Looks like my block heater crapped the bed…

[mcmxi]

Direct quote from a leading block heater manufacturer (Phillips & Temro, Zero start):
"
I have had two heaters fail right after I installed. Can you tell me what is happening?

The most likely cause is that there isn’t sufficient coolant covering the heater. One of the possible issues is that the vehicle is started while the heater is still plugged in the power. This can cause an air pocket to form around the element, preventing the transfer of heat and causing the element to burn out."

Insufficient coolant around the block heater can cause a failure for sure. And without knowing any details, this is possibly why this individual had problems "right after I installed". Maybe the individual was damaging the heaters during installation.

But think about that last part. So the block heater is sitting there immersed in coolant and it's hot. It's not air around the element unless there's something amiss such as insufficient coolant or air pockets, and the use of the word air is telling. It's water vapor if anything. So what changes as far as the element is concerned when the engine is started and coolant starts to flow? What changes that would cause the element to fail? Nothing changes that would cause the element to fail, in part because it's not subjected to sudden thermal shock.

I've only had one heater element fail and that's one out of seven diesel engine powered pieces of equipment and I assume that was because I left the BX block heater plugged in and on for at least two winters. Maybe they're only good for X number of hours and I exceeded that. Maybe it overheated, maybe it was defective. I don't know, but when I installed a replacement and used a timer the heater had zero issues for the next three years and counting. Starting an engine with a block heater plugged in does nothing to damage the block heater or shorten its lifespan assuming that the cooling system has the proper amount of coolant in it and air has been evacuated.

 

[rjcorazza]

Suit yourself, but there is no advantage to starting a machine with the block heater plugged in. It could be that the manufacturer is grasping at straws to explain a failure. I have never experienced a element failure and will continue to unplug the heater prior to starting.

 

[mcmxi]

Suit yourself, but there is no advantage to starting a machine with the block heater plugged in. It could be that the manufacturer is grasping at straws to explain a failure. I have never experienced a element failure and will continue to unplug the heater prior to starting.

Do whatever you like, but if you're going to emphatically state that starting the engine with the block heater plugged in will damage the block heater, I'm going to ask you to provide some explanation as to why. Paraphrasing a generic response by some customer service type is not an explanation.

I start two tractors and a truck regularly with the block heater plugged in and powered up. Once the engine is running I unplug the extension cord without any issues whatsoever and have been doing this for years. The only downside to doing this as @GreensvilleJay says is that it increases the likelihood of taking off with the extension cord plugged in.

 

[Mowbizz]

I have been starting my BX with the heater still plugged in this winter. Whether that’s the reason it failed or NOT we’ll never know. From now on as a precaution, I will unplug it before starting…just to say I’m doing something different in hopes that I get more years out of the next one. Who knows?

 

[rjcorazza]

Do whatever you like, but if you're going to emphatically state that starting the engine with the block heater plugged in will damage the block heater, I'm going to ask you to provide some explanation as to why. Paraphrasing a generic response by some customer service type is not an explanation.

I start two tractors and a truck regularly with the block heater plugged in and powered up. Once the engine is running I unplug the extension cord without any issues whatsoever and have been doing this for years. The only downside to doing this as @GreensvilleJay says is that it increases the likelihood of taking off with the extension cord plugged in.

The image below is page 177 from Phillips Temro's Technical information book:

 

[mcmxi]

The image below is page 177 from Phillips Temro's Technical information book:

Seriously, the use of the term "air bubble" is questionable here and doesn't fill me with confidence. Notice also that their only concern about plugging a heater in that isn't submerged in a liquid is the risk of causing burns. Nothing about the likelihood of damaging the heater. The heater that's supposedly damaged while immersed in coolant with the engine running.

So is the theory that coolant flow causes a region of low pressure on the downstream side of the element which causes a water vapor bubble to form? If so, that's a plausible explanation but it's highly dependent on flow rate, heater geometry, cooling jacket geometry and coolant temperature, not to mention time.

The liners in diesel engines are subject to cavitation erosion due to water vapor bubbles forming in regions of low pressure and then collapsing. This is why diesel engine coolant is often specific or proprietary.

 

[mcmxi]

Talk about perfect timing. One of my favorite YouTube channels is Squatch253 and he posted this video today. They have an L4701 but don't feature it too much. They use it a lot but the channel is about amazing projects such as restoring Caterpillar dozers, various tractors, machinery and property related. Anyway, Squatch senior installed two 450W block heaters and they fire up the tractor with the block heaters powered up. I guess they just ruined those block heaters.

I plan on installing a block heater in the LMTV M1078 with the Caterpillar engine.

 

[BobInSD]

How ?
One way,
start it up, drive out of the garage, snags the power cable ( still in....), strips it, shorts it, ZZZZAPPPP, EMI kills the computer, tractor stops....

I've done that twice this year (this winter, not since the weekend!). My previous two tractors had the heater on the left and I never forgot. This one is underneath on the right and can't be seen from the seat. I started draping a bright yellow extension cord over the hood when I plug it in. I haven't missed that one (yet). I consider myself very lucky that mine still works after not one, but two colossal screw ups.

We're supposed to have 12 inches by morning, I gotta go out and put it on the timer before bed.

 

[BruceP]

The only downside to doing this as @GreensvilleJay says is that it increases the likelihood of taking off with the extension cord plugged in.

(hand raised)

Yes, I did this once.... drove my pickup truck about a mile on paved roads at 5:30AM -15F temperature.
There were NO OTHER VEHICLES ON THE ROAD at that hour in my neck of the woods.

Pulled to side of road and the extension-cord was STILL connected to my block-heater plug with the end dragging behind my truck. (that 'locking' female plug really works well)

I still have that extension-cord and it still works just fine.

 

[DustyRusty]

I also drape the electrical cord over the hood to remember to remove it. Easy to forget to unplug it unless you do something similar. Once forgot to move the cord out of the snow leading to the shed and the snowblower ate the cord.

 

[BAP]

Easiest way to remember to unplug your extension cord is to run it through the steering wheel or if you have a cab hitch it to the door handle. As far as unplugging first or starting first, we used to plug in the loaders and tractors we used to feed and clean the cows, almost every night for 3-4 months. Never made any difference in wether they were unplugged first or last. Eventually, after a few years, sometimes they needed changing.

 

[RBsingl]

I suspect these "drive away with cord connected" incidents is one reason that Ctek uses a low force release connector between the battery maintainer cord and whatever set of connectors are used for the vehicle. I own a Corvette Z06 and later gen Corvettes come with a dedicated 12V port in the rear interior designed for using a battery maintainer. Last spring I parked next to another Corvette which had the connector part still outside the hatchback and I suspect the owner drove off with the maintainer plugged in and never realized it.

A good quality block heater is thermostatically controlled and it should not be damaged by being plugged in when the engine starts. Standby generators in cold areas have block heaters that will definitely be active when an emergency (or exercise run) results in a start and they last for many years in that service.

I do use a heavy duty relay activated by my generator to kill power to its block and oil pan heaters when it is running but I suspect most people don't bother.

Rodger