boxerblues

Hi all,

Looking for some help if possible, I am running a hatch STI that has been remapped with bolt ons and is running in the region of 370bhp at 1.5bar on the standard VF48. It has been running without fault for around 10k miles but I have just started to notice some issues with the coolant. If I drive it off boost, I see no issues, but if I take it out for a spirited drive is starts to empty the coolant from the header tank into the overflow tank. It hasn;t ever reached the top of the overflow tank and spilt out into the engine compartment, it's a few inches off that. Sometimes it'll suck the coolant back, sometimes it doesn't and I am having to drain some out of the overflow tank and pour it back into the header tank. It isn't burning off any of the coolant, if I drain the exact amount from the overflow tank to take it back to the full mark, it is exactly the correct amount to fill the header tank back to the top. The car never overheats, there is no white smoke and drives perfectly. I have replaced the cap on the header tank with a 1,3bar item I had from a previous car and the problem persists. Once or twice it has been enough to completely drain the header tank to empty, but like I say it's just sitting in the overflow tank.

Am I seeing head lift? or would this be attributed to early head gasket issues. I haven't performed a sniff test yet, but there is no smell of fumes in the coolant and the coolant is clear and like new.

Anyone shed any light on anything I may be missing here?

Thanks in advance.

1509joe

iTrader: (2)

You've answered your own question either way its a head off job.

Don Clark

Sounds like classic symptoms of both,(one leads to the other) if running at that BHP (what's the torque figure?) without Head Studs (ARP,RCM) rather than the OEM head bolts.
Has it been forged/rebuilt??
Not a good picture but the result of running just 340BHP/360Lbs ft on OEM bolts.

boxerblues

Thank you both, torque is 390lbft on standard block. I know I am pushing the standard bottom end a little, and I will be forging the engine if it comes out, just wanted to check it's not something else that I am missing. I have replaced the header tank cap, but not the radiator cap, but I assume this wouldn't make much a difference if it's emptying from the header tank. I've searched the forums but there seem to be other issues that people see alongside mine, such as overheating which mine has never done. Sounds like I'm over the limit of the standard head bolts allowing lift which is pushing the coolant around.

1509joe

iTrader: (2)

If you want to satisfy your curiosity take the wee pipe that goes to the expansion bottle off the header tank, put a length of hose from the header tank to under the windscreen wiper on the passenger side. Let the engine warm up then go for a run off boost then when you've satisfied yourself give it some boost and you will see it escaping out of the end of the hose.