Thermostat question

[Hughandjen]

2005 4200cc
Hi guys my water temp gauge used to always sit at 90 degrees. For a couple of days it started to only get to 45 degrees. Winter in UK so it was cold so thought no more of it.
then I went for a drive and parked it up. Noticed that there was a pool of coolant under the car and the reservoir was low. When I looked I could see a drip from the water pump area so assumed I had a problem there ie O ring worn.
I’m wondering now if the temp sensor is faulty and the car, thinking it’s only 45 degrees didn’t start the fans and the water has boiled out of the overflow?
My question is where is the outlet of the overflow, is at near the front of the engine? And would a faulty sensor cause my problems?
Thanks in advance

 

[CatmanV2]

I suspect what's happened is your sensor is now reading air temp not coolant temp. And you've got combined oil / water pump failure.

Hopefully someone else will have a more positive spin on the situation

C

 

[Hughandjen]

I suspect what's happened is your sensor is now reading air temp not coolant temp. And you've got combined oil / water pump failure.

Hopefully someone else will have a more positive spin on the situation

C

Why would it read air not water??. Sorry bit confused

 

[CatmanV2]

Why would it read air not water??. Sorry bit confused

Because most of your coolant has dribbled out and the sensor is sitting in an air pocket.

It makes no difference what the UK temperature is. The operating temperature should always be 90. It might be the sensor is done. I really hope so, but with a low coolant reservoir and drip from the oil / water pump that would be two (maybe 3) faults simultaneously.

C

 

[Hughandjen]

Ah I see that makes sense. But the temperature was sitting at 45degrees for a few days before there was any sign of a leak. Then all of a sudden I get this 1/4 pint leak under the car after a fast drive.
while the car was on axle stands I thought I would get the car warm and see if I could see any leak more clearly and the temp went and stayed at 90degrees and no sign of any leaks at all!!!
That’s why I was wondering if the sensor has an intermittent fault?
Thank you for your thoughts. I did think it was originally a fault on the water pump but now I factor in the low temp readings I’m hoping it’s just the sensor

 

[zagatoes30]

Ah I see that makes sense. But the temperature was sitting at 45degrees for a few days before there was any sign of a leak. Then all of a sudden I get this 1/4 pint leak under the car after a fast drive.
while the car was on axle stands I thought I would get the car warm and see if I could see any leak more clearly and the temp went and stayed at 90degrees and no sign of any leaks at all!!!
That’s why I was wondering if the sensor has an intermittent fault?
Thank you for your thoughts. I did think it was originally a fault on the water pump but now I factor in the low temp readings I’m hoping it’s just the sensor

Here's hoping its the sensor much more cost effective repair

 

[CatmanV2]

What angle was it on the stands? Level, or perhaps tilted back towards the sensor?

Fingers crossed.

C

 

[Hughandjen]

What angle was it on the stands? Level, or perhaps tilted back towards the sensor?

Fingers crossed.

C

It’s was reading only 45 degrees while on wheels. Hope it’s the sensor

 

[Hughandjen]

Here's hoping its the sensor much more cost effective repair

 

[Oneball]

It could still be the thermostat, if it’s stationary there might not be enough air flow to keep the temp down even with a stuck thermostat. Doesn’t explain any leak though.

Have you topped the coolant up?

 

[Hughandjen]

It could still be the thermostat, if it’s stationary there might not be enough air flow to keep the temp down even with a stuck thermostat. Doesn’t explain any leak though.

Have you topped the coolant up?

Yep coolant topped up. When (if) it ever stops raining round here I will take her for a spirited drive and see what the temp gauge does and if any leaks appear

 

[CatmanV2]

Check your oil as well.

C

 

[Hughandjen]

Oil is good, no sign of emulsion and level spot on. Had a service 300 miles ago

 

[Hughandjen]

If the coolant boiled where would it come out? From the radiator or the the expansion tank? Or is there a blow off valve somewhere with a drain pipe?

 

[CatmanV2]

If the coolant boiled where would it come out? From the radiator or the the expansion tank? Or is there a blow off valve somewhere with a drain pipe?

Expansion tank I'd expect

But may not be obvious.

Or you've just leaked enough from your pump.

C

 

[Hughandjen]

Quick update. I forgot to mention I got a P0116 twice when the temp was showing 45 degrees. Hopefully this is another indicator of faulty temp sensor

 

[philw696]

If the coolant boiled where would it come out? From the radiator or the the expansion tank? Or is there a blow off valve somewhere with a drain pipe?

It comes out through the cap on the expansion tank.