block heater popping out of block

[Jim P]

Last night while towing my trailer with my tractor on, the block heater popped out of the block and I was leaking antifreeze.

This is the second time that this happened. It did it about a month ago also. I upgraded to the newer high volume water pump about 2 months ago but I never got the dual thermostat crossover. I am wondering if this is causing too much pressure in the block and causing this block heater to pop out. When the block heater pops out, it doesn't appear to have anything wrong with it. I am not getting any excessive pressure in the top radiator hose when I first start it and it uses no coolant at all as long as the block heater stays in.

What do you guys think?

[Kennedy]

Sounds like a good example of why the cooling mods is done as a pkg.

[rjschoolcraft]

An article titled "1999 GMT800 6.5 Cooling System" in the The 6.2L/6.5L Diesel Page 1998 Feature Articles and Product Reviews (http://www.thedieselpage.com/back98.htm) talks about GM testing with the HO pump and single t-stat. It mentions GM's findng that cavitation (due to flow restriction) caused pressure pulses that blew out "soft plugs" in the block. Sounds like the same thing.

[TurboDiverArt]

I think it makes sense when we think about it. You are putting more volume into the block, what 40% more? This is pulled from the radiator. You then have only one therm as an outlet. This being more restrictive than 2 thems you are going to have higher pressure in the block. If the engine is not very hot then the single therm is not going to be wide open. This would cause higher pressure in the block, especially at higher RPM's. You are not going to experience higher pressure in the radiator because you are pulling out more volume from the pump but not putting as much pressure back in because of the bottleneck in the single therm. You will not see the radiator overflowing in your situation unless the engine is really hot and then that

[TurboDiverArt]

Originally posted by ronniejoe:
An article titled "1999 GMT800 6.5 Cooling System" in the The 6.2L/6.5L Diesel Page 1998 Feature Articles and Product Reviews (http://www.thedieselpage.com/back98.htm) talks about GM testing with the HO pump and single t-stat. It mentions GM's findng that cavitation (due to flow restriction) caused pressure pulses that blew out "soft plugs" in the block. Sounds like the same thing. I should have waited a few minutes for your post before writing my dissertation... smile.gif

Art.

[Jim P]

I think that I am going to upgrade to the dual thermostat crossover. Does anybody know where the cheapest place is to buy one? I guess I also need a new hose also.

Both times that this happened, I was running at pretty high rpms(about 3500). This time, I had just taken off at a light and was going up a grade. I had went through 2nd gear, then 3rd and was just ready to shift when she blew. The truck was not hot by any means. the gauge said about 200 but I think it is a little off because it was not even steaming.

I am not using any sealer on the block heater because it has an o-ring. It seems to just slip out of the block far enough for the o-ring to pop out and allow the antifreeze to leak.

[rjschoolcraft]

I bought my cross over at the dealer. Kennedy sells a complete kit, though.

[chickenhunterbob]

Jim,

If you're still looking...

They come up from time to time on eBay,

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7913600868&category=33603

edit - typo

[More Power]

I think that I am going to upgrade to the dual thermostat crossover. Does anybody know where the cheapest place is to buy one? I guess I also need a new hose also.

Both times that this happened, I was running at pretty high rpms(about 3500). This time, I had just taken off at a light and was going up a grade. I had went through 2nd gear, then 3rd and was just ready to shift when she blew. The truck was not hot by any means. the gauge said about 200 but I think it is a little off because it was not even steaming.

I am not using any sealer on the block heater because it has an o-ring. It seems to just slip out of the block far enough for the o-ring to pop out and allow the antifreeze to leak.

I saw this old thread while searching for info about another topic. I just wanted to add a bit of info... :)

A head gasket sealing problem could allow combustion pressure to find its way into the cooling system. This will raise average cooling system pressure above the typical pressure of 8-10 psi to the regulated surge tank cap pressure rating of 15-psi. And, a cap that doesn't vent till somewhere above 15-psi could produce a variety of cooling system leak problems that don't make sense - like block heaters popping out. If excessive pressure is the problem, you should see evidence of it in other ways too... like coolant leaks at hose fittings, leaking water pump seals, leaking heater cores and so on.

So, I'd recommend making a fitting (splice into a hose) that allows you to measure the cooling system pressure - especially while under load/high rpm.