....cooling issues ever seemed to be a hot topic (pun intended)
...More than happy to be corrected if I have made any mistakes..
No problem. Fire away!
....the hard plastic expansion tank, and as already been explained the radiator is fitted with a blank cap, thus the flexible tube from the filler neck of the rad that connects to the bottom outlet of the expansion tank is free to transfer the coolant as it warms and expands, into the expansion tank.
Yes I had one of those myself..(below) Remember my first Plus 8 was made just a few months before yours. Sadly, it melted in the aftermatch of our 2002 accident. I first switch to its copy in black metal and then to large prettier tanks as time went on. Not sure why the switch from plastic to black metal, though the later is said to release heat much more efficiently. LR/Rover stuck with black metal of different (lager sized tanks) after that.
the pressure cap setting (15lb on my +8)
Mine as well. Plus 8 water pumps (until the crank driven GEMS) should not take much more. And the engine innards are not set up for more.
On my +8 as can be seen in the pics the water level in the sturdy plastic expansion tank can be clearly seen through the material the tank is made of which is perhaps worth noting as the tank itself has moulded lettering with arrows indicating WATER LEVEL....
Convenient, though on a proper system, the water always returns to the same place unless one mistakenly under fills.
...my carb fed and standard tune mid 80`s+8 The thermostat opening temp is listed in a Rover 3.5 V8 manual as being 82Deg C (180Deg F)is 90Deg C
Here is the crux of it. We are addressing different things. Though my first car was made earlier than yours, it was an EFI, not carb'ed. All EFIs are required to run hotter, for a more efficient, reg-compliant burn. The fine spray mightily increases the bhp and therefore the need and production for the heat. All Morgan LR/River EFIs from the optional (L-Jet) ones in 1984 to the last of the stock line in 2004 (GEMS) have a thermostats that begin to open at 88C and should have rad fan switch ranges 6C+ higher than yours. Few are properly set up. (And sadly, owners are sold whatever replacements that are close to hand from non-savvy suppliers.)
However, the MMC did not alter their Plus 8 cooling system from your carb system for 1another 5 years, creating a generation of worried owners and lots of radiator aftermarket joy. (wryly) Bill Beck only began to work on that with GEMS Plus 8s, when he installed SPAL fans in 1999 IIRC.
I suspect the height of the expansion tank seems unlikely to be critical...?
It is critical. As the expansion tank system and the hose to it is part of the entire system, as you well understand, it makes no sense to try to fill from the bottom up.
The thermostat opening temp is listed in a Rover 3.5 V8 manual as being 82Deg C (180Deg F)
Only in the Manual specific to your car.
https://www.gomog.com/allmorgan/39Plus8Handbook.pdf[quote=Luddite] Reluctant to type this.... But my Mog has not ever overheated,
That's great! But you have a significant advantage from the EFI crowd. EFIs of the same era and later have the same cooling system and components as you, along with a higher opening thermostat and rad fan. Keeps their owners worried.
I boiled over once, where spirited driving in Dordogne on a hot day, while I still had the original 3.5, brought this common fault into my life.
https://www.gomog.com/headgaskets.html Actually, I wouldn't change a thing of that day. I swapped in a tuned 4.6 on my return to England. I have a picture of the gasket.
gmg
