High Coolant Temperature Warning Light On Gen2 Prius

[kissinger]

So I've had this Prius around 3 months and it's never given me a problem. I go to start it this morning (which I should mention has been by far the coldest morning since I've had it) and it wouldn't properly turn on initially, but when I turned it off and then back on it started as usual. I thought everything was fine and just put it down to the cold weather.

Then when I got onto the motorway I got a warning light on the dash followed by a 'problem' notification and high coolant temperature warning light on the info screen. The car didn't seem to degrade in performance at all, but this light remained on for most of the rest of the journey.

Has anyone seen this happen before and does anyone know what might be wrong, if anything (I'm hoping it's just a sensor error due to the cold weather)?

It was serviced just a couple of months ago at my local Toyota dealer and it's ran fine both in the city and on the motorway since then.

[PeteB]

I've never heard of the high coolant temperature light coming on in a Toyota Hybrid; I've had 6 Prius in nearly 14 years and covered over 260,000 miles. Also, I managed a fleet of over 200 Prius for a while.

First thing, did you check the coolant level?

It could be a sensor or wiring fault, but if the engine really is running hot it's bad news and if it were me I'd be getting it checked out urgently.

[kissinger]

I've just checked my levels and the engine coolant reservoir seems fine (it's full right up to the start of the upright bit that has the cap on it), but the inverter coolant reservoir was actually quite low -- way below the 'Low' mark, with only around an inch left in it. I suppose that would be my problem. I'm sure that would have been replaced at the service only a couple of months ago, but then again I have done a lot of miles lately so that's maybe why it's ran down.

The manual says to only use 'Toyota Super Long Life Coolant', but I can't seem to find that for sale in the UK. Would this be an acceptable alternative?

http://www.halfords.com/motoring/engine-oils-fluids/antifreeze/comma-g48-antifreeze-and-coolant-rm-5l.

[drives]

Did Toyota tell you they'd changed the coolant? Its a pretty long interval, before its due to be changed. I certainly wouldn't rely on them to check levels properly either so wouldn't necessarily assume it has happened in the last couple of months. I'd get the right stuff from the Toyota dealer (assuming that's what's already in it) top it up and see if it solves the problem, and keep a close eye on the level to see whether there's a leak.

[kissinger]

Having looked at my documentation from the dealer it would appear that they didn't actually do anything to the coolant, so perhaps that explains it.

I will buy some SLLC tomorrow, but is it definitely okay for me to just top up, bearing in mind I don't know which coolant brand the previous owner put in it (even though I can see it's the right colour -- i.e., pink)?

[drives]

Having looked at my documentation from the dealer it would appear that they didn't actually do anything to the coolant, so perhaps that explains it.

I will buy some SLLC tomorrow, but is it definitely okay for me to just top up, bearing in mind I don't know which coolant brand the previous owner put in it (even though I can see it's the right colour -- i.e., pink)?

I'd make an educated guess from the service history- has it definitely (ever) been changed/is it full toyota SH? As said it's a pretty long interval, certainly for the first change.

If it's pink, then I think the chances are it will be the Toyota one. That's what I'd go for, rather than taking a punt on something from Halfords.

Plus you can get Toyota antifreeze on eBay...

[kissinger]

You know, I just remembered that I did have a bit of work done on the heating system a while ago (they replaced the water pump) and when they did that, at Toyota, they did replace the coolant, so I think I can be confident that a top up with SLLC will be fine, but I just wonder if that means that they somehow messed up the repair. Is the inverter anything to do with the heating system?

[drives]

I'd imagine that it must be the ICE coolant system that is connected up with the heater core.

Have you done any searching re: whether the warning light is definitely applicable to the Inverter coolant, ICE coolant or both? Its obviously a coincidence that it comes on and the inverter coolant is low so common sense would suggest that is the culprit...

[FROSTYBALLS]

Super Long Life Coolant available from the Official Toyota Store - http://stores.ebay.co.uk/ToyotaOfficialStore?_fsub=&_nkw=&_nkw=Super+long+life+coolant&submit=SEARCH&LH_TitleDesc=1

You could also send Parts King a personal message, giving details of your car (regn no as a minimum) and what you want.

[kissinger]

I ended up going to my local dealer to pick up some TLLC. Car seems to be working great now. It's also a bit quieter when you first start up and the engine kicks in while stationary. It sounded quite ragged for a few days there.

The guy at the Toyota parts stall said that the low inverter coolant level could have been down to one of 3 things:

1. They didn't fill it properly when they replaced it recently.

2. They did fill it but air in the system, which has since came out, accounts for the low level.

3. There's a leak.

I'm hoping it's either 1 or 2 for obvious reasons and I think I'm okay because I've never seen any patches of fluid under the car where I park it on my drive.

Thanks for the help guys.

[drives]

I ended up going to my local dealer to pick up some TLLC. Car seems to be working great now. It's also a bit quieter when you first start up and the engine kicks in while stationary. It sounded quite ragged for a few days there.

The guy at the Toyota parts stall said that the low inverter coolant level could have been down to one of 3 things:

1. They didn't fill it properly when they replaced it recently.

2. They did fill it but air in the system, which has since came out, accounts for the low level.

3. There's a leak.

I'm hoping it's either 1 or 2 for obvious reasons and I think I'm okay because I've never seen any patches of fluid under the car where I park it on my drive.

Thanks for the help guys.

Glad you got it sorted, as said just keep an eye on it. A coolant leak might not always be immediately obvious from patches underneath. I'd might not be a bad idea next time you take the car on a decent run, just keep it running, pop the bonnet open and have a good look in the engine bay and underneath to see whether there are any drips. The leaks normally manifest themselves once everything is up to operating temperature. It also leaves a white-ish residue in places where it is leaking.

[kissinger]

So bad news on this one. I filled the coolant to the max level yesterday and it's already gone down by at least an inch and a half. Surely that can't be normal?

I still can't spot any leaks on the driveway, but I did notice some steam on the outside of the front windshield, which is a bit unusual (although this was after I stopped midway through a journey to look under the hood).

Any ideas what could be wrong and what it might cost me? I will be annoyed if I have to take it back to my local Toyota dealer/garage already. I only had it serviced 2 months ago.

[drives]

Was it topped up when the car had been driven for a while/heated up or when cold? Likewise did you check it hot or when cold? Obviously level will be higher when coolant is hot.

[kissinger]

Was it topped up when the car had been driven for a while/heated up or when cold? Likewise did you check it hot or when cold? Obviously level will be higher when coolant is hot.

I topped up when cold and then checked when it was cold-ish (i.e., I had driven around 5 miles and then left it for an hour).

[drives]

Perhaps where the coolant was low this may in itself have introduced air into the system thus when topping it up there may have still been a bit of air in there somewhere?? Depends how low it was I guess. Not wishing to divert from the benefits of this forum but have you tried posting on Priuschat? That forum appears to be more DIY/technical from what I have seen and there seem to be some really knowledgeable folk on there who do their own maintenance, so someone on there with more of an idea on Gen 2 specific common faults who may be able to help.

[kithmo]

IIRC most coolants have fluorescent dyes in them these days to help locate leaks. If you can get hold of a UV-A (ultraviolet) lamp and scan it around the engine bay and underneath, in the dark, it should be easy to spot any leaks.

[drives]

Did you ever get to the bottom of this- was there a leak?