Block Heater Thermostat Corrosion/Errosion

[JD5652]

This is a pic of a Kim Hotstart A-2822-0M Thermostat that was installed in the FW cooling header on my 671-TI's. It has been installed for almost three years. The case material is aluminum and the cooling header is cast iron. I have my opinions on what caused this, but I wanted to throw this out and get other unbiased opinions first.

BTW, this mates up with a Kim Hotstart DD-151 750W immersion style block heater.

Any ideas?

[Storm]

Looks like a classic example of electrolysis. Not sure, but I believe that's why Caterpillar replaced the aluminum adapter plates on 3196 after-coolers with bronze adapter plates.

Aluminum is a highly sacrificial metal, therefore vulnerable to electrolytic or galvanic corrosion. It's also a lightweight and ductile metal, susceptible to fatigue from vibration induced stress. It also has a high thermal expansion coefficient, which makes it vulnerable to expansion/contraction related fatigue.

Storm

[clt_capt]

What condition are your engine zincs in?

[JD5652]

Looks like a classic example of electrolysis. Not sure, but I believe that's why Caterpillar replaced the aluminum adapter plates on 3196 after-coolers with bronze adapter plates.

Aluminum is a highly sacrificial metal, therefore vulnerable to electrolytic or galvanic corrosion. It's also a lightweight and ductile metal, susceptible to fatigue from vibration induced stress. It also has a high thermal expansion coefficient, which makes it vulnerable to expansion/contraction related fatigue.

Storm

Storm-

Definitely looks like a classic case of galvanic corrosion to me as well. I didn't really think about when I installed them, but now it makes sense. I'm going to give Kim Hotstart technical guys a call and ask if they have a solution for this. I have to find out how to electrically isolate the threads from thermostat aluminum body to the cast iron FW header.

What condition are your engine zincs in?

Capt Fred-

These are installed on the fresh water cooling side....so no zincs. But the raw water zincs are wearing normally.

[Mackey]

This is one of the reasons I like the Wolverine Block Heaters that attach to the bottom of the oil pan. They do not need to heat the whole cooling system to warm the oil, no corrosion and no additional holes in the engine to fail.

I would check your coolant ratio. Does not seem to be protecting the light metals in the cooling system.

[Storm]

I had the same thought about isolating the threads. Was wondering if teflon tape or liquid teflon might work. Probably not well enough. Most likely a nylon bushing wouldn't take the temperature. I think some silicone-type liquid thread sealants are supposed to reduce electrolysis. Not sure which ones. You'd definitely need a liberal coating.

[JD5652]

This is one of the reasons I like the Wolverine Block Heaters that attach to the bottom of the oil pan. They do not need to heat the whole cooling system to warm the oil, no corrosion and no additional holes in the engine to fail.

I would check your coolant ratio. Does not seem to be protecting the light metals in the cooling system.

I'll definitely give it a check...thanks for the reminder. One reason I did not go for the Wolverine fix was the inevitable prep work required to clean the bottom of the oil pan. I've heard of a few stories about the pad not adhering to pans that were not new and pristine. Also since I have Detroits, I wonder if the occasional oil leak would eventually deteriorate the bond?.....might be the way to go if I don't find a reasonable fix for this issue.

I had the same thought about isolating the threads. Was wondering if teflon tape or liquid teflon might work. Probably not well enough. Most likely a nylon bushing wouldn't take the temperature. I think some silicone-type liquid thread sealants are supposed to reduce electrolysis. Not sure which ones. You'd definitely need a liberal coating.

Ever heard of "dielectric fittings"?....check this out.....

http://www.corrview.com/tech_p_10.htm

Here's a couple thread sealants I came across..... anyone have any experience with these?

http://www.tef-gel.com/contain.php?param=tefgel_infor

http://www.lanocote.com/

[Storm]

Interesting products, but I haven't tried any of them. I applied dielectric grease to most of the electrical connections when I wired my boat. That was an attempt to repel moisture rather than anything else. Looks like you'll probably need some adapter bushings if you go with the dielectric fittings. That might be the only drawback.

I like the looks of the tef-gel. I might even have to buy some for future projects.

The only problem I've had with liquid teflon, which might be similar to the tef-gel, was when I tried to apply it to stainless fittings that were already wet with steering fluid. The fluid wouldn't allow the teflon to stick. The solution was to use teflon tape which doesn't wash off. You have dry fittings and you're not dealing with oil, so you won't have this problem to cope with.

Good luck with whatever you use. Looks like you're on the right track.

Storm

[Elite Diesel]

Are you running pencool 2000 in the engine?
Aluminum prefers pencool 3000.

[JD5652]

Are you running pencool 2000 in the engine?
Aluminum prefers pencool 3000.

I use a 50/50 solution of Detroit Diesel PowerCool (the red stuff) and distilled water.

Do you think the Pencool 3000 would be easier on the aluminum?