86 6.9 keep leaking out the left rear injector return

Azidiguy · Sep 27, 2022

Hello

New here but not to idis but im having a problem with the return cap on the left rear injector keeps leaking despite multiple caps and o rings.

Thoughts on this done lots of these never had this issue.

Thanks in advancep

Nero · Sep 27, 2022

String of bad luck with parts, or maybe a damaged injector.

Azidiguy · Sep 27, 2022

Nero said:
String of bad luck with parts, or maybe a damaged injector.

Maybe, those caps bad out of thebox often?

captain720 · Sep 27, 2022

I’ve got one that sometimes weeps a little, after probably 6 brands of o rings I gave up. If anyone has a great idea let me know

WrenchWhore · Sep 27, 2022

My gut says check the cap itself. I just measured some of my original Ford return line caps and all measured about .631" on the inside. I bought a return line kit off amazon that was "German made" and the caps that have a 90 degree turn in the back cylinders (7 and 8) were oversized by more than .010". The straight caps in the middle cylinders were oversized but not bad enough to case a leak. If it isn't an oversized return line cap then I'd look at the bottom of the hard line to make sure it hasn't split. It's unlikely but it happens.

captain720 · Sep 27, 2022

WrenchWhore said:
My gut says check the cap itself. I just measured some of my original Ford return line caps and all measured about .631" on the inside. I bought a return line kit off amazon that was "German made" and the caps that have a 90 degree turn in the back cylinders (7 and 8) were oversized by more than .010". The straight caps in the middle cylinders were oversized but not bad enough to case a leak. If it isn't an oversized return line cap then I'd look at the bottom of the hard line to make sure it hasn't split. It's unlikely but it happens.

This could be my problem, although mine are classic diesel designs.

Brian VT · Sep 27, 2022

Many here have run into this problem. Have you tried different brands of o-rings?
The ones that came with my injectors and caps weren't sealing well so I went and got a box of assorted from Harbor Freight and those happened to work great on my injectors & caps. Cost me $10 to use 8 of these o-rings but they did the job on mine. Worth a try?

Viton O-Ring Kit, 180 Piece

Amazing deals on this 180 Piece Viton O-Ring Assortment at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

Others have also had success with buying them from McMaster-Carr.

Azidiguy · Sep 27, 2022

WrenchWhore said:
My gut says check the cap itself. I just measured some of my original Ford return line caps and all measured about .631" on the inside. I bought a return line kit off amazon that was "German made" and the caps that have a 90 degree turn in the back cylinders (7 and 8) were oversized by more than .010". The straight caps in the middle cylinders were oversized but not bad enough to case a leak. If it isn't an oversized return line cap then I'd look at the bottom of the hard line to make sure it hasn't split. It's unlikely but it happens.

Line hasnt split it eas leak free for 20 miles when first done. Got a whole new set different brand too so we will see if that helps

Azidiguy · Sep 27, 2022

Im temped to get r&d rails at this rate

WrenchWhore · Sep 27, 2022

captain720 said:
This could be my problem, although mine are classic diesel designs.

That was my problem. Did the return lines 3 times with different brand O-rings before I finally caught what was happening. I installed my old caps and have had zero issues ever since.

Jesus Freak · Sep 27, 2022

This could be part of the under carriage rust prevention built into these trucks. Especially since it's consistent and at the back of the engine. The diesel will mix with the oil that's mysteriously leaking back there and the thinning will allow it to coat the whole bottom of the truck more efficiently. It's genius really, how this was designed.

Jesus Freak · Sep 27, 2022

WrenchWhore said:
That was my problem. Did the return lines 3 times with different brand O-rings before I finally caught what was happening. I installed my old caps and have had zero issues ever since.

I've discovered that the caps that come off are best myself. I mean really, how can they wear out just don't break them when you take them off.

Azidiguy · Sep 27, 2022

Jesus Freak said:
This could be part of the under carriage rust prevention built into these trucks. Especially since it's consistent and at the back of the engine. The diesel will mix with the oil that's mysteriously leaking back there and the thinning will allow it to coat the whole bottom of the truck more efficiently. It's genius really, how this was designed.

This is true its huge step in rust prevention lol

WrenchWhore · Sep 27, 2022

Azidiguy said:
Im temped to get r&d rails at this rate

They're extremely nice pieces of IDI jewelry but I don't think they're mandatory. I'd try and fix what you've got but i'm sure you're pretty frustrated with it by now as I was.

WrenchWhore · Sep 27, 2022

Jesus Freak said:
I've discovered that the caps that come off are best myself. I mean really, how can they wear out just don't break them when you take them off.

I suppose the heat gets to them like all plastic over time. I just keep spares with me when I go on long road trips just incase. I've been very lucky to say the least with my 600 mile road trips.

86 6.9 keep leaking out the left rear injector return

Azidiguy

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Viton O-Ring Kit, 180 Piece

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