Boost leak near TB

[matthewdesigns]

I have finally fixed all of my intake leaks below the TB But now I'd like to know where/how many places a boost leak can occur past the TB elbow and on the back of the motor/valve cover. I've looked through a bunch of boost leak threads and can't find a list clearly defined.

I have a leak somewhere in that general area and can't pinpoint it, even using Windex. I've fixed one at the sensor under the TB elbow (idle air control? bad o-ring) which was very obvious.

I know that the TB shaft seals can go bad, but don't see any bubbles on it at either end while testing (there are seals on both the firewall side and the TPS side of that shaft, right?).

Where else can air be leaking out? It sounds like it's coming from the area between the TB/IM and the back of the block, down in the crevices where I can't see anything, let alone get a tool into.

A clear list of possibilities would be very appreciated!

Thanks, Matthew

 

[Calan]

$10 says it's the shaft seals...

While pumping in air for a boost leak test, open the throttle lever a few times. You'll probably here the hissing sound change.

Shaft seal leaks don't show up easily because they are in the TB and under the throttle return springs, TPS, etc.

Just went through this and replaced mine a week ago.

EDIT:

I was also getting boost leak around the lower injector seals when I first got the car a month or so ago. Someone had hacked (lost) the spacers and the seals were crushed. I could hold my hand over the injectors and feel the air blowing straight out. New injector seals and spacers fixed that right up.

 

[matthewdesigns]

I did notice a change in pitch when I twisted the throttle shaft...thought it was relieving pressure somewhere else though.

I just called the Mitsu dealer and he said that the shaft seals are not available...that I have to buy the entire TB assembly

Do you have part numbers for the seals? Or is it a matter of disassembling the TB and finding o-rings that fit?

Thanks

 

[Dream On]

http://www.plymouthlaser.com/tbor.htm

http://www.ca.dsm.org/faq/tb-shaftseals.html

 

[Auto RS T]

TB Shaft Seals (under TPS and TB springs)

Lower Injector Seals (where injector seals to head)

Throttle body to intake manifold gaskets

BISS screw o-ring (idle adjustment screw)

PCV Valve

Intake Manifold gasket

EGR Valve or EGR blockoff plate gasket

 

[Calan]

I did notice a change in pitch when I twisted the throttle shaft...thought it was relieving pressure somewhere else though.

I just called the Mitsu dealer and he said that the shaft seals are not available...that I have to buy the entire TB assembly

Do you have part numbers for the seals? Or is it a matter of disassembling the TB and finding o-rings that fit?

Thanks

Take a look at the links above that DreamOn posted... they are two different VFAQ's that will walk you through it. And FYI... the comments they make about breaking a throttle plate screw, and the possibility of the spring getting a finger... they are true

I went to Ace Hardware and bought two #7 o-rings for the shaft, and a #5 for the BISS (The VFAQ has the exact dimensions). Popped out the existing seals (carefully so you don't bend them up too much) and used a Dremel to remove the leftover rubber (which takes some patience)... lubed up the new o-rings and placed them in the old seal's metal "rings" and that was about it.

While you're at the hardware store buying the o-rings, you might as well pick up a couple of screws for the TB plate... just in case. I think I used M4 x .7, 10mm in length. And some lock-tite for them wouldn't hurt.

It took a couple hours and about $1.50 in parts..... mostly because I was taking my time and goofing off. Really easy except for the tempermental plate screws, and the tedious work of cleaning out the old rubber from the original seal rings.

Good luck!

EDIT:

I assume you have tools and such, but if you don't you might want to add an inexpensive easy-out kit to your shopping list for extracting the stripped plate screw... which you will probably have It's a piece of cake though if you have a small bit and easy-out.

 

[Calan]

As AutoRST mentioned, the TB gaskets are also likely suspects. Since you are pulling the TB to fix the shaft seals, might as well replace both TB gaskets as well.

Not sure if this is "recommended" or not, but I used a very thin layer of copper RTV on both sides of the gaskets... just because

 

[talontedtsi1995]

How do you get the idle control screw (biss) out? I unscrewed mine all the way because it leaks but can't get it to come out of the hole?

 

[Calan]

I used a really strong magnet and slowly worked it out.

 

[Dream On]

My throttle plate screws came out very easy. I just sprayed both sides with some pb blaster, and put the TB in a vice. Then I took a cordless drill, pushed down as hard as I could, and they came right out. No stripping or mangled head either.

 

[matthewdesigns]

Calan and DreamOn: Thanks for the insight into the TB seals. The links to the VFAQ's are a great help, too. Looks like a PITA, but if I take my time and mark everything I have faith that I can pull it off

Auto RS T: Thanks for the list I requested in the first post. That's a great help. I think I'll attack some of the more easily accessible parts you listed before I dig into the TB.

And I had the same issue with the BISS last weekend. Couldn't get the screw out. Thanks for the extra info there for TalontedTSI1995.

 

[Calan]

The TB seal replacement is really a lot simpler than it looks. Just requires some attention to detail, like anything else

Good luck!