Haynes manual suggest silicone dielectric grease for ignition module?

SirRobyn0 · Mar 21, 2023

It seems to depend on who you ask if dielectric grease is good enough or not. But think back to the 70's when that Hayes book was likely written. Back then they'd write those books with the everyday person in mind and it's not like you were buying thermal paste at the local auto parts store in those days and I'm sure they felt dielectric grease was better than nothing. So that's my take.

Snoots · Mar 21, 2023

Hugomartin said:
So the Haynes is wrong?

Haynes is wrong. Period.

Doppleganger · Mar 21, 2023

I have heard that dielectric grease is more apt to liquefy over time than the white thermal paste. I know what I put on ceramic fuses was a greasy mess after a few years, whereas the white paste that was put on the back of ignition power stages was still there in its original form after 20yrs.

Then there's this.....Permatex' safety data sheet for their dielectric grease. YMMV

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gmbellew · Mar 21, 2023

and always carry a spare AC Delco ICM with you. it's probably the most likely thing to leave you stranded that you can change on the side of the road with a minimal amount of tools.

Hugomartin · Mar 21, 2023

Would there be a specific ingredient to look for when buying thermal paste heat sink

Bextreme04 · Mar 21, 2023

Hugomartin said:
Would there be a specific ingredient to look for when buying thermal paste heat sink

This is probably what the guy who wrote that section of the hanes manual was looking at when he wrote it.
https://www.amazon.com/dp/B0044NI2M2/
Thermal paste is dielectric(usually), but not all dielectric grease is a good thermal conductor. For things that call for dielectric grease I use a tube of Dow Corning DC-4. It is cheap and will last forever. It is called out specifically in a lot of aircraft maintenance manuals and I have seen it come out still looking like new on 40 year old aircraft connectors.

For something that you want to work to transfer heat away, use a thermal paste. The link I gave you above is a Silicone dielectric thermal paste grease. It checks all the boxes of everything that everyone has said and is a whopping $15. I'm pretty sure I've seen it on the shelves at a few auto parts stores too...

Bextreme04 · Mar 21, 2023

Or, if you don't want to wait a day for the amazon guy to deliver it, you can get a tube from Best Buy or similar stores for about $7. They usually come in a small syringe.

Matt69olds · Mar 21, 2023

Thermal paste is NOT dielectric grease!

Dielectric grease is designed to seal connections from moisture, and to allow easy disassembly.

Thermal paste is designed to help transfer heat.

In my 35 years of driving, I have had 2 modules fail. One would quit once the engine got hot, the other flat out died and wouldn’t start.

The first few years of HEI production did have some module reliability issues. It didn’t take delco long to figure out the problems. I’m willing to bet the cause of repeat module failure is no thermal paste.

The cheap parts store modules are junk. The factory Delco modules will vary dwell based on RPM. The cheap modules have a fixed dwell figure, you can see it with an old school dwell meter.

In all honesty, I’d prefer a good used 20 year old Delco module over the cheap parts store crap.

gmbellew · Mar 21, 2023

agree, only use an AC Delco ICM. they still make them, although probably not as good as they used to ....

Doppleganger · Mar 21, 2023

Hugomartin said:
Is this the proper paste?

Never seen this stuff - always got the stuff that comes in a syringe or a very small tube - the PC shops will have it en mass. Whenever I bought a new Bosch power stage, it would always include one of those small condom packets of thermal paste (looked like the ones the parts stores peddle brake grease in).

75gmck25 · Mar 21, 2023

As already mentioned - thermal paste is used on the heat sinks in laptops and desktop, so it’s stocked at Microcenter and other computer stores. It’s also readily available nline.

Camar068 · Mar 21, 2023

Matt69olds said:
Thermal paste is NOT dielectric grease!

Dielectric grease is designed to seal connections from moisture, and to allow easy disassembly.

Thermal paste is designed to help transfer heat.

Amen.....someone finally got it right for a description of both!!

Hugomartin · Mar 22, 2023

Bextreme04 said:
Or, if you don't want to wait a day for the amazon guy to deliver it, you can get a tube from Best Buy or similar stores for about $7. They usually come in a small syringe.

That’s what I bought it’s a grey sticky mess I hope it works

gmbellew · Mar 22, 2023

Hugomartin said:
That’s what I bought it’s a grey sticky mess I hope it works

you just need a thin layer, dont go crazy. the idea is it fills the microscopic voids at the surface and makes better thermal contact between the module (heat source) and distributor (heat sink).

Bextreme04 · Mar 22, 2023

Camar068 said:
Amen.....someone finally got it right for a description of both!!

Not necessarily. As I said before, they are simply characteristics. They are not mutually exclusive.

You can have a Thermal paste that is also dielectric(most are, but NOT all).

You can also have a dielectric grease that is not thermally conductive.

The DC-4 is not a good thermal conductor and is a silicone dielectric grease.
The Super Lube Heat Sink compound I linked above is a Silicone dielectric grease that has metal particles blended in to make it a good thermal conductor.

They are both silicone based dielectric greases, but only one of them is also a thermal paste.

Haynes manual suggest silicone dielectric grease for ignition module?

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