Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Coolant Refilling

Hi all. I have a 4/4 with the Zetec silver top engine. I have just replaced all the coolant hoses with new silicone hoses. I'm having trouble refilling the system. About 8lts came out but I have only been able to replace around 4lts. Any ideas on how I should go about it? I did remove both the expansion tank cap and radiator cap, I presume the thermostatic cap goes on the radiator, or have I replaced them the wrong way round?
Any suggestions?
Thanks in advance.

I am sure the thermostatic cap is on my expansion tank and ordinary cap on radiator.

On my 1999 Plus 8 the plain cap is on the rad and the pressure cap on the overflow tank.

Is the valve to the cabin heater core open?

I would be surprised if the position of caps would make a difference to how much coolant you got in. I too suggest the heater core; maybe an air lock so remove one of the heater pipes to see if coolant or air flows out.
One other thought: has the engine been left empty of coolant for few days? It is possible that the thermostat has rusted closed. That happened recently to a friend’s +8 when he was awaiting delivery of a new water pump. First time out, it boiled over within couple of miles from home.

I would try briefly running the engine at idle whist topping up.

BTW if there is a narrow bore overflow pipe running from radiator cap neck to expansion tank then the cap should be the usual half turn spring loaded pressure release item (not thermostatic!). The expansion tank cap is usually a plastic item with built in pressure release although this may not be obvious.

Here's what I was taught in my youth...
Radiator cap is simple seal. Expansion cap has a spring loaded seal. This loading can vary with engine type but the usual load is 15psi. Check your engine spec for type needed. This raises the system pressure slightly resulting in a corresponding boiling point rise to supplement the coolant additive effect. The expansion tank collects some coolant as the engine warms it up and when things cool it gets sucked back. If the system pressure gets too high ( greater than the cap rating) the cap spring gets pushed up to allow excess pressure to release. It's a pressure relief valve rather than thermostat. The actual thermostat is elsewhere and restricts coolant flow on cold start so that running temp is reached sooner. Fuel efficiency and emissions improved when cold. The expansion tank level when cold is what you check for coolant volume. Most will have a tab inside to show correct level BUT the Plus CX don't. There is a label on the side so a dipstick is used to check. I use my middle finger as it reaches the correct level. GRRR. Old school tab would be easy.
Bit of a minor rant.....Same for oil level...no dipstick and the on-board " computer" needs a warmed engine running. Stop the car on the level. Press a button. Wait as the system checks. Watch the screen whilst it runs. Progress eh!

Sospan,
I have a plastic rod with a mark at 50% to measure on my CX. I agree a tab would help.

Robrhi,
I f you can fill the car on a slope with the front at the high point. Ensure the heater is on full heat and keep blipping the throttle & topping up.
The heater matrix are a high point on the circuit and it maybe you haven't got coolant into it.