now that the car is up and running i may have an issue with the cooling system . i need to vaccum fill it and have another bleeding session but it seems to be struggling to flow properly as the pressure builds in the header tank at the back and once the front fans kick in the rad goes pretty cool as if the coolant isnt flowing properly .

here is my plumbing which i used on the twin bike engine set up although the top hose at the front was above the top of the water level in the engines at the back



looking at the elise and vx220 it doesnt look much different but i may have missed something , the only issue i can see is the bleed to header tank is at the same level as the stat housing rather than coming from the top of the rad as it did in the donor car



the cap on the rad at the front is 1.1 bar and hasnt vented and it certainly seems like an air lock as the water temp is around 90c at the header tank

I'd have a bleed at the top of the rad, looks like an air trap

Absolutely, you need a bleed from the top of the rad back to the header tank, no way at the moment for air to get out the rad. You can take it from the neck just under the cap.



Cheers

Fred W B

[Edited on 2/10/11 by Fred W B]

[Edited on 2/10/11 by Fred W B]

[Edited on 2/10/11 by Fred W B]

can the bleed follow the front to back pipes and still work properly ?

quote:

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Originally posted by froggy
can the bleed follow the front to back pipes and still work properly ?

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From that diagram you appear to be pumping coolant straight into the header tank. The coolant has nowhere to go except back to the head via the top bleed pipe. If you have replaced the engine's belt driven pump with an electric one, the new one should pump into the original's inlet, i.e. into the block.

The header tank bottom pipe should tee into the return pipe from the radiator, before the inlet to the pump.

You need a bleed nipple on the top of the rad somewhere. There is no need to provide a bleed pipe back to the header tank. You will need to open it to fill the system, and maybe periodically open it to remove any trapped air.

The heater should take its feed direct from the head, i.e. not controlled by the thermostat. The heater return is ok as you have it.

Cheers R

Two header tanks is a no-no -- one header tank and one presure cap .

I you want the heater to work you need to plumb the heater in on the engine side of thermostat, to do this it must either fed directly from the head or you can do what some MGTF and Lotus Elise owners have done, remove the existing thermostat and fit an external Rover/LandRover PRT thermostat (sometimes called a PRRT) in the front compartment. If you search on PRT conversion you should find the info you require, the parts required are a Landrover TD5 thermostat and a 32mm tee (as sold for fish ponds plumbing) both are available very cheaply off ebay

[Edited on 2/10/11 by britishtrident]

i used the filler on the rad to bleed the front end and the pipe from the water pump to the header tank is the same as the factory set up . the only difference is the bleed to the header is coming from the head before the thermostat rather than from the top of the rad .

to copy the saab system i would need to run a bleed hose from the front of the car to the header tank and use the current bleed hose to get any air out of the head with the stat shut .

one thing niggling me is the diameter of the hose from the top of the water pump to the header which may be fine in the saab with the short coolant lines but it might be too long and the flow is going straight up to the header tank and may need a restrictor to force the coolant through the block instead

And another thought: Would the coolant take the easiest route through the heater matrix rather than the main rad? Have you tried fitting a restriction into the heater hose (or clamp it with moleys).

I put a cable operated valve in the inlet hose so I can block the line into the heater . Il try clamping the line from the top of the water pump to the header and add a bleed from the Rad to the header tank . If I copy the saab layout and it still struggles to keep cool idling it must be flow as the system
Is definitely big enough to do it

The mgf has a bleed on the rad, a bleed on on the heater matrix and a bleed on the engine coolant pipes.

When the system is filled, all three of these need to be bled to ensure there are no water traps.

quote:

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Originally posted by froggy
i used the filler on the rad to bleed the front end and the pipe from the water pump to the header tank is the same as the factory set up . the only difference is the bleed to the header is coming from the head before the thermostat rather than from the top of the rad .

to copy the saab system i would need to run a bleed hose from the front of the car to the header tank and use the current bleed hose to get any air out of the head with the stat shut .

one thing niggling me is the diameter of the hose from the top of the water pump to the header which may be fine in the saab with the short coolant lines but it might be too long and the flow is going straight up to the header tank and may need a restrictor to force the coolant through the block instead

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The pipe from the bottom of the header goes to the water pump and the vac point on the rad filler neck is blanked off so it's not drawing as it cools down . I will alter the heater circuit to copy the Saab layout but the valve is closed at the moment so as long as it's bled it should work , il do some more bleeding tomorrow

clamped the bleed line from the heater outlet on the head which is before the thermostat and all is well now . hopefully i can live with the system as it is with the header tank a good eight inches above the head it shouldnt give any issues.