ZZ

I replaced my ignition control module, and out of curiosity I tried the mod listed on shoebox's site, and compared it to not using spacers. First I took the temp using a Fluke 52 temp meter without the spacers, and the heat sink ran right at 200-205, as did the cylinder head. I then used a few washers to space the whole coil bracket back about 1/2" from the head, and retested. The heat sink measured anywhere from 20 to 30 degrees F cooler with the mod. Proof positive

I was having drivability problems, hesitation at first, and a year later the car would just quit like the key was turned off. It wasn't the opti, and there was enough heat sink compound. It just decided to get screwy after 10 years. It would get heat soaked and crap out. The car always restarted once cooled down. Hopefully this mod will keep the problem from returning. Just some FYI

shoebox

Hey, that is cool.

ZZ

Well, here's the down side. After running for a while, it stayed cooler, but after shutting down and watching the temp differential, the module/heat sink didn't cool off very fast, and actually stayed hotter after the heads dropped in temp below the module. I'm thinking of adding a small 12V fan and see what happens. The problem will be keeping it from splashing water on the electronics. Maybe I'll set it up on a timer that starts when the engine is shut off.

BennyBoy

I wouldn't worry about a fan. I would think that the faster you cooled something off, the more wear and tear that object would be subjected to. Besides, if you aren't using the thing when the car is shut off, why care about how long it takes to cool down?

superal

Well holy crap I think you just saved my sanity. I've been battling this strange problem of the car shutting off when it reached 180* or so. Then it starts back up like normal when it's cooled down a bit. Good thing I read this thread now after testing every freakin sensor in the car with no success. Was even gonna buy a new icm tomorrow and ect sensors. Hopefully this cooling shindig will solve my problem. Prom is only a week away so hopefully this works!

shoebox

I am curious of how long it stayed hotter. Plus, if it was already cooler than the head when the engine was running, it might not be a real factor.

ZZ

I checked it about 20 minutes after shutting the engine off, and it was still at 170º I guess it doesn't have the head acting as a heat sink, and retains the heat. Of the two choices, running hotter, or staying hot longer, I think the 2nd choice is a no brainer. I have all sorts of aluminum heat sinks laying around from old power supplies, so I'm going to do a ltiile tinkering this weekend with it after I get back from Carlisle, and see what I can come up with.

Dee94Z28

Hey ZZ where did you get the heat sink ? I went to Radio shack and they had no clue about heat sink.





94 Z28 Teal T-tops
BMR strut tower brace
Car sound hi flow cat
Moroso CAI
Magnaflow cat back

superal

I did the little mod today and my car shut off sooner than it did without the mod. Maybe my icm just needs replacing? I can't think of what else it could be. I do have a slight miss at all rpm's if that helps.

ZZ

Your ICM should be mounted to a heat sink from the factory. It's the finned aluminum piece.

butterbobbuick

This is an old thread so I'm posting this for my own future reference as much as anything.

I've had a '79 Pontiac since new, 231 Buick engine w/4 pronged ICM in distributor(over 500K miles). It routinely burns thru an ICM every 12-15K miles. That's a lotta ICM's over the years! I also have owned a '90 Buick for ten years, 3800 engine w/ the rectangular ICM mounted on the engine bracket. It also burns thru an ICM about every 15K miles. I just had another one to go out and found this page looking for answers. I've been convinced for years(decades) that the Pontiac's design was absolutely cooking the module, no doubt. Thermal grease(yes, I used it) doesn't help when the engine temp exceeds the module's.
I've now become convinced that the Buick's design does the same thing. All I have to do is drive the car until it's at operating temp. then park it. As soon as it's turned off the heat flows from the head toward the ICM. Just loosen the 3 mounting nuts as soon as you shut off the engine. Feel the bracket temp. and then the bottom of the ICM. Bracket is far warmer to begin with. As the engine rests the bracket gets even hotter, thus making the ICM a heat sink for the engine. My last ICM died after sitting for about 1 hour on an 80+ degree day. One ICM got so hot that the sand/glue mixture ran down, exposing the electronics. It lasted quite a while despite that.

So, I've decided to use fiberglass header wrap between the ICM and bracket. I've idled it up to operating temp. and the bracket is much hotter than the module, especially after resting a while. Can't touch the bracket, way too hot, but I can now touch the ICM. Current mileage is 159,375. We shall see. Considering this long hot summer(2016) cooked another module, and their prices keep going up, there's not much to lose. I have a couple of Fords w/ fender mounted ICM's that easily go well over 100K before dying. They never even get hot to the touch. Slightly warm, but not scalding hot. No comparison.