Heat-conducting "grease" coats KATS 5/8 x 3-1/2-inch cartridge block heater?

Before inserting the 400-watt electric block heater into the heater hole of the RX350, some kind of heat-conducting material is to fill in any gaps between theater metal jacket and block metal.

Any ideas of what heat-conductive material should be used?

Thank you.

The same paste you would use between a computer’s CPU and it’s heatsink. @cwatkin might know where to get it.

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I just got this. Sorry I have been REALLY busy with work due to COVID-19.

Anyway, heatsink compound comes in many forms. You probably don’t need the most expensive stuff or the hard set type. I would probably get the white ceramic based stuff since it won’t crack with vibration and isn’t super expensive. I don’t know what volume you will need but you might need multiple tubes. This stuff should work.

One other thing… What is your max working temp? http://www.arcticsilver.com/arctic_alumina.htm It is rated for 125C/257F for extended periods. It will not work as effectively if run above these temps for long. http://www.arcticsilver.com/arctic_alumina.htm

Arctic Silver 5 has a higher temp rating. http://www.arcticsilver.com/as5.htm

I think I would do the AS5 personally due to the higher heat rating and the fact it is based on silver. 12g is about the size of a typical injection syringe so you may need many of these. https://www.ebay.com/itm/Arctic-Silver-5-Thermal-Paste-12-grams-CPU-Heat-Sink-Thermal-Compound-AS5-12G/170749489791?epid=13035044138&hash=item27c176727f:g:IhgAAOSwfedeRfjW

Also, you might check out this for extra high temp. https://www.thermon.com/us/products/steam-heating/heat-transfer-compounds/t-99#:~:text=T-99%20is%20a%20specialty,-conductive%20(when%20cured).

My main concern is that the mechanical vibration and excess heat of automotive applications might not work well with something designed around computers. I really think it should be good enough for a block heater though.

Many of my automotive projects have been on hold due to a crazy work schedule but I have a few I will get back to once I get a tad more time.


Hey Conor. Nice to see you, it’s been a while. Hope you’re staying safe and healthy. Thanks for helping out.

Maybe I don’t remember correctly, the block heaters I had installed in ND used a molly bolt type thing and a gasket or pressure or o-ring to fit into the hole from a removed freeze plug. Any type of caulk to hold it in place will probably fail, and worrying about heat conducting sounds ridiculous in my book, as the heater element is immersed in the coolant, and sure it only got to -40, but was told the wattage was about the same as a 100 watt bulb. If you are looking at a magnetic mount don’t waste your time and money on it. Looks like NAPA is 400 watt https://www.napaonline.com/en/p/KAT11461?partTypeName=Engine+Heater&keywordInput=block+heater


Thank you.
This heater inserts into an existing dry hole in the metal block.
Instructions warn thathelement may getoo hot and burn out if theat is not pulled away due to any gaps.

The problem withe magnetic heater is that when I get home in the middle of the night, it is a mess reaching under the slush-dripping vehicle to attach ito the oil pan.

Now using a 250-watt outdoor flood light bulb mounted straight up on a 2x4 slid under the oil pan. A bedsheet from Goodwill covers the hood andrapes down over the grill.

When I ordered a car with the carb yet, I would always order the block heater and heavy duty cooling. The block heater was the best option for cold weather. With computers and fuel injection, it is not a problem anymore. Years ago a heavy hitter lady at work insisted someone stole her magnetic heater in our parking garage. Like who would do that? My investigation went no where but she couldn’t believe that she lost it on the road somewhere. Block heater installed by dealer yes. Cord hanging through the grill for easy plug in. Heated garage better if its that cold. Just IMHO.

Ha! I found her magnetic heater and used it 2 years until it burned out.

Too expen$ive to heathe garage.
Want justhemergencyehiclengine warm - no time to let it warm before under load.

For high heat applications like this I suggest using silicone materials. At work we use silicone gaskets or adhesives doped with thermally conductive powders. They aren’t cheap, but the do the job. Basically they fill the air gaps. Air is a great insulator. Thermal greases work the same way, except they don’t cure. Make sure you clean the surfaces well before applying the thermally conductive material.

