Hey guys,

So I just purchased a 98 Grand Prix GT - 3008 series II NA. Looking it over there seems that there is a slight coolant leak around the plenum bolts along the firewall side. So what I'm I looking at replacing here? Should I replace the UIM and LIM gaskets? Do I need a to replace the actual UIM itself?


I can post pics if needed as well.

The coolant is probably seepage up the LIM bolts. This would be LIM gaskets and I'd recommend the UIM at the same time. They can degrade and cause engine problems.

Thanks Bill, you are talking about just the lower and upper gaskets right? I thought I read that the actual intake may need to be replaced due to a defect with the egr passage or something...

Just wondering if I do this job if it would be a good idea...

No, not just gaskets.

LIM gaskets and
Option A: UIM and it'* gasket
Option B: Plug the LIM coolant port where it flows into the UIM and then your UIM is bulletproof.

Ok I think I'll try to tackle this on the weekend. What parts do I need to complete the job fully.So far I have

Dormon Intake
Felpro LIM gasket 2nd design
Motormite Heater Hose Fitting (coolant elbow)
T-stat gasket

Anything else? only other thing I can think of is possibly injector orings and maybe a TB gasket...

Thanks

The Dorman UIM will come with injector o-rings, pcv etc.
Coolant elbows are dorman (aka motormite) part number 47065
On the LIM gaskets, please get the aluminum ones from a GM dealer. More pricy, well worth it.
A tube of RTV and some cleaners etc.

Hmm ok so the felpro is no good? I thought the 2nd design was to fix the issue with the gasket...

Any idea of the part # for the gm gasket?

FelPro first design didn't have pins for the rubber end pieces because 96/97 blocks were cast w/o any pin holes. 98+ appear to have them (TMK) and the only thing is does is help hold the end rubber piece in place. Second design had the pins on the rubber end seals. Fel Pro is still using the plastic gasket though.
The GM dealership ones will have the pins (aka second design) and be made of aluminum which to my experience is holding up perfectly.

Part number.. Here'* a link to all the common parts we will usually see
BonnevillePRO.com • View topic - Common Part Numbers

hey thanks so much - called the local dealer and they have 2 in stock so I'll pick one up after work!

I'm sure I'll be back later in the week with more questions once the car is apart

Ok so I would like to get my valve cover gaskets replaced at the same time i do the UIM/LIM job. I noticed that there is a dogbone mount in the way of the front valve cover. Am I ok to just remove this without supporting the engine in any way?