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  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 Mustang Tech

1991 5.0 Heater Pipe Fitting

  • Thread starter Thread starter HotRodBlack
  • Start date Start date Nov 4, 2017

HotRodBlack

Active Member
Apr 24, 2017
31
15
28
Nov 4, 2017
#1
  • Nov 4, 2017
  • #1
Hello guys I am trying to figure this out and am looking for a picture to confirm what I need to get to fix my leak

Leaking coolant from the heater pipe. Its spewing out from the fitting that is screwed into the intake manifold. I recently replaced my lower intake manifold, its an Edelbrock Performer. (The old one was warped and simply would not seal to my heads)

Leak started up about two weeks after the engine was assembled, I put it back together exactly as it was but it may not have been correct in the first place.

Like I said, it leaks from the fitting at the lower intake. Its as snug as I can get it but i can move the tube up and down. What I am trying to figure out is if there is supposed to be another fitting screwed into the manifold in between the line and the manifold. It would make sense, being that it's a flared line and fitting similar to a brake line. If that's the case, then a replacement tube will do the same thing.

If anyone has any pictures or information I would really appreciate it!
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,236
17,922
224
Massachusetts
Nov 4, 2017
#2
  • Nov 4, 2017
  • #2
It's a tapered pipe fitting into the manifold. In general the taper provides the seal the tighter you get it, but NPT fittings in general are not that great under higher pressures.

I'd try a pipe thread sealant and see if that helps. I'd also inspect your manifold in that area for cracks and such.

A new pipe would probably give you the same issues

You can see the red sealant uses on the threads.
 

General karthief

wonder how much it would cost to ship you a pair
20+ Year Stangneter
Aug 25, 2016
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polk county florida
Nov 4, 2017
#3
  • Nov 4, 2017
  • #3
I take it the leak is coming from the threads and not the pipe fitting itself, like stated above, try thread sealent. If it is the pipe that is leaking around the fitting there is an o ring that is in there that can be changed but it's tricky.
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,236
17,922
224
Massachusetts
Nov 4, 2017
#4
  • Nov 4, 2017
  • #4
Good catch. There's an internal o ring to allow the fitting to swivel while you screw it in. This can fail. I've never personally changed one, so unsure how this job would be done.

Verify it's the seal or the threads
 

General karthief

wonder how much it would cost to ship you a pair
20+ Year Stangneter
Aug 25, 2016
27,892
10,553
203
polk county florida
Nov 4, 2017
#5
  • Nov 4, 2017
  • #5
Here is a link to fix the o rings, cheaper than a new pipe.
https://www.stangnet.com/mustang-fo...pair-your-leaky-coolant-hardline-pics.866543/
 
Reactions: jrichker

HotRodBlack

Active Member
Apr 24, 2017
31
15
28
Nov 4, 2017
#6
  • Nov 4, 2017
  • #6
karthief said:
I take it the leak is coming from the threads and not the pipe fitting itself, like stated above, try thread sealent. If it is the pipe that is leaking around the fitting there is an o ring that is in there that can be changed but it's tricky.
Click to expand...

Yeah the coolant is coming out between the pipe and fitting, not fitting and manifold. I will deal with it. Its just so odd to me it was fine for weeks, and then all the sudden LEAKS!!!

It may be worth mentioning that while I cannot tighten the fitting any further, i can move the pipe up and down. I can also see that someone has cut the little eyelet off near the back, apparently they struggled? Maybe without this holding it in place the pipe moves around and leaks.

New pipe seems to be the solution. Thanks for the help boys
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,236
17,922
224
Massachusetts
Nov 4, 2017
#7
  • Nov 4, 2017
  • #7
Just replace the o ring.
 

General karthief

wonder how much it would cost to ship you a pair
20+ Year Stangneter
Aug 25, 2016
27,892
10,553
203
polk county florida
Nov 4, 2017
#8
  • Nov 4, 2017
  • #8
One way is money spent
Other way is time spent.
Pipe will move with tight fitting, thats why the o ring is there
 
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