IS300h low coolant - check hybrid system message

[Undecided400]

Hi everyone. I have a 2014 IS300h and have been enjoying it, fault free for almost three months now. 
 

However, last night while driving the message ‘Check hybrid system stop the vehicle in a safe place immediately’ came up along with the yellow warning triangle light and check engine light. The car was still driving normally. 
A short while later the battery/hybrid display on the screen showed that no charge was going to or from the battery/generator or to/from the engine. I was running on the ICE only at all times and felt like reduced power. 
Around 8 miles later I could stop and did so. 
 

I’m not technically or mechanically minded and don’t have access to diagnostic software. I decided to drive 35 miles back home rather than continue my journey. While driving back the sound of some fans started very loudly (sounded like they were coming from the front under the bonnet annd didn’t change with the air con on or off) and at no time did the hybrid system seem to kick back in. The Battery indicator mostly stayed the same but did sometimes reduce, but then go back up again without ever showing any ‘flow’ like it usually would. 
 

Today, first thing when it was light, I checked under the bonnet to find that the coolant tanks were both empty. I have filled up with the proper Toyota pink coolant that a friend had and started the car. The warning remains but there is no fan noise and so far, after 5 minutes of running in Ready mode in park, the level has remained the same. 
 

To the experienced and knowledgable good people on here, what is the likely issue and is it all bad news? What are the likely costs that I’m looking at? 

I’m trying to remain optimistic until the dealers open again on Monday. 

[ColinBarber]

How much coolant did you have to put in?

When you say both tanks can you be clear on which ones, as there are three caps you could put coolant into.

[Undecided400]

14 minutes ago, ColinBarber said:

How much coolant did you have to put in?

When you say both tanks can you be clear on which ones, as there are three caps you could put coolant into.

The more rounded one which has a label on it saying ‘Inverter coolant’ around the middle of the engine bay, near the engine itself and there is another at the front of the engine which has a small rubber hose coming from it at the cap, an overflow I think. 
 

It was a one litre bottle and almost all of it went in before bringing it up to just below the full mark of the inverter coolant bottle. The front tank also then went up to between the two marks after filling it up. There’s a small amount left from the one litre bottle.

 

Thanks so much for answering and assisting. I’m concerned as to what this all could mean and the potential expense ahead. 

[ColinBarber]

What is odd is that the engine cooling system and the hybrid cooling system are independent - a leak on one cannot affect the other.

Do you know if the levels were fine before you had this problem, or this could just be a slow leak over a long time period?

 

Ignoring the engine coolant for now, the main issue is the hybrid system (inverter) cooling system. It obviously detected an issue and shut down. It only contains around 2.2 litres so almost half has disappeared.

It is quite a small and simple system so it should be easy to diagnose with a pressure test and fix. Keep a careful eye on the level until you can get a garage to look at it.

 

[Undecided400]

16 minutes ago, ColinBarber said:

What is odd is that the engine cooling system and the hybrid cooling system are independent - a leak on one cannot affect the other.

Do you know if the levels were fine before you had this problem, or this could just be a slow leak over a long time period?

 

Ignoring the engine coolant for now, the main issue is the hybrid system (inverter) cooling system. It obviously detected an issue and shut down. It only contains around 2.2 litres so almost half has disappeared.

It is quite a small and simple system so it should be easy to diagnose with a pressure test and fix. Keep a careful eye on the level until you can get a garage to look at it.

 

Thank you for your help and explanations Colin. Much appreciated.

I did get the coolant topped up in the ‘inverter coolant’ bottle the day after I got the car as it was on the ‘L’ line. Kept an eye on it a for a couple of weeks after that and the level hadn’t moved so thought no more of it.

You would be inclined to say it could be a small leak somewhere then?
 

Would any issue with the inverter or inverter pump itself ever cause such symptoms and loss of coolant? 

And would driving it last night with no / very little coolant have caused damage to the inverter or pump? 
 

I’ve topped it up for now but the warning message still remains. Will that clear itself or does it need a dealer to clear it? 
 

Thanks again.

[Undecided400]

So after having topped it up I have been out for a drive - 5 miles in total.

Warning message is still there but after the drive I checked the coolant levels again and the one for the hybrid system (marked inverter coolant) is way down past the ‘L’ mark again. 
The one at the front of the car, for the engine I think, is still on the same mark but looks wet as if some has spilled over from the small rubber overflow tube. 
 

Clearly when the car is in drive coolant is being lost. While running in Park, none is lost. I’m baffled. 

