Boost leak test

[spoolintsi97]

I just did a boost leak test and i found a pin hole on the nut on my hallamen boost controller is that suppossed to be there and leak like that

 

[donmagicjuan]

Yes, you either have to turn your boost controller up high enough so that you don't reach its setting, or remove it from the system when doing a boost leak test.

 

[spoolintsi97]

The reason i am testing this is because of a vaccum leak would this cause it to have low vaccum at idle right know at idle it r4eads a steady 10 mm hg

 

[oldman]

I just did a boost leak test and i found a pin hole on the nut on my hallamen boost controller is that suppossed to be there and leak like that

That is called the "wategate pressure relief hole" and every mbc requires it. It's function is to relief the pressure trapped between the ball and the actuator fitting coming off boost in order to prevent the actuator/flapper from staying open in between shifts. This is also one of the many reasons why the BOV line is the worst place to tap for your mbc.

 

[donmagicjuan]

Are you positive it's a vacuum leak? You list in your mods that you have aftermarket cam gears. I would check the valve timing first to make sure its correct before going on a wild goose chase to find a vacuum leak.

 

[spoolintsi97]

Whats the easiest way to check the timming on this car also i found a leak somewhere near the throttle body but i cant pin piont it yeat its either the gasket of is coming out of the postion sensor

 

[donmagicjuan]

Whats the easiest way to check the timming on this car also i found a leak somewhere near the throttle body but i cant pin piont it yeat its either the gasket of is coming out of the postion sensor

A leak coming out of the TPS is usually the TB shaft seals. Not an impossible thing to fix, but certainly not one of the most fun. Read about it here.

As for the timing, all you need to do is pop off the upper timing belt cover, rotate the engine to TDC for #1, and verify the timing marks on the gears lie on a straight line through the center of the cam gear bolts. This, of course, assumes that you have these marks on your cam gears. Here's a link that discusses tuning your cam gears, which you also might find useful. http://diy.prostreetonline.com/techtips/showarticle.asp?articleid=7

 

[spoolintsi97]

Well for now my throttle body is definitly leaking so im just going to replace it and use all new gaskets. When i did the pressure test it would leak when i hit 5 psi and would stay there so is that a possible cause for the vaccum leak

 

[donmagicjuan]

If you're not able to register more than 5 psi during your boost leak test, then you definitely have a major leak somewhere. If it's downstream of the throttle body, then you could see it as a loss of vacuum at idle, but it would probably be accompanied by an abnormally high idle speed if it was too large for the ISC to compensate. If you have a normal idle speed, I would err on the side of maladjusted timing as the cause for a low vacuum reading.

 

[spoolintsi97]

well the idle seems fine i put a peice of hose up to my ear and and around the throttle body when it was idling and you could hear a leak i just hope it is not the timing because that seems like a pain to fix also the cam gears are both set at zero if that helps

 

[Eastwood95]

did you use the spray bottle trick when boost leak testing? If not, just put some dishsoap and water in a spray bottle, shake it up, and spray down your testing areas before doing the leak test. It should help you pinpoint the leak....

 

[dnhieu]

turn the pressure up on your air compressor to around 20psi and get a spray bottle and fill it up with soapy water then spray the throttle body and it should bubble up around where the leak is. also i have rebuilt about 5-6 throttle bodys for various friends and its not that difficult. just take your time and remember to get the CORRECT SCREW DRIVER for the throttle body plate or you will strip the screw head and will have to drill them out....


Also, i have always been very confused on one part of the boost leak test. when you guys say hold 20psi for 30 seconds what do you mean exactly??? sorry if that sounds dumb...

 

[oldman]

Also, i have always been very confused on one part of the boost leak test. when you guys say hold 20psi for 30 seconds what do you mean exactly??? sorry if that sounds dumb...

Boost leak test isn't an exact science but generallly speaking, with the compressor regulator set to about 25-30 psi, you want to be able to pressurize the intake up to 20psi (what is showing on the boost gauge) or 5psi above your boost level and allow no less than 30 seconds before it bleeds down to zero. Obviously the longer it holds the better.

 

[spoolintsi97]

Well i went to replace the gaskets on the throttle body and there was no gasket between the throttle body and elbow so i put the new ones in and my vaccum still reads ten there is no leaks at the throttle body though i am going to cheak the leak test again when the engine cools

 

[daren_p]

Make sure you spray down everything with the soapy water (ic couplers, ic core, TB, BOV injectors, vacuum lines, etc), there will more then likely be more leaks then just the ones you can hear. To hear them they have to be pretty major, you would be surprised how many leaks you can find with soapy water. If you still have a leak in the TB area, move the throttle plate back and forth (throttle cable) while doing the test, if the pitch changes you have leaky TB shaft seals, which is a common place for a leak. While a boost leak test is something you should regularly do, I too think the low vacuum might be a timing issue.

 

[spoolintsi97]

I want to check the timing so what is the correct way to move the pulleys to line up with each other to see if they are correct

 

[tstkl]

poor vac at idle generally means there is a leak at or after the throttle body, like say.... where the flange of your smim meets the head because one of the bolts bottomed out and stripped the threads in the head and caused more problems then you have ever had before in your entire life...

but the throttle body shaft seals are probably your problem.

I've also noticed that running extremely rich will cause poor vac at idle, as will a really cold day. Or was it hot, I can't remember, one of the two. Extreme weather conditions, how about that?

 

[dnhieu]

Boost leak test isn't an exact science but generallly speaking, with the compressor regulator set to about 25-30 psi, you want to be able to pressurize the intake up to 20psi (what is showing on the boost gauge) or 5psi above your boost level and allow no less than 30 seconds before it bleeds down to zero. Obviously the longer it holds the better.

alright cool im doing it right then. i was just making sure the proper way for it to be done...

 

[spoolintsi97]

Anyone know a good website were you can buy good vaccum hose like the kind that comes with the greddy bov