The purpose of this thread is to see if rubber foam weatherseal can be a substitute of GM'* heater core seal kit. GM'* heater core seal kit is very expensive, and very few small town GM dealers stock it. The seal kit goes around the heater core to protect from shock, vibration and possibly air drifts.

The generic weatherseal is sold at many hardware stores and big stores like Lowe'*. It runs about $8 for 10 feet of 1 1/4 wide and 7/16" thick. The weatherseal says all seasons on its package, but does not pinpoint maximum temperatures. The GM kit seals for around $36 retail, and from the pictures contains about 2 feet of product.

My test is to see if the weather strip can sustain a temperature of 225 degrees and then 350 degrees in a oven for five minutes.

The test of 350 degrees showed some degration of the foam, but not real bad. Very little smoke, of which I think was the adhesive. I tested the 350 degree first at my Wife had some food already in the oven. At 250 degrees at 15 minutes, no issues of smoking or major change in shape, it was a little softer.

Car engines run around 200 degrees. Based on this test, I think the rubber foam weatherseal is a safe substitution for the GM heater core seal kit.

I wouldn't worry about 350*. If it gets that hot, you wouldn't have to worry about the truck again.

When you start putting parts in the dishwasher, I'm gonna get worried.

350* was what the Wife had dinner cooking at; I could not wait to start the test so I started at 350 and then went down to 250. I will be using the weatherstrip I purchased at Lowes in place of the GM OEM heater core seal kit.

I love using other things in substitution of expensive OEM parts. Especially when I can save a lot of money!

Keep us posted!