Brake fluid shooting out of remote reservoir?

[banditt1979]

I have completely rebuilt my entire brake system in my 1971 M35A2 with the single master cylinder, adding a small remote reservoir in the cab next to the drivers seat in the process. Using clear tubing I keep the fluid level close to the floor line. When I have air pressure in the tanks and I pump the brake pedal I get fluid shooting up out of the reservoir if I leave the cap loose. Doesn't seem normal, can anyone confirm or deny that I have a problem somewhere? Master cylinder is rebuilt, NOS air pack, all new lines and wheel cylinders. Thanks in advance for your thoughts.

 

[davidb56]

If you drained the air pressure to zero, and pumped the brakes, would it still pump out into the reservior? Like a bad master cylinder would do? Im curious because I have a dual circuit and dont have a remote reservoir.

 

[banditt1979]

If you drained the air pressure to zero, and pumped the brakes, would it still pump out into the reservior? Like a bad master cylinder would do? Im curious because I have a dual circuit and dont have a remote reservoir.

I
I want to say no but I can't remember now. I'll have to check after I bleed down the air.

 

[Barrman]

Do you still have the vent line hooked into the reservoir system? This happening with or without air really helps narrow things down.

 

[banditt1979]

Do you still have the vent line hooked into the reservoir system? This happening with or without air really helps narrow things down.

No I disconnected the vent line to the mc, plugged