Ok so I will try and keep this as short as possible. 2010 JCW modded/tuned. Stock turbo, 20psi Mario tuned, 3" DP/Exhaust, intercooler, etc. Not sure if any of this matters.

Issue(s): Coolant has some sort of internal leak I think, oil is not milky, looks fine. Also car is all of a sudden making no boost, well...2-3 psi max at WOT high rpm.

Recent work done: Thermostat housing/water pipe/coolant hoses, oil change, spark plugs. All new.

Timeline: After completing the above work everything was good for the first few hundred miles. Went to drive it to work on Monday morning and the coolant started getting hot so I drove it home and parked it (~3 mile round trip, max temp it got to was 237°F). Investigated the next day, found that my reservoir was very low, filled it up, warmed up the car and saw a leak coming from the bottom of the reservoir. Hose clamp wasn't super tight so I cinched it up and fixed the leak. Topped it back off, drove it around, all seemed good. Drove it to work again on Wednesday. Car ran great on the way to work, temps didn't go above 200°F, boosting to 20psi as normal, etc. Car sits at work for 10.5 hours. Driving home about ~15-20 minutes in and I go to accelerate on the freeway from cruising speeds and notice the car is not making boost anymore. Other than that it is running fine. About 5 minutes later the temps start to creep up again slightly, but stabilizing around 220°F. Let it sit overnight then I went and checked it this morning. Coolant reservoir was super low again, topped it off, and turned it on without the cap on the reservoir so I could see what was happening. Coolant level immediately dropped way down again, filled it back up while running and it seemed to stabilize. No visible leaks, and for the amount of water that the level went down it would have to be a pretty big and fast leak. I threw the cap back on, and test drove. Temps were ok but still wasn't boosting. Checked all of the intercooler piping and all seemed okay. There's no CEL, scanned for codes and nothing.

Questions: Where is all of this water going? Again, oil is not milky at all, looks great so I don't think it's head gasket. Is there an issue that is know that would also cause the ECU to cut boost? Not sure if the issues are related or not.

Notables: I originally bled the system after the t-stat change with 50/50 European car blend coolant and yes I had the heater on while bleeding. Since, I have been topping it off with distilled water because that's all I have in my garage but at this point I have probably added an entire gallon of it. And again, aside from the original leak that I fixed there's no visible signs of a leak. No puddles, no steam.

Thanks in advance for any help!

 

Nobody?

Update:
On the disappearing coolant. I re-checked all of the hose clamps and re-torqued the thermostat housing bolts. Re-bled the system with 50/50 coolant. No visible leaks, no smells, no steam, no codes, no oil mixing with coolant. Heater does work. The coolant level seems to be fine until the car gets driven then sits overnight. For instance, if I top it off, drive somewhere, then bring it home the level is back to being really low the next morning. No puddle in the driveway but it is also Las Vegas in July. As long as I top it off the coolant temps are rock solid at least for 40 minute round trip commutes. I still have absolutely no idea what could possibly be causing this rapid of a coolant loss without any visible signs of leaks or steam.

On the boost issue. The car has a stock JCW turbo with damaged impeller blades. Was like that when I got it. Previous owner said he replaced the intercooler and had the engine inspected to make sure the impeller debris didn't get into the engine. Said he drove it with the damaged blades for almost 60,000 miles. I am a few months into ownership and it has always boosted to 20psi no issues until the other day. Thinking the turbo has finally just let go and it's a wastegate issue. I have a new turbo waiting to go on so I am not too worried. If that doesn't fix it then I will start to investigate the rest of the system. I re-checked all of the turbo piping connections and hoses and all looks good.

 

The water coolant passages are closer to the cylinder than the oil galleys. As such its possible that while the car is shut down over night the engine cools and coolant can leak into the cylinder. Stand behind it during first startup and look for white vapor. Also when cold open the reservoir cap, start the motor and quickly rev the engine a few times. Look for air bubbling up in the reservoir. If you have a compression / leak down tester you can do the same test on a per cylinder basis without running the engine.

Turbo sounds to be toast. They are precision balanced and operating one in a damaged state will play hell with the bearings.

 

Thanks for the reply! No white vapor coming from the exhaust, I will do the other test today, but I am back to thinking it's a leak that is only happening while driving. Yesterday I took it to work again. I had to top it off in the A.M. and then the reservoir was empty again at the end of the day. Filled it back up and drove home. Once I got it home I immediately put some cardboard under the engine bay so I could see if there were any leaks. About 20 minutes later it was cool enough to open the reservoir cap and it was empty with just a few drips on the cardboard. So it has to be draining while driving, not while parked. It doesn't do it at idle even when warmed up. Gotta be a pressure related leak. All of the hoses are brand new silicone but maybe there's a bad one. I will have to go to a shop that can pressure test the system.

As for the turbo, I saw it coming I just thought it was odd timing with this other issue so maybe they were related.

 

They make inexpensive fluorescent coolant dyes that will glow brightly with a blacklight. The same types of dyes are also available for oil, trans, fuel system, etc.. You can find LED UV flashlights pretty cheap to. Just a thought.

 

Great idea! Thanks!

 

Look for coolant on top of the transmission, on the right hand side of the engine as you are facing the open hood. Use a flashlight, it will be down under the big intake hose from the air filter box to the turbo and all the hoses below it.

 

Any new about this? I have a similar problem in 2010 JCW