Frostheater Operation Question

I recently installed a Frostheater(FH) on my MK4 ALH TDi.
The install was quick, easy and painless. I lost MAYBE half a gallon of G12(being extremely cautious and mindful)

After the install, I topped off the coolant(slightly over Max) and drove around for nearly 50 miles, without shutting down. FH Suggests 30 miles before testing the heater. Naturally the system used some to fill air gaps maybe and I am now right below MAX, perfect.


So, I "tested" it this morning. Plugged it in, checked to make sure it wasn't smoking or starting a fire.. Checked acouple more times, then, i didn't come back for nearly 4 hours. after 4 hours I unplugged my FH, Popped my hood and boy was it WARM!(nearly HOT, or very WARM) Valve cover, coolant hoses, everything up top was nice and toasty @ 40° outside. COOL!!!!!

now to the question:

**The FH unit was making an almost boiling sound, or maybe hissing**

*Is that normal, have any of you users noticed that noise?

**How can I make sure my coolant is circulating properly to avoid frying my new FH?

I love the idea of having it, even for chilly mornings! and I want to make sure it functions properly. I figured id ask some hands on users, as opposed to emailing FH about a simple question. I'll Email them if you guys dont have any similar experiences. Thanks!

Cleaned up the plug in with a Marinco 150BBIW

Dannyboy said:

So long as it's got coolant in the system it SHOULD never boil dry,
It does sound like a kettle boiling but should never sound like a rolling boil.Sounds like pop fizzing
Just enjoy your winter ready car!

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Definitely didnt sound like a rolling boil, but ill keep an ear on that.
Tomorrow will be the first test where I will actually be driving. It'll be in the mid 30's and normally I would idle my car for 10 minutes in the apartment complex parking lot before setting off for work.
Thanks for the reply!

Have nearly same bumper plug in mine to keep it clean looking. I have mine setup to a high amp timer to kick it on 3 hours before I leave in the am. The frost heater was the first thing I did when I got the car and worth it. Nice install.

ItAintRodKnock said:

Definitely didnt sound like a rolling boil, but ill keep an ear on that.
Tomorrow will be the first test where I will actually be driving. It'll be in the mid 30's and normally I would idle my car for 10 minutes in the apartment complex parking lot before setting off for work.
Thanks for the reply!

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WHY would you idle for 10 minutes before driving off, when it has been proven that the most effective method to warm it up would be to start, wait until it's smooths out (usually about 30 seconds - a minute or two), then drive off ? As long as the proper oil has been used, it will be everywhere it needs to be and flowing within 5 - 15 seconds.


Adding a frost heater is more of a comfort thing than a necessity in the lower 48 (unless you're see -35 or colder on a regular basis).

scooperhsd said:

WHY would you idle for 10 minutes before driving off, when it has been proven that the most effective method to warm it up would be to start, wait until it's smooths out (usually about 30 seconds - a minute or two), then drive off ? As long as the proper oil has been used, it will be everywhere it needs to be and flowing within 5 - 15 seconds.


Adding a frost heater is more of a comfort thing than a necessity in the lower 48 (unless you're see -35 or colder on a regular basis).

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Well, several ways to answer this.
One, its documented my car uses a quarter of a quart per hour to idle, that isnt much...
Two, I live within 2 miles of the interstate and it isnt good for the valves to rev high while cold. If I crank up, wait 60 seconds and drive to work they would be cold and doing 70+ mph( higher rpm) for many miles before budging on the gauge....
Three, the car gives me full heat only acouple miles down the insterstate after idling. Without the idle, that is extended(again the creature comfort part of this)

I totally agree that this is for my comfort. Although, it is better for the motor to be near operating temp, as the computer send fuel differently based on operating temp...

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Duke_962 said:

Have nearly same bumper plug in mine to keep it clean looking. I have mine setup to a high amp timer to kick it on 3 hours before I leave in the am. The frost heater was the first thing I did when I got the car and worth it. Nice install.

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Next step is getting the timer, but i intend to do the same.

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My FH is silent.
I wouldn't idle that engine that long, they don't really warm up like gassers do. Fire it up, check your mirrors, put on your seat belt, plug in your phone or put on some music and just set off. It warms up when driven.

Votblindub said:

My FH is silent.
I wouldn't idle that engine that long, they don't really warm up like gassers do. Fire it up, check your mirrors, put on your seat belt, plug in your phone or put on some music and just set off. It warms up when driven.

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This!... my FH runs for 4 hours before I leave. I get in and follow this exact same process for my 9.5 mile drive.

It is key to have the heater at the lowest point. Heat rises which is how the flow part works.

On my 81 rabbit diesels that Terry made a kit for me I could actually get it to defrost and melt snow off the windshield if i left the defrost vent open. The heater will get the temps up to around 210 I have seen if plugged in all shift at work. Not a required to have one of these but it is easier on the starter, battery, lub system, glow plugs and the driver. I had my 04 golf start on fire with a really cold start after night shift. Shorted out near the starter. They didn't have plugins. My new location does so I just ordered a heater for the 05 golf now that I can use a plug and am back on nights again.

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JDSwan87 said:

This!... my FH runs for 4 hours before I leave. I get in and follow this exact same process for my 9.5 mile drive.

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It is clear that with the FH, i no longer idle AT ALL, right? lol
Prior to installing my FH, I DID idle, and I can notice a difference between idling and not idling~ and which exit on the interstate I'd reach 190 degrees, as I passed.
Also, I am not arguing that Diesel's are or are not thermally efficient. I'm just stating that idling does make a difference for the creature comfort focus.

10 mins at 30f wow. That’s not even cold!!!!!

coalminer16 said:

It is key to have the heater at the lowest point. Heat rises which is how the flow part works.

Not a required to have one of these but it is easier on the starter, battery, lub system, glow plugs and the driver.

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* Should it be sitting lower than the lowest hose?(slight downward slope from the oil cooler into the FH?) *

I hadnt seen any particular statements on that but had read that the FH's mount may need adjusting, and the Power steering bracket may as well.(PS is no issue)

fouillard13 said:

10 mins at 30f wow. That’s not even cold!!!!!

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I'm not going to dispute that at all but it certainly makes me shiver.

Ofcourse, the FH is ideal for much lower temps than that.

I'd bet an hour at 30 degrees would be plenty... keep in mind, it isn't free to run.

mine is completely silent.

All 4 of mine gurgle.

ItAintRodKnock said:

Definitely didnt sound like a rolling boil, but ill keep an ear on that.
Tomorrow will be the first test where I will actually be driving. It'll be in the mid 30's and normally I would idle my car for 10 minutes in the apartment complex parking lot before setting off for work.
Thanks for the reply!

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It's essentially a water heater if you listen to your water heater when it heats, you will hear the same thing, just like sticking a kettle of water on an electric burner in the kitchen.


Water has to reach 212 to boil and the boiling point of coolant is a good bit higher than that, especially under pressure as the cooling system should be.