(2011 PPT 62K/mi)
On a hot day (105+) I received a coolant low warning. The reservoir was down one half gallon. Since that day I've been monitoring the coolant level often, and I have noticed a few ounces disappear/evaporate/or leak after every drive or two. Nothing is on the garage floor, I can't smell or see coolant anywhere, the exhaust does not have water or steam in it, so I'm not sure where to look or what to do to diagnose. If there is a leak, its very slow, for now. Any constructive ideas to diagnose this issue? Or, is it normal to have to add coolant/distilled water to the system now and then, say every month or two?

 

Not normal. You d have get it up on a lift and remove the lower panels and look. If it s leaking onto something hot it would evaporate and not leave any puddles on the garage floor. Might just have a loose hose or clamp somewhere.

 

Finally gave up looking for it and brought it into the mechanic, who quickly identified the issue as a plastic piece below the intake manifold that failed. After removing the manifold it was obvious something else needed attention; the carbon buildup in the intakes. After a walnut shell blasting all intakes are much better. Looks like these Direct Injection engines need a blast sometime between 40K - 60Kmiles. See the before and after pictures of the two worst intakes below.
#5 Before



#5 After



#7 Before



#7 After


Picking up the car in a couple of hours, should be great! Mechanic says to use BG 44K every now and then to clean fuel system injectors and piston tops. I will from now on!

 

wow!

 

 

it's a fuel additive that will clean out the fuel injectors and the top of the piston - won't do anything for the carbon build up shown in his pictures

 

That's shocking for a modern engine to have build-up like that. Not every production DI engine can possibly look like that without running issues. Did you have any running issues and/or CEL?

 

It ran great before and after the service, maybe just a bit peppier afterwards. I was told to expect 10 more HP afterwards. The Indy knew the Intake was going to look like that because ALL direct injection engines do, he said, before the coolant pipe repair. I had him take the pictures to prove it to me, also because I'm 45 minutes away from them. I plan to do it again at 120K miles.

 

All DI ed ngines get this build up because fuel is injected into cylinders befow the valves, directly into cylinder. Hence durect injection name.
Other engines inject fuel from over top of valves, so fuel actually cleans valves as it is pushed into cylinder from above valves.

Yes, all DI engines will have build up.
Yes, it has yo be cleaned out with blasting.
No, I would not expect 10hp, thats likely idealistic #.
No, fuel additives wont help because fuel does not touch top of DI valves at all.

 

That is correct. I was told the additive is good for fuel system and everything below the valves such as piston and head chamber. I buy it.

 

What about the exhaust side? Good luck cleaning that with the exhaust manifolds in place.