I have searched on this and would still appreciate a couple of thoughts. Did a bit of lite mods over the winter on the sprint car V3 STi, main part being a VF34. Recently I've noticed after a sprint the coolant is overflowing and can be seen slightly bubbling out of the small tank behind the battery. Car starts fine and pulls like a train. Maintaing 84 degrees when idling this rises to 96 ish after a sprint according to the Apexi commander. Something isn't right,the fans work,heater is hot but the bottom hose remains cold. Car was left idling for 15 mins before sprinting at Anglesey on Sunday, hose still cold. I'll drop the bottom hose today and look at the thermostat, I think these are all the same on the Subarus and should open at 78 degrees.

Thanks in advance for your suggestions.

 

The bottom hose should be "cool" The water flows from the engine through the thermostat into the top hose, cools in the rad. then back to the engine via the bottom hose. Is the top hose hot? If it is, then water is flowing. The operating temps. you quote seem fine.
JohnD

 

Top hose is hot but bottom stone cold ie not even warm that's what puzzles me I thought it would be at least warm after a thrashing !!!!

 

I think Johnd is wrong, the Bottom hose should at least be warm once running, sounds like the stat is not opening. Radiators aren't that good at turning almost boiling water cold again

 

When I said "cool" I was trying to compare the temps of top and bottom hoses. Indeed, it should be warm.
If the thermostat remains shut, water will not flow into the top hose but, as the poster said the top hose was hot, one must assume some water at least, is flowing?
If they fail, thermostats usually fail open.
JohnD

 

agree there mate,leaving the car ticking over wont get the bottom hose hot.after a run pull over and feel it straight away

 

Sounds like an airlock within the system, ensure your system's bled and ensure there are no leaks - first place to check would be the turbo supply lines as you have recently been working here.

 

sounds like heads are lifting on boost and leaking some combustion gas into the water system that then blows out the overflow by the battery.
do a carbon test on the water to see.

As you just sprint the car and as long as temps remain okay you could run it until a convenient break between sprints before doing the gaskets..

the sti3 standard metal gaskets are pretty good.. use ARP head studs for an extra safety margin.

Simon