The drip pan under my 2005 X 6.0 was relatively full with coolant last week. The leak is intermittent, but persistent. After investigating, it appears to be coming from somewhere on the driver's side on the back of the engine. The coolant is running down the seam where the transmission mounts to the block, but I can't get my mirror back there to see exactly where it's coming from. It's not coming from the side of block and there's no evidence of coolant on top (in the valley).

I've only been doing "city" driving (no towing or highway trips) since before the leak began and the max ECT I've observed is around 205*, with 40-60* ambient temps. It's not overheating, but I have noticed the heater air is cool when I'm at a stoplight, suggesting the coolant level is low (I've refilled coolant once and heater worked fine afterwards).

I have not observed oil in the degas bottle, but have not yet checked the dipstick for coolant bubbles in the oil. Also, FWIW, I had to replace my degas bottle back in October after it cracked on the side. I do use ELC free, red coolant, have a coolant filter and flushed the system about 18 months ago.

Thoughts on source of coolant leak? (Please don't say head gasket, please don't say head gasket... ). Thanks in advance and Merry Christmas.

 

There's a heater core line that runs along the firewall area from passenger side to under degas (coolant) reservoir. Check that area

 

Will do. Thanks.

 

The cross over heater hose has been known to rub on the FICM case.

 

Update: it's not the heater hose going around the back, near FICM and firewall. After looking underneath again, the leak is wetting the driver's side head/block seam (running down it). There's no oil in the degas and no apparent bubbles on the oil dipstick. When I came out this morning, there was a steady drip-drip, suggesting the leak occurs from gravity driven as well as perhaps under pressure (though I don't hear a "hiss").

Thoughts on other possible leak sources? Thanks!

 

Did you feel real well the underside of the degas resevoir. I've seen them crack along a mold seam and be almost undetectable.

 

I replaced the degas about 2 months ago due to a crack along the seam. I was in a pinch and bought the Advance Auto version (Dorman, I think). I'll check it again. Thanks.

 

I know you said it looks like it's coming from the back drivers side, but you might want to check the hose that comes out of the Oil Cooler and connects to the EGR Cooler. It's at the back of the engine more towards the passengers side. Look under the turbo. I think the updated hose should be blue vs red/orange (maybe the other way around, can't remember). Anyway a non-updated hose is notorious for leaking.

 

Thx jfirstford. I'll check it too. If the degas is leaking, I haven't found it.

 

Have you checked the y pipe yet that is just below the dead bottle? That's probably one of the first things you checked. It's common for those to fail.

Anything in the valley can run down on either side of the divine engine, but you said you checked that.

It could be leaking in front and running the joint between the head and block.

Get a pressure tester and run it up to 14 psi and see what happens.

 

I second Jfirstford's suggestion, similar problem with my 2004 6.0 in my Excursion. It still had the red EGR cooler hose...changed it out for the blue updated hose, leak solved.

Hopefully it helps

Dan