Temp Gauge Fluctuating

[glynreaper]

I was on my way to work yesterday morning when i happened to glance at the temp and the needle was at about 3 o clock
obviously i nearly had a fit as i was about to get on the motorway, i sung the van round and found a safe place to stop an killed the power.
I had a look under the bonnet and there were no other obvious signs of over heating. coolant lever was full and i couldnt see any leaks.
As I was not far from home I decided to let the van cool down and then try to limp home.
Started up and drove home. only this time the temp remained normal.
so I (maybe stupidly) drove to work, the journey was normal with no signs of over heating.

The journey home, again needle read high, and as I was on a dual carriage way i had no where to stop.
the needle went back to its normal position. this continued during the course of the journey with the gauge fluctuating between its normal position and over heating.
There were no other signs that anything was wrong, at least not to my untrained eye.

Ideas on what may be wrong?

Thanks

Glyn

[francophile1947]

3 o'clock - what gauge have you got fitted
By the time the gauge gets to H, your engine should be boiling away. As it clearly isn't, I suspect it's an electrical problem, but that's where my knowledge disappears
Good luck, I'me sure somebody else will be a long with some suggestions

[scanner]

First question is - has the gauge been modified to give an accurate reponsive reading or is it as standard?

[glynreaper]

Hi the gauge hasnt been modified and has always given a constant reading.

The only time this hasnt been the case is when I had a blown radiator, this was replaced and everything seemed to be normal.

[scanner]

Hi the gauge hasnt been modified and has always given a constant reading.

If it hasn't been modified that is ALL it will do as they are too heavily damped to give a realistic reading.

Unmodified they are meaningless until what happened to you happens and unfortunately as many people have found out that is sometimes too late.

You need to find out what is causing the overheating before you drive anywhere. To do that you may need to bleed it properly as well in case any air has got into the system..

[glynreaper]

So it may possibly be an air lock.

How do I go about bleeding it

[scanner]

So it may possibly be an air lock.

How do I go about bleeding it

There is a video on YouTube I think* - but if there is an airlock you need to find out if the airlock caused the overheating or the overheating caused the airlock.


* Someone will no doubt be along soon to point you in the right direction.

[teenmal]

Hi glynreaper,

Sounds like the thermostat could be Dicky.

Cheers.

[bongo frenzee]

I had a similar problem when I first got my Bongo, although the needle was dropping (down to cold/9 o'clock) rather than rising up to 3 o'clock - it was the connector between the thermostat and the gauge that was loose - once replaced it has been fine.

Sorry I'm not in the slightest bit mechanically-minded but if you can work out what bit I mean it might be worth checking!

[Northern Bongolow]

if the wire to the temp gauge/sender, or the sender is faulty (to earth) it could show hot (full).
i would recomend all the above.do a pressure test to establish if you have a leak, replace the stat if you dont know its age,replace the sender,then do a bleed.
make sure the bleeder has seen the videos on how to do it,or use one of the established methods . it is very important to do this correctly.