[HPsauce]

My T5 is over 5 years old, so well out of warranty, but for a while now has occasionally thrown a low coolant warning.
It's fairly "In your face" and tells you to stop ASAP, but I don't because I usually can't safely and it goes away quickly.
In fact it usually appears when the car is cold and almost immediately drives onto a steepish downhill section. It then goes off again after a minute or two.
The first couple of times it happened I had nowhere to stop anyway and it went away before I could pull over.

In all cases the level was around minimum on the header tank, so I topped it up and this generally lasted some weeks/months.
There's no sign of any drips or overflow, though I haven't done a close inspection underneath. And the system is definitely holding pressure fine.

A retired garage proprietor friend of mine had a quick look today and was of the opinion that it was "probably" a slow leak from the water pump when it was being driven.
His advice was: Don't panic, don't waste any time/expense on further investigations unless it gets a lot worse, monitor and top up as necessary and replace the water pump when the timing belt is done, though this should happen anyway.
He guessed the timing belt would be due at 7 years age, which is about 18 months away. Annual mileage isn't high so that wouldn't trigger it.

So my questions are:
1. Does this analysis sound plausible?
2. When is the timing belt due for replacement?
3. Would it be standard to also replace other belts, water pump and related items such as thermostat, guides/tensioners etc.

 

[RS3100]

My T5 is over 5 years old, so well out of warranty, but for a while now has occasionally thrown a low coolant warning.
It's fairly "In your face" and tells you to stop ASAP, but I don't.
In fact it usually appears when the car is cold and almost immediately drives onto a steepish downhill section. It then goes off again after a minute or two.
The first couple of times it happened I had nowhere to stop anyway and it went away before I could pull over.

In all cases the level was around minimum on the header tank, so I topped it up and this generally lasted some weeks/months.
There's no sign of any drips or overflow, though I haven't done a close inspection underneath. And the system is definitely holding pressure fine.

A retired garage proprietor friend of mine had a quick look today and was of the opinion that it was "probably" a slow leak from the water pump when it was being driven.
His advice was: Don't panic, don't waste any time/expense on further investigations unless it gets a lot worse, monitor and top up as necessary and replace the water pump when the timing belt is done, though this should happen anyway.
He guessed the timing belt would be due at 7 years age, which is about 18 months away. Annual mileage isn't high so that wouldn't trigger it.

So my questions are:
1. Does this analysis sound plausible?
2. When is the timing belt due for replacement?
3. Would it be standard to also replace other belts, water pump and related items such as thermostat, guides/tensioners etc.

I can't really answer #1 except to say that if the level in the header tank keeps dropping, there is clearly a leak/pressure loss somewhere or it wouldn't be happening. But if it is dropping as slowly as you say, it probably wouldn't register on any tests, the cost of dismantling and testing/inspection would far exceed the minor inconvenience of keeping an eye on the level at the moment, so I would agree the best course of action is to monitor the rate of coolant loss and keep an eye on it for now if there are no obvious external leaks or excessive water vapour in the exhaust.
#2 I believe timing belt replacement on the VEA engine is now 90,000 miles or 10 years. It used to be something like 140,000 miles or 10 years, but they shortened it.
#3 The belt kit (genuine Volvo at least) comes with the pulleys and bolts that should be replaced with it (adjuster and idler pulleys). The crankshaft pulley vibration damper should also be replaced, along with the centre pulley bolt. The water pump on the petrol engines is electrically operated and attached to the side of the block. It has no connection with the timing belt and I don't think any routine replacement interval is mentioned.

 

[HPsauce]

Thanks, I also found something on Wikipedia that says the same about an electric water pump.
So, hopefully it can be inspected and replaced independently and with less difficulty/cost?
Unless anything dramatic happens in the interim I'll wait to the next service before enquiring about both the water pump and timing belt.

 

[HPsauce]

So, strange events today, the heating isn't working, very noticeable as it's a cold day. Did 2 long (each over an hour) journeys and not an iota of heat.
The fan didn't want to speed up whatever I set the cabin temperature to, but I suspect that's a control mechanism with a water temperature sensor saying the core was still cold.
Interestingly I had the bonnet open before setting off and the coolant level in the header tank looked fine. No coolant level warning.
It may have been like this for a while, only short journeys recently.

One REALLY interesting diagnostic symptom though. I went round a long fast S-curve on a motorway junction and it fired up for a brief period.
I heard the fan speed up and felt warmth as we straightened up but it very soon faded away. So some hot coolant must have moved in the turns!

For those that know I was leaving the M25 Eastbound onto the M11 Southbound which is a long tight right then a less long tight left as you speed up to join the M11, so both (can and did) have significant sideways G. I don't know which turn kicked it off, though I might go and experiment on some local roundabouts and bendy roads tomorrow to see if left or right differ.

Whatever the result of that this tells me there's probably coolant not getting into the HVAC system, but why? Could it be an airlock or is there a pump for that job separate from the main engine water pump?
The fact it came on without touching any controls suggests there are no problems with sensors, valves, flaps etc. probably just a lack of hot liquid in the right place.

