Talk Morgan Forums Morgan Sports Cars Morgan Plus Four, Supersport & Plus Six (CX & CXV Generation Vehicles) Plus Six radiator failure - again

Hugo and Sir Percival. Sorry you’ve had radiator issues. We’re these since the pot and brake recall ?

Nick

plus four ,4 radiators 20000 km , nothing since 7000 km and swirl pot installed

Before in my case Nick.

Sir P

Our car is not alone at the dealer with recent radiator failure, they have several other CX cars awaiting radiators. Our car has had one radiator fail before the swirlpot was fitted at 2K miles and one radiator fail after the swirlpot at 3.5K miles. I am hopeful the final fix is the ECU flash, as it appears its the ECU on the CX generation that control how the thermostats open/close.

May I join in this discussion, even though I no longer have a Morgan?

The Porsche Boxster S I now drive is a 2.5L flat 4 with a turbo and intercooler. The ECU manages water flow, there is no thermostat as such, but multiple sensors and ECU controlled valves.
At start up the coolant goes from the cylinder head to heater matrix, then to the oil and transmission fluid intercoolers to help support a fast warm up. The engine, even in winter, was up to 100c within 5 mins off start.
The coolant is then used to manage intake air after the intercooler and finally the radiators. This is dynamic, the ECU's aim is to make the engine as efficient as possible.

I previously had a BMW M140i with the same glorious engine as the PlusSix. It had an equally complex cooling system, with two radiator header tanks and a complex plumbing system.

Both the Porsche and BMW have to have their cooling systems filled whilst the engine is running and the car connected to an external computer, this ensures all the valves are opened at the right point to make sure there is no trapped air or empty parts.

My much loved Plus 8 had a much simpler cooling system, it was flawless and over almost 50,000 miles never lost a drop of fluid!

So, what has gone wrong? My guess is that the MMC plumbing design is not perfect causing hot spots and cavitation resulting in vibration that cracks the radiator. I suspect that those who have had zero issues have a cooling system that, by chance, is correctly filled and works as BMW intended. The others were imperfectly filled, especially by dealers fitting replacements and who have been imperfectly trained.
The engine isn't the problem, it is MMC's cooling system design and implementation.

Thanks Peter, after considering this. I have been wondering if the issue is how the ECU controlled valves are actually operating the coolant flow. As you say, its a complicated system. Its possible that on the cars with no recorded issues the ECU is operating the valves in the design of the program, but in others the ECU may not be doing this as exactly.. I would think that the cooling system is finely balanced for flow and that the valve operations must be gradual and very controlled.. If this was not happening in some cars and the valves were opening ( or closing ) too quickly/slowly this may increase the risk of thermal shock.
Anyway, just an idea..based on the fact that the new radiators are coming with a ECU flash.

I wonder if MMC actually have a program to enable the ECU to open all the valves, whilst filling the cooling system, to prevent air locks. Well maybe, but I bet the dealers do not.

Just the radiator statistics on my MY2021 Plus Four:
- 1st Radiator leaking at about 1400 miles
- 2nd radiator installed with no leaks for app. 300 miles
- 3rd radiator installed as precaution together with the swirl pot at 1700 miles

Car has now about 9000 miles on the clock and the last 7300 miles no radiator issues. I hope it stays that way ;-)

I was told by a Porsche technician when asking about the cooling system, that the Porsche computer has a special drain and fill the cooling system program so that the valves are opened in the correct sequence to ensure that when draining there is no fluid left anywhere and when filling it fills every part.

I share your concern that some dealers may not have the training to properly follow the procedure. Replacing a radiator would not, I would have thought, be foreseen as a regular service activity.

Interesting topic.
Not sure if this helps or is relevant but a brief as I can;

I bought a ex works Morgan Plus Four in April with around 13500 on the clock.
Now has just over 15000.
Middle of June was a weekend tour of around 400 miles in searing heat and the car was impeccable.
However on the way home it suddenly overheated.
With the gauge in the red I was rescued by the RAC who topped up the header tanks, (the cap of one did not appear fully tightened).
RAC man run the car to operating temperature with the caps off to make sure no airlocks and I set off again as all seemed well.
After an hour running in heavy traffic the car overheated again.
Managed to top up again and drove home very steady.
Next morning no water in header tank on nearside. (I am certainty not technical and was told later the offside header is something to do with cooling the turbo).
Garage were tremendous, picked up car and established problem was airlocks and the system had to be drained and refilled in a specific way numerous times.
The level in the header tank is evidently critical and should not be over filled.
Done about 300 miles since and no issues.
Any work on the cooling system would appear to need detailed knowledge.