Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Cooling system

am looking for advice, I have a 1979 4/4 crossflow, the cooling system has an expansion tank. The question is two radiator caps, one 13lbs and one flat (not pressured)which way round do they go? Ie the 13lbs on the radiator or the expansion tank.

Many thanks in advance

It’s usually flat on the rad and pressure release on expansion tank.
That’s my experience where that twin cap is used. My Plus8 had them.
The expansion tank is there to deal with coolant expansion as it heats up. It catches the increased volume and returns it to the system as it cools. Excess coolant and pressure build up opens the cap on the expansion tank to let it escape via a drain pipe. When excess pressure is released the cap closes up again. Basically an excess pressure release valve.

As Philip says - flat cap on the radiator.

Thanks, that’s the way I have it but after a short run the expansion tank is full, although the gauge always reads normal, do I need an electric fan?

The advice I had from Phil at Allon Whites was not to fill the expansion tank up, just ensure there's a bit of coolant at the bottom.
coolant level can be checked and topped up if required in the radiator (when cold enough to open) that was on a 93 +4 T16.

When hot the expansion tank could well be full. The important thing is that it resets back to your cold levels when cooled down. If not then you may have a leak on the pipe connecting the expansion tank to the radiator. JBK (above) is spot on - the expansion tank needs to be just showing coolant when all is cold.

I keep my expansion tank about half full. To monitor the level I stuck a small inverted tape triangle with the top level with coolant cold.

So after a run I can see exactly if the level is constant. Usually this never budges. After a thousand miles round Scotland it had dropped a couple of mm, but the level also varies slightly with ambient. In winter it drops two or three mm.

Interesting thread.

My 2003 4/4 has the Ford 1.8 ‘Black top’ Zetec engine.
The expansion tank fitted (from a MkI Ford Focus) has a lower section marked with a Min and Max level; so very easy to check levels.
Filled to the Max level would still leave 75% of the volume of the tank remaining empty, when cold.
No problems; other than the tank once leaking from a weak seam. (Local Ford dealer supplied a replacement tank for £23).

However my 4/4 suffers very slight and occasional incontinence from the bottom hose connection, to the Mulfab Al radiator.
A problem that I’ve never managed to completely solve.

Bud
4/4 - Stanley

Just wondering why there is an expansion tank fitted.

My 1971 4/4 doesn't have one and doesn't run hot at all

Also 13lb for the cap seems a bit high - I run a 4lb cap

Arwyn

Check the level in the expansion tank when cold. The one on my 2002 Plus8 had a tab inside to indicate the cold level. It was at about 50% full level.
The rad top filler cap was useful when filling up during a coolant change. It helped get rid of air and final topping up.
No coolant losses over 10+ years of ownership and just occasional very small top ups to the expansion tank. In my view the aluminium Morgan rad that a previous owner had fitted ( possibly a replacement based on dates in the file with the car)is slightly under capacity for cooling. It was very sensitive to airflow through the core and the fan cut in during slow/static driving. Never overheated, just the fan noise!