Insulating block heater?
 

Hello all, I have recently installed a block heater on my 2004 Honda Civic 2.4 (the kind that replaces the block drain plug) and I quickly noticed that the outside brass part of the block heater around the heating element gets incredibly hot within seconds of plugging it in. Never used a block heater before but I would assume that this is normal. Anyways, I am thinking about wrapping the exterior of the heater in a piece of a fiberglass insulation strip I have to keep the heat in the coolant directly surrounding the element and therefore keeping more of the heat in the engine. A decent size chunk of brass can dissipate quite a bit of heat at a well over 100 degree F delta T and I would much rather have that heat in the engine than wasted heating the air surrounding the heater.



The only concern I have is whether insulating the exterior of the heater could cause the element to overheat and fail prematurely, boil the coolant in the heater around the element, etc. I wouldn't expect that this would be a problem since I would think the coolant in the engine block is more than enough to adequately cool the element with or without the exterior of the heater dissipating heat to the air, but I don't have much experience with block heaters so I wanted to check first and any advice is greatly appreciated.



This is what the block heater I installed looks like. As you can see, quite a bit of the heater is exposed to the outside air.

Let us know how it turns out?

If I end up trying it (and I probably will) I definitely will :) What's the worst that could happen? The element is still surrounded in coolant

Try spraying it with eight coats of Plastidip.

What would be the benefit of Plastidip over wrapping it with fiberglass insulation? I'm not sure Plastidip would tolerate that much heat for long, it's only rated for 200 degrees F. I doubt it's a great insulator either compared to fiberglass.

Don'r know about high temps. I thought a spray-on coating would fit better than wrapping with tape.

Then how about shrink tubing? It comes big enough to fit over the sensor.

I'm not sure if shrink tubing comes that large but even if it did I doubt it would have much insulating value as thin as it is. I thought about trying to find a piece of foam pipe insulation that size because I hate fiberglass, but as hot as that thing gets it might melt foam insulation so I think unfortunately my best bet for insulation would be a piece of fiberglass pipe wrap held on by a couple zipties. The brass part gets hot enough to boil water and it's right under the exhaust header, so I don't want to put anything flammable or meltable on it.

I'm probably going to wrap it tonight, leave it plugged in overnight, and see if it gains any noticeable heating efficiency. If it survives that is ;)

Edit: This is what I came up with. Not very pretty or permanent, but effective. There is definitely more heat transfer to the block now. The part of the block that the heater screws into is now burning hot for the first time after just a couple minutes, normally it's just warm. There isn't noticable heat radiating off the heater anymore either. I will report back with results in the morning.

Update: The block heater survived the night. Just not sure about what long term effects insulation may have on it. I think it should be fine since the element is still submerged in coolant but I'm no engineer.

As for whether it worked any better, it may have by a few degrees. Last night we had a low of 46 degrees and the coolant heated up to 101 degrees according to my Scangauge. Night before last, we had a low of 49 degrees and the coolant reached 100 degrees.

I certainly wouldn't call a 4 degree difference over a single test conclusive by any means though as many other variables as there could have been such as varying winds.

I think the block heater is boiling the coolant because now as the system doesn't fully depressurize after using the heater. I haven't used the block heater or run the car for a couple days and the cooling system was still under pressure when I took the cap off from when I last used the block heater. Not good.

I think I may know what the issue is. On my engine, there is a small plug inside the large hole for some of the blocks that don't have an oil cooler. Although I removed the plug, the hole is still quite a small diameter and the block heater is a couple inches away from the water jacket so I wonder if the small hole is restricting the convective flow of warm coolant out of the block heater and into the block, causing the block heater and the coolant within it to overheat. Since convection is the only force circulating the coolant, it's path needs to be pretty unrestricted for flow to be decent.

I bet if I bored out the small inner threaded hole so it was the full size of the outer threads that would help a lot, but I can't think of a way to do that without getting a lot of crap into the block. I wish I thought to do that while I had the block torn down before I put it in the car :mad:

Might be simpler to add a small pump to some circuit like the cabin heat. Doesn't take much. The remaining pressure thing is odd, however.