Mysterious brake fluid loss

[rlwm211]

The plug on the hydraulic end of the air pack (small end) is where the brake pressure switch that operates in the fluid line would normally go. Your truck has the air switch upgrade for the brake lights. The air end is bigger.

The bleeder in pic 3 is to remove air from the air pack before bleeding the wheels.

As there are no leaks you are still on the hunt for the destination of the brake fluid you are losing. Be doubly sure you are not losing the fluid to a leak in your external resevoir system. I would hate to see you tear into a perfectly good airpack if it is actually something else that is leaking.

You could remove the remote resevoir and check the level in the master over a period of a few days and see if it is in fact a leak in the brake system or otherwise.

Also, as I recall, you had mentioned you were losing brake fluid without driving the truck. The only way you can lose that much fluid is by gravity helping out and I really doubt it is making it into the cannister on the air pack. Besides, if you had lost as much as you said, your air pack would be hydrolstatically locked by now and non-functional.

You mentioned you replaced the rear brakes, wheel cylinders etc, but did you service the fronts?

RL

 

[3rdmdqm]

Did not service the fronts. But funny you mentioned the gravity aspect of the fluid leaking out. The fluid only leaks out down to where the hose connects to the bottom of the reservoir. At least that is where I caught it the last time it got that low. However I cannot find any evidence of leaking around the reservoir. It only does it when the truck is sitting for a long period of time. It does not do it when driving it or actually using the brakes. At least not that I have noticed. Each time I finish driving the truck, it is at the full line. Days later after not using the truck I notice the level going down. So far the brakes are working fine, no issues, no change in pedal hardness/play etc. With the vented cap I'm sure its not evaporating. If it were leaking around the connecting line whee the reservoir sits on top of the mounting bracket I think I would have gotten some visible indication or evidence of a leak by now.

 

[Darwin T]

i have not read all the posts is keep that in mind. i had an issue where my breaks when soft while i was coming down a big bridge on the 4th of july behind several cars (high pucker factor). brought it to my mech and he found one lose hose fitting. the leak seamed to be only while i was driving because there was never any sign of the leak before then. so (fill it, drive it, check it) and see if that helps.

 

[73m819]

this only STARTED after the rear brake job????, then it HAS to do with that, look,look,look

 

[littlebob]

Like was posted earlier, I think the plug you need to check is the one thats on the rear of the airpack, which is the bigger part behind the M/C. It's small(1/4NPT) I think.

 

[m16ty]

You don't have a buddy paying tricks on you do you?

This kind of reminds me of two local farmers. They were both farmers and like most farmers, monitored their rain gages every time it rained. One of them played a trick on the other. Every time it rained he would go over to the other farmers house and either add water or take away water from his rain gauge. Whenever it rained the talk at the coffee shop would be about how much it rained. This one farmer would always have way more rain or not nearly as much as other farmers in the area. This went on for years before he found out what the other farmer was doing.

 

[rlwm211]

I would offer that the plug on the end of the airpack that is in the air cannister is not at the bottom and would not be indicative of brake fluid being present. The other thing that makes the presence of brake fluid possible in the air cannister, is that it is getting past the main piston seal of the hydraulic bore and if it is, then you could get brake fluid in the air pack piston, but on the back side of the piston. This is not accessable from the plug, or the pressure side of the air pack air piston.

If the amount of brake fluid that has been lost has all accumulated in the air pack, the air pack would most likely not work. I mentioned before that hydrostatic lock can immobilize the air pack piston the compensator valve assembly,or else the brake piston.

I strongly believe that the brake fluid is going somewhere else and this is all academic. As it was point out above, you have to check the work that was done, if you were not losing brake fluid before the work was done.

As much as I would like to say "Hey, this is the problem" I cannot think of anything that has been offered that is a smoking gun pointing to your problem.

RL

 

[3rdmdqm]

I'm going to start taking stuff apart on Sunday until I find it. I'll post the results.

 

[stumps]

The skid pan under the air pack can hold quite a puddle of brake fluid... especially if it has a generous dollop of dirt in it.

-Chuck

 

[tonidial]

airpack

should you find yourself in need of an airpack let me know - i just got a couple new old stock ones i haven't post up yet in the classifieds cuz i'm up to my eyeballs in filters and small parts and still sorting through the horde of plenty I just picked up.

 

[3rdmdqm]

Interesting how a few key words in these posts spawn additional avenues to check. Kind of like the tv show "House" with everyone brainstorming with ideas until the correct diagnosis is identfied. I LIKE IT! When RL mentioned gravity, I recalled the fluid dropping only to the bottom of the reservoir where the hose connects. Running my finger around this area I noted wetness from brake fluid. However there was no evidence of any drips on the bottom of the outside of the reservoir and no evidence of any wetness on the hose itself where I would think anything would run down. The reservoir was slightly loose. I have fully tightened the clamp which secures the top of the reservoir to the lower bracket (there is a rubber O ring inside that the clamp tightens around. I am hoping this solves the problem, although I don't know how, there is no evidence of drips or leaks etc around the hose or exterior bottom of the bracket. If this does not work, my next question is this:

If there was an air bubble in the top of the master cylinder (I did not fill the master cylinder up to the top when we installed the reservoir, we filled the master using the reservoir from above and only bled the airpack bleeder valve which is actually below the master cylinder) could that air bubble be slowly working its way up and out replacing itself with the fluid?

