boost leak at wastegate (and throttle body)

[Hiitman]

Finally got a compressor so now Im going over my whole setup checking for boost leaks. I found two. One at the wastegate and one at the throttle body. Ive got a turbosmarts streetgate 38. The leak is coming from where the shaft exits from the top of the wastegate. the other leak is coming from around the throttle body. I havnt figured out if its either the IC pipe-TB gasket, TB-intake manifold gasket, or the o-ring where the throttle cables attaches to the trottle body (couldnt find the name in either manual). i included pics of both.

 

[hopwoodp]

It may be that your throttle body shaft seals are bad and the gasket in the wastegate is leaking. When doing a boost leak test, don't go over 20 psi. How are you testing your wastegate?

 

[Hiitman]

heh i cant even get above 5 . ive got a defi boost gauge. the car is on when testing. ive got my boost leak tester bolted up to the intake on my turbo. my boost controller goes from the lower nipple on the wastegate to the turbo.

 

[hopwoodp]

You can't get above 5 psi? That sounds like a massive leak. Throttle body seals don't cause that much of a leak. Check you hoses and clamps on your intercooler piping and make sure you have good gaskets on the throttle body elbow and the throttle body to intake manifold.

Make sure that you tighten down the bolts/nuts to the throttle body. Sometimes, when people work on it they forget to tighten all of them down. Do all those things and check for leaks again.

 

[RayPeters]

the car is on when testing

I think this would account for a "big boost leak". I do my tests with the engine at ~TDC where all the intake valves are closed the engine NOT running.

 

[Hiitman]

im wondering if its a combination of my wastegate leak and tb leak. i just read on machv.coms website that when throttle body seals go the throttle sticks (another issue i was having) could also be that my compressor isnt strong enough. its only a 3hp (2hp when compressing) 11 gal tank. my compressor at work is a little stronger. what im trying to figure out is why my wastegate is leaking. my boost controller is setup correct right? lower nipple-boost controller-turbo.

 

[Hiitman]

sorry engine isnt on but ign is so that my defi gauge will read.

 

[hopwoodp]

Hitman - your car better not have been running when you did the test. You just turned the key to on to read the gauge right?


Edit: I saw the above post. Good, so just do what I said above and we'll go from there.

 

[Hiitman]

just clearing things up for ray. didnt know if he thought i was running the car or not. ive got the seals coming from machv. once they get here and i get them in hopefully ill be good on the tb. might be the end of next week. still dont know why the wastegate is leaking though. any thoughts?

 

[hopwoodp]

Could you explain more on where the leak is coming from, how long you've had it and what brand it is? Also, what is the spring rated at? My only guess is that the valve seal is blown.

 

[Hiitman]

ive got a pic in my first post that shows where the leak is coming from. its a turbosmart 38mm streetgate. ive had it for almost 2 years now. my springs is rated at 10psi.

 

[hopwoodp]

That is kind of hard to tell exactly where it is coming from. Are you talking about the side wall of the wastegate or a sealed surface? Can you see any cracks in the housing?

 

[Hiitman]

ill have to look closer. its leaking from where the valve comes down from the housing.

 

[daren_p]

Easy way to tell if its your shaft seals are leaking on the TB is, when your doing a boost leak test listen at the TB & then move the throttle plate open & close. If the pitch of the leak changes, that your TB shaft seals.

 

[Hiitman]

awesome thanks for the input. any ideas on the wastegate?

 

[Boosted98gsx]

Sounds like either a poorly designed wastegate, or a bad diaphragm inside it. Either way, expensive to fix.

 

[Hiitman]

just to clarify, having air leaking out here during my boost leak test is no bueno right? just checking before i go and buy a new wastegate.

 

[Boosted98gsx]

To a degree where you cannot hold 5 psi worth of static boost? That's a definate no. Your system should be able to be pressurized to 20psi PLUS with no leaks.

 

[Hiitman]

thanks for all the input guys but it turns out that it wasnt my tb that was leaking it was just this little guy. gonna replace and ziptie. but now with my boost controller line that goes to the wastegate plugged and by pinching this line i can get it up to 15 psi

 

[Boosted98gsx]

All those emission lines are a pain in the ass and can spring leaks when you don't expect (or where you can't find them, since they run under the manifold). But what's with the grease on the firewall? Get some engine bay cleaner!

 

[Hiitman]

quick update. replaced and ziptied all the lines up top there. compressed it to 15psi and it took about 32 seconds to leak down to 0

 

[Boosted98gsx]

That's better, grab yourself a squirt bottle with some soapy water in it, and go to town spraying trying to find any more leaks. I would say you should test to 25 psi JUST to be sure.

 

[Hiitman]

i will if my weak ass compressor can handle it. only a 3 hp 11gal. ive got a bigger one at work that ill use when my wastegate comes.

 

[Hiitman]

kindof off topic but not really. would these two big leaks cause tuning problems? i was having horrible knock issues (10+ deg at wot and 20psi) my fuel trims were all over and so was my a/f ratio (yes i have a wideband)

 

[dsm-onster]

It may be that your throttle body shaft seals are bad and the gasket in the wastegate is leaking. When doing a boost leak test, don't go over 20 psi. How are you testing your wastegate?

On the subject of boost leak testing: Just curious as to why you came to that conclusion. I've boostleak tested my cars to 25+ psi for years. . .