During a road trip the engine began to overheat, didn’t go into the red but was almost there.

I drove the last 150kms at 70kms/hr with the heater on full blast and the engine did not overheat

1st attempt:

Removed and inspected the water pump, looked fine so reinstalled it.

Replaced Auxillary Fan (old one was seized)

Replaced the Thermostat

After this the disco runs for around 15 mins and began to overheat, will not actually overheat as long as the heater is on full blast and I don’t go over 70kms/hr

2nd attempt

Suspected the new Thermostat wasn’t opening so hollowed out the old one and reinstalled it (effectively running with Thermostat continually open)

Little or no improvement

3rd Attempt

Figured the viscos clutch was not working, fixed it (literally fixed, by drilling a hole through 90% of the way through it and then breaking it off, so that it now runs 100% of the time.)

Little or no improvement

4th attempt

Wondered if exhaust gases where getting in via a head gasket seal, tested using an exhaust gas detector kit, did not detect any.

Was going to take off the radiator and perform a flow test, found a new one for $100 so just replaced it.

Replaced the Expansion Tank Cap.

Also put in a 2nd new Thermostat

Little or no improvement.

Nothing is leaking, hoses are not crunchy, when I originally drained the fluid it looked in good condition.

No water in the oil

At this point I’m not sure what to try next, any suggestions welcomed

 

I am beginning to suspect the temp sending unit. Get a cheap ir thermometer off of ebay or amazon so you can check to see if it is actually hot.

Does it overheat idling? If so, try this - drain the coolant and set aside. Put that gutted thermostat back in. Disconnect the top radiator hose at the radiator and shove a garden hose in the radiator. Run the engine and see if it still runs hot. How hot is the water running out of the hose?

Any bubbles in the tank?

 

Thanks for the feedback

I've monitored the temp using a Bluetooth odb2 transmitter and the "odb check" app. it is actually getting hot have seen it as high as 119C
No bubbles in the tank
I'll try the garden hose procedure tomorrow, will let you know how it goes

Thanks again

Barry

 

@Barry Hillier 119C that is very hot.

As your heater is blowing you have some coolant flow, if you can respond with temps in F rather than C it is more commonly used here.

 

119C = 246F, very close to the theoretical boiling point of 50/50 at 15lb/psi

For the past few weeks I've only been driving from home to work (<4 miles) which doesn't give it time to get too hot

 

Coolant always flows through the heater core regardless of the heater setting. Having the heater blowing is just using it as another radiator which is helping to reduce the engine heat..
The OBD readings are using the same temperature sensor as the gauge in the dashboard. If that sensor is bad, your OBD numbers are going to be inaccurate too.

 

Exactly, that is why you need an ir gun/pen device.