Brake fluid leak at banjo bolt on air-pack

[Valence]

After replacing my master cylinder and air pack on my M35A2 with new ones, I have a slow leak at the air pack banjo bolt on the line from the master cylinder (not the banjo bolt to the rest of the brakes), and I just can't seem to get it to stop.


On this reused banjo bolt, I have installed a new copper crush washer, and a very nice, new, copper hard line from the master cylinder to the air pack.

My current thought is to take out the banjo bolt yet again, and see if I can clean it with a nylon brush and brake cleaner. Then put on another new copper crush washer and, here's the key, Teflon tape on the banjo bolt threads. When I installed my remote brake fluid reservoir I had to put Teflon tape on the old master cylinder cap to stop it from leaking. Do you think it is a good idea to try this Teflon tape idea on the banjo bolt? The banjo bolt appears to be like pipe thread and certainly doesn't form a flare fitting on the inside.

 

[pjwest03]

A banjo bolt is typically going to have 2 washers. One under the bolt head and one under the line fitting/hose end. The mating surfaces should be pristinely clean and free of paint. The bolt threads should play no part in the seal. As I recall, the deuce washers are smooth. Some applications use a washer with ridges and there are matching ridges on the mating surfaces.

 

[Valence]

Well, I did use a smooth washer (I bought extras too) and I did keep the old washer. I shall inspect and compare the two tonight and report back. I only saw the one washer on the air pack side connection, but you're saying there is a washer inside the flare fitting with the hard line?

 

[pjwest03]

The banjo head with the flare fitting should have one washer on the air pack side of it and one washer under the bolt head. The washers sandwich the banjo head.

I have seen banjo bolts installed without the washer under the bolt head. I never figured out how people get them to seal.

 

[jbayer]

Banjo bolt is a straight thread, hollow bolt. Teflon tape will do nothing because the fluid is already past the threads, and in the bolt. A crush washer under the banjo, and one under the bolt head is the only way to seal them. I'd look for a crack, or scratch in the bolt, banjo, or air pack.

 

[yolner]

Are you talking about the adapter that goes from straight thread to inverted flare? Mine seeped a bit but stopped after I tightened it down just a bit more. I'm pretty sure there is only room for one washer between the adapter and the surface of the airpack. Could the leak be coming from the flared connection not the adapter to airpack connection?

 

[bonedoc]

I agree with Yolner. Mine did the same thing. I actually re torqued it several times. It did stop leaking

 

[Valence]

Are you talking about the adapter that goes from straight thread to inverted flare? Mine seeped a bit but stopped after I tightened it down just a bit more. I'm pretty sure there is only room for one washer between the adapter and the surface of the airpack. Could the leak be coming from the flared connection not the adapter to airpack connection?

Yes, this bolt, or adapter, exactly. Perhaps my use of terminology has been in error. It doesn't have a second nut. My apologies.

I thought that it was leaking from the flared connection and that's why I replaced the hard line with a brand new, very nice and pliable copper line. As best as I can tell, the bolt head and flared nut and threads on the line aren't wet and I've seen drips collecting right below the adapter's washer on the air pack.

I have tightened it twice, and I'm not sure much more would be a good idea, but perhaps it's best that I check it and try again now that that the copper crush washer has had time to sit.

 

[yolner]

Yes, this bolt, or adapter, exactly. Perhaps my term is wrong. It doesn't have a second nut. My apologies.

I have tightened it twice, and I'm not sure much more would be a good idea, but perhaps it's best that I check it and try again now that that the copper crush washer has had time to sit.

Yeah I have no idea what the correct term is for it. If you look in the big brake info thread there is a part number for a new one (i found it when i was doing this same job). So you can replace it along with a new washer and eliminate that as a source of your problem. Of course that won't help you if the leak is due to some kind of scratch on the airpack sealing surface. Not sure what to do for that other than take to to a machine shop. Plus like I said you want to double check that the flare on the brake line itself is good. Could be coming from there and not the adapter/airpack side.

 

[jbayer]

As they say "a pictures worth a thousand words"

 

[Valence]

I have 3 extra of these fitting adapters from forum member red's deuce's air pack and master cylinder. Upon digging them out today, two of them used to have sealant tape on them - probably from the military that way. I don't believe red ever needed to work on his master cylinder/air pack.

Seen in the below two pictures are 2 loose copper washers. The one on the left is the original I replaced and the one on the right is an extra I purchased from O'Reilly's that is the same as installed on my truck.


And here's the offending leaking fitting. I was able to turn it some more (I didn't Heman it(. It's pretty dang tight though.



