Heater 'growling' when engine is stopped

This autumn a new noise has appeared in my UK 2004 Prius. When the heater is calling for heat and the engine is not running (i.e. coolant temp is above 63degC), a sort of 'growling' noise can be heard somewhere inside the heater core or beyond. A low-pitched rattling/rumbling which sounds rather like coolant mixed with air-bubbles going through a pump.

The only change there's been that might account for this is that I had Jemca Toyota in Bracknell carry out the hybrid coolant pump replacement (campaign 2509L). But I thought the heater was only fed by engine coolant, not hybrid coolant?

You can hear this noise stop when the engine starts, and restart when the engine stops. The Haynes manual seems to indicate that there's a pump for just this eventuality.

Any thoughts or ideas?

Richard (squarewheels)

 

Many thanks for replying so quickly. Good point... just went outside (with headtorch, it's nighttime here in Blighty ) and looked. The coolant was about one inch below the filler-neck's top; the level rose if I squeezed the hose at the right-hand end of the radiator.

I've topped up the coolant-reservoir 3 times (350g each) in nearly 4 years / 55,000 miles, I think it weeps out around the coolant-pump seal (but in a manner that I took Hobbit to suggest is not cause for concern).

What might I look at next?

Is it worth investing in the Mini VCI / Techstream (as mentioned by Britprius) in order to bleed the engine coolant properly?

Many thanks!

 

I'll try that – thanks. Seems probable that there is a bit of air in there somewhere.

Some coolant-crust on the underside of the air intake hose and on various other parts that are in the line of fling . In nearly 5 years that I've owned the car it's always flung a little line of coolant-crust onto the inside of the bonnet – not much – and as the level is healthy currently and I only added a total of 1 litre in all that time, I don't sense that the pump is deteriorating. As Hobbit said, it's better that a small amount weeps past the seal and lubricates it than the seal run unlubricated; I ought to adjust the tension on the pulley and see if this reduces (further still!) the coolant-consumption.

But if it's pulling air in through there as the engine cools, then that's not so good. Maybe that's happening?

 

Thanks John, and indeed thanks Patrick Joe & dorunron for your wisdom.

Richard (Squarewheels)

 

Thanks for that, John. I like the idea of the Mini VCI tool anyway and at the sort of price mentioned (and WinXP already virtualised on my Mac!) it seems an obvious thing to go for. Good tip!

 

Fair enough, and many thanks for posting the writeup - I shall add it to my worksheet of things to do in due course. I guess at 10 years it's a reasonable time to change the serpentine belt anyway before it ossifies. Preventative maintenance always good.

BTW I wish I'd been reading a related post from you before I took the splash guard off recently (to help with changing the WS ATF, a little late at 70k but it wasn't too thin/filthy/particle-y) – I spent ages failing to understand the 'square' plastic fixer that has 'ears' in the wheel-arch!

You've hit on one of my main bugbears of owning a UK Prius – things we can't look up and have to guess/infer! The Haynes manual, the Bentley manual, everything at techinfo... it's all for USA Priuses, and so refers to the CHS tank and to rear drum brakes (UK Prius has discs at all 4 corners).

Ah. Again, fair point so I'll be guided by that. So with the radiator-cover off and removing the radiator-cap (the one that undoes by about 160 degrees) what you're saying is that the coolant should be right there, lapping over into the overflow tube towards the centre of the car, not sitting an inch down the narrow neck that leads down to the elbow by the top of the radiator?

Many thanks for your kind assistance. Richard (Squarewheels)

 

Thanks Patrick. The fastener is easier once I saw what it should have looked like before I tried to destroy it with pliers Thanks for the link to the EU website. I'll try adding coolant to the radiator neck as a stop-gap measure.

 

Thanks for that. Seems very probable that air is getting into the heater core circuit and making the 'growling' noise in the heater-pump when it runs. Will inspect all.