Morris Minor Owners Club

As warming the car uo today I noticed the rad snd top hose were hot but the bottom hose was not near as hot.The heater was blowing cool which it never does.Does this sound like the thermostat please.

Have you checked the level of coolant in the radiator?

It is normal for the top radiator hose to become hot as soon as thermostat opens. At that point the bottom hose will still be cold.

The top hose is the "flow" from the engine to the radiator. The bottom hose is the return. As the car is warming up the top hose will be hot and the bottom hose still cold.

It doesn't sound like there is a thermostat issue to me. The fact your heater is cold could be: low coolant level, blocked heater matrix, general sludged up cooling system, water pump not operating properly, heater valve not opening properly.

Stephen

Thanks very much yes could simply be low as did not have time to check with other car and mounting jobs so will be next port of call.

If the top hose (which comes from the Thermostat) and the Radiator top are hot, then the Thermostat is fine.
The Bottom hose will be much cooler because the Radiator is doing it's job.

What you have is a problem with the Heater part of the system.

Check the radiator actually has the right coolant level, though I suspect it has unless it's just steam making the top hose and radiator hot...

Assuming you are a later model car than the basic Tap, is the Heater Control Valve working? They have a poor reliability reputation.
It could be sludge in the heater system, but if it's suddenly happened, I'd look to the Control Valve first.
I would expect Sludge to be a more gradual degradation in performance.

Thanks it was simple operator error.Now filled not that it looked low and now giving heat.

Classiccars wrote: ↑Sun Nov 17, 2024 2:18 pm Thanks it was simple operator error.Now filled not that it looked low and now giving heat.

Thanks for giving us a result to the tale; it's infuriating when people post problems and never give the final outcome.

Point taken thank you.