Help - Water Temp Gauge Up and Down Like a Yo Yo

[Iaing01]

Hey folks, well took the Noble out today for the first time in a few weeks and as I was getting to work the water temperature gauge started going from the middle where it normally sits up to 120 the back to the middle very quickly.

The car is definately not overheating as the outside temp this morning is below freezing and its only a very short drive to work.

It looks as if the temperature sensor is knackered but i'm no Noble mechanic. Any ideas what this might be? If it is this how easy is it to fix and where can I get the parts from?

Thanks in advance

Iain

Edit- Forgot to add the car's an M400

Edited by Iaing01 on Wednesday 13th February 09:31

[GTO400]

Ian,
The gauge is controlled via the ECU which in turn gets it's temperature signal from a sensor in the water near the engine, the ECU is set to ignore small fluctations in temp which is why it normally reads so constant but if it goes above a preset point the gauge will shoot up to 120 as a warning so it could be that you are actually overheating ! Possible thermostat sticking ? Fans not running ? or could be faulty sensor.
Kevin

[Iaing01]

The fans are definately kicking in.

It doesn't stay at 120 it goes back and forth quickly.

Iain

[NobleGuy]

GTO400 said:

...if it goes above a preset point the gauge will shoot up to 120 as a warning so it could be that you are actually overheating...

I got that when I had a coolant leak - middle temp to maximum in the blink of an eye.
Certainly encouraged me to stop the engine and fill with water at a nearby hotel even though it was 2 in the morning.

Could air in the system temporarily block the coolant flow, releasing as pressure builds and blocking again for a short time? I'm probably talking crap...

[Iaing01]

Strange as it maybe but it seems to have cured itself!

Ran it at lunch both moving and static for a good 10-15 minutes. The water temp gauge stayed bang on centre or ever so slightly past. It didn't seem to climb much and the fans kicked in.

I think the problem is possibly a sticking thermostat which i've heard is common on cars that dont get used much?

Iain

[Iaing01]

I obviously spoke to soon, driving home from work. The same thing happened again, this time I turned the ignition off and tried to re-start it a second later. It really struggled to start then when it did the temp dropped back to normal opertating temp?

Iain

[BrianJ]

Do check the coolant out - this happened to me when the radiator leaked.

[NobleGuy]

Does sound like a leaky-type problem. Check the car after it's been stationary for a bit and see if there are any fluids on the ground. Might give you an idea if there is a leak where it's occurring, although of course it may drain at a different location - mine was near the drivers seat although the leak was at the hose joining onto the radiator.

[Iaing01]

Thanks guys, will have a look today

Iain

[JAZ 34]

NobleGuy said:

mine was near the drivers seat although the leak was at the hose joining onto the radiator.

Me too!

My coolant was way down when I found the leak but the temperature never rose.

[AMG Merc]

See my new thread on split hoses.

[Iaing01]

Checked my coolant at lunch and guess what its low! Topped it up with a bit of water. Looked at the hoses at the back and cant find anything leaks, however under the front clam to the right(if your sitting int car) of the radiator there is a small puddle where some water has collected, this could be either rainwater or coolant i'm not sure. Its spagetti junction in there so is very difficult to see if there is a possible leak.

Iain

Edited by Iaing01 on Thursday 14th February 13:18

[NobleGuy]

Iaing01 said:

Checked my coolant at lunch and guess what its low! Topped it up with a bit of water. Looked at the hoses at the back and cant find anything leaks, however under the front clam to the right(if your sitting int car) of the radiator there is a small puddle where some water has collected, this could be either rainwater or coolant i'm not sure. Its spagetti junction in there so is very difficult to see if there is a possible leak.

Iain

Edited by Iaing01 on Thursday 14th February 13:18

Same location as mine - check the metal pipe that runs from the front drivers side wheel area to the radiator. Mine was leaking from the hose joining this to the radiator and fluid was running down the pipe into the undertray. Check if it's oily/coloured: yes - coolant, no - rain.

[Iaing01]

Hard to tell because its clear. To be honest its looks like rainwater but i'm not 100%

The plan tonight is to clean around the under tray and top up with proper antifreeze coolant. I should then be able to tell if its leaking or not...

Going to go to Halfrauds to buy coolant after work. What kind should I buy?

iain

[Naso Grande]

Iain,

I've been using the Shell Coolant which I bought from the garage just up the dual carrage way from where you are.

HTH,
Graeme

[NobleGuy]

Yes. Don't mix the two types of coolant that are out there - turns to glue inside.

[Iaing01]

Yeah I heard that.

I'll swing in by Shell after work.

Cheers folks

TBC...

[joust]

Iaing01 said:

Hard to tell because its clear. To be honest its looks like rainwater but i'm not 100%

The air conditioning will create a puddle of 'clear' water due to condensation, so make sure you aren't chasing that.

J

[sean_goodman]

Iaing01 said:

Hard to tell because its clear. To be honest its looks like rainwater but i'm not 100%

The plan tonight is to clean around the under tray and top up with proper antifreeze coolant. I should then be able to tell if its leaking or not...

Going to go to Halfrauds to buy coolant after work. What kind should I buy?

iain

taste it, rain water tastes like ran water (suprise) coolant tastes like coolant, works for me every time

[F.C.]

sean_goodman said:

Iaing01 said:

Hard to tell because its clear. To be honest its looks like rainwater but i'm not 100%

The plan tonight is to clean around the under tray and top up with proper antifreeze coolant. I should then be able to tell if its leaking or not...

Going to go to Halfrauds to buy coolant after work. What kind should I buy?

iain

taste it, rain water tastes like ran water (suprise) coolant tastes like coolant, works for me every time

Hmm carcinogen springs to mind.
F.C.