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Just curious why the aversion to the tried and true freeze plug block heater? So if I understand correctly your option is just heating the metal block, and the cold is going to waste most of the heat in the exterior metal, please enlighten me. I have had to clean old dried up heat sync paste for computer processors enough to think you are making things more difficult than needed.

My recommendation is to throw away whatever it is that you have and go to the dealer to have a block heater installed. I’m sure the cost is more now but I had to have one replaced and it cost something like $25.

The last quote I got was $135 to install a block heater. DIY cheaper of course.

Letsuck recommended using theater which inserts into the hole in the block.
Theat should diffusenough through the aluminum and also heathe coolant.
The coolant emersioheater is fine,xcept for the mess and having to replace coolant after installation.

Who is Mr. Letsuck? At any rate, are you trying to heat the actual engine metal? Some heaters heat the coolant, some heat the oil, but never heard of trying to heat just the metal. A gallon of coolant costs maybe $20. Just in my opinion anyway. Don’t need it anyway with Fuel injection and my garage rarely goes below 40 degrees.

Letsuck dealer recommended using theater hole in the block.
Justrying to keep the RX350 ready to quickly attaihigh speed with minimal engine damage.
(No time to warm unless I remote starthengine - in the closed garage.
In Park witho load it poorlyvarms while I am getting into my uniform.

With all this trouble, my floodlight and sheet seems a better idea.
But whehome I must get down and position the floodlight under the oil pan.
At 0400 plugging in a power cord is much easier.

That is this clowns term for Lexus . It seems after all these years he still can’t solve his engine heating problem .

You sound like you are serious, joke, RIGHT? Maybe you could start a go fund me site to get a freeze plug block heater.

The outdoor floodlight in a weatherproof socket on the 2x4 stud, is aimed straight up. It is about 1 inch from the oil pandoes a good job.
The sheet keeps mucheat in thengine compartment.
If the floodlight bulb ever shatters, no sparkshould reach the sheet.

There would be no need for any type of heatsink compound on that freeze plug engine block heater. This works more like a water heater element based on the picture. The heater element is actually in the coolant. I was picturing something that fit into a recess or flat surface of the block and needed something to conduct heat. The NAPA unit pictured is immersed in the coolant. A water heater element will burn out if run dry as well. I suspect this is much the same except that many water heaters run at 4500W or more.

You might put a thin coating of RTV around that O-ring for extra security against leaks. I personally like the black RTV.

Yes, I have been quite busy. Everyone in the IT world is swamped right now. Demand for laptops, printers, etc. is now about quadruple of normal with everyone trying to work from home. Scammers/hackers also realize people are home and not always the most secure so they have been targeting people working from home or bored on social media. Between setting people up and fixing all the damage caused by the scammers, I have been extremely swamped. Then there are the people going to school from home plus the home entertainment aspect of tech these days.

Anyway, I have been staying healthy so that is the good news. I have to have been exposed so many times and just not been aware based on how much I have been out and all the various places I have been going. IT pretty much fits into every definition of an essential worker I have read so there was no slowing down or staying in.

I did buy a project somewhat on topic with this subject, thinking I was going to be stuck at home and needing something to work on. It has an engine block heater. Anyway, I bought a surplus short bus that had come from a local school district not long before to make into a camper. It is a 1996 GM G30 6.5 Diesel with a 12 ft box. I got a deal since everyone was in a panic and not buying but haven’t had enough time to work on it myself. Anyway, I have gone through and changed the transmission fluid, coolant, oil, and some other things I always do when I get something new. It came from the southernmost part of my state where it doesn’t snow so rust was minimal. I know the GM 6.5 isn’t the greatest but this isn’t going to be a daily driver and for those who say “It is only a 300,000 mile engine”, it only has 95,000 miles so has a lot of life left. I am going to do the PMD relocate and fix a few other things that these engines are known for lacking. This is my first diesel so I am still learning. It is a non-turbo by the way so not a powerhouse but good enough for what I do. It did come from a flat part of my state but has the “hill” gearing so I am happy about that.

I see what is going on here. Someone is being penny wise and pound foolish. Scrap the computer heatsink compound. Just throw money away on a wasted electric bill and risk causing a fire in the process. I also call this behavior “saving yourself poor”.

Either get a dipstick heater or a coolant heater like the one linked. This hairbrained idea will waste more electricity in a month than just paying to do it right from the start.