A quick drive at below freezing temperatures

[kees]

Between engine and thermostat or between radiator and thermostat?
Kees Oudesluijs

[slotcarone]

The temp gauge sender is on top of the cast iron front cover between the upper hose/thermostat housing and the heater hose connections.

[kees]

In that case it will register the coolant temperature in the engine. This should remain more or less constant when the engine has reached the operating temperature. If it does not reach the operating temperature or the temperature drops during driving the thermostat is suspect, probably (partially) stuck open.
Easy and cheap to replace.
Kees Oudesluijs

[Steve Payne]

Easy and cheap to replace.
Kees Oudesluijs

I take it you have never replaced one? Easy job on a car with no A/C but the compressor gets in the way, 1/4 drive 9/16 socket with a wobbly drive will just get in there as long as it is not to tight

Steve .

[Grant]

I take it you have never replaced one? Easy job on a car with no A/C,
Steve .

I think they are referring to Felix's CV8 Stevey.. so I doubt if he will have air-con on there... but I guess you never know.. I'm sure if it was your car.. you would have fitted A/C

[slotcarone]

If your car performs correctly temperature gauge wise in hot weather and you have good heat in cold weather then your cooling system is fine!!

[Steve Payne]

If your car performs correctly temperature gauge wise in hot weather and you have good heat in cold weather then your cooling system is fine!!

Agreed.

Thinking about this I wonder if the very cold air is over cooling the water in the radiator because the thermostat is shut and when this rush of cold water enters the engine as the thermostat opens is making the gauge read low. Only a theory but I know my thermostat is working and I have seen my gauge do the same thing as Felix's gauge.

Steve

[Per]

That cold rush can happen if there is no leak by at all. And it is the very reason Jag V12 thermostats have the tiny hole as the rush does an all aluminium engine no good at all.

The temp drop won't last long so the gauge will not settle at that level. If it is cold enough it will eventually shut again even if travelling at the same speed. When stopping heat soak will bring the needle up again before the slow cooling off of the whole lot.

I have experienced temperatures low enough that even with a cold rad heater output dropped and temp needle also. But we are talking -30C or below.

[felixkk]

2018-03-05 15.15.30.jpg (168.28 KiB) Viewed 2148 times

[felixkk]

Spoke to the man who knows my car better than I do:
RPM reading: I shouldn't trust the gauge
lower final drive: he doesn't know
temperature gauge: sounds fine
he then went into a litany of other things I should worry about first on the car

[Per]

The tacho has a tape covered hole at thr back which gives access to a trim screw. Check actual rpm with a separate known good instrument.

[felixkk]

Thanks Per- his words exactly. But it didn’t sound like it was on the top of his things to do list...