For the last few weeks, since putting on the IH water pump with spin on filter, I have been experiencing an intermittent coolant leak from the driver's side head area. I couldn't find exactly where it was coming from till today while I was waiting for the RTV to cure on my front diff cover. I searched high and low for anyone with a similar problem on this site and other sites. I could not find anything!

I found the leak was splattering/dripping all over, which made it hard to source. Turns out it was coming from the heater return line from the rear heater. This return line runs from a fitting on the passenger side firewall just above the other heater lines. It connects to a hard line that is fastened to the firewall as it crosses over to the driver's side of the engine bay. It then dives down and connects to a brass fitting on the rear of the driver's side head just below the "dog house". I thought that fitting was leaking, but I found today that it was a clip fitting for the soft hose connecting that hard line just above/adjacent to the turbo.

Here is where it was leaking. The fitting had a bunch of scale built up in there, and one of the two o-rings had failed.


Here is a shot of the short gap the rubber hose spans to make the connection from the hard line to the head.


Here is the hose.


Here are the innards of the connection. O-ring then plastic spacer then another o-ring.


Here is the fitting after I cleaned all the corrosion off of it.


Dug into my stash of o-rings


And I found the correct size. Replaced the o-rings and put the now clean fitting back together. I found the fitting WOULD NOT go back together until I put a little white lithium grease on the o-rings. Once I did that, it snapped right back together with very little effort.


I can only speculate as to why this fitting and o-rings failed, but I suspect it is because we very rarely use the rear heater down here in Texas, and that fluid in the line had gotten stagnant in the line. Just a guess...maybe someone else has a theory???

 

So is this something easy to see on the truck? I've got some coolant leaking going on that I can't quite pinpoint.

 

It was once I climbed on top of engine with a clean rag and started wiping wet spots away. Do you have a 7.3? Don't see one in your sig, and not sure if 6.0 is the same.

 

your garage looks like mine. the only suggestion I would make is to use silicone plumbers grease instead of lithium grease. there is a chance the lithium grease will deteriorate your O-rings.

DOE

 

Another great write up, thanks

 

Hey just a little fyi. I have a 04 ex eb edition with the 6.0. I started having a small leak on the drivers side too. On the 6-0 (at least mine) that hose is a bit different. It comes from the underside of the degas bottle at a Y connection. Runs back to the firewall and then turns. after the turn it becomes metal tube then across the firewall and then Y's. after the Y it turns to rubber again and goes two different directions. One turns and goes to the heater core for the front. The other turns down and turns to metal again to go between the fire wall and the passenger side front fender liner where it has a connection to the pipe that runs all the way to the rear heat. It is all one piece where the rubber is connected to the metal pipe with crimped on connections. It is a Ford only part that runs around 130.00. You have to pull the right front wheel off and remove the fender liner to get to it. The leak came from where it turned around the drivers side of the engine it had rubbed a hole on the corner of the FICM. two small nuts hold the metal pipe to studs on the firewall to hold if back off the engine. Talk about a pita! Gotta love those engineers.

 

04ebex, does it connect in to the driver's side head like the 7.3 does? The metal pipe running across the fire wall and anchored by two bolts is the same set up as the 7.3 in that regard. Thanks for sharing the info! I am sure it will help some 6.0 owners out later.

Doubleott, thanks for the tip. I will have to pick some plumber's silicone up for future use.

 

you got it, thanks for the write up.

DOE

 

I changed out that hose on my 05 6.0l last spring. Took me about 4 hours and was a huge PITA. Ended up cutting a piece off the old one and wrapped it around the new hose where it had rubbed a hole. Hopefully that will help in protecting the new hose.

 

Great information - good write up. Noted for future use if needed. But my rear get's a fair amount of use up here in the rust belt.

 

Nicmike, on the 6.0 it does not connect to the head.
LionFan, I did something similar. I took a piece of water tight plastic electrical flex and split it. Rounded off the edges and corners so it kind of clipped around the hose right at the FICM. I will keep an eye on it as this was a pita and a bit expensive.

 

What is the part number for that hose, i need one now.

 

You need the part number for the short rubber hose that runs from the head to the hard line on the firewall? I can look it up if that is what you need. I re-used mine.

The manual refers to it as a "heater return line". This is for the short rubber piece and the hard line fastened to the firewall. Strangely, there is no part number given.

 

sorry to dig up an old thread but I'm dealing with the same issue. do you think a dayco part# 88418 is the workable replacement part?

 

I don't think that dayco part will be long enough at 12 inches. I ended up buying a piece of heater hose 3 feet long, and a heater hose quick connect fitting. I removed the old line, and I put the new line with the quick connect added to it on the truck. No leaks since. Very cheap fix.