K series - mysterious coolant problem, UPDATE - possibly sorted . . . .

[Smithy77]

Bit of an old thread to resurrect, but did you ever get to the bottom of this Steve?

I have just inherited Mankee's PRRT for my newly built 230bhp K and I'm keen to understand your issues. The reason being that Mankee decided to ditch the PRRT after experiencing near identical symptoms as you with the expansion tank overfilling after a track thrashing, but I think he experienced coolant being blown out of the expansion bottle cap too. He did also have a weeping radiator too, so hopefully this was the cause for him.

So far I've done 300miles of running in and all seems fine (aside from one or two weeping joints I need to resolve), but I got my first trackday at Hethel on 9/10 and am obviously conscious of this problem happening to me.

[Grubbster]

I did cure it in my car, trying to remember what it was that did it, it wasn't any one thing that suddenly fixed it as far as I can remember, I ditched the PRRT and had a QED remote stat fitted by Tom New, I moved the coolant sensors from the water rail and put them in the section of water rail cut into the coolant hose on the opposite side of the engine (so not above the exhaust) and I can't remember what else. I may have had a head gasket changed as part of a partial strip down (but I'm really not sure as it came apart a couple of times for other reasons). The coolant level still rises a bit in the tank but not to the point of blowing it out of the cap. I did a fair few trackdays since and never had any more problems. Sadly I no longer have the car but as far as I know it's still going ok.