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.

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.

Bump, anyone?

Learning Coolant Fundamentals

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:

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

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:




Here is the reply from the other.

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:


So... yeah, not very helpful.

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

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.

Thanks for the idea Andrei. That is definitely a possible and good solution.

For me, I have in the works an electric water pump which I'll be able to turn on when I plug in the block heater. Circulating the coolant should prevent the coolant from boiling inside the heater. This will be done either way as its one of my next mods to do to the car. But, I also wanted to gather info for myself on use with other vehicles and for other ecomodders on this topic.

I have already tried this.
A low wattage block heater uses a lot more power to reach the same temperature as the large one.

My 3500 watt coolant heater can raise the temperature of the coolant in the engine from freezing to 75'F in 20 minutes, using just over 1kwh.
To get the same effect with a 600 watt block heater you have to leave it plugged in for hours to get the same results. Any more than 2 hours and you are at 1.2kwh.
To warm the coolant by 40'F with the smaller heater it takes around 3 to 4 hours if it can even raise the temperature 40'F. That adds up to a lot more than 1kwh.
So in the case of coolant heaters more is actually less.
That is why with the suburban engine is going to have the 5500 watt coolant heater plus two 600 watt heaters. The faster you can heat the coolant the less heat you loose to your surrounding environment.

Then even if you go to a lower wattage heating element the heating elements just get smaller. So the surface of the heating element likely gets just as hot. My 400 watt coolant heater is slightly smaller than the 600 watt elements I typically use, the newer 1,000 and 1,100 watt up grade heaters are about double the size of the 600.
The only way to get a lower heating element surface temperature is get a very large heating element such as a 1000 watt 120v element and run it on a varrac and dial the wattage down to what ever you would like to see it run at.
Or get a 240 volt heater and run it at 120 volts.

Indeed, you are totally right. With a small heater the rate of heat gain is considerably affected by the rate of heat loss to the surrounding freezing environment, making the overall duration much longer and resulting in more electricity/power used.
The electric water pump is probably the best solution.
Doax, can you share the pump power (W)? It should be fairly low power, so negligible running costs, right?

I'm very interested in your findings about the coolant life expectancy given the localized boiling, although based on the manufacturers' responses so far, we may never know the truth.

I'm assuming anyone using a grille block will also run into a similar situation, making coolant fluid changes needed sooner than scheduled, right?

Test it and find out.
You know that it turns acidic as it breaks down and I'm sure you have a few drops of fresh coolant to test to get a base number, and maybe a friends car to compare.
So go to the drug store and get a box of ph test strips.

Thanks for the feedback guys.

I did measure the outlet temperature this morning. Ambient temp was about 9F out. I had it plugged in for roughly 20 minutes. I could hear it boiling as I shot the picture below. But, low and behold, the outlet temp was...

http://ecomodder.com/forum/attachmen...1&d=1455716002

I moved the IR temperature gun all around and 160F was the highest I saw.

But, I can hear it boiling! It sounds just like boiling water on a stove top, and the manual says it boils it too... So, now I'm confused haha. :confused: Any ideas?

I don't have power consumption numbers yet. My next step is to put the motor in and test it. My thread on it is here:

http://ecomodder.com/forum/showthrea...eap-29896.html



I disagree with this. A grill block shouldn't increase operating temperatures of the engine. The coolant temperature should still be thermostatically controlled via the thermostat. You should definitely get up to temperature quicker with a grill block, but you should not sustain higher temperatures once maximum operating temperature is reached. If you are, your grill block is too big. However, I've run full grill blocks on a couple vehicles and I've never had a problem with this. My radiator fan will kick on and cool things down even with a full grill block in place. However, if your fan was to fail you would definitely have problems.

I bet it boils like a portable electric water boiler does.

Soon after you flip the switch they start making a rumbling noise, caused by tiny bubbles of steam expanding on the heater plate and collapsing when they break loose and rise in the colder water above.
When that gets hotter the bubbles grow bigger and collapse more slowly, making the sound drop in pitch and intensity - until the bubbles reach the surface when it is done.

When you look inside a boiler when the water is still cold you can't even see the bubbles that are making all the noise; they are that small.

Your heater is operating in the same phase as a cold filled electric water heater.
Only a very small amount of coolant gets converted to steam (and back to fluid when it breaks free of the heater core).
Therefore I think degradation is not much of an issue.

One more reply. This guy actually seems to care:

So, I replied telling him the outlet temp is ~160F, but I can hear it boiling. I think the boiling is localized to the heating element itself.

I'll update as I get more info.

Forced circulation will further reduce the level of hissing, crackling and popping you hear as compared to natural convection.

When I turn the electric coolant pump on in my diesel the 600w heaters get noticeably quieter.

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.

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

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

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.