[PaulWhitt20]

Was the last service by a Lexus Dealer? If so you should have the 10 year warranty. 

[ColinBarber]

2 hours ago, Undecided400 said:

Warning message is still there but after the drive I checked the coolant levels again and the one for the hybrid system (marked inverter coolant) is way down past the ‘L’ mark again. 
The one at the front of the car, for the engine I think, is still on the same mark but looks wet as if some has spilled over from the small rubber overflow tube. 

It's possible the air was just purged from the system through the vibration of driving the vehicle. I'd top up again and take it out for another small drive.

Not sure whether the error will clear itself or it needs to be cleared, either with a diagnostic tool or disconnecting the Battery. Given that the coolant level is still going down at the moment it is probably best that it is locked out for now.

[Undecided400]

31 minutes ago, PaulWhitt20 said:

Was the last service by a Lexus Dealer? If so you should have the 10 year warranty. 

Last service by Lexus was back in 2019 and since then just independent garages. 
 

I haven’t had it long myself but it’s due a service now anyway so I will be having a full service along with a hybrid health check as soon as they can fit me in. Hopefully this week anyway. 

[Undecided400]

24 minutes ago, ColinBarber said:

It's possible the air was just purged from the system through the vibration of driving the vehicle. I'd top up again and take it out for another small drive.

Not sure whether the error will clear itself or it needs to be cleared, either with a diagnostic tool or disconnecting the battery. Given that the coolant level is still going down at the moment it is probably best that it is locked out for now.

That eases my mind somewhat. Hopefully it was just trapped air that had taken a long time to escape the system. I’ll keep an eye on it. 
 

I don’t have any more coolant to top it up with at the moment. But I did take it for another 5 mile drive. On starting it again - no fault. No warning lights or message and the hybrid system is back working as it was before, including the regenerative braking. 
 

Checked the coolant level again after and it hasn’t moved this time. So while it is below the ‘L’ line, it hasn’t used more and it’s driving as it did before this all happened. 
 

To say I’m perplexed would be an understatement. I’ll get a hybrid health check done as that includes checking the coolant system anyway. 
 

Just as a side note - could the 12v aux Battery causes false readings to do with temperature/coolant pressure etc? Just seems strange that it happened so quickly and has resolved itself so quickly too. 
 

Thanks for the replies and help.

[ColinBarber]

I suspect you have a small leak and the level got to the point where the pump couldn't circulate the coolant correctly and the hybrid system shut down because of overheating. Whatever error was produced seems to have cleared by the normal 3 good engine start up cycles rather than needing manual intervention.

The noise you heard would have been air in the electric cooling pump.

You really don't want this to happen again so you should top up the coolant before you need to go on a long drive, even if it means adding water as that is better than nothing - but then get it all drained and replaced with proper Toyota pink coolant when the issue is fixed.

 

A low 12v aux Battery can cause all sorts of weird error messages, but they normally occur on start up, not once the engine is running as the hybrid system is then providing all the vehicle electronics with 14.4 v. This also isn't just a Battery issue, you had noises that suggest air in the system and a low coolant level.

Hopefully it is something simple such as a hose split or not clamped properly. I've not heard of these water pumps failing but it is possible. The pink coolant is easy to spot so it should be easy to tell where it is coming from.

[Undecided400]

54 minutes ago, ColinBarber said:

I suspect you have a small leak and the level got to the point where the pump couldn't circulate the coolant correctly and the hybrid system shut down because of overheating. Whatever error was produced seems to have cleared by the normal 3 good engine start up cycles rather than needing manual intervention.

The noise you heard would have been air in the electric cooling pump.

You really don't want this to happen again so you should top up the coolant before you need to go on a long drive, even if it means adding water as that is better than nothing - but then get it all drained and replaced with proper Toyota pink coolant when the issue is fixed.

 

A low 12v aux battery can cause all sorts of weird error messages, but they normally occur on start up, not once the engine is running as the hybrid system is then providing all the vehicle electronics with 14.4 v. This also isn't just a battery issue, you had noises that suggest air in the system and a low coolant level.

Hopefully it is something simple such as a hose split or not clamped properly. I've not heard of these water pumps failing but it is possible. The pink coolant is easy to spot so it should be easy to tell where it is coming from.

Thanks Colin. I know that to many who visit these post, as well as myself, your shared knowledge is so invaluable. 
 

Thank you so much for taking the time to respond and share your wisdom and so often. I really mean that. 

[Kermitpwee]

Water pumps are being replaced under warranty in Ireland on the is300h , I have no idea about the UK.