i have a problem that has me scratching my head a lot. i figure i might put it up here to get a 2nd/3rd.... opinion.

ok i have a stock engine, running stock radiator, stock radiator hoses. the TB has been bypassed. and the car is 8 year old now. also i have been running 25-27psi boost with stock head studs. previously i had a BBK Lite, now i have a MAP EF3.

about 5k ago i noticed very high temps and so stopped and checked the car had no water in the overflow bottle and was very very low in the radiator. since then the car will regularly loose water. i have had the water system pressure tested at a workshop and they didnt find any leaks, they replaced by 1.1bar water cap with a 1.3bar one, but no change. i have physically looked (as well as the workshop) and cannot find any obvious signs of coolant leaks anywhere in the engine bay.

there is no cross contamination, in either water or oil. so no oil in water and no water in oil. the oil is not bubbly in anyway. also the water is not bubbly. and with radiator cap off it does not show any bubbles or overflow when engine running. the water has not come out of the overflow bottle.

but it does suck water from the overflow bottle. if i go for a 30min normal sedate drive, the water level drops by just under 1cm. today i went and gave it beans for about 15minutes and the bottle is practially empty.

seeing the radiator is pressure tested fine, the next culprit seems the headgasket or possibly a lifting head (stock headstuds). could it be anything else, incase i missed something obvious. i have a headgasket and ARP head studs which i will put in soon.

 

Check your upper rad hose where it connects to the engine. Could be your uic pipe rubbing the hose clamp. It won't show up during a pressure test but only when the engines moving back and forth.

 

A few ideas:

Weep somewhere in the radiator core
Radiator gasket leak
Pinhole in a coolant hose
Crack in the jug
Weepy water pump
Heater core

 

what pressure did you test the system at? have you visually inspected the TB hoses? they are known to crack. another thing to consider, some leak points don't actually **** fluid until car is at operating temp...

I had an issue like this, but it turned out there was an air bubble in the system after my most recent turbo swap and it just gradually worked its way out, sucking from the res tank and empying it a few times. I really thought it was an hg issue but couldn't see any reason why coolant would empty inward against all the pressure instead of being pushed out of the overflow....

I cant speak from experience on the high pressure rad caps, but our stock one is 0.9bar i think?? subjecting the system to higher pressure by using a 1.1-1.3bar cap may expose a weak point somewhere. do you run an undertray? they not only keep things clean/protected/aero but they work great in identifying leaks that may only occur during peroids of driving...

 

thanks for the suggestions.

i am not sure what pressure the workshop boys tested it at. the original cap was 1.1 the new one is 1.3bar. since i did the last turbo swap i havent put the under-tray back on. and the water issue was before the turbo swap.

the only worrying thing is that the rate of water loss is quite high when i am boosting.

 

Im not familar with your turbo but is it water cooled? could be pushing past the seals and you wouldnt know.

Do a compression test and that will rule out your HG right away. A leak down test would be best though.

 

^^unless only a water channel was leaking.... anyway had a talk to the mechanic he is sure its engine... just gota find time to do the HG/studs

 

Coolant flows through a cavity molded into the turbo cartridge and out the other side. There are no seals other than where the hoses connect. The cartridge would have to crack for coolant to escape.