Peculiar cooling system problem

[andy-xr]

Heater matrix isn't getting flow, check and bleed system

[Faust66]

Have you made sure that there are no air locks in the system? They can give all sorts of strange symptoms. Do the top and bottom coolant hoses both feel hot? Is the top and bottom of the rad itself the same temp?

My missus has a 1999 V70 2.5 and I found that it can be a bit of a sod to bleed all the air out of the system.

With the car on level ground and the heater set to hot (to make sure there is no air inside the matrix) run the engine for 20 odd mins with the cap off the expansion tank - squeeze all the hoses you can reach to try and persuade the air out (watch out for moving fan belts etc). When you stop seeing bubbles in the coolant the system should be bled. Be warmed that you might have to repeat the process a few time.

It probably is your 'stat that is causing the problem, but it's always good practice to try the obvious (and free!) checks first.

ETA: beaten to it by Andy XR.

[Tunku]

Finlandia said:

On a Volvo T5, when at idle or driving slow it reaches normal temperature, but driving 50+ the gauge drops quickly, to rise again once slowing down. I have tried it with the torque app and normal temperature is around 84-92 on a 90 degree thermostat, on motorways it barely reaches 70.

The thermostat is new and tested to work in boiling water, no error codes, car runs fine but doesn't blow hot air inside like it used to, no leaks in the cooling system.

Could it be the temperature sensor, even if it's newly changed too? Or if anyone has any suggestions on something else?

Sounds like the new one opens all right but doesn't close all right. For the price, I'd try yet another one, preferably one recommended for the car.

[andy-xr]

The heaters on hot thing, it took me a while to work this out but what you're doing is helping the car cool when you've lowered the boiling point of the coolant (by removing the header cap)

Coolant should flow through the matrix regardless of the heater blowers, its just a flap adjuatme t that determines whether you get the hot air coming from the matrix

One other thing to check would be that you've got enough coolant in there to begin with, though I'd expect the app is reading from a sensor around the head somewhere rather than rad temps

[Finlandia]

Thanks for all the replies and help.

I will try a new thermostat before doing anything else, then get one of those IR thingies too.
I thought the Volvo cooling systems are self bleeding, leave the cap off and run the car at idle for 10 minutes and let cool, top up coolant and done?

Will try a more thorough bleeding once I have the new thermostat in as well.

[andy-xr]

Just feel the hoses to the matrix, either they've been plumbed back in wrong or there's an airlock that's stopping heat getting around that part

That doesn't solve the main problem which I think is a stat that's either fighting the fan or sticking open

[Finlandia]

andy-xr said:

Just feel the hoses to the matrix, either they've been plumbed back in wrong or there's an airlock that's stopping heat getting around that part

That doesn't solve the main problem which I think is a stat that's either fighting the fan or sticking open

The hoses to the heater matrix are thin and well insulated so cant really feel anything, but I will try bleeding the system properly once I have a new thermostat in there too.

[Sogra]

Worked in the automotive /CV/ Industrial cooling industry for many years in the past. I dont know this model but it sounds a lot like air in the system. Feel the radiator as its heating up top and bottom / left and right and you should have one part that gets hot then as the stat opens you will feel the rest of the rad heat up, you can also feel the main radiator top and bottom hoses. Depending on where the header or filler is, it is often not the highest point on the system so it helps to park one side on the kerb to raise the header. Fill with warm water slowly with the engine running leave the cap off and you should see the air bubble out, make sure you dont let it overheat. do all this with the heater valve open so the matrix has flow

Could also be a blocked heater matrix that has become full of crud when you have been filling the system / doing whatever job you were doing. The matrix has fairly small tubes for the water and have what are called turbulators in them to disrupt the flow of water to give better heating from the matrix, these get debris attching to them.

Could be the stat, leave it out and see if if the system gets hot.

Be carefull as you can get blow back (ooerr missus) when the air escapes and boiling water strips skin right off.

[anonymous-user]

My MX5 did exactly this when the head gasket had gone and there was air getting into the cooling system.

[Tunku]

Finlandia said:

Thanks for all the replies and help.

I will try a new thermostat before doing anything else, then get one of those IR thingies too.
I thought the Volvo cooling systems are self bleeding, leave the cap off and run the car at idle for 10 minutes and let cool, top up coolant and done?

Will try a more thorough bleeding once I have the new thermostat in as well.

When I changed the thermostat in my V70, al I did was take off the thermostat cover, change the thermostat, check the water loss which was negligible so didn't even bother to top up the expansion tank, which still hasen't changed after 40,000 miles. It may be different if yours has that horrible electronic thermostat that some models came with.

[morgrp]

Jimmyarm said:

Put a genuine Volvo thermostat in it

^^^This, non genuine stats are ste on T5s - I should know, I've owned several and replaced the thermostat on all of them

[Finlandia]

So I went to the local dealer and bought a new Wahler/Volvo thermostat, fitted it and bled the system with the heater on max, while keeping an eye on the dash gauge as well as the Torque app, and it works!
The car now gets to temperature and stays there no matter what.

Thanks all for your help and suggestions

[B'stard Child]

Finlandia said:

So I went to the local dealer and bought a new Wahler/Volvo thermostat, fitted it and bled the system with the heater on max, while keeping an eye on the dash gauge as well as the Torque app, and it works!
The car now gets to temperature and stays there no matter what.

Thanks all for your help and suggestions

Confused earlier in the thread in response to this

Finlandia said:

Jimmyarm said:

Put a genuine Volvo thermostat in it

It is a genuine Wahler/Volvo one, may try an aftermarket one tomorrow just to be sure.

So the original one was duff - did you get a refund or was it aftermarket?

Just to add with all Vauxhall/Opels I've had aftermarket ones can be very poor and no substitute for genuine items.

[Finlandia]

I had the top off for some work and a new thermostat was fitted during that, a genuine Volvo made by Wahler, which was the one that gave these issues, today I bought another new Volvo/Wahler thermostat, which seems to work fine.

Will be going back with the old new one tomorrow.

[morgrp]

andy-xr said:

Heater matrix isn't getting flow, check and bleed system

T5 engine has a self bleeding system - I've never had to bleed one - One of the reasons they can soldier on for years with a weeping head gasket as they are constantly relieving pressure in the system. One issue they do suffer with is cracked expansion tank caps - prob worth replacing it too - just make sure it is the correct kPa rating

[Finlandia]

morgrp said:

T5 engine has a self bleeding system - I've never had to bleed one - One of the reasons they can soldier on for years with a weeping head gasket as they are constantly relieving pressure in the system. One issue they do suffer with is cracked expansion tank caps - prob worth replacing it too - just make sure it is the correct kPa rating

That's what I thought too, but I let it run with the cap off for a while and the heater on max, just to be sure. I also replaced the cap earlier, the old one was worse for wear, with a 150kPa green one.

[Faust66]

Finlandia said:

So I went to the local dealer and bought a new Wahler/Volvo thermostat, fitted it and bled the system with the heater on max, while keeping an eye on the dash gauge as well as the Torque app, and it works!
The car now gets to temperature and stays there no matter what.

Thanks all for your help and suggestions

Good result.

Can't beat having a nice warm Volvo on those cold winter mornings!