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

Did you try and obtain at stat one with a lower initial opening temperature than the original Neil albeit with OE fully open temp . If not your local motor factor should be able to help, they are available with greater hysteresis. Failing that try say an 80°C stat. FWIW this was the solution offered by SiFab to cure same issue on 4/4's fitted with their aluminium replacement rad.

Your measurements suggest the OE one was not opening soon enough given the thermal dynamics. I fear that if the new 85°C stat matches OE you will see little or no improvement to the overheating issue.

Apparently there are quite a few low quality parts out there, a friend searching for a stat for his 3L Capri tried two different "manufacturers" brands before being advised by someone who apparently travels the world sourcing classic car parts that those marketed under the brand name GATES were good quality, he bought one, which solved his issue relative to gasket thickness and fitting, whether it will operate correctly ..? Time will tell as the engine is not back in the Capri yet..

Ok but just bear in mind that one feature of a 'cold side' stat is an opening delay, and that can be bit of a game...

Before the stat can be fully opened there has to be enough heat in the bypass coolant (easy if you have a V8) to crack the stat and let some cooler coolant from the bottom of the rad creep past, and then only for it to be closed again as the temp within the stat housing drops. This open/close cycle looks to be repeated multiple times until the coolant in the rad is raised enough to hold the stat open. The delay will depend on a number of variables like the air speed through the rad, the ambient air temp, the rad efficiency and the longer the delay in opening, the hotter the engine gets.

The stat on my little 1.8 with its huge radiator poking out the bottom of the car would open normally if I let the engine warm up from idle with no air flow through the rad, however it was moving fast it was a different matter. The engine temp could rise dramatically as the hot bypass coolant from head struggled to get enough heat into the stat housing to open the stat, sometime it just wouldn't open.

Something to keep an eye on and perhaps come back to if you run out of other suggestion. Have fun

That’s a good suggestion, problem is that I can’t source a lower opening stat. The new one I fitted has the stat welded into the plastic housing, not just a basic stat that can be replaced into the same housing.There was an earlier suggestion about doing away with the cold water stat and replacing it with a stat on the hot water side, maybe that’s the way to go.🤔
But then again all the laser temp readings around the engine are always normal🤔🤔🤔

Note with stat in bottom hose cooling systems the stat sensing side faces inwards to the permanent narrow bore hot coolant bypass and heater return. When it opens cooled coolant mixes with these before feeding water pump inlet. The stat housing location becomes critical therefore.

As an example see cutaway below of Ford Cyclone (also part of wider Duratec family) fitted to later Roadsters.



The mixing chamber can be seen near centre above stat with bypass (diagonal casting below blue label) directly facing it. Chamber then routes coolant direct via internal passage to pump inlet. Top and bottom rad plus heater return hose unions can also be clearly seen. Your Duratec will likely work in a similar fashion.

Rogers comments made me remember the 'stat mods I use on Mini's (may be worth a try Neil as 'stats are so cheap) I drill 3 x 1/8" holes in the baseplate so they constantly bleed some water flow

I just read this thread and it remind me about my solution 4 years ago which is still working today. After a lot of trials after the head gasket was blown due to too high coolant temperature after purchasing the more effective radiator I just had to reduce the radiator surface. It was the only way to get arranged with the logic of the Ford coolant system.

Here is what I did then.
https://www.talkmorgan.com/ubbthrea...the-cooling-water-temperature#Post713083

You just reminded me Jon of a similar mod I made to a vintage narrowboat engines thermostat. Here I drilled a 2mm hole which aided bleeding as well as providing a bypass trickle. If the stat has a horizontal component to its mounted position the hole needs to be at the highest point.

Thinking further about Neil's issue it may be the best answer to his overheating. I would cautiously start with maybe just one say 2-3mm bypass hole in the periphery of the stat and see how the engine responds. Note stats are usually manufactured with a bleed hole anyway, partially filled with a captive jiggle pin to aid same.

Has the radiator and the cooling system been flushed through and new antifreeze and water been added, just to ensure there is no sludge build up in the radiator etc restricting flow, which can happen with cars over time and those subject to periods of inactivity. It's one of the first things I get done when I purchase a Morgan, as invariably like spark plugs and brake fluid changes is not always attended to as it should be.

OK, latest update guys, I took the advice of Rog and Heinz and fabricated a blanking plate for the rad and made it to cover approximately half of the rad surface area (mounting it to the lower portion of the rad). Initially I found that the temp held better at around 84 for the first 20 mins or so of normal driving which is definitely an improvement. Then I came to a small town and had to queue and the temp rose to about 95 which was fine. I then went onto a faster road and found that as the car was pulling up to 70 the temp started rising again up to about 112 and I eased off the throttle, the temp then very slowly started dropping back. I’m now wondering if I should decrease the size of the blanking plate to allow more air through at the higher speeds or increase it further. Incidentally on returning home I could easily hold both hot and cold side rubber hoses, there didn’t seems to be much difference between them temperature wise.