I had my UIM replaced several years ago when it cracked and the motor hydrolocked. Fast forward to today (at about twice the mileage), I'm having a lot of the same symptoms: coolant slowly disappearing, and a little puff of white smoke when I start the car in the morning.

Did GM ever issue a corrected UIM for the Series II like they did with the metal LIM gaskets, or are we NA owners stuck with this problem?

Also, what would I need to replace the manifold? I already have a used manifold in good shape. Some gaskets and O-rings?

Yep, replace the gasket and o-ring. Iv'e heard some people block the coolant ports to the UIM so coolant cant flow into it.

Is there sleeved units that help with the issue? Or am I thinking of something different?

Not sure, but I think the more expensive UIM kits come with a different type of EGR stovepipe. But, if you block off the coolant ports, you won't have to worry about coolant getting into the UIM area. Which is a common failure area.

Aluminum gaskets will fix the always failing plastic LIM issues.

when mine went, it was getting into cyl 6. i was traveling at the time and had to have my wife take it to a shop we go when i cant work on something. in talking to him after he said he has done hundreds of them and the aftermarket ones are alot better, he gets his parts all from napa not sure of what brand or anything. that was at 65-75k and now i have 175k. pretty sure he didnt do anything to block the coolant port though i do remember a thread from dan or bill that they siliconed a coin in there

I know on the L67 LIM manifolds, the 2 coolant ports are recessed and just big enough to tap a dime into each one. Which is what I did to mine. But on the L36 LIM, the holes are not recessed. So, I'm not sure how it could be done to block them. I guess you could use some JB Weld and put a dime on it to block the flow, but not sure if the UIM ports would be able to clear the raised dime.

What others have done also is have the holes threaded, and put hex head plugs in them. That is not even counting shaving the UIM down some if needed.

I know you can tap and plug the L67 LIM like already stated, but the L36 LIM deck is not as thick as the L67 LIM. But then again, I have been wrong before. Just never seen it done on a L36.

This is the UIM I recommend going with, it has an added steel collet where the EGR port is, which along with the reduced diameter EGR Stove Pipe is supposed to keep the EGR area from ever leaking.
GM Intake Manifold Kit
For the lower intake manifold, I always recommend getting the Fel Pro LIM Kit FEL-PRO Part # MS98014T, it has all the gaskets and o-rings you need, unless you block the coolant ports to the throttle body, if you tap and plug those then you really should open up the coolant water bypass a bit.


https://www.gmforum.com/gearheads-11...od-lim-301972/
Here is a thread Bill posted, he mentions L67 and L36, and I have heard of others plug the L36'* TB ports, but everybody says to open up the coolant water bypass ports a bit.
And they also mention rougher running at first when starting the car in winter, since the TB'* air coming in is a lot cooler with those ports plugged..

Glad I have an L67 that I converted off of Dex-Cool.

Once I replaced the LIM gaskets with the good Fel-Pro stuff I shouldn't have a problem.