Rotax 912 fuel return Banjo leaking

[Jerrytex]

I am battling a leaking banjo fitting on the fuel distribution block where the return line takes off. I had to re-position the banjo fitting to route the return line. Since then, I cannot get it to stop leaking. I replaced the crush washers and it still seeps. I Put an extra pound on the torque value and still it continues to seep. I even tried annealing the copper washers to make them softer and still no luck. I am about at witts end. Anyone else have this happen? Any remedies? I just ordered 2 more washers from leading edge.

I read about the ends of the banjo bolts contacting each other before the washers squeeze enough, hence the reason for replacement. The ones I used are 1.5mm thick. The high dollar rotax ones are 1.4 mm so I cannot see that as a problem.

[Dave S]

Hi Jerry,

A leaking banjo fitting is not real rare - they do happen.

A couple things to check.

To check for a bottoming bolt, try screwing the bolt through the fitting, fingers only - no wrench for this!) without the washers and measure with a feeler gauge if there is any space where the washers would be to compare how much crush you have.

The banjo fitting can sometimes develop a burr or defect on one of the sides of the fitting. Doesn't take much.

A bad or slightly bent bolt can be a problem.

Annealing the copper washers as you did is a good thing to do.

When tightening a banjo fitting, I like to use my free hand to rotate the fitting back and forth slightly to help the sealing surfaces fit.

Personally I think good luck plays a role in this too!

[jiott]

Could it be the hose connection to the banjo, making it look like the fitting is leaking?

[Jerrytex]

I thought the hose was leaking at first. I replaced the hose and used a Oetiker clamp so I feel confident that the hose connection is good. I will say that rotax uses a weird barbed connection. The barbed rings look like a pex connector more so than a rubber hose barb. I halfway thought about looking for a banjo fitting with a flared end and convert from barbed to an AN fitting. I can see the fuel seeping from between the fitting and the copper washer. It's crazy that something so stupid simple has me on the ropes.

I'll try and check the gap without the fitting or washers in to make sure the bolts are bottoming into each other.

I might try doubling up on the copper washers?

You wouldn't normally use sealant on something this but I am also considering that option or maybe a combo washer with an o-ring and crush washer built together?

Thanks

[Benbell4140]

I’ve never tried them but I have seen banjo washers with a rubber seal made into each side.


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[desertdave]

Banjo fittings are the curse of Land Rover diesel motors. Bad words would come out of my mouth every time I crack one open. For that reason I always swapped out the copper washer whenever I even loosened one and my garage became G rated again.

[jrevens]

I’ve never tried them but I have seen banjo washers with a rubber seal made into each side.


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One design I'm familiar with are called Dowty Washers. Similar types are used as gaskets on the oil drain plug of many cars. I've used them with good success, including on the drain valve of my oil tank. They're used on many hydraulic system fittings also. If you can find the proper size and material, they'd probably be an excellent choice. I've seen them in Aluminum and S.S. with a bonded rubber inner seal. Possibly try Summit Racing or eBay, etc. Other types have a thin rubber material bonded to both surfaces of a metal washer.

[Slyfox]

only thing I can think of is to take a file and run it on the sealing surface, might have a bur or something on it.

[Jerrytex]

I found some of the Doty washers. I think I might try them if the rotax washers don't work.

I'll double check for burrs.

What's crazy is I just loosened it, turned it like 5 degrees and re-tightened it. Had I known it was going to turn into an ordeal, I never would have touched it and just left the fuel line slightly curved. HA!

[efwd]

Ahhh, the old "if it's not broke, don't fix it" got you.

[Jerrytex]

So just a follow up and might save someone else a alot of aggravation.

So after much frustration including machining new copper washers and then ordering new Rotax washers, and then changing out the fuel line to 3/16" thinking it was the actual line leaking, I finally figured out what is going on. With the naked eye, the surface of the distribution block looks fine. Being at witt's end, I took a photo of the sealing surface. Hard to believe but the iphone saw the problem. At first I thought it was a crack but it appears that it is some kind of a molding, machining, or forging line from when it was machined. You can't even feel it with a fingernail and sure cannot see it. A new block costs $123!!!! so I block sanded the surface, reinstalled, torqued down and no more leak. It must have been just deep enough that the copper washer couldn't fill it. Either way it was a frustrating challenge.
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[avidflyer]

On my new kitfox 4 build, I have moved the coils and modules back to where they wont vibrate, and the fuel and cross over tube moved some as well. Just yesterday, I made up a new manifold for the fuel pump, carb feed, and return line connection. I don't feel so bad that it took an hr, if the new rotax one is $122. Hope it don't leak.... JImChuk