it doesn't matter if they leak a little in the reverse direction so the aftermarket parts aren't designed with turbo cars in mind.

I don't know how big a compressor you were using to testing the intake. It might not be able to put out enough air for you to hear the other places the air is going.

Steve

ddavisaf · 01-10-2006, 11:46 AM

Hearing isn't always the way to find your leak. You need to spray everything down with soapy water and repeat the test. Get a gauge that you can run inline from the compressor to the tester to see how much air the compressor is putting into the system. Test the system at three different points. The Turbo Inlet, the LICP, and the TB Elbow. While testing pay special attention to the throttle body seals, the intake manifold gasket, the intercooler.
I recommend running a compression test also. Post up your numbers.
If your compression test is good, run a leakdown.

FORMONTOYA · 01-10-2006, 12:00 PM

Quote:

Originally Posted by ddavisaf

Hearing isn't always the way to find your leak. You need to spray everything down with soapy water and repeat the test.

i second that!!
my biss o-ring was the biggest leak on the whole car. you could not hear it but when the soapy water hit it you would have thought i was boiling water.

jim

alIan · 01-10-2006, 01:44 PM

i am having a similar problem... i am going to be doing a soapy water spraydown today and then continuing testing...

another thing i would be concerned about is your electric pump... it may be rated to higher PSI, but a simple bike pump can probably outflow it with a decent sized guy behind it. higher flow rate makes you able to get more air into the system even with a leak, and makes the leak easier to find. you might even be able to hear it then

johnwohl · 01-10-2006, 09:40 PM

Hrm, i think i am going to replace that pcv valve with another oem one from the stealership unless i can get it cheaper online. I will also try the soapy water if I can find a spray bottle and I guess I'll have to shell out for a good air compressor after all. While im getting an air compressor what kind of flow rate should i look for to be able to power basic air tools (impact gun, grinders, etc)? I figure I should be able to use it for something besides leak testing right? All I've got now is a cheap inflator type deal from sears. It's really loud besides so that doesn't help with the hearing of leaks. So what kind of compressor should I get?

oldman · 01-10-2006, 10:19 PM

Do not plug the breather valve unless you want to blow engine seals and gaskets during the pressure test. Air out of valve cover means pressure is leaking through pcv and/or valve seals/guides and/or piston rings. Open your oil cap on your next pressure test so pressure won't build up in the crankcase. Retest with the pcv pluged, if leaking in crankcase stops or you're able to hold more pressure, the pcv valve was the or part of the problem. If leaking persists, then you move on to checking the valve seals and rings. Is your car smoking?

johnwohl · 01-10-2006, 10:31 PM

No smoke except right away at cold start. My compression numbers are from 149-154. I'll unplug the valve cover for sure next time I try the test. I'm going to replace the pcv valve tomorrow and I'll report back then!

FORMONTOYA · 01-11-2006, 06:24 AM

Quote:

Originally Posted by johnwohl

While im getting an air compressor what kind of flow rate should i look for to be able to power basic air tools (impact gun, grinders, etc)?

You will want an air compressor that puts out at least 5cfm @ 90psi and imo at least a 5 gallon tank, more is better. Most impact guns will use about 4-1/2 to 5cfm. The best bet is to go and look at the tools you think you will use, especially a grinder because of the continuous use it may use more, and see what the needs are then you now what size compressor to get.
But stay away from the 2 gallon, $40e-bay units, most of them do not flow but about 2-1/2 to 3cfm and it will have a hard time trying to keep up with you.

Jim

I forgot to mention to look in pawn shops as a new one that will work can get expensive.

vintagemuscle · 01-23-2006, 05:26 PM

i have a similar problem with alot of air under the valve cover. i would pull the valve cover off and do a leak test listening closely for air leaking out any of the valve seals. today i discovered that the valve seals on cyl. #1 and #3 are shot . do you have good vacuum at idle?

johnwohl · 01-24-2006, 01:09 AM

Actually, I just got access to a decent air compressor, and a lot of air is escaping into my valve cover as well. The head is a recent rebuild so I don't know if the valve seals would be the issue but how do i test for that? Any other ideas? Also, i changed the pcv valve for an oem one.

johnwohl · 01-24-2006, 06:13 PM

I think I have good vacuum, I get about 25-30 of vacuum.

bryan_tberry · 01-25-2006, 05:18 PM

Hey, I have the same leak! It's right at the TB Elbow||TB gasket or somewhere in that region. I thought it was normal at first but it hisses LOUD with just a few pumps of a bike pump. Even worse with a compressor. From what it showed me, it only held 3-5 PSi. Not good. I hope I can get this fixed, my car is really boring at the moment.

oldman · 01-25-2006, 05:47 PM

Quote:

Originally Posted by johnwohl

Actually, I just got access to a decent air compressor, and a lot of air is escaping into my valve cover as well. The head is a recent rebuild so I don't know if the valve seals would be the issue but how do i test for that? Any other ideas? Also, i changed the pcv valve for an oem one.

Where are you testing from, TB elbow or turbo inlet? How much pressure are you able to pump into the intake? You should perform a dry and wet compression test next, this will tell you the conditions of the rings.

johnwohl · 01-25-2006, 09:16 PM

I am testing at the tb elbow. It is able to hold about 3-5 PSI. I can hear the air coming into the valve cover if I take off the oil cap and listen. wierd thing is that the car is still quick as far as I can tell. although i've never ridden in a dsm in perfectly running condition (do those exist?) so I have no way to tell how it 'should' feel. I'll go out and do a compression test though.

johnwohl · 01-25-2006, 09:48 PM

Results of the compression test are from 152-147 with the cylinder opposite the cam gears being the low (147) one. A wet test on that cylinder resulted in a reading of 250psi...?

compression · 01-25-2006, 09:52 PM

edit: i didnt see that you fixed the tb leak my bad

johnwohl · 01-26-2006, 03:43 AM

Ya, I fixed the TB leak and I know my leak tester is not leaking, but I can really hear the air coming from the valve cover. If my valve seals were shot I wouldn't have good compression would I? I mean, I don't have 'like new' compression, but it's not bad eh?

oldman · 01-26-2006, 07:40 AM

How much oil did you use for the wet test?

johnwohl · 01-26-2006, 10:31 AM

Probably too much, heh. I think I remembered 2 capfulls instead of 2 teaspoons.

oldman · 01-26-2006, 10:56 AM

Quote:

Originally Posted by johnwohl

Probably too much, heh. I think I remembered 2 capfulls instead of 2 teaspoons.

1/2 cap full is all you need, small caps not the big caps like on the new Mobile 1 bottles. Though 142 isn't bad to begin with, I would repeat the wet test on all four, be precise and cover all tracks when troubleshooting.

That said, 3-5 psi at TB elbow means you have alot of leaks or you're using a bike pump, are you using a bike pump or a compressor. If you're using a compressor (a REAL ONE with a tank, not the type you plug into the cig. lighter), I want you to repeat the test again at the TB but this time I want you to do the following.

1. Disconnect the pcv hose from the intake manifold and cap off the fitting, I know you have already replaced the pcv with an OEM pcv.

2. Spray soapy water on everything that is connected to the intake manifold, injector seals, IM gasket, all four fittings coming off the IM, TB gaskets, BISS, shaft seals (you said you chenged the seals, real shaft seals or just o-rings?).......etc. Don't forget the EGR.

3. Rotate your engine CW to about 30* after TDC.

4. Put your ear up to the tailpipe and listen for leaks.

Good luck.