Tr3 Temperature Mystery

[Classic7]

I would welcome advice on a mystery. I start my TR3 from cold and drive away and the temp slowly climbs all the way up to 3/4 on the guage and stays there. However, if I stop the car for a while and restart, the temp settles at a needle's width under half (normal) and stays there for the rest of the day. The guage has been calibrated by Speedograph with 'no fault found'. I am on my third thermostat with identical results (1 x Waxstat, 2 x bellows and ring type). I changed from Evans coolant to 50:50 water:Bluecol.

 

NB when indicating 3/4 on the guage the electric fan isn't operating so the temp in the bottom hose is a lot cooler. Something is causing a high temp in the thermostat housing until it resets itself following a stop.

 

As it runs at normal temp once 'reset' there can be no permanent problem such as a blocked rad.

 

Please help.

 

Chris

[BlueTR3A-5EKT]

Do you have a blocked or restricted bypass hose?

It needs a min1/8" upto 3/16" diameter bleed hole through the bung that may be fitted in it to allow some circulation and pump bleeding.

 

My car runs up to 3/4 hot from cold then drops back to just under 185 - almost as if the thermostat is sticking or is jammed closed to start with.

The needle hunts up and down around 185 when driving in mixed traffic/open road.

Peter W

[ianc]

Air lock? - but these usually disappear fairly quickly, especially if using conventional antifreeze/water mixture, which expands as it warms.

Is your heater circuit open, so as to permit circulation through?

Lift the front of the car about 4", remove radiator filler cap and run the engine at tickover. See whether it burps! You can shake the car from side to side to assist this (just like burping a baby!).

Ian Cornish

[Graham Harris]

It sounds like your thermostat is not opening and the water is circulating via the bypass hose until you stop the engine and the temp rises and opens the thermostat .I would try a normal thermostat and a restrictor in the bypass and see if that fixes it.

 

Graham

[Fireman049]

 

Edited May 21, 2017 by Fireman049

[Classic7]

Thanks all so far. The bypass is not deliberately restricted though the opening into the water pump is narrower than I expected. I had come to the conclusion that it must ne some kind of airlock issue. Peter W's car sounds very similar. I agree with Graham that it seems like a jammed thermostat but, as I said, I am on the third stat having checked the current stat in a pan of water with a thermometer and checked it was not too tight a fit in the housing.

 

I will do my best to burp the baby.

[Lebro]

I had a fairly similar problem last year - the temp gauge would oscillate either side of the central mark.

It turned out to be a very small head gasket leak - pushing gasses into the water jacket.

Cure (much to my relief) was to re-torque the head. I got at least 10 thou of movement, because on replacing the rockers all the gaps had gone negative.

 

Worth a try.

 

Bob.

[qim]

Hi

 

Sightly off-topic. Could you tell me WHEN you had the gauge checked at Speedographic, please? I had mine done there also with problems.

[Classic7]

qim,

 

The guage went to Speedograph last November. Came back with no fault found and no charge which I thought was good service.

[RdeJ]

I have more or less the same issue. Bellows/sleeved thermostat, no bypass restrictor. Car warms up to 3/4 on the gauge and stays like this. The phenomenem started after installing an alu radiator. Though when releasing the pressure by temporary opening the (4 psi) rad. cap, the needle drops back to the center and there it remains.

Gonna check if the small valve in the thermostat bleeding hole is stuck. Perhaps should just remove the valve completely?

 

Robert

[Graham Harris]

I had the same problem with the bellows type thermostat so i changed it back to a standard type with the restrictor in the bypass and its been perfect ever since .

 

Graham