UIM Replacement

[chief153]

Although my `97 Lesabre with 151,000 miles is not losing any water I think I will go ahead and replace the UIM along with the LIM gaskets. There are two listings for the LIM gaskets;1st design and 2nd design. The first design has rubber end gaskets, the 2nd design has rubber/plastic end gaskets with locating pins, which design is used on the `97 model?

[HotZ28]

Click Here for more info.

[chief153]

Thanks for directing me in the right direction HotZ28.

[BNaylor]

Also, keep in mind that there are aftermarket UIM and LIM gaskets just as good if not better than the GM ones. I prefer using the plastic framed FelPro brand. Part number MS95809-1. See pic. These are the pinned LIM.

There are anecdotal reports on the Net that the revised aluminum framed LIM gaskets may be causing an electrolysis issue that is eating away at the lower intake manifold. Chunks of metal has been seen.

In any case the most important part of a LIM gasket job is properly sealing the 4 corners where the port gaskets and end seal gaskets mate up. After assembly at least 24 hours cure time should be given to the hi-temp RTV silicone used before firing the engine up.

[chief153]

Appreciate the additional info BNaylor...glad you told me about the 24 hour cure time. I would have fired it up right after completion to check for leaks.

[BNaylor]

Most of us are pros at doing this type work on NA Series II 3800 engines and I am quite sure you will get more suggestions concerning the job or feel free to ask. Here is a pic of the LIM port and end seal gaskets installed using the FelPro. Since this was a '99 SII 3800 the gaskets were pinned and I've seen '97 in a similar situation. On the UIM plenum since you have a '95-'98 vintage be sure to check for any possible EGR stovepipe damage at the coolant passages and throttle body area and UIM warpage. If visible replace the UIM with either the GM revised ('99 and up), Dorman or APN aftermarket brands which will have a new smaller diameter EGR stovepipe that will be installed on the LIM. Or you may not see any damage so only the UIM gasket will need to be replaced. However, getting all the baked on carbon off the inside of the UIM and port runner insert will not be fun and very tedious.