03 V40 Struggling to get up to temperature fully

[Fabi05]

Hi everyone,

Been looking around the forum for this issue and I can't seem to pin it on anything.

I can start and drive the car for a few minutes and it'll get up to just under the middle of the temperature gauge (image attached).

If I let it idle for a while or if I drive it unusually hard it'll usually make it to the middle of the temp gauge. I've also noticed that having the AC or fans on heat sometimes seems to make it struggle to reach the middle (still not 100% sure if this is a coincidence or related)

I've seen a few people mention the thermostat and how to check (something along the lines of starting it from cold and feeling the top coolant hose by the thermostat for it to get warm) but it doesnt seem to result to what they've said indicates a faulty thermostat.

Does anyone have any similar experiences or any ideas as to what this could be or how to diagnose anything? If I can't find anything I'll likely look into buying a thermostat as they seem to be relatively cheap but I thought I'd ask incase anyone might have any input.

(The image below was after a 15 minute drive at around with a good few minutes at 60mph - however ive had 1+hr drives with the temp needle rising to middle and falling back down to just under the middle marker)

[Clan]

Originally Posted by Fabi05

Hi everyone,

Been looking around the forum for this issue and I can't seem to pin it on anything.

I can start and drive the car for a few minutes and it'll get up to just under the middle of the temperature gauge (image attached).

If I let it idle for a while or if I drive it unusually hard it'll usually make it to the middle of the temp gauge. I've also noticed that having the AC or fans on heat sometimes seems to make it struggle to reach the middle (still not 100% sure if this is a coincidence or related)

I've seen a few people mention the thermostat and how to check (something along the lines of starting it from cold and feeling the top coolant hose by the thermostat for it to get warm) but it doesnt seem to result to what they've said indicates a faulty thermostat.

Does anyone have any similar experiences or any ideas as to what this could be or how to diagnose anything? If I can't find anything I'll likely look into buying a thermostat as they seem to be relatively cheap but I thought I'd ask incase anyone might have any input.

(The image below was after a 15 minute drive at around with a good few minutes at 60mph - however ive had 1+hr drives with the temp needle rising to middle and falling back down to just under the middle marker)

Those are classic symptoms of a thermostat which is stuck open. That's the first thing to change. Get one from volvo which will have the correct opening temperature. Its quite rare for a volvo to need a thermostat however old it is ...

[Kev0607]

Agreed. Sounds like a thermostat issue. Not reaching temperature when it should won't help your fuel economy either.

Don't buy a cheap thermostat. Get a decent one.

[Fabi05]

Cheers for the replies, I'll be ordering a new oem thermostat soon. If im not mistaken the temperature sensor for the coolant is just by the thermostat - would you guys suggest replacing that too whilst I'm in there or is that generally reliable enough to not worry about?

I also plan on flushing the coolant whilst Im at it as it looks as if it's seen better days! I've seen others say flushing can be done with distilled water to clean out the system, is this as simple as draining the current coolant, filling with distilled water and going for a small drive, drain then repeat once or twice?

[Kev0607]

Originally Posted by Fabi05

Cheers for the replies, I'll be ordering a new oem thermostat soon. If im not mistaken the temperature sensor for the coolant is just by the thermostat - would you guys suggest replacing that too whilst I'm in there or is that generally reliable enough to not worry about?

I also plan on flushing the coolant whilst Im at it as it looks as if it's seen better days! I've seen others say flushing can be done with distilled water to clean out the system, is this as simple as draining the current coolant, filling with distilled water and going for a small drive, drain then repeat once or twice?

Temp sensor is generally reliable. Being honest, so are the thermostat's, but I guess everything has a life span. I guess whilst you're there, you could replace it.

Flushing the coolant is a good idea (make sure you get the right coolant!). Yep, drain the old stuff. Fill with distilled water, go for a drive to get it up to temp, drain again. You might need to repeat the process to get the best results. You'll be able to tell when you drain the distilled water if its still dirty or not. Repeat until what you drain is as clean as you'll get it, then do your final fill with the correct ratio of coolant to water (50/50 usually).

[Cloth Ears]

If you're going to replace the temp sensor too, I might suggest doing this in stages. So, thermostat first, see if the issue resolves. If not, temp sensor swap, see if the issue resolves. That way you'll have a good idea which was the faulty item. If you replace both at the same time, assuming the issue resolves, you can't tell whether it was the thermostat or the temp sensor which was playing up.

[Fabi05]

Does anyone happen to know the torx bolt size for the thermostat housing? I've bought a torx set that has T30 and T40 on the upper end but T30 feels like the tiniest bit too small and 40 does not fit - just wanted to confirm as I really do not want to end up accidentally rounding the screw!

[Simmy]

socket type torx bits tend to be better as you can apply downward pressure to stop it slipping which is more difficult with the bent allen key type

[precisionguesswork]

Originally Posted by Fabi05

Does anyone happen to know the torx bolt size for the thermostat housing? I've bought a torx set that has T30 and T40 on the upper end but T30 feels like the tiniest bit too small and 40 does not fit - just wanted to confirm as I really do not want to end up accidentally rounding the screw!

You're not going to round them off. If you are really worried using some penetrating lube, let it sit for 10-15min. Then crack on

[lynns hubby]

Penetrating oil is OK for exposed threads. No good just spraying the torx heads and hoping it will get down under the head if it goes into a blind tapped hole. The head being made of steel will have a bite into the softer aluminium housing. Allays amuses me when I see the manuals etc coming out with the same statement.