Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing 2008 4/4 temperature issue

OK, latest update is that I’ve installed a new temp sensor which has made no difference whatsoever. Gauge and OBD still reading anything up to 120, fan kicking in when gauge and OBD read 100 but laser temp check at site of sensor shows a nice working temp of 85-90. Scratching my head with this one now🤔🤔🤔🤔🤔

Presume you've unplugged and re-plugged all the relevant connectors in case of a dodgy contact? .... and did you replace the voltage-regulator (if your car uses one (my car is old-school so I've been caught out before commenting on modern models 🙂)

As the IR tells you nothing is amiss beyond the gauge I'd check that the gauge rises 'normally' from cold and let it sit til the temp rises and triggers the fan... then watch for it to fall back as they run.

At that point I'd put a spot of paint on the glass to mark where the new 'normal' was and drive it until Winter ... but then, I'm a barbarian!

K

Sorry to hear that Neil. Just bear in mind the limitation of the laser reader. It will only be reading the temp at the surface/air boundary which is very different to the internal temp. That will be a gradient across the head anyway. The sensor however is recording the coolant flow coming from around the combustion chambers which is much more pertinent.

Also if the sensor was faulty or out of range the ECU would be throwing an error code.

Are you seeing 120C when the car is traveling or when the car is stationary/idling?

I’m seeing 120 when the car is travelling but it doesn’t drop when it’s idling and the fan running but the laser temp gauge shows normal readings on all points around the engine (hoses, rad, block etc) so I can’t think that the engine is actually overheating.🤔

Did you do the bottom hose test, stop the car and quickly check the stat was open/closed? Was the bottom hose too hot to keep your hand on or was it cool/warm?

Yes, it was a lot cooler than the top hose.

As you say the fan is triggered around 100C so at the point the cooling system should be fully functioning with the stat wide open (and the bottom hose too hot to hold).

However if your bottom hose was cool enough to hold then maybe its an indicator that the efficiency of the rad is overwhelming the stat and keeping it closed whilst the car is moving? That might be why you are seeing those high cylinder head temps as the bye pass coolant short circuits the rad.

Maybe try a stationary test for comparison? When the engine is cold start the car and let it idle until the fan kicks in at 100C. Then again feel the bottom hose. Is the cooling system now working normally with the stat open and the hose too hot to hold? If yes then the stat is perhaps not being overwhelmed here as the rad's delta T will be much less without the moving airflow passing through it.

I’ll give it a go👍

When I had that problem exactly on my Alpha 3.0 Spider it was the gauge.

So, the latest, let the car run until 110 reached on gauge and was same reading on OBD. Using laser temp reader following results achieved:
Top Hose 78
Bottom Hose 66
Rad top 66
Rad botom 54
Temp Sensor location 82
Coolant expansion tank 87
I’m really scratching my head over this one🤔🤔🤔🤔