Not sure if this is in the right section but done a boost leak test today only pressurised it to about 8 psi but there is a audible hissing noise from the throttle body is this normal or does it mean that my throttle body shaft seals need replacing?

 

Yes

 

Cheers! wheres the best place to get some of these seals from can they be had from a mitsubishi dealer?

 

http://www.worksevo.com/store/produc...roducts_id=415

 

Soapy H2O is your friend, find out exactly where it's coming from first.

 

Yes its normal and yes they need to be replaced - sooner or later every evo will have to have these seals replaced. They cannot be purchased from the dealer and why would you want to? Obviously the stock ones don't hold up

Works or machV sells these seals or you can always get the SKF 3930 seal.

Also if you want to know for sure do the leak test and grab the throttle lever and move it back and forth if the hissing changes tone then its def. the TB seals.......but I can tell you it is.

 

That's a big leak if it's happening at only 8psi.

 

could be the throttle body gasket also. or a vacuum line off.

 

Well if he's going to pull off the tb, might as well change the gaskets and the tb seals just to be certain.

 

Just ordered some from works I think its def the seals now as i did notice when doing the test that the sound would change when messing with the throttle.I know its always best to be leak free but has anyone actually seen boost pressure drop or noticed any other problems when there seals were leaking reason I ask is my car seems to hold boost just fine even though the seals are leaking.

 

It could be the throttle body gasket, but luckily the link I have in my above post comes with a new throttle body gasket with the seals. If it was a vacuum line, the idle would be very unstable and erratic.

 

And it would probably feel like a dog if a vacuum line was off.

 

Thats the tell tale sign. The install isn't too tough. There is a good write up in the How-To forum.


A boost leak doesn't mean you will see a drop in psi, it just makes your turbo work harder to meet that PSI. It can easily take the stock turbo out of its efficiency range.

 

Thanks for all the help guys Once i've sorted out the seals should i then pressurise the system to 22psi as thats what boost im running.

 

how many miles for these shaft seals usually go bad?