confusing temp gauge

Hi all, bit of advice needed regarding my temp gauge. I was driving through town this morning in not particularly heavy traffic, when the temp gauge on my 110 suddenly shot up through the red and right off the end of the gauge. I pulled over as soon as I could and stopped the engine. When I looked under the bonnet, there was no sign of coolant loss, and the top rad hose was firm, but not too hard, and I could hold it without burning my hand. I have checked the oil, and that appears free from water contamination, and there are no bubbles or over pressure in the coolant. I left the landy parked for a while before starting up again. All was well for 10 mins before the temp gauge did the same thing again. I got to the local main dealer, and bought a new temp sender and fitted it, but it still does the same thing. I have checked the wire and connectors, but all seems ok. Does anyone else have any idea as what this could be please?

Forgot to add, engine is a 3.9 V8 with a 3.5 inlet manifold & carbs.

think maybe the thermostat took a **** by not opening

possibly, hadn't thought of that. That might explain why the water temp dropped back to normal quite quickly, but also climbed again so rapidly.

martin1512 said:

possibly, hadn't thought of that. That might explain why the water temp dropped back to normal quite quickly, but also climbed again so rapidly.

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is defo a nakered thermostat then. When temp gauges start doing wierd stuff thermostat is cheap and first to check, then on to water pump. How fresh is your coolant

How durdy is your radiator

Thor1950 said:

is defo a nakered thermostat then. When temp gauges start doing wierd stuff thermostat is cheap and first to check, then on to water pump. How fresh is your coolant

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coolant is very fresh, just replaced ahead of the cold weather we are expecting in a few days. It will take a couple for days for a new stat to arrive, so may take it out and drive without it for a couple of days see if that make a difference.

Does the wiring to the sender check out ok?
Just thinking as a good few years ago I had a temp guage on an old BiTurbo had a life of its own...cause was a short in the sender wire chaifing on the bulkhead metal, and it only shorted when I put my foot down as the engine mounts flexed

just an idea to throw into the mix

joe1972 said:

Does the wiring to the sender check out ok?
Just thinking as a good few years ago I had a temp guage on an old BiTurbo had a life of its own...cause was a short in the sender wire chaifing on the bulkhead metal, and it only shorted when I put my foot down as the engine mounts flexed

just an idea to throw into the mix

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Wire seems ok, no obvious points of chafing or thin insulating.