Hi all ,this is strange ,when im driving around the streets my temp gauge is fine about 1/3 of the way up but as soon as i start driving on a major road up to at least 50 the gauge goes down to the bottom white line ,but back to normal when i do local driving ,any ideas

 

Sounds like an air lock.
Get it investigated before it's too late.
HINT: there is NO known way to bleed the system, empty it and refill properly.

 

No thermostat installed?

 

i had this exact fault on my classic

i changed the thermostat,still did it, changed the coolant, air locked job several times, still did it

you know what it was ?

It was the actual sensor that is in the alloy water pipe, i changed this and its spot on now, stays where its meant to ! wasnt expensive either

 

Cheers guys for your help, think i will have to look into that rig cheers

 

Do you get hot air from the heaters during the time that the gauge is at the bottom if so it sounds like a gauge fault / sensor.

 

Hi Rig is that the thin sensor with only one wire on ,or the one with the plug on cheers

 

Its the one wire one the other one is for the ecu

 

Cheeers Baz is it hard to get to ,do you have to strip everyting down