Running rough in cold weather - suspect cooling system?

ramilio · Post by **ramilio** » 10 Jun 2020, 19:44

Hi,

It’s getting colder where I live and my 1997 S70 20V N/A has been displaying some odd behaviour.

Each morning, I’ll drive from cold for 7-8 minutes until the temperature gauge is at the (normal) 3 o’clock position. Once this point is reached, the thermostat presumably opens and then the temperature gauge drops to 5 o’clock as the cold water from the radiator enters the engine.

When this drop in temperature occurs, the car starts to run rough to the point where it feels like it is going to stall. The car is fine when it reaches the normal operating temperature again.

During the last episode the lambada light came on.

Just wondering if this sounds like a oxygen sensor (i.e. lambada) related issue or
more likely a cooling system issue? I do not have access to an obd reader unfortunately ☹

Has anyone else experienced this issue or know what it might be?

Any help appreciated

Thanks
Ramilio

Post by **Chuck W** » 10 Jun 2020, 20:32

Check your coolant temp sensor and connector.

Could be corrosion on the connector pins causing an errant reading, or a bad sensor.

Post by **abscate** » 11 Jun 2020, 02:53

The temp gauge should reach the 3 o’clock position ( 9 o’clock in AUS

and then stay there. If the gauge behaviour is systematic and reproducible, I would guess your thermostat is malfunctioning. Replace it with OEM Volvo or Wahle

ramilio · Post by **ramilio** » 11 Jun 2020, 17:15

Hi Chuck/Abscate - thanks for the advice.

I'll change out my thermostat/temp sensor and report back.

Post by **misha** » 14 Jun 2020, 17:04

Thermostat is at fault here...use Wahler(oe,oem) or Vernet.
N/a use 87-90C.
Turbo 87C.
ECT must be oe Volvo(which is Valeo btw) or at least Vernet.

Like upper advice...before change ECT check both connectors for corrosion.
They rarely go bad....mine is still original.

ramilio · Post by **ramilio** » 23 Jul 2020, 19:09

Hi All,

Just following up.

I was convinced that the thermostat was the issue so I replaced it only - The problem still persisted.

I then replaced the coolant temperature sensor and voila! the problem was resolved. My car is running normally again.

Replacing the thermostat did help the issue slightly. I noticed that the OE thermostat is rated at 85 degrees Celsius whereas the OEM one I had fitted previously was 92 degrees Celsius.

Thank-you all for your help!

bronco · Post by **bronco** » 23 Jul 2020, 19:25

abscate wrote: 11 Jun 2020, 02:53 The temp gauge should reach the 3 o’clock position ( 9 o’clock in AUS and then stay there. If the gauge behaviour is systematic and reproducible, I would guess your thermostat is malfunctioning. Replace it with OEM Volvo or Wahle

Don't you mean -3 o'clock?

Post by **misha** » 24 Jul 2020, 03:05

Thermostat was allready been replaced then...because OE Volvo (Wahler)for non-turbo is 90-92C...(92C for very cold climate area).
87C for turbo engines.