Big block heaters boiling & degrading coolant?

[ksa8907]

Originally Posted by Andrei_ierdnA

I have a suggestion if you cannot get to the bottom of this dilemma:

* sell your large 1kW block heater and with that money buy a small block heater 125-250 W.

So instead of heating your coolant in 20 min and having a localized boiling point, you will have to plug into a timer and let it heat the coolant for several hours overnight. Same end result, same electricity cost, but with a lower and more gradual heating of the coolant and without any localized boiling.

Just an fyi to the OP and anyone else curious. I have an OEM 400w heater in my car on a timer that turns on at midnight and off at 6:30. I park in an uninsulated and unheated garage and the car is between 85 and 100 degrees when i leave. Within 2 minutes of cranking and 1 mile down the road it will be about 150 to 160. If the temps drop to around 0°F, it only gets to around 140 in that time.

[Daox]

Here is the reply from the previous post. The answer seems quite reasonable.

It is pretty much impossible for us to answer your question conclusively, simply because we have not done the product testing necessary to determine the answer; all of our product testing is conducted to determine how our product performs in an automotive cooling system.

Having said that, the scenario you describe is not all that dissimlar from what takes place in an automotive cooling system, where the cooling passages in the cylinder head are directly adjacent to combustion chambers that see temperatures in the neighborhood of 600°F. The only recommendation I can make is to monitor the system as best you can, try to inspect the fluid every couple of months to see if any sediment or corrosion is evident in the fluid. If the boiler is turning on and off around the clock, you may wish to change the fluid every 3 years instead of 5, since that service life is based on a car that is only driven for a couple of hours a day rather than constantly.

[Ryland]

Why not just do a ph test to decide when to change coolent?

[Daox]

I will after a while. I was just trying to collect some info from the experts. The block heater has only been installed for about 3 months now. Come spring/summer I'll probably test it.