XC90: Intermittent temperature/shift issues

[whilewait]

We had an issue with our '14 plate XC90 (115k miles) which was described here: https://www.volvoforums.org.uk/showthread.php?t=339205 - initially we thought it was a gearbox issue, though, it seems that this was down to a transmission fluid leak from the union joint at the top of the radiator.

Since had this fixed and the transmission fluid refilled appropriately. All appeared well, and we had been driving for 2-3 weeks with zero issues with general usage - shifting is absolutely fine, until we went to tow our caravan back to storage. With the car up to temperature before starting, we managed 6 miles before the temperature gauge started to rise to about 3/4 on gauge, and was slow in shifting up from (I think) 5th to 6th.

We since have seen similar behaviour happen 2 or 3 times without towing, but only on dual carriageways - last example I was doing a steady 70mph on flat, 6th gear, ~2.2k RPM. The gauge went from normal (mid way) to just over 3/4 on the gauge in about 15 seconds - after this I had to slow for a junction, but on pulling away again, with the temperature returning to normal, it was a little slow in changing up from 5th to 6th, but it did do so successfully and subsequently everything went back to normal.

Prior to the issues with the gearbox/trans fluid leak, we've not had any other issues with the temperature or shifting. There are no warning lights on the dash when this happens, and it usually cools back to normal reasonably quickly after lifting off, and as yet with no repeat.

The mechanic looking at it (they are a gearbox specialist) is unsure where to go with it - in his testing, he can't get it to reproduce the issue, and there are no relevant codes in the engine or gearbox - everything appears to drive perfectly normally. His thoughts are that it is engine/cooling system related, but without throwing parts at it, we're both not sure where to go with it - he's obviously reluctant to do a gearbox reconditioning without any obvious indication as to what might be wrong, as it appears to be working perfectly normally, though the issues have only apparently started since the trans fluid leak.

We use the car for towing during our summer holiday in France, so need to get the bottom of it so we're confident that we're not going to break down so looking for ideas as to what might be up here - can anyone suggest what we could look at here?

Some thoughts:

* Mechanic (based upon experience with another car, different make) did wonder if there was any software update available that might resolve - the last one we had on it from Volvo was around 2018 with our last dealer service (indies since)
* Timing belt/water pump replaced Feb this year.
* Radiator is about 5-6 years old after the original developed a leak
* Coolant level is normal (we had a coolant hose replaced while repairing the transmission fluid leak as it looked weakened so the coolant was checked then as well)
* No apparent leaks anywhere else that we can see
* Sticky thermostat or temp sensor issue (though it's so infrequent is this likely?)
* Never really noticed the main fan come on except when in the heat in France or when we had the lack of trans fluid issue - when should this kick in? (Is it likely to make a difference anyhow if driving at 50mph ?!)

Thanks for any ideas....

[whilewait]

This video shows one of the instances of this happening - here was travelling at a steady 70mph - temp rise starts at 30sec or so.

https://vimeo.com/954305520?share=copy

[Tannaton]

Your may have more than one issue at play here, but my strong advice would be get to diagnose the engine temperature issues first... that's the one where unresolved the car is most likely to leave you stranded and empty your bank account.


If you are not losing coolant then either you are getting air pockets in the system (head gasket or block/head cracks) or the water pump impeller is loose (had this on VW before but never heard of it on a Volvo) or potentially a sticking thermostat (unusual on a volvo). Could also be the sensor but again that would be unusual. Can't think of anything else?

I'd change the thermostat first and flush the cooling system as that's the simplest and cheapest option. you might want to try removing the coolant expansion tank cap whilst the engine is stone cold after a long run - do you get a hiss of gas (you shouldn't). I wouldn't normally advocate doing any work without a confirmed diagnosis but this is a tricky one.

[whilewait]

Thanks, it is frustrating - even more so as noone has much idea where to start from...

I'll check out (or get the mech to check out) the coolant pressure - perhaps a hydrocarbon check in the coolant as well - thermostat and coolant flush is probably a reasonable start as well.

[TruckbusUK]

Just a comment, but surprised you needed the pump changed in Feb this year, normally they run forever and as long as the bearings are smooth then Volvo say it doesn't need changed.
Was it replaced with a genuine Volvo pump, or another manufacturers part?

[whilewait]

Believe it comes as part of the kit with the timing belt - that was replaced as per service schedule (10yrs/120k miles). I'll have to check which manufacturer.

[TruckbusUK]

Hi, I dont believe there is a "kit" from Volvo that includes the pump, the belt is indeed to be changed at 10years or 108K miles on your age of XC90.

In my experience Volvo pumps are really robust, I have had one still ok at 327k miles on a 240 I owned.

[kdst5]

I was surprised how many genuine D5 timing belt "kit" are being sold on eBay with a water pump. I presume that the "kit" was something the person selling had put together as a "kit". My guess would be so many people expect to do the water pump that it easier to just sell it than having to explain it is not normally needed or lose the sale to someone who was selling it with a water pump

[whilewait]

The saga continues.

Thermostat & Temp Sensor replaced with genuine Volvo parts. No hissing at coolant when cold, and passed the test for hydrocarbons in the coolant, so think head/head gasket are likely OK. Drives around fine in general town use and 10-12 mile runs at 50/60, but after 2-3 miles on the dual carriageway at 60 with caravan on back, temp gauge started to rise again up to about 3/4 way on dial.

Fan runs loud when it happens and gears drop into 5th (and later 4th). Pull over, temp returns to normal, and shifting back to normal - I'm under the impression this is working as it should (to reduce output to prevent overheating).

Given it can run fine in general use around town, but seemingly has a lack of cooling capacity when being worked hard, question is where does the lack of cooling capacity lie. Issue with (new) aftermarket water pump? Will cooling flush have any effect given we've had the coolant completely changed in sorting out the earlier hose replacement? If so, what exactly needs to be asked for here?

We will get the software updated (last update 2018) in due course, but I feel that's not the fix.

[Kev0607]

I'm suspect of the water pump, which isn't genuine.

You purchased a "kit" that had a pump in it. Genuine Volvo cam belt kits don't include a water pump. The reason being is they're so reliable that they don't need to. I think the seller likely added the pump and made his own "kit", as kdst5 said above. Its likely that pump is a cheaper aftermarket one, which could create problems.

A water pump is far cheaper than a head gasket. I'd suggest you buy/fit a genuine pump (buy it from Volvo) and take it from there.

When you said you had the coolant changed, what colour is the coolant? Genuine Volvo coolant is a blue/green colour. If your car has another colour coolant in it, change that and replace it with genuine Volvo coolant too.