Ignition Control Module Heat Sink Question

[George7941]

The Ignition Control Module failed for a second time on my truck. First time was in 2011, so the replacement genuine GM ICM lasted fifteen years. After the first failure, I bought a spare module and left in in my glove box. This time, when the module failed, I recognised the symptoms, changed the module in the Home Depot parking lot and was on my way without a tow and not missing a day of work.
I bought a cheap ICM off Amazon to keep as a spare. I tested it and it runs my engine

https://www.amazon.ca/dp/B0C4TSLHR1

The mounting surface of this module is not flat as on the GM module, but has a recessed portion. I filled up the recess with thermal paste and bolted the module to a spare heat sink and left it in my glove box in case the ICM fails again.
I was wondering why the recess.

 

[Trav]

Use this on the recessed portion.

https://a.co/d/02N6HsAl

 

[grasscutter]

This is the stuff I used on my ICM :

https://www.amazon.com/dp/B019MSVEBY?ref=ppx_yo2ov_dt_b_fed_asin_title

 

[George7941]

I used something similar

This can is about forty years old . I don't think they deteriorate with age.

 

[Lubener]

This is the stuff I used on my ICM :

https://www.amazon.com/dp/B019MSVEBY?ref=ppx_yo2ov_dt_b_fed_asin_title

Won't do a thing in his case if the recessed heat pad isn't contacting the heat sink.

 

[George7941]

Use this on the recessed portion.

https://a.co/d/02N6HsAl

Thanks, Trav. That does seem to be the best product to fill the gap. I wasn't aware that such a product existed.

 

[blain450]

Use this on the recessed portion.

https://a.co/d/02N6HsAl

Good solid recommendation.

 

[dogememe]

I wonder how much longer these things would last if they included high quality thermal paste and people cleaned the old one off well on the mount?

 

[George7941]

I wonder how much longer these things would last if they included high quality thermal paste and people cleaned the old one off well on the mount?

When I installed the ICM in 2011, I cleaned off really well and used quality thermal paste and got 15 years out of the ICM. The factory installed ICM only lasted five years. Google Vortec ICM to see that they are problematic. The heat sink is really not large enough and it is mounted just above the valley of the V engine and does not get cool air blowing over it. If I was going to keep the Sierra much longer. I would relocate the ICM into a cooler spot , with a larger heat sink. The Sierra is showing its age, having been in daily use, in the rust belt, for twenty years. I won't be keeping it much longer.

 

[tcp71]

If the recess is more than 0.3 to 0.5mm deep, the heatsink paste is actually insulating the two parts, thermally, from each other. Heatsink paste isn't there to fill any real gaps, but to bridge the microscopic pores between to parts. A far better choice is a thermal pad that you can buy to fill larger gaps: