The patient is a stock 2006 6 port that had a new engine put in about 10k miles ago. Car and anything rubber on it have 80k miles. I didn't do the work so have no ideea how well it was done or in what condition everything else around the engine is. I'd not unplug everything to find out.
It's been slowly loosing coolant for as long as I've had it. ~ 6k miles. I'm sure it's not burning it or leaking inside the sump. It seems to lose it only when the engine is on, and the rate of loss is higher if car is driven hard. Needs 1 qt of coolant every 500-700 miles or so.
Coolant cap is holding pressure and it's not overheating - never exceeding 190F(due to a PCM reflash). Makes slushing sounds from the heater core area when first started after a long time sitting. No signs of coolant loss anywhere in or out the cabin. Given that it only leaks with the engine on, any leak dries off immediately. Apart from topping coolant like I do with oil, everything is fine.

What I'd need is some pointers where to look first as I'd not tear apart the entire engine bay and every coolant hose looking for a common failure point I'm not aware of atm.

 

Usually what i will do is pressurize it to about 15psi and see if you can see a leak.

If it holds pressure static it can be a leak in the water pump that only occurs when it is turning.

Just went through this with a BMW... everytime i fixed something it blew another crappy plastic component someplace else.

At least we don't have crap like that going on

 

It doesn't _really_ hold pressure; it loses 1psi in 10-12 hours. That much I know, but I can't see any leak without ripping apart and replacing every rubber hose in the engine bay.

 

You would have noticed traces of a quart per 700 miles by now. Coolant is hard to hide. I'd say if it's not coming out of the engine, it's going into it. How are you sure it's not burning it?

 

Because it's never made a puff of smoke of any kind.

 

That's not a conclusive indicator. It sounds like a very small leak, a pinhole. Depending on where in the combustion cycle it is, it could only suck in coolant under high vacuum, when you're decelerating and not looking at your tailpipe.

 

Initially mine was the same, and its just gotten progressively worse.
My symptoms are
1. slushing behind the dash
2. difficulty starting despite confirmed good compression
3. when it does start, its on one rotor for a little while first
4. exhaust smells of coolant
5. coolant pressure test showed a 2 psi drop in 10 minutes
6. no bubbling in the overflow tank at all

If you can't smell the coolant being burnt yet then you might have some time, I've been driving mine for a year since it's been like this and at the start it didn't smell of coolant at all. Recently it's really been falling off a cliff in terms of difficulty starting and coolant exhaust smell, still no white smoke but it very clearly smells of coolant at this point. I'd suggest preparing for a rebuild if you can--once you can smell the coolant in the exhaust, I'd say it's a good indicator that it's bad enough that you'll want to rebuild asap to increase the odds of parts being reusable.

 

i just noticed a water leak from my car. It’s above the transmission and behind the oil filter. I’m looking through the parts catalogs and can’t tell what lines run back there, or if it’s just dripping down from somewhere else? Any thoughts? Right now the car is also too hot to reach my hand down there to feel around.

 

Here’s a photo of the leak. It’s about 4-6” behind the oil filter

 

That's likely the A/C drain. It is where the water from the evaporator drains out...


So expected place for water to come out.

If coolant is coming out there its likely a heater core leak...

 

I first thought this was coolant. But I collected the water in a pan and there’s no coolant smell. I was also able to get to the source and it’s a duckbill. Is this just a drain for a rainwater collection spot?

edit: oops posted after your response. Thank you.

 

🙂 no problem... the "ducklips" is a well known water leak spot

And a lot better than when it plugs and the water drains on the passenger side floor...

 

thanks again for your help. Is there some other chemical that might be mixing with the water because it’s staining my garage floor. Maybe the area just needs to be cleaned, but I’m guessing that’s a lot easier said then done?

 

What colour is the stain? Normal condensation from the air conditioning drain is as pure as can be, shouldn't stain anything.

If it's greenish then it's coolant. If it brown but not oily it might be rotting leaves and debris caught in the ducting.

 

It could be aluminum oxide or rust too from running down the side of the motor and transmission

 

There is no real color. It’s just darker than the rest.

Ill probably just get a mat to park over

 

Figured out my slow and steady coolant loss. I noticed that trying to keep the coolant bottle full was pointless - it would be gone within the first fuel tank. But then I could drive for as long as I wanted with no problem or overheating. So I figured something - I can't be leaking inside the engine or within the heater core loop. If it did, the engine would have run dry and judging by the rate of coolant loss with the coolant bottle full, within 300 miles it would be toast. That got me thinking... once coolant level drops below some point, the loss ends.
So, time to rip the engine bay apart from the top down. Began with thr. body hoses. Apart from being bone dry, nothing wrong with them. Took the chance and deleted that useless loop of coolant. Then - coolant bottle. The bottle itself wasn't leaking and so were the rest of the hoses tied to it. I started digging deeper and of course it was that damned radiator nipple that always breaks off. Mine was in such a sorry state that I tore it apart with my pinky. The bits that flew off were as tough as some dried orange peels. Looking inside the radiator via the new created access port - coolant! Stting just tall enough to cover the aluminium core.
New rad coming in tomorrow.
LE: 2 fuel tanks after putting a new rad in, coolant hasn't dropped a bit. Before this, the coolant bottle would have been empty already. I'm sure this was my issue.