Block heater failed

Yesterday morning I plugged in the block heater on our 2010 Prius. Luckily I had the hood up for an oil check, because about a minute later I started hearing a popping sound, smelled something burning and a bit of smoke.

Luckily it subsided quickly, before I even got to unplugging it; guess it ended up as an "open" circuit. No household breakers tripped either.

I phoned local dealership parts department, asking about price and availability of the block heater. They kindly checked if there was any outstanding service bulletins or whatever, but there isn't. Anyway, there are blockheaters coming in about 2 weeks, and he reserved one for me: $90 CDN.

I decided to try to remove the one installed, both to see that I could do it, and to verify it was failed, and how. I opted to leave the wipers and cowl as-is, try to reach it mostly from below. With a little help from the internet I managed to extract it.

Some observations:

1. The electrical wires failed directly beyond the plug into the block heater heating element. I unwrapped the white tape at the junction, it was somewhat brittle. The inside is black with soot, and has a burnt smell.

2. The plug into the heating element seems to pretty much welded on, and the plastic of the elbow connector is brittle/fragile. I only pried it up slightly before it started coming apart, so I stopped, left it thus.

3. Both the bore and the heating element look perfectly clean. There's no evidence of heat transfer grease. Not even the very tip of the heating element.

We got this installed at time of purchase ($400 charge). We've used it very regularly, for going on nine years now. I'm a little concerned about the clean appearance, doubt the heat transfer grease could have completely vapourized and left the element completely clean looking.

I also have an ongoing concern, that a replacement block heater might do the same thing, down the road, and we wont be so lucky.

Tempering that thought: maybe the heat transfer grease was never applied, and this meant it was working less efficiently, and lead to the overheating and failure??





^ perfectly clean, as it came out.

Anyway, emailed the above story to the Service Manager, and he got back to me: they will spring for the cost of replacement block heater, and they would like the old one, want Toyota to have a look. (My paranoid side: they want to destroy the evidence?)

Anyway, I'll give that go. I'm a little gun-shy actually, don't want to incinerate my car and/or burn down the house...

Some info:
old p/n: PU140-00900
new p/n: PU140-00905 (hopefully improved)

Techno-Fandom block heater install link:

3rd-gen block heater

Toyota info attached:

 

Hey I gave that block heater a work out.

Here's a great video for showing the Toyota block heater location. It's explained in the first minute or two, and then he rambles on. Very peaceful voice though, if you need a nap.

 

No, it was dry as a bone. And very clean, not like something was there, but dribbled out over time.

Yeah I'm just using Toyota's terminology. From the attachment:

84K kms, roughly 53K miles. We've used that block heater a lot, pretty much before every cold-start.

 

I use it year 'round.

 

I don't think it's that practical on a Plug-In, would be most effective on days where you commence driving in hybrid mode. If you pre-heat the coolant, but then drive 20~30 miles electric-only, most of the heat will dissipate?

 

Earlier Priuschat discussion, on the efficacy of the heat-transfer "gel": Post #3 is a little troublesome, @efusco notes that he installed his block heater with the heat grease, and when he removed it two years later the grease was more-or-less gone.

Enigne block heater gel | PriusChat

Our Honda block heaters were always immersion type, didn't have that issue. OTOH, block heater install spilled a lot of coolant.

 

I found coolant temperatures plateau around 25~30C above ambient. That typically takes around 2 hours, a bit more in cold winter mornings. That basically gives you a "leg up" on warm up, and gives the engine an easier time I'd think.

 

The block heater can be plugged into a timer (wall mounted at the outlet), then run an extension cord. That helps with the plug in, at least.

Speaking of extension cords, it's good to consider what will happen if you forget to unplug; it will happen eventually. Make sure the extension cord is secured on something, and the block heater cord will pull out easily, and is also well secured so it won't end up dragging on the ground.

I've broken all of the above rules...