Omega bizarre temp gauge problem - Daz
For the last 4 days or so my temperature gauge which normally sits about 92 is suddenly starting to shoot up to just over 100 on slowing down/stopping in traffic. As soon as I pull off it returns to normal and whilst I've not had a chance to pop the bonnet up it doesn't appear to be overheating.

Am I right in thinking that the temp gauge sender unit needs replacing?

Omega bizarre temp gauge problem - Aprilia
Possible, but unlikely.

More likely is:

a. Water pump problem (insufficient circulation at low rpm)
b. Cooling fan or fan-supply fault (switch/fuse etc).
Omega bizarre temp gauge problem - Daz
The fan appears to be cutting in as it comes on when u turn the key to ignition when car has just been stopped.

Dodgy water pump could be a problem as it is connected to the timing belt - oh joy!
Omega bizarre temp gauge problem - Civic8
I would suggest you pull the bonnet catch and have a look.sounds like it is a prob with low water level rather than anything else.You can stand me corrected here but it seems that way.I would like you to let me know
Omega bizarre temp gauge problem - Daz
I have not had a chance to pop bonnet for a full inspection but on arriving home yesterday there was not any steam pouring out of the engine as temp gauge was on 105 o C.

Also the heater in the car is warm at anything over 2000rpm but cool if less than 2000rpm.

I'm guessing here that maybe the water pump is at fault but not being mechanically minded I don't know.

The fault (so far) hasn't affected the running of the car but if u know the history behind it and the fact the water pump is somehow connected to the cam belt you will understand my concern. Any help would be much appreciated as I refuse to deal with the incompetent fools at the Vauxhall dealership.
Omega bizarre temp gauge problem - rileyrm
I dont believe is a gauge problem,has your water level warning ever come on? My famous 3way valve failure on H J earlier in the year caused loss of water and cooked the thermostat on my V6,a major job to change. The symptoms were as you now have.

Omega bizarre temp gauge problem - Daz
No, no warning light has ever appeared.

Can u elaborate on the problem and likely cost involved at all please?


Omega bizarre temp gauge problem - Dynamic Dave

What John is refering to is here:-

And the solution is mentioned here:-
Omega bizarre temp gauge problem - Civic8
Untill you pop the bonnet there isn`t anything anyone can say.I can`t without more info.after your inspection under the bonnet.sorry
Omega bizarre temp gauge problem - Daz
Just been out armed with torch and put around 1.5l of water in expansion tank to bring it back to the cold level as engine.

There are no obvious signs of any leaks that I can see, any suggestions?


Omega bizarre temp gauge problem - Civic8
That may have been the will soon find out.let me know.No modern engine likes being low on water/oil how often do you check the levels
Omega bizarre temp gauge problem - NormanB
Judging by the time elapsed since your reported the problem to checking the level in the expansion tank leads me to the conclusion you do not pop the bonnet too often! (Forgive me if I am wrong).

I say this not to have a 'pop' at you but merely to put things in context. It may be you have been running the engine with a low water level for some time (Only you know the true answer as to how long). What do I mean? Well, if you had lost 1.5L in a week that is a significant leak but over a year probably less so.

Tracing the leak is probably easier if you can stick the car in your garage this time of year and stick a sheet of cardboard underneath engine bay - the drips will give clues to location (but not precisely!).

Things to consider

1. Hoses.
2. Expansion tank cap (passing when hot and under pressure).
3. Water Pump - normally a tell tale is fitted to assist diagnosis but some stripping of covers may be needed.
4. Radiator itself, stubs or matrix (unlikely).

Hope this is helpful to you.

Omega bizarre temp gauge problem - Daz
Oddly enough I usually check the levels every fortnight last time from memory was about 3-4 weeks ago (typically). It definitely has lost this amount in less than a month.

Oddly it went for MOT and they didn't mention that it was leaking which I'm sure they would have done and that was only a fortnight ago.

I did have a horrendous journey across London sitting in traffic for hours could this have evaporated some of the water away?

Cheers for your help

Omega bizarre temp gauge problem - NormanB

Well --- I am not familiar with Omegas............

But in principle to lose 1.5 litres in 2 weeks is significant - not a huge f'n leak but a significant one.

It could be the pressure cap on your expansion tank - if this is 'tired' it will not maintain design pressure and you could lose water through the vent to atmosphere - particularly when in adverse conditions - idling and no poor air flow (traffic jams!).

I would keep a close eye - maybe put a bit of masking tape on the exterior of the tank to indicate todays level when cold, then check periodically (evry day/every couple - when cold). A new pressure maintaining cap will not break the bank and if you continue to lose water it will eliminate it from the diagnosis.

Good luck and let us know how it pans out.

Omega bizarre temp gauge problem - Daz
Cheers for the advice, will monitor situation and report back.

Omega bizarre temp gauge problem - NormanB
I forgot to mention - coolant level ain't an MOT check. The tester would not report a leak to you unless it dripped in his eye or on your cheque!
Omega bizarre temp gauge problem - Daz
Hi, have only used my car three times since the last post.

Once on an hour and a half's round trip whereby the next day I had to top up by 0.5l and one hour round trip followed by a short 10 minuite round trip and when I checked the levl before setting off this morning it was as it should be.

I will check the level again before using the car tomorrow but this seems to confuse things even more!
Omega bizarre temp gauge problem - NormanB
Hi Daz

So you may still have a problem then?

Did you read this thread as advised by another forum member who experienced similar?

And have you replaced pressure maintaining cap on expansion tank?

Omega bizarre temp gauge problem - Daz
Yes I did see that thread thanks, I don't really know if I still have a problem as I've hardly used the car the last two weeks due to illness but it will be used for regular long journeying again from tomorrow so only time will tell.

As for replacing the cap no I haven't as yet.

Naturally I shall report back later in the week but the main problem is that I keep the car at the side of the house on a grassed area and with it being dark at nights it is difficult to work out if any leakage is occuring!
Omega bizarre temp gauge problem - Daz
Hi, I've used the car Wednesday, Thursday and Friday on 3 long journeys and a couple of short runs and the water is still on the cold mark as it should be. I've also sat endlessly in traffic jams on the A12 without the temp gauge rising bizarrely.

Could it be something as silly as perhaps after my last check sometime ago I did not tighten the coolant cap sufficiently?

Also given the loss and change in weather I reckon I ought to put some more anti-freeze in!
Omega bizarre temp gauge problem - Civic8
I don`t think replacing the cap will help if if there is a problem.from what you have said so far more likely to be thermostat opening too late.on occasions putting too much pressure on cap thats where the loss comes.Unless you have the tools suggest you take it to garage for test on anti freeze.if you put too much in will make things worse I think 40%/50% max
Omega bizarre temp gauge problem - king arthur
It's important that when you top up the coolant, you don't overdo it and put too much in. If there is a hose that is leaking slightly or loose, and there is no room in the expansion tank for the coolant to expand into, it will force its way out through that hose and make the leak worse.

Make sure you are always checking the level with a cold engine, otherwise the level can be misleading. You may also have had an airlock which caused the temperature to rise and the heater to blow cold, which has now been eradicated, hence the temperature now staying normal.
Omega bizarre temp gauge problem - Daz
Thanks, yes I meant I was going to drain some water out via the bottom hose then top up from expansion tank. As I've lost somewhere in the region of 2-3 litres of water over the last few weeks I felt putting a litre of anti-freeze back would be a good move?

Value my car