Car Temperature Guage dropping

Connavar

Hi Guys,

I recently brought my car in for a service and since then the temp gauge is behaving oddly.
When I'm driving along it moves up to about the halfway mark(it used always just stay there once it reached that point). After a minute or two, it just drops back to zero again.
There had been a smell of burning from the engine, but I presume that was just spilled oil as it has faded away.

I was on my way back to the garage yesterday with it, and it suddenly started working as normal again, so I turned back but it seems to be back again this morning.

Any ideas what might be causing this? I checked the oil levels and they seemed a bit on the high side. Could this be the issue?

Cheers for the response

EDIT: Its a 01 VW golf and in the service they read ecu and reset a fault code(lambda sensor, and they replaced spark plugs, nothing else unusual for a service)

Anan1

Is there enough coolant in it? I'd bring it back straight away anyway.

CJhaughey

Could be that the coolant is low and the gauge isn't reading coolant temp but air instead!
Have you check that there is coolant in the rad?

Connavar

I haven't checked the coolant yet. Will take a look when I get a chance in a while. Thanks for the quick responses

old_aussie

Maybe the thermostat is staying open after the car heats up.

Moanin

My guess is that you have a faulty temperature sensor. It's a fairly simple fix. What you are describing are symptoms of this.

A quick google will pull up a guide of what's involved in replacing it.

Connavar

Moanin wrote: »

My guess is that you have a faulty temperature sensor. It's a fairly simple fix. What you are describing are symptoms of this.

A quick google will pull up a guide of what's involved in replacing it.

Seems odd that this would suddenly become an issue after a service though?

cletus

Most likely if it is a faulty sensor the two are unrelated

Connavar

Just an update. Checked the coolant level and it was fine, so I managed to get back to the garage at lunch. They said the engine wasn't overheating and it was just a faulty gauge.

Thanks for the ideas on it lads

Dartz

Thought it might've been ab air-bubble getting pushed around the circuit myself.

It reaches the coolant sensor and the sensor can't read the temperature of the air too well, so it drops, then pops back up again as the bubble is shifted on by the pressure behind increasing.

Anan1

Dartz wrote: »

Thought it might've been ab air-bubble getting pushed around the circuit myself.

It reaches the coolant sensor and the sensor can't read the temperature of the air too well, so it drops, then pops back up again as the bubble is shifted on by the pressure behind increasing.

Me too, which could lead to localised overheating?

Dartz

Not for very long. Maybe for a few moments as it circulated through the system if it passed through the engine block. It probably only started moving when the thermostat opened as the engine got up to temperature, so might've been in the radiator, heater core or coolant hoses.

Unless it happens again, or there're a lot of bubbles in the circuit.

Start from cold with the cap off the expansion vessel, and let the engine warm up while idling. Turn on the heater to keep fluid circulating and eventually it'll push the air out of the circuit and through the open cap.

The system wont boil if you start from cold. Opening the cap on a hot engine will lead to a faceful of hot steam. Don't do it.