Morris Minor Owners Club

The original Minor radiator which came with my car was beyond repair, got a brand new Escort rad for a snip at £20, so preceded to fit that along with an expansion tank and made up fittings (difficult ). However the water is refusing to circulate, stays in the head and will boil if I let it, thinking it was a couple of duff thermostats, (now on the third) it can't be.

Any one cobbled together a similar system?, must be a air lock aided by the expansion thank filler tube connected wrongly, would a bleed valve in the top hose help or should I reroute tank tube.[frame][/frame][frame][/frame][frame][/frame]

Looking at your photo and comparing it to the later 1275cc Midget cross flow arrangement I feel that the radiator is too low and the hose arrangement for the top hose does not help circulation.
The later high capacity pump from Mini Spares Pt No: GWP134 would help with circulation.
See the Moss parts list attached for the Midget and you will see what I mean.
http://www.moss-europe.co.uk/Shop/ViewP ... dexID=1327
I found that fitting a Marina thermostat cover with filler allows for the filling of the block and bleeding the radiator.[frame][/frame]
With the radiator in the boot I have an electric water pump fitted to aid circulation.
Slightly enlarging the stud holes in the Marina thermostat cover allows it to be turned to suit.

Tanks for the idea of using a Marina thermo top and hi flow pump.

Where is the expansion tank plumbed to>
It looks like a Tee into the heater circuit, it shouild be connected above the pressure cap, I don't see one of those anywhere.

Yes your right heater / bottom hose,I guess I wasn't thinking just thought it would easier to plumb it in there, the only pressure cap is on the expansion thank, first photo.

I consider that the expansion tank as fitted will have little adverse effect on the cooling system as the heating circuit is subject to the same pressure and expansion limitations/considerations as the main coolant system and the way the pipework is fitted it is not shut off from the main coolant. The expansion tank is just an adjunct to the main cooling system. What really matters is that when the coolant expands/contracts it is allowed to flow to and from the expansion tank into the main coolant system and as such the system fitted appears to allow that to happen. The cap on the expansion tank fitted undertakes the same task as one fitted to a Minor and any major expansion of the coolant is discharged through the yellow overflow pipe.
When I fitted the rear radiator to my Minor the most important consideration was to get the water and flow levels right. The expansion tank is just taken off the radiator to the standard BMC/BL expansion tank with a standard BMC/BL pressure cap (similar to the MG Midget see link above).
Whilst the pipe work may look complicated it works.[frame][/frame]
I am pretty certain that your problem lies in the radiator arrangement and that you cannot bleed any air out of the radiator.
Air will only go UP and NOT down. I suspect that the top half of the radiator is full of air so not allowing the cross flow of coolant.
What you could do is to solder a bleed screw onto the copper pipe from the thermostat housing to the top of the radiator at its highest point. That would allow you to bleed the air out of the radiator and the block.

The expansion tank shouldn't have any effect on the circulation anyway.
As long as the thermostat is working then an air-lock seems to be a likely cause.
It may be better to try filling it from the heater hose than the expansion tank.

How old is the Pump,its not unknown for the vanes in the pump to corrode over the years,it may have been OK with the original sysytem, but the new plumbing may be too restrictive. If it were mine I would go back to the original system,I think you may allways have trouble as it is.

the system you have needs a hose connected to the blanked of pipe on the header tank and too the top of the t -stat housing otherwise the water in the tank cannot be drawn into the cooling system as there will be a vacuum in the header tank and the effect of the coolant expanding with heat will also keep it there , the small link hose will bleed the top of the rad initially and after the t -stat opens will return any air in the system to the tank , the main feed from the tank should be connected to the bottom hose so the coolant can circulate and bleed before the stat opens , has your t- stat got a small bleed hole in it ? if not drill a 2mm hole in the base so that air will bleed out of the cylinder head

The pipe with the yellow end at the header tank should exit to atmosphere as explained in my post above. If it is blanked it should not be. By all means fit a pipe from that outlet to exit below the car so that any overflow of coolant does not come into contact with the bodywork.
If you have a pipe from the thermostat housing to the yellow connection on the header tank 2 things will happen:-
1. Any pressure in the cooling system will bypass the pressure relief cap (on a Minor the radiator cap) and cannot escape to atmosphere; it will be retained in the header tank with the possibility of either splitting the header tank or blowing a water hose pipe.
2. The pressure relief cap on the header tank becomes redundant.
Even a small i.d. pipe between the thermostat housing and the header tank as proposed above is sufficient to transfer pressure and coolant to the header tank.
The system then becomes totally sealed and there is nowhere for any coolant expansion/pressure to go.
It would have been better for the header tank to have had a direct connection to the radiator but the system fitted is not totally deficient and so long as coolant can be made to flow across the radiator it should be satisfactory.

if you vent the header tank to air there will be no system pressure , this is a header tank system not an expansion tank system which relys on a radiator cap to efectivley control the escape and return of excess coolant like the marina set up , the header tank systems requries a coolant return and vents excess pressure through the cap

If that is the case I stand corrected.

Yes I did call it a expansion tank and I think the correct name is header tank, this is from a Ford Fiesta and the little yellow plug I believe is a high pressure blow off valve. Job's done today........ fitted an 8mm copper tube to the top hose and changed the other fitting comming from the tank to suit, so now it will fill from the top .Also removed the bottom hose T piece so now it's near standard there, yes I did drill a water bypass hole in the thermostat so I'll see if fills okay now without air locks.

I can't see any great problem with your install either (but is it worth it ??) - are you sure the rad is not blocked internally ?? Fill and run the engine with the rad cap off and watch for bubbles coming out - once the air is out it won't go back in. All failing as has been suggested - check the pump impeller.

I always ran the engine with the cap off, bubbles were reluctant to come out without a little squeezing of the bottom hose, it's a new radiator and so I'm assuming it can't be blocked. If it's still the same after finishing the filler pipe on the top hose I will change too a better pump as suggested.

I suppose it's possible there is too much resistance to flow through the rad - and it's all just circulating round the bypass hose. I would block that off if it's open.