Overheating - or is it?

[MTFC Derek]

So, the temp gauge on my 1300 spitfire engined Herald went into the red. Fitted  new thermostat. Fitted a new pump. Flushed system.

Still in the red.

Ran it without thermostat - all OK.

Tested thermostat - opening at 82 degrees.

Just ran it with thermostat back in - back in the red.

I'm flummoxed.

[glang]

Is there a problem with the temperature sender so that it gives an excessive reading for the higher temperature produced by running with a thermostat?

[Wendy Dawes]

Good call, just what I was thinking 👍

[drofgum]

Hi,

What does the fuel gauge read? it is possible the voltage stabiliser has stuck on and the gauges are getting 12 V instead of 10 V. Incorrect readings from the temperature sender usually are wrong from first installation of the sender.

ISTR the Heralds didn't use a voltage stabiliser, at least early ones, so the gauges and possibly senders would be different to those in a Spitfire.

Best of luck,

Paul

[Clive]

Does it go to teh red immediately, or slowly build up when running? Any indications (apart from the gauge) that it is overheating?

And was this a sudden change in behaviour? 

A new (correct for the car, not the engine) sensor would probably be my next step. I have had a sensor fail, and the gauge went straight to the red. During a late night 200 mile journey home, which initially caused a panic but once I realised everything else appeared OK, I just ignored it until I got home. Heater temperature gives a bit of an idea.

 

[WIMPUS]

Get a infrared temp reader from amazon.

Very easy to see the temp of thermostat housing, rad hoses etc.

Been using this on a few cars with 'overheating' problems.