Peculiar cooling system problem

Peculiar cooling system problem

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Finlandia

Original Poster:

7,803 posts

230 months

Monday 20th October 2014
quotequote all
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?

TooMany2cvs

29,008 posts

125 months

Monday 20th October 2014
quotequote all
Finlandia said:
The thermostat is new and tested to work in boiling water
That's nice. It's still duff, though.

Finlandia

Original Poster:

7,803 posts

230 months

Monday 20th October 2014
quotequote all
TooMany2cvs said:
Finlandia said:
The thermostat is new and tested to work in boiling water
That's nice. It's still duff, though.
Lets hope you're right, but I don't really see how it can be faulty when it opens and closes as it should in a pan of water.

ADEuk

1,911 posts

235 months

Monday 20th October 2014
quotequote all
What temp does it open at in the pan?

littleredrooster

5,523 posts

195 months

Monday 20th October 2014
quotequote all
Thermostat should regulate the temperature, so that sounds like the problem to me. T5 isn't one of those daft cars with TWO thermostats, is it?

If it doesn't blow hot through the heater, that kind-of suggests that the sender is telling the truth.

Finlandia

Original Poster:

7,803 posts

230 months

Monday 20th October 2014
quotequote all
I haven't actually measured the temperature when it opens, but before the water is boiling it's open and closes as the water cools down again.

There is only the one thermostat in the old T5, at least to my knowledge.

littleredrooster

5,523 posts

195 months

Monday 20th October 2014
quotequote all
Finlandia said:
Lets hope you're right, but I don't really see how it can be faulty when it opens and closes as it should in a pan of water.
As you bring the pan up to heat from cold, at what temperature does it open; and just as important- at what temperature does it start to close?

My money says it may open and close in warm water, but nowhere near the correct temperature.

GroundEffect

13,819 posts

155 months

Monday 20th October 2014
quotequote all
It doesn't sound particularly odd. To me it sounds like a cluster issue.

Cruising along with a normally low ambient (i.e. ~15C) would see a 70C ECT. I have seen those temps before in testing.

Typical thermostat failure modes are:

1) (if stuck open) the system never warms up unless excessive load
2) (if stuck closed) fine operation at low loads/town work but overheating at higher speed/load

Your heater comment is too subjective to diagnose. What is the time to temperature? Get a thermocouple in there and do a test!






Finlandia

Original Poster:

7,803 posts

230 months

Monday 20th October 2014
quotequote all
littleredrooster said:
Finlandia said:
Lets hope you're right, but I don't really see how it can be faulty when it opens and closes as it should in a pan of water.
As you bring the pan up to heat from cold, at what temperature does it open; and just as important- at what temperature does it start to close?

My money says it may open and close in warm water, but nowhere near the correct temperature.
You have a point there, will check and see the temperatures. On a 90c thermostat, when should it start opening and when should it be close?

DonnyMac

3,634 posts

202 months

Monday 20th October 2014
quotequote all
I had the exact same problem on an old 5 Series 15-20 years ago just after a major service.

The car eventually seized.

The dealer had put the brand new thermostat in the wrong way around.

BMW gave me a new engine, which was nice.

Finlandia

Original Poster:

7,803 posts

230 months

Monday 20th October 2014
quotequote all
GroundEffect said:
It doesn't sound particularly odd. To me it sounds like a cluster issue.

Cruising along with a normally low ambient (i.e. ~15C) would see a 70C ECT. I have seen those temps before in testing.

Typical thermostat failure modes are:

1) (if stuck open) the system never warms up unless excessive load
2) (if stuck closed) fine operation at low loads/town work but overheating at higher speed/load

Your heater comment is too subjective to diagnose. What is the time to temperature? Get a thermocouple in there and do a test!
It doesn't really sound like it would be stuck open or close, maybe just not opening and closing at the right temperatures. Will have to check further.

At what temperature should a 90c thermostat start opening and closing?

Jimmyarm

1,962 posts

177 months

Monday 20th October 2014
quotequote all

Put a genuine Volvo thermostat in it smile

Finlandia

Original Poster:

7,803 posts

230 months

Monday 20th October 2014
quotequote all
DonnyMac said:
I had the exact same problem on an old 5 Series 15-20 years ago just after a major service.

The car eventually seized.

The dealer had put the brand new thermostat in the wrong way around.

BMW gave me a new engine, which was nice.
Mine is the right way in there, but the thought of the engine running cold is a bit worrying and I really don't fancy having it seize on me.

Finlandia

Original Poster:

7,803 posts

230 months

Monday 20th October 2014
quotequote all
Jimmyarm said:
Put a genuine Volvo thermostat in it smile
It is a genuine Wahler/Volvo one, may try an aftermarket one tomorrow just to be sure.

ShayneJ

1,073 posts

178 months

Monday 20th October 2014
quotequote all
  1. Your thermostat is buggered#
replace it also i don't know if
the T5 has a viscous fan or electric
but maybe check if viscous that the clutch hasn't seized
or leccy check the switch is not failed short making the fan run constantly

Finlandia

Original Poster:

7,803 posts

230 months

Monday 20th October 2014
quotequote all
ShayneJ said:
  1. Your thermostat is buggered
Starting to sound like it.

ShayneJ said:
replace it also i don't know if
the T5 has a viscous fan or electric
but maybe check if viscous that the clutch hasn't seized
or leccy check the switch is not failed short making the fan run constantly
It's electric and seems to be working as it should.

feef

5,206 posts

182 months

Monday 20th October 2014
quotequote all
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?
To clarify, it SHOULD be sitting at 84-92, but the dash display and the Torque app are showing it as <70?

Finlandia

Original Poster:

7,803 posts

230 months

Monday 20th October 2014
quotequote all
feef said:
To clarify, it SHOULD be sitting at 84-92, but the dash display and the Torque app are showing it as <70?
On the dash, when the temperature is where it should be at 3 o'clock, the torque app shows the temperature range at between 84 and 92, this is idling or driving slow city traffic, when doing motorway speeds the dash gauge falls to 4 or 5 o'clock or around 70 on the app.

Jimmyarm

1,962 posts

177 months

Monday 20th October 2014
quotequote all
Did you get the new one from a Volvo dealership ?

It sounds like it is sticking open, when you are pottering around town etc it will mostly be open. Obviously once you hit ze autobahn the cooling effect of the radiator is greatly increased and it should start to close.

The other possibility is that it is getting stuck on something in the housing, I think they are pretty simple on those (metal job on the top of the engine ?

I take it the heater is nice and hot when idling/around town and it drops off once on the motorway ?

TooMany2cvs

29,008 posts

125 months

Monday 20th October 2014
quotequote all
The dash display and app both get their reading from the same sensor and same ECU, so you'd expect them to tally. Get a <£10 eBay IR thermometer,and cross-check with the temps on the hoses and rad.

Does the rad get warm before the gauge is up to temp?