New Caterham Overheating

[softedave]

Hi, I have a new Caterham 1.6K Series that I built over the winter. I have done around 600 miles in the car most of it trouble free. However, occasionally when I get the car out it overheats very quickly - the bottom radiator hose is cold indicating that the thermostat has not opened. I have changed the thermostat for one that opens at 80 degrees but it has not helped. Caterham think that I have an air lock (and I agree). I blow fluid through the system and I can clear all the air out - the car then runs fine until it is left to cool down. The next time it is started (sometimes) the problem returns. It's driving me mad - I never know when the car is going to overheat.

Any thoughts?

Dave

[softedave]

Thanks for all the replies - there are some really good ideas here.

I am fairly sure the problem is air locks and not the fan switch as the pipes are cold. When I do manage to release all the air (by raising the front as you suggested) the fan kicks in.

My main concern is that once all the air is out the car runs normally all day; then I put it away for a day or two and the problem re-occurs. I may try re-routing the top hose from the manifold back to the expansion bottle so that I can vent the radiator via it's small top hose (as suggested by Peter-2006). If that fails then perhaps some holes in the thermostat (or remove it completely??).

The radiator has no bleed at the top and uses the new Caterham self bleeding system. I am using Comma fluid (the pink stuff recommended by Caterham).

Finally (Jack and MLE) even with the lid off the coolant bottle I never get a flow of coolant back to the expansion bottle. Some liquid comes out whilst it is heating up but there is certainly not a constant flow - is this correct?

Thanks again to you all, love the car - so frustrated by the problems. Dave