i am so confused on why you plug the l.i.m? why wouldn't u just use the new style gasket?

i do that too, i am not a fan of dex it makes your whole cooling system look like chocolate pudding. and they didnt have the updated style stuff or at least i was not aware of it back then. it was just delco replacement stuff

I had a local mech tell me if i buy the parts he will do the UIM,LIM gaskets,flush coolant,chg oil and filter and change coolant elbows for 240.00

If thats the case I probably wouldnt plug the uim I would use the Dorman and felpro lowers....andyone know the best place to get the lim gaskets and is there just one felpro set ?

you plug the lim coolant holes that go to the UIM so even if the egr pipe burns thru the uim there is no coolant in the passages

are these both the correct part numbers for the lastest and greatest ?

DORMAN Part # 615180 {#12537425, 24506013, 89017272, 89017274} Includes Gasket Plastic
Upper
$64.79 $64.79
Engine : Intake Manifold GasketRelated Parts
FEL-PRO Part # MS958091 Set
2nd Design; w/Rubber-plastic end seals w/Locating pins; Lower set
$29.99


Also should I have the thermostat chgd too ?

I have used Dex for the life of my car, and I went with Dex after my UIM/LIM job, I have always changed my coolant regularly though, as well as made sure no air is in the coolant system, and my radiator coils look nice and shiny, I am more convinced improper maintenance is what leads to the Dex problems, like mixing coolant types, and leaving air in the system.


As for plugging the LIM/UIM coolant ports, I don't see that as something you have to do as long as you replace the LIM'* EGR Stove Pipe, replace it with the reduced diameter EGR Stove Pipe, and the EGR gasses won't cause any problems.


As for the parts, DORMAN Part # 615180 is the correct UIM part number.
That is not the LIM Gasket you want though, it is the same known to fail nylon framed LIM Gasket, you want Felpro MS 98014 T, that is the aluminum framed gasket, it costs more, but it is worth it.
You are also going to need the coolant elbow, they have an aluminum elbow now, it is Dorman 47065HP.
Changing the thermostat is not needed if it is not bad, but a new one is so cheap that I went ahead and replaced mine.

Tip, make sure the mechanic knows to replace that EGR Stove Pipe, it comes out with vice grips and a little force, and you can use the old one you pull out, you put it over the one you are installing, then just tap on it till it seats the stove pipe, which is almost flush.

Let me attach some pics of when I changed mine.

yep you need the elbow, because the old one will break into 50 pieces when you try to pull it out and you got to fish the chunks out of the manifold and tensioner.

as far as the dex though its not lack of maintenance. or air or any of that crap. i bought my 03 monte in 04 with 18k and the overflow was starting to turn, by the time i had35k in 2005 you couldnt see through the bottle and i had to flush it 3 times and put prestone in it. my mom bought her 03 imp about 07 with 35k and the coolant was bad already and couldn't get the bottle clean no matter what. gm says its supposed to last 150k and neither had there systems opened up at all

So what exactly is it that causes the coolant to turn to sludge?
I have read numerous threads, and most say negligence is usually the culprit, I have heard of some mixing a coolant with Dex Cool that is supposed to be compatible, but it really should not be mixed with Dex.
I have heard that it is believed that the EHA2 causes the LIM Gasket failure at the coolant ports, because EHA2 is a known plasticizer, which helps to soften plastic, but I am not sure about that one, because it should only be a plasticizer when the plastic is being formed, at least that is what I have read.
If that is the case, then the EHA2 softens the plastic of the gaskets, and lets that softened nylon 6,6 material into the cooling system, to be sure a chemical analysis would have to be done on some already turned to sludge.
I bet in some cases regular garden hose water was used, I have only put distilled water in my system, I have never used a garden hose, not even when flushing.
I had a guy that explained it all better than I can, of course he has a degree on chemical engineering, so he understood it all better than I do.
I'll try to find the posts he made in regards to the EHA2 in Dex Cool, but I don't want to turn the thread in a Dex Cool debate, there have been enough of those on the net already, no need for another.

Maybe I am just one of the lucky ones, but my Dex Cool has always looked like it does when new, of course I never let it go 5 years or 150k, I'll change it at around half that time/mileage, as I don't think the stuff really holds up well for that long.

I've been using the cheap no-name Autozone 50/50 for years. No sludge build up. Wait...it might be because I'm constantly cycling engines in and out that sludge doesn't build up. Hmmm, flush it every 2 years, you will be fine. That seems to be the frequency of my engine changes.

well for the folks that dont change their engine every 2yrs or 24k, i would change the coolant at that time. i dont know what causes it, but engineers tend to think too much. when i get a gm new or old, i put one of those garden hose adapters on it and flush the dex out and put prestone in with water from my garden hose and the brown crud stops forming. thats all i care about.