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Big block heaters boiling & degrading coolant?

So, earlier this winter I installed a 1kw block heater on the Metro. It is absolutely wonderful. 20 minutes of preheat and I jump into a car that is almost ready to blast my cold face with heat, and it doesn't idle high at all. I am really enjoying this modification.

However, I am also worried about it. When I go to unplug the heater in the morning, I can hear my coolant boiling in the heater itself. The heater is designed this way purposefully. Here is a quote from the installation manual.

Quote:

This unit operates on the principal of thermosyphoning. There is no mechanical pump contained in this unit. This unit boils the coolant and this action will move water from the top of the heater into the engine block and continue to circulate the coolant until it reaches a temperature of at least 150 degrees.

My question is, does boiling the coolant degrade it in any way? I know polypropylene glycol (used in solar hot water setups) is definitely degraded by getting too hot. I'm not sure about ethylene glycol (used in cars) though. Everything I looked up online was about cars overheating, not the effect on the coolant itself.

Learning Coolant Fundamentals

Quote:

In general, coolants degrade over time as the ethylene glycol breaks down into primarily glycolic and formic acids. Degradation occurs more quickly in engines operating at higher temperatures or those that allow more air into cooling systems. The coolant should be tested on an annual basis if it is intended to operate the system for several years between coolant changes, and particularly where the coolant is used in severe applications.

I imagine that coolant boiling will mean that elevated temperatures exist right at the point where film boiling of the coolant occurs.

Time will degrade the coolant more than using it.
If you are that worried about it plug in the coolant heater and circulate the coolant.
It has an electric coolant pump correct? If so then use it, or start the engine.

If the coolant pump is electric build your self a high voltage pump controller to automatically power the pump with external power like I have been working on.
http://ecomodder.com/forum/showthrea...ler-33118.html

I am going to run the 5500 watt coolant heater plus two 600 watt heaters and I am not worried about the coolant heaters effecting the coolant life at all.

The electric water pump is not yet installed on the Metro or I would definitely be using it during preheat. But, I also know others using this or a similar setup and brought this up for them as well.

I ended up emailing a few different manufacturers to see what they had to say about this issue. I'll let you guys know what they come back with.

Oh man! Boiling engine coolant is not a good thing. It will definitely degrade the coolant and I'd expect it would introduce air locks. It doesn't have to get that hot, does it? I mean for coolant in a pressurised system to actually boil.....!

Haha, so far I've gotten two replies from the manufacturers. Both of them have claimed that block heaters don't boil coolant and it shouldn't effect coolant life. I've replied to both with a link to the install manual that specifically states that it does in fact boil the coolant and that I can hear it boiling when its been plugged in for any length of time.

One of them did mention that elevated temperatures will reduce coolant life. I asked for further clarification as how that manifests itself.

First one back that didn't need clarification:

Quote:

High surface temperatures are normal within the engine, and to a much larger scale, so I don’t think you’d see much effect. I assume there would be a thermostat on the unit so it would cut off if above a set temperature, so that would limit the “on” time also. It is common for a vehicle to require a coolant change at 150,000 miles or 5 years, so I suppose it could cut into your mileage allowance slightly, but probably not significantly.

It seems the others don't want to believe me that its actually boiling the coolant. Here are the replies I've gotten.

Quote:

The temperatures produced by this heater will have no effect on coolant life.
Block heaters warm the engine coolant to approximately 180 ºF and do not boil the coolant.

To which I replied that it does boil the coolant, the manual says so and I can hear it boiling when I go to unplug it. Their reply:

Quote:

A 50/50 mix of coolant and water in a cooling system, will not boil until it reaches temperatures above 260 ºF.

The temperatures produced by the heater will not effect coolant life.

Here is the reply from the other.

Quote:

Typically, a heater of this nature will warm the coolant to roughly 160°F-180°F, which is colder than normal operating temperature range of an engine. The coolant should not be "boiling" at this temperature. Your engine will typically operate around 210°F, which would be the normal temperature for your coolant to be. As temperature rises, the life span of the coolant will begin to shorten.

To which I also replied with a link and quote to the install manual saying it does boil and I can hear it boiling. Their reply:

Quote:

The 150°F temp will not degrade coolant in any way as this is colder than what the engine itself would heat the coolant to. The engine should heat the coolant anywhere between 200°-225°F, which is normal operating temperature for both gas and diesel engines. There is no degrading to the formula at these temperatures.

So... yeah, not very helpful.

Perhaps a video where you can hear it boiling is in order.