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

No problem Neil and good luck resolving it.

Roger’s explanation of modern engines cooling systems is so right. Just look at the radiator problems with the plus six & 4. Whilst the older V8s needed more cooling, just using a fix all aluminium radiator from Mulfab or Simon imho showed a fundamental misunderstanding of what is required. My plastic radiator is hanging on, just, as in very cold weather it just starts to weep at a seam. Luckily so far not once warm or during the summer. I have put off changing it until I can source an aluminium version of the same size. Some quotes I’ve heard of are astronomical in price.

Rog raises a good point regarding just the 4/4 models with aftermarket aluminium rad. There have been several reports involving the greater efficiency of same ironically causing overheating particular on fast motorway driving.

The increased cooling seemingly delays the opening of the thermostat such that any sudden increase in power demand causes overheating which the thermostats hysteresis can't accomodate in a timely manner. The recommended cure from one of the rad manufacturers, was a lower opening temp thermostat. Another option was using the smaller aluminium rad used on cars with air conditioning to accomodate the extra rad.

Higher power Mogs and particularly Roadsters don't suffer from this issue at all.

That might be prudent Bob. Actually Mulfab's Sigma version does look a little smaller than their Duratec version.

Back in 2016 when I fitted an ali rad to my Duratec 4/4 I noticed the change almost straight away. Previously my cooling fan rarely if ever came on. At that time I lived on top of a steep 250ft high hill. Previously the hill was not an issue for the car but after the swap whenever I drove home and came to a stop in the garage the fan was running and later discovered the stat would also be shut.

After multiple component changes and thermocouples placed all over the engine recording the operating temps I eventually came to the conclusion that ECU controlled cooling systems with stats on the cold side turned everything that I thought I knew about cooling systems on its head.

Richard - I even replaced the regular 90C stat with a 82C version.....

As I've mentioned before it's not just the quoted thermostat temperature that affects the thermo dynamics in engine cooling systems its the hysteresis as well. I was once given an 80°C thermostat to replace a 72°C one fitted to a vintage diesel in a narrowboat, to cure an overheating issue. This worked because the stat started opening at 65°C. It didn't help that the high flow seawater pump had been retained for originality and was pushing coolant through the closed circuit skin tank so quickly it didn't allow enough time to dissipate the heat.

Modern cars often use ECU controlled coolant thermostats. They operate a tiny heater in the stats wax chamber that quickly opens same to be ahead of the game when there is a sudden high demand placed on engine.

The ECU controlled stats with heater elements were used on the first generation Duratec engines. By the time the engines were put in our Morgans around 2005 (4/4 and +4) Ford had already phased these out on the 4 cylinder Duratecs although the ECU input still remains, albeit unconnected.

My Roadster from 2005 still has the original brass radiator. Well metal anyway. What I did soon find out was that the thermostat opened really late. Having always being used to the top hose thermostat, this was a new experience. The early flow was from the small bore pipe from the top of the radiator, through the header/swirl/level tank, then the heater matrix and picking up the flow from the heat exchanger at the oil filter. On cold days, the bottom hose stays cold for a very long time. The temp gauge is usually rock solid and in the 85/100 range. However, on the NC500 there was a single occasion, on a slow climb, single track, quite high up when It behaved unusual by climbing to over 110, and staying there for several miles. On the descent, it dropped slowly back to normal, and never repeated so must have been just those circumstances.

My GDI with Sifab radiator runs much cooler than before, but the fan still kicks in at 100. The heater is less capable than before, but good enough!

Have sent you a pm , I have a spare plastic rad off my old 3.7l Roadster if you want it

If you want to risk just a few £, bung some K-Seal in...surprisingly good

https://www.kseal.com/uk/products/k-seal

Seems like I’ve sparked an interesting discussion thread. The ally rad was already in my mog when I bought it and the temp issue has always been a headache but, to be clear, my mog is not actually overheating. As I previously mentioned when the temp gauge and OBD shows 116 a laser temp reader aimed at the sensor shows 85-90 which is fine. The fan kicks in when the temp gauge and OBD show 100 despite this not being the actual case. That’s my issue so I’ve ordered a new sensor and will post the result when I’ve fitted and road tested it.