Intermittent coolant leak 2017 - can't find where it's coming from

[youngster3322]

I have an intermittent coolant leak. I've had it looked at by a trusted mechanic and pressure tested hot and cold. They can't find a leak or any sign of a leak. I looked it over myself and can't figure out where the leak is coming from. It started when I added coolant to bring the level up within the cold fill range. When it leaks, it's all at once, and usually on my garage floor. Then it's fine for a week or two. This continues until there is no coolant visible in the degas bottle. I've watched YouTube videos and read through this and other forums, but none of the suggested common leaks apply. Any help would be greatly appreciated.

 

[99WhiteC5Coupe]

Two possibilities:

The water pump is leaking intermittently. My first guess.

The Degas bottle nipple (the one with the metal insert) is cracked and leaking. You may have to wiggle the fitting to see a small, hairline crack. Look for coolant residue.

Both happened to my 2015 Expedition Limited.

 

[youngster3322]

Thanks. My mechanic insists he checked the water pump for signs of a leak. I checked the degas bottle nipple based on other reports and I don't see any coolant residue there either.

 

[99WhiteC5Coupe]

Thanks. My mechanic insists he checked the water pump for signs of a leak. I checked the degas bottle nipple based on other reports and I don't see any coolant residue there either.

My water pump would only leak while the engine was running, and a pressure test (engine off) by my Ford dealer did not detect the leak.

I had to return to the dealer and insist the mechanic inspect the water pump area - and he found coolant residue indicating a leak.

 

[stilbo]

Turbo coolant line fittings..
There’s a TSB or two out there

 

[Hamfisted]

Are you or your "mechanic" pressurizing the coolant system when you look for this leak ? Throwing a dye in the system and using a UV flashlight will also help make discovery much easier.

Coolant System Pressure Test Kit on Amazon

Coolant System UV Dye on Amazon

Bright UV Flashlight on Amazon


.

 

[Full-Race Geoff]

more than likely its the jiffy-tite turbocharger return fitting on the back of the cylinder head, near the firewall. This is a common failure point on these engines. You can replace it with stock parts or in a few weeks there will be some new product alternatives

 

[youngster3322]

I appreciate all of the tips. So far, no signs of coolant residue anywhere. Based on where it's dripping, it has to be above the belly pan, so for now I'm discounting turbo fittings since they're too far back to be the issue. I'm going to remove the belly pan and drive it like that for a few days. That way I can see where it's dripping AND see if it's truly intermittent or if it just leaks when the absorbent pad on the belly pan is saturated.