Hello,

In the process of installing a dual fan system on my 1990 XJ-S. Does anyone know if the following is important.

When I removed the two ignition modules from the radiator bulkhead to move them out of the way, white paste was present between the module component and the silver plate. The paste was dry and fell off, so can't reuse.

What was the paste?, and is it important perhaps to make a better contact between the two parts.

Thanks for the help

Toby

1990 XJ-S
2007 S-Type R

 

Perhaps a hink sink compound designed to help the heat transfer out of the modules an into the mounting

Cheers
DD

 

Heat sink or thermal transfer paste.

 

Yes that is heat sink compound and you should put new when you reinstall them. It aids in transfering heat away from the component and can cause premature failure due to overheating of component. Most auto parts stores or electrical wholesalers should have it.

 

That white paste is Zinc Oxide. Usually in a silicon oil base.

There are other thermal compounds, such as graphite and that weird grey stuff that looks like modeling clay. Don't use modeling clay. Also stuff for CPU heatsinks.

And if you are in a pinch, you can use Zinc Oxide ointment. You know, sunscreen for your nose. Try to get the most ZnO2 you can in the product. Oddly, some diaper rash ointments have Zinc Oxide in them.

You can use rubbing alcohol (isopropyl alcohol) to clean the Zinc Oxide residue from the mating surfaces and prep them for fresh compound.
When you apply new compound, apply only enough to cover the mating surface and make good contact. Too much of this goop will actually be detrimental, because the compound as a whole has a lesser heat transfer coefficient than the heat sink material.

 

For those who do not dabble in computers. Heat sink compound is commonly available for mounting heatsinks to cpu's.

The cheapest grade will do for the job at hand. You will need more than commonly used with cpu's. You don't want the latest whizzbang stuff because it is made thinner and runnier.

 

Thanks for the education.