333pg333

Strange issue occurring recently. We went to the track 10 days ago and discovered that we were using a lot of coolant. Temps were ok but we had to top it up by 5 litres for the day. There was no sign of it on the pit floors which is where you would notice it if we had a leak or were overheating. So we presume that after 7 track days and 3 dyno sessions we’ve just gone through another Cometic headgasket in a similar timeframe to what we were seeing on the old 2.5L motor.

I had really thought that by going to the new motor with massive 9/16”s headstuds and a deckplate that the old situation of ‘tearing’ the Cometics around the seal/rings would be a thing of the past.



To throw another thing into the mix. This morning Paul has just put a pressure pump on the system up to 15psi and the pressure is dropping. This with the car stone cold and motor not running. Again, no sign of the water. Where is it going?

Clearly there’s no headlift occurring right now so we can only think that the damage has been done to the headgasket and could the water be leaking into the dry sump pan? Going to check the oil tank obviously but if we find no sign of water where to next? We can take the sump off of course but you’d think that if we lost 5 litres of water and it was getting into the oil system then we’d see clear signs of it in the oil tank? Somewhat stumped….

Paulyy

There's no other place for it to go other than the cylinders.
Out of curiosity, have you tried running a standard HG before?

rlm328

I have been fighting this battle. I had a head gasket leak. The cylinder would over pressure the gasket enough for blow by. I now have the Cometic, and I am starting see water use after about 10 track days. I will be doing diagnostics after I replace my suspension system that broke this weekend.

refresh951

Definitely sounds like the HG. What is your CR? What is boost set to at the track?

333pg333

8:1 & 22 psi.
I think it has to be the hg too. Apparently signs of detonation are not always visible and may just be overly high peak cylinder pressure.

refresh951

Do you monitor and log knock?

Tom M'Guinn

Normally when the HG is leaking under boost, the combustion gases will pressurize the cooling system and you will get coolant spitting out the overflow tube. If you have a catch can for coolant overflow, you may not be seeing it? If all you have is coolant going into the oil, don't overlook the possibility of bad oil seals in the oil thermostat housing. You can usually (not always) tell the difference because the oil seals will leak whenever you run the motor, whereas a bad HG will often only leak under boost when it's first going bad.

+1 on knock data... Also, how much ignition advance are you running at 22psi at WOT? And what type of ignition? What octane/type fuel and AFR?

333pg333

When we go to the track the engineer monitors knock. Have Motec Knock block in place and when it goes on the dyno the tuner puts something on the intake to amplify it further.

Don't have my current Ign map yet. Only got retuned week before last and I wasn't there. These guys are good but always busy and hard to get data out of them. My ign map was very conservative prior to the new turbo and fuel. He said he was able to add some more timing in this time but don't know how much more. Ignition is CDI sequential running Bosch coils. Octane of the fuel this time is supposedly 116 E85. The last fuel was more like 105 or 108 E85. Perhaps the damage was already done previously but then we would have seen the need to top up the coolant. We do run a separate overflow tank which I'm pretty sure goes to atmos. If it was pissing out coolant on the track though we'd soon know about it either by spinning or a bunch of other competitors banging on our garage door! If we don't find something else obvious staring us in the face we'll take it to a dyno and run some clear tube in the system so we can view the coolant moving under boost.

Oh, and we were running 1.5 bar as opposed to 1.3 previously. (Car felt quite nippy btdubbs!)

Paulyy

Anyone got one of them camera scope things? pressurise your cooling system and look down the cylinders for any signs of coolant.
Only a suggestion.

333pg333

Yeah looked in there today. No sign of any water. Maybe today's pressure tester seal was bad too?
Going to run it up on a local dyno to get some visuals under boost. Otherwise, we'll be entering it on the Magician's club circuit. 'Amazing car makes slimy green liquid simply vanish!'

Thom

Never seen any white smoke in the exhaust?

Maybe a wild guess, but I am tempted to think you cooked your previous turbo because of excessive EGTs (too little timing considering the big cam with stock intake), and perhaps you are starting to cook your turbo seals...

333pg333

Not bad. I'll put it to the board. ;-)
But no, didn't seen any evidence of smoke out the pipe so perhaps not. If it was that, we'd see a ton of smoke with 5 ltrs.

Willard Bridgham 3

My cometic leaked both combustion gas and coolant. Changed back to stock gasket and no leaks.

Max boost 15-16 psig

Chris White

Highly recommended 'cheap' mod - add a pressure sensor to your coolant expansion tank and datalog the results. You will see the signs of a failing headgasket there long before it does any damage. I have that sensor (an oil pressure or fuel pressure sensor will work fine) hooked into my ECU and programmed to kill boost if it sees over 17psi (you have to set is just at or slightly above above you cap pressure).
I also found a nice bleeder to replace the stock screw - http://www.summitracing.com/parts/de...Fe1QOgod-jIA7A you just push it in and it will vent the air. it takes all of 2 seconds and it can be done after each track session to double check the coolant system.

Hmmm...I wonder why I pass on all my little secrets? I should charge you guys for these gems!!!

Dutch944

Wow Chris! Real nice found.. Ordered one already.. Don't have a driving car yet but you just need this..