Tom M'Guinn

Agree it's worthwhile, and a great diagnostic tool, but once the HG starts to leak under boost enough to detect, they only seem to get worse from there. It's good for avoiding catastrophic failures and might let you nurse the HG a while, but once the coolant pressure starts to spike when on boost, it's probably just a matter of time....

Dwane

Just to clear this up in my head.
You set your sensor up for a maximum of 18psi and if it goes over that you know you have a HG problem.

Dubai944

You should write a book with all your secrets in it. I'm sure plenty of guys on here would be happy to pay for it.

Ronin-951

Wonder if you still have a Heater in the Car? Pressure Tester can miss the Hose going from the Heater Control Valve [takes Vacuum to operate and is 'suppose' to fail Open] to the Firewall. When that Hose leaks, Coolant falls right onto the Exhaust Pipe and turns to steam.

catamount

I too had a mystery coolant leak. It turned out that there was a hairline fracture in one of the hose nipples on the expansion tank. Oddly, pressure testing when cold didn't really reveal it. It wasn't until we tested at a warm temperature did we discover it.

rlm328

I am running an analog water pressure gauge. I tapped into where the bleeder valve goes.

odurandina

water injected, through the pipe, and out the back.

and maybe even a slight overall power increase.

mahoney944

So this will replace the stock vent bolt on the front of the head? I would assume this uses a one way valve that works similar to a shop like quick disconnect? .....As the site explains, i over looked the description on the site lol.

Chris White

If you exceed the pressure rating of your cap then you have 'a problem' - either overheating or pressurizing the coolant via a head gasket leak. Either way you should stop what you are doing and figure out what it wrong!

A common failure on a head gasket is the #4 to coolant jacket breach - when that happens the pressure from the cylinder will over pressure the coolant jacket in the block and start blowing out the coolant from the expansion tank. Depending on how bad the breach is it will take a little while for the coolant temp to spike - and once that happens its usually too late to back off, the damage is already done.

Chris White

Yes, you can either drill and tap another location or replace the stock bleeder valve. ITs a simple devise, a spring holds it close as well as any coolant pressure. Simply push the top down and it vents the pressure. If air comes out something is not quite right. If coolant comes out all is normal.

Some track cars seem to develop localized boiling and they create air pocket over time - once you have enough air you will get more boiling and eventual a major overheat. This will help get the air out of the system.

Chris White

True - the major reason for the warning is to stop running hard before you do permanent damage to the head / block.

odurandina

wouldn't he see a spike on the temp guage due to the steam bubble in the head... accompanied with vapor [near coolant temp] exiting out the overflow vent.... but before the rest of the engine actually overheated ?? ....thinking the guage spiking would be like advanced warning.

Chris White

I have found that myself and most other tack drivers don't stare at the temp gauge looking for a 'wiggle' while we are at speed!

The order of events would be the increase in pressure due to the breech and then, after a while, the increase in temp due to air in the system. The steam comes after the increase in temps due to air in the system. By then you are well down the road to serious head gasket failure.

333pg333

Data showed that our water temps may have gone from 90-92 degrees so they didn't climb or spike radically. We don't have the stock tank setup either. Have a single smaller bottle with cap and a secondary tank elsewhere. I suspect the headgasket leaked and the water must have escaped out of the 2nd container which eventually vents to atmo. Just that we would have expected to see evidence of the leak at 5 ltrs?
There was no water in the bores or oil. Going to test on dyno to make sure it's the h/g and then change it. Just wasn't expecting to have this issue so soon like many of us have had running higher boost and E85 with Cometic h/gs. That we were able to top up the first time with a couple of ltrs and run another session shows how these gaskets can work. With a stock gasket it's game over and with a road driven car, it's a looooong tow home.

theedge

Patrick I once had a tiny pinhole in one of the hoses. It would ONLY leak during or immediately after hard driving. It would fire out this tiny little stream of coolant but as soon as it cooled slightly (like idling) it would close up and stop leaking. I could only find it by driving hard, stopping really fast and getting the hood open really fast to catch it. It didnt cause 5 liters to disappear but it was significant enough.