Checked all over the airpack. I do not have a plug in the rear of my airpack, only the J-pipe connection. I also looked at another members airpack and his does not have a plug at the end of the airpack either.

Also pulled and inspected the protective bottom skid plate under the airpack, no fluid their either.

 

[3rdmdqm]

Attached is a photo of the remote reservoir.

 

[rlwm211]

Well, an air bubble is possible especially when the exit from the master is a 1/16th inch hole. Certainly this bears some patience and checking in the next few days.

As to lubricating the air pack. Here are my thoughts and a couple of options. I rebuild these for a part time occupation. In my opinion the lubrication needs to be applied to the air valves as well as the piston. If you lube only the rear of the air pack you are only applying lubricant to the piston seals and that is about it. I believe that a small amount of air tool oil applied to the inlet of the air line to the air pack does more good than any amount of oil at the rear.

You can lube your air pack one of two ways based on what I just wrote.

1) Pull the J tube and put a couple of quirts of air tool oil in the back of the air pack on the piston. Reinstall the J tube and you are good to go.

2) Remove the inlet air line from the air pack and squirt a couple of shots of air tool oil into the line preceeding the air pack. Once reassembled the air movement will pull the oil in, and through the air pack, lubing the valves and the piston and this would replicate the required oiling done when rebuilding an air pack.

You can choose either path. Remember that a little oil goes a long way so do not put more than a couple of squirts perhaps an eyedropper full of oil. Too much just makes a mess and does nothing to improve upon a good thing. Another risk of too much oil is to cause the piston to not retract fully if you really get out of hand and squirt in an ounce or two of ooil into the area at the end of the piston.

As most of the maintanence manuals indicate, just enough, done often enough is the way to go.


Hope this helps

RL

 

[DieselBob]

3rdmdqm. I just install the exact same reservoir today in the same location. There was quite a few bubbles that came up into the reservoir from the connecting hose when I filled it. My MC was full to the top because I had just power bled the system. I'll check mine tomorrow and see if it has gone down any.


rlwm211. Thanks for the info on the air pack lubrication.

 

[LowTech]

I've been wanting to do this to Elise's "She Beast" as well. Can I get a parts list from you? It looks like you had to get the reservoir, mounting bracket, clamp, and line? I know that I need to change the vent on the MC to a barbed fitting. Did you use a 90deg fitting?

 

[3rdmdqm]

LowTech, here is the parts list from Pegasus:

www.pegasusautoracing.com

1 medium tilton 6.8 oz. reservoir tank - #3558
1 Tilton remote reservoir mounting bracket with O-ring #3557
1 clamp for Tilton reservoir #3577
1 large filter screen for reservoir - #3559
1 threaded cap for reservoir (vented) - #3564
5 ft of remote brake reservoir hose 5/16" ID - #3575

 

[DieselBob]

Checked the level this evening and no change just sitting. Didn't have a chance to drive it any to see if the level would change. Sorry, not much help.

 

[3rdmdqm]

It has been over a week now since I last had to add brake fluid and now the level is staying constant. Still no evidence of any exterior leaking and the fluid loss has now stopped. Total brake fluid loss was a little over 9 oz. total. It is now holding a steady fill level. I am going to assume since I did not fill the master cylinder to the top when the brakes were bled and the reservoir was installed that it was a large air bubble in the master cylinder that has finally worked its way out. I have no other explanation. Brakes work fine and no evidence of leaks anywhere. If you are going to do the remote brake reservoir I suggest the following:

1) Make sure the clamp which holds the reservoir to the mounting bracket is tight. There is a rubber O-ring between the two which when tightened makes a seal between the two parts to keep the fluid in the reservoir. After install thoroughly dry around the outside with a paper towel or rag and check periodically for a week or so for dampness where the two parts meet. Mine was damp and required tightening, however it was not leaking enough to cause over 9 oz of fluid loss and there was no evidence of pooling or dripping anywhere around the connection.

2) When I replaced all of my wheel cylinders etc, I installed the remote reservoir and added fluid to that when bleeding the brakes. I flushed the system with new fluid. If you do this, make sure you have filled/topped off the master cylinder when adding the remote reservoir and prefill the hose from the master to the reservoir to remove as much air as possible. An air bubble in the master cylinder is my only explanation for the fluid loss in the reservoir at this point.

If something else develops I will update. For now all seems to be ok.

 

[rlwm211]

Great news on the brake fluid level!!!!!

I agree and am glad that you have solved the mystery, even if it was that nothing was wrong to begin with. Better to know and be sure if you know what I mean and the experience you had is a good lesson to all who are contemplating a remote resevoir on a deuce that the Master can hold a significant amount of air and burp it out later on.

RL

 

[ranchhopper]

Some air pacs do not have the plug at the rear of the canister I have two trucks that had plugs but the 53 studebaker had none it could be just an omission on earlier air pacs.Im sure my air pac on the studebaker wasnt original as they upgraded it to a diesel engine and air shift TC years ago.