UIM/LIM/TB coolant passages

[ablebakercharlie]

I am getting ready to do the LIM gasket replacement on my 128K 03 SLE.

The posts and wisdom here are all for replacing the UIM while you've got it apart with an improved UIM that keeps excess heat away from the manifold so that there is a reduced tendancy to burn/erode through to the coolant passage and then leak.

Why is there coolant in the UIM/TB?

Is it there to warm the TB for emissions reasons?
Is it there to cool the EGR passage so it doesn't burn through?

It seems to me that a more permanent and less expensive fix would be to plug the coolant passages althogether in the LIM. A few minutes with a drill and tap and a couple plugs and it's done. If there's no coolant in the UIM then no UIM is needed and the problem cannot repeat itself...and, if the TB is cooler, that means lower intake air temperature and more power...

What's the downside?
Anyone else do this instead?


Ed

[00Beast]

It's there to prevent the TB from icing up, and help with emissions. I honestly don't think it hurts anything, and provided you get a steel sleeved UIM you should never have an issue again.

[ablebakercharlie]

The throttle body will never ice up. Icing occurs when there's a temperature drop at the throttle and the air flowing through it meets a certain set of conditions of humidity and temperature. The temperature drop that causes icing occurs in carburetors and throttle body injectors where fuel is evaporating and in that process taking a lot of heat out of the air. The throttle body on a port fuel injected engine doesn't see that fuel evaporation-based cooling.

I would be willing to bet that it's got coolant flowing through it to speed up warmup at low temperatures, to get and keep the engine in closed loop/catalysts functioning mode at cold temperatures.

In other engine families where bypassing the coolant in the throttle body is easy, multiple, back to back, dyno tests show power gains by bypassing the throttle body coolant passage.

My UIM is not yet burned through and is otherwise fine. Why should I buy a new one? Further, by not having to strip everything off it the job is easier.

Again, has anyone here plugged the coolant passages? Why or why not?


Ed

[willwren]

Some have plugged the passages, but in all honesty, the gain is so minimal, it's not worth the trouble.

Your UIM has not burned through YET. It's not a matter of IF with the OEM manifold. It's a WHEN. WHEN it happens, you will suck coolant in, mix with the oil, and if you don't catch it in time, it will cost you the bearings in the bottom end.

Dozens of L36's on this Forum since 2002 have seen this happen. This is why we keep telling everyone with an L36 to change the UIM BEFORE it fails. And do not use the GM 'improved' design. We've seen those fail as well. I changed one on a 96 that had been previously 'GM improved', and it was nearly burned through.

[00Beast]

Also, you DO have to remove the UIM to remove the LIM. There are 4 bolts that are on the inside of the manifold under the UIM that hold the LIM to the heads.

Not replacing the UIM with the upgraded sleeved unit while everything is apart would be incredibly short sighted, IMO, especially with a part that is so prone to failure. Everyone I know with an L36 has had to do the UIM. My grandpa, my buddy with the 05 SLE, my aunt, etc. Do it once, do it right and forgeddaboutit.

Looks like ineedparts changed their site around, here's a link to the kit: http://www.ineedparts.com/index.php?tar ... t_id=17806

Looks like they also offer aluminum LIM gaskets as a kit w/ the UIM that look like Fel-Pro's.