The header tank hoses are 8mm. The top one goes into the main pipe into the heater, the bottom 8mm hose goes into a T in the main pipe from the thermostat to the bottom of the rad.

The main pipe from the front right top of the engine goes into the top of the rad, the thermostat pipe goes into the bottom of the rad.

I'm currently getting overheating problems, it will be fine for a while then the engine will overheat but often the rad will be cold. Seems to me like a bleed / air in the system problem, and I may well have plumbed it wrongly.

One suggestion I've had is to replumb the top bleed hose from the header tank into the main pipe from the head into the top the rad, instead of into the heater hose.

One more thing to add is the rad sits low in relation to the engine, but the header tank is the highest point.

Your thoughts on this would be much appreciated as it's driving me nuts.
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Hi Jasper

Not sure about your plumbing but if the rad is cold at the top when the stat is open then its full of air not water.

Can you bleed the rad ?

Or release pressure at the header to move the water round.

Took me a while to loose the air locks on the zetec with a polo rad but luckilly the polo rad can be bled at the top.

Must have bled the system about 4 times now, done everything I can to get all the air out, I think it must be down to plumbing.

Has your thermostat houseing only one outlet/inlet ?

Yes, comes straight out of the thermostat into the main hose to the rad. Check the thermostat is opening fine which it is, even had the water pump off and all seemed perfect there to.

I'm thinking top of header tank needs to come from engine ie thermo as suggested.

Also thermo house on both engines i have used runs to top of rad just to make it even more confusing.

Yup - James suggested to run the top header tank hose to the top engine main hose to rad, instead of the heater hose.

In the production car for this engine the main hoses go the way I've plumbed them, thermo hose to bottom, top hose at engine head to the top of the rad.

Remember water pump would normally pull water from bottom hose/rad flow would go through engine back out to top.

I'm sure someone will be along soon to put us all right.

I'd suggest running the header tank fill hose to the bottom hose and not the top one.

It is on the bottom one, bottom of the header tank to bottom of the rad....

All sorted, swapped the 8mm filler hose to the header tank for 16mm, and took another bleed point right next to the head, and used the bleed screw to get the last of the air out, never goes over 95 deg now Thanks guys.

i have the same issue, but mine just gets very hot, im going to re plub my rad feed into the bottom hose, how did you fit another bleed?