trackday, ford x/flow, 22 degrees outside: my car was running rock-steady with ~85degrees water temp (original pick-up point in head) for around 15min.
i have a huge vw golf/passat rad , no thermostat, xr2-thermostat housing with 20lbs double-seal pressure cap and an open overflow tank.


than my car spin, due to some oil on the track. engine went off. i let some others pass, engine was re-started around 20sec. later.

gauge showed 100 degrees. nothing uncommon after you shut off the engine under such conditions.

theoretically the temperature should have lowered within the next seconds during driving...but nothing happened!!! even with activating the fan.

after another lap, antifreeze started to escape on the pressure-cap (xr2 thermostat housing), some went into the open overflow tank, some onto the ex-manifold (which is strange as the 20ls pressure cap has 2 seals)...gauge showed 105degrees.

i drove the car back into the pits and thats how it s now. any ideas?

by the way: the day b4 trackday, i drove the car 140km in the mountains, also motorway with 31degrees outside temp....water temp was 80-85 degrees

Force of spin could have caused a few things
Airlock
Waterpump impeller come loose
Sudden lack of airflow causing temp to rise and damaging thermostat.
Or just random fault that is not related to spin, just fluke it happened at same time.

Even waterpump is new ( unknown aftermarket pump) might be a reason...there is no thermostat...so no problem here...

Not much to go wrong on a xflow without a thermostat. It can only be circulation. So either water pump, drive to water pump or an airlock.

My first check when cooled down would be the coolant level ,followed by leak check and possibly blockage to the radiator airflow?

Hardly any coolant left. Flow through rad perfect and ducted. Found a loose generayor bolt....msybe the drive belt slipt

Check the ignition timing is advancing with rpm, nothing will make an engine boil quicker than retarded timing.

[Edited on 17/9/16 by britishtrident]

Everything fine...i even tested4 degrees less today...total max advance 35

2nd day....new rad cap...tighter drive belt....same...after 12 min...temperature climbing...after 1 further lap...cooling system empty

Next stage is a cooling system pressure test or even a cylinder leak-down test.

Flat out to engine off for 20 seconds? Heat soak is a possible causing a localised boil and loss of coolant and or airlock to disrupt flow.

After some beer i decided to take off the head....here we go...1st cylinder....headgasket wasnt well positioned from engine builder...and firering burnt towards waterchannel. Problem solved...i thought..

what we alos found: the engine was fully rebuilt without machining the block-face, nor the head-face.


Next race....same problem again....after 15 min sudden temperature rise....



[Edited on 18/9/16 by alfas]