Thoughts anyone?

 

[HPsauce]

So after a few experiments I've concluded that it's not sideways G, but rearwards G that's needed. Accelerating hard up steep hills seems to get it working. And that M25/M11 junction does finish going fairly steeply uphill where you accelerate to join the M11 carriageway.
I found a few steep roads nearby and burnt some petrol. For now I have heating.....
Explanation anyone?

 

[HPsauce]

Touch wood I'm back to normal. Solution (for now) as follows:
Park facing uphill on as steep a slope as possible with the engine cold. (Cool enough to safely remove the coolant pressure cap)
Remove coolant header tank cap (carefully) and top up to at least minimum if necessary. Run engine (with cap off) until temperature reaches normal and let idle for a few minutes.
Turn heating controls to HI to see if you have heating. It won't kick in unless there's hot water reaching the HVAC system.
You will hopefully observe bubbling from the thin overflow/vent pipe the connects to the front of the tank; the pipe seems to emanate somewhere around the nearside of the engine.
Temporarily replace cap if you need to move the car then allow engine to cool with the cap off. Replace before driving anywhere!

Repeat the process as often as necessary until all seems normal. You might need to wait a day in between for proper cooling.

 

[RS3100]

Sounds like you had an airlock in the cooling system. Has it previously been drained and refilled, and if so was a vacuum kit used?

 

[HPsauce]

Thanks, it does indeed sound like an airlock.
The ONLY people who have EVER worked on the car are my local Volvo Main Dealer at annual services (five so far) who are part of the Endeavour Group.
Do you know if a coolant change is part of the service schedule for a T5?
I would assume they know how to do such a job correctly, if indeed they did.

I can't readily find all the paperwork to check. But I will eventually and report back.

 

[RS3100]

I don't think a coolant change is included in any service interval. It's supposedly "for life" with modern coolant formulations, although a change is normally recommended after about 10 years. I can only imaging it might have been changed or topped up if some work was done which necessitated it. If you've only had scheduled services and no other remedial work that should be discounted.

 

[HPsauce]

Hmmm, gases are still finding their way in somehow, so cabin heating disappears and can be reinstated by facing steeply uphill and letting the system vent.
As a precaution I've ordered a simple combustion leak tester kit to see if combustion gases are getting into the coolant or it's something else.
I've not topped the system up recently and the oil filler cap looks "normal" on the inside. No dipstick on these engines to look at the oil sadly.

 

[HPsauce]

Currently the electric water pump seems the most likely culprit, can anyone describe where it is and how to inspect it - looking for for leaks?

 

[RS3100]

The most likely culprit IMO bearing in mind that air seems to be replacing water in a pressurised system, is the head gasket. Have you tested for exhaust gases in the coolant as you intimated? The other test would be a pressure test of the cooling system which would also indicate if pressure is leaking back into a cylinder without the engine running.

 

[HPsauce]

I only ordered the combustion gas tester this morning........

But I have done a pressure test and it seems OK. In fact it's typically even pressurised when stone cold, as is revealed when loosening the cap.

 

[RS3100]

You'd expect it to be pressurised even with a head gasket failure, if pressure from a cylinder is pushing air into the system. I can't see the coolant pump being responsible. For air to get into the system through the pump and from the external environment you would also be seeing obvious signs of an external coolant leak.

If there are no signs of external leakage, the coolant that is being replaced by air must either be blowing out of the pressure cap if the system pressure exceeds maximum, or into a cylinder and being burnt by combustion and/or leaking into the oil.

I would do a proper pressure test of the cooling system with the spark plugs removed, and also a leak down test of each cylinder. If the gas test is positive, you may still need to do a leak down test to determine which cylinder(s) are affected.

Hopefully, that will rule the possibility out, but I can't see any other explanation if there are no external signs of coolant loss. If air is getting into the system, the displaced coolant has to be going somewhere.

 

[HPsauce]

Thanks for the explanation, not looking good is it? I'll update when I've done the gas test.

 

[HPsauce]

Well I couldn't do a gas test and as it's in for service today I've paid the local dealer a small fortune to investigate.
Nothing obvious found so they're doing a drain and refill to eliminate any airlocks in the cooling system and we'll go from there.....

 

[HPsauce]

Update. They say they've been talking to Volvo technical who are not satisfied and want to do more investigations.........

 

[RS3100]

At least it seems that they are taking it seriously. Fingers crossed they find the cause and it's nothing too serious or costly!

 

[HPsauce]

Well they still have the car and have been talking to "someone" - implication is a technical group inside Volvo.
Latest is that it might actually be the water pump and more tests are required........
They don't need the loan car back until at least Tuesday they say if that's fine with me (which it is).

 

[HPsauce]

Further update, I've been talking to the technician who's been liaising with Volvo and testing the car. Definitely a failed water pump.
None in the country so it's wait several days until they can get one from Sweden.

And I'm also not convinced that the head gasket isn't leaking, maybe damaged by overheating due to the failed pump?