Technically the plastic (nylon 6,6) is supposed to be able to handle the temperatures that it is exposed to in our LIM Gaskets, it is 30% glass fiber reinforced, and its short term heat tolerance if 355F, the long term is 170F, of course that does not mean over the years the gaskets won't become brittle, and break up from all of the heat cycling.
Some say the 2-EHA in the Dex Cool is somewhat responsible, as it is a known plasticizer, but I do not totally believe that as it is really only a plasticizer when it is used in the manufacturing process of some plastics.
I have ran DexCool for the life of my car, and have never had an issue, of course I service my coolant regularly, and I always make sure there is no air left trapped in the system.


Nylon 6/6 Specification Data

More specifically I think it is to prevent icing of the throttle body in extreme cold, which would make it stick or jam open.

I have yet to hear of an incident however, but also not too many people block off the coolant ports. If I was left with the choice, I would probably do it in my current climate, I would be leery of it in a Colorado/Kentucky type climate, and I probably wouldn't do it in a Minnesota/Canadia type environment. Worst case scenario you simply have to contend with an iced up throttle body if you do it when you shouldn't have, and most that know what they are doing can mitigate issues that may arise pretty easily.

I think we've had a few northerners do it. I've done it. No issues yet.


And think about it. If its going to be THAT cold, where is the moisture going to come from? It will already be frozen probably in the form of snow.

Alll you need is a air flow high enough and some moisture to get a iced up condition
draining the old 120 gallon air compressor
even when was 95 out side it would ice up then stop draining.
Then melt and start draining again air and water
in the USAF the good old gas heaters the carb would ice up
as long as the butterfly not open much and that was here in Texas
dry out side at 30 F
I would think the TB would be harder to ice up with the heat from the exhaust pipe
right under it rising up even if you plugged the coolant from going to it.

like i said we have days or sometimes several days were its never over zero and wind chills of -20 to -30 and she drives it to work and its left out in the snow and wind and she never said anything about a stuck throttle or poor running

If it was cold and fog with the throttle not open much for long period of time it could ice up but on these engines you have the exhaust pipe right under the TB with heat rising so it ever happening not likely. Its more the liquid moisture condition in the air then air temperature with the carb out in with no heat at all around it that ever caused that condition

I did not get very far today on the repair. However, I did start and I did not find any coolant in the intake duct. That leads me to believe that the TB gasket is not leaking; at least not out into the intake duct and the amount in the photo could have built up over a period of time. There were significant lost of coolant in the reservoir; so I must be burning coolant. I drove the car Sunday for around 72 miles. Monday I got the tractor out of the shed and made space for the Buick and got it in Monday evening; so Sunday was the only miles put on the car.

I got everything out of the way but have yet to pull the UIM. Here is a photo looking into the UIM and you can see the coolant sludge on the inside. Is it possible to clean that mess out? Also, how can I tell if the UIM is the new replacement? Should I go ahead and pull the UIM? I was looking at the corner of the LIM and head and I am seeing a metal gasket, or what looks to be metal. I check with the previous owner and they are unsure if they pulled the LIM or not. If it is the metal gasket, do I need to go ahead and pull the LIM? All the stuff in the way is now out of the way so maybe it would be a good ideal to just go ahead and put new gaskets all around? What is the advice with this? I hate to replace the LIM gasket if it is good because I could mess up and cause a leak that is not there.

I pulled the upper intake and notice a puddle of coolant in the lower intake. I am going to pull the lower intake even if it does have the metal gasket; with the work done it is foolish to not go ahead and replace the lower intake gasket.

My main question here is if I need to replace the upper intake since it was already replaced with the new and improved model according to the previous owner. Can the members here tell if that intake is OK and I can just buy the gaskets?

Hard to tell, looks like the gaskets been hot near the egr port towards the tb gasket. Hows the upper manifold look?