And here are the same fittings on the front of the air pack and back of the master cylinder. I reused them and didn't replace their washers. No leaks.

 

[rustystud]

Valence, you might have a busted fitting. Do you have access to a sandblaster ? If not then clean that fitting up as best you can and inspect it with a magnifying glass for any hair-line cracks. Busted fittings are quite common, that's why at work we where told to always replace them. Better safe then sorry kind of thing.
It also could be leaking from the inverted flare fitting. That is another good reason to "clean" that fitting with a sandblaster. It can get down to the flare sealing surface. Or just buy a new fitting. Any hydraulic supply store would have them in stock.

 

[Valence]

Thanks Rusty for the suggestion. I'll see if I can't replace it, or, at minimum, clean up and use one of my spares.

 

[searls84]

I agree with Rusty, I've had it happen twice where a fitting was cracked after replacing an airpack. As best as I could figure out it came from using a standard open end wrench to tighten it, guess it was directing too much pressure in too few places of the soft brass fitting. I started using a flare nut wrench to tighten and loosen and haven't cracked one since.

 

[Valence]

Today I spent over 4 hours visiting and calling 6 additional businesses. Two of them were hydraulic shops (one was even called "Hose & Fittings"). None of them could match this fitting. However, the latter hydraulic business did indicate that they possibly could make me a custom hose with the necessary adapters directly to the air pack - if I so desired. This second place also thought that the solution Evco House of Hose presented was a possible viable solution:

Bonded Sealing Washer
(It seems to have a number of different names)

On my receipt it is listed as:
FA-OR-BSPP-04
9900-04 BRITISH BONDED SEAL

I was told that this washer is commonly used in high pressure hydraulic lines, which is basically the definition of this part of the brake system. As can be seen, I bought two of them and gave the fellow a good smile when I quoted ol' rustystud "Two is one, and one is none". He said "you must have served..." as he pointed to a Vietnam patch of his. I told him I knew good people.

I also stopped at Boyce Equipment and Dallas (the owner's son), personally dug through parts bins and finally out into a trailer in the yard that held a very clean and nice looking, used short style air pack, and sold me one of the shiny fittings on it:



I topped off the remote brake fluid reservoir and will check for lost fluid and leaks tomorrow!

(Yes, I put the fitting on the air pack with a 6-sided socket and used a flare wrench for the hard line - just like last time too).


Edit:
Viewing the pictures on the computer, referring to the second from the last above, I now notice what appears to be a heavy scratch (?) in the upper right where the previous copper crush washer sat. I wonder if *that* was the root cause of the leak or if it's a trick of the light/perspective due to being wet with fluid... Enlarged here:



I didn't take any pictures, but the copper crush washer on the fitting that I removed, didn't look all that good, or even. So at the moment, I'm still blaming that washer.

 

[rustystud]

I've used those "bonded sealing washers" before. They do work great and considering that scratch on the housing I would use one here. Here's hoping the leaks stop now !

 

[Valence]

An update:

Well, it hasn't stopped leaking, but it certainly is much, much reduced. I'm sick of working with it. It's reached my "disgust" meter. I don't know what else to do and don't know if I want to do more.

At least I can easily check it and keep topping it off.

 

[TGP (IL)]

Call a vendor unless someone has a aftermarket number, and get a new fitting.
Just because you got a used one, don't mean it doesn't have the same problem.

Also you sure the flare on the pipe is not leaking?

It's either cracked or deformed.
Tom

 

[yolner]

An update:

Well, it hasn't stopped leaking, but it certainly is much, much reduced. I'm sick of working with it. It's reached my "disgust" meter. I don't know what else to do and don't know if I want to do more.

At least I can easily check it and keep topping it off.

I wouldn't drive it with a leaking brake line. Replace the fitting and use a new copper washer. Here is a link to the part numbers you need: http://www.steelsoldiers.com/showth...hs-fittings)&p=1735080&viewfull=1#post1735080

Also take off the brake line and make sure the flared end isn't deformed or off-centered. Could be coming from the brake line connection not the airpack connection.

 

[rustystud]

An update:

Well, it hasn't stopped leaking, but it certainly is much, much reduced. I'm sick of working with it. It's reached my "disgust" meter. I don't know what else to do and don't know if I want to do more.

At least I can easily check it and keep topping it off.

Don't give up yet. Just like Yolner mentioned it could be the flare on the line itself or the actual housing of the air-pack could be cracked. Either way don't stop until you find it. The problem could get worse. It could mean "life or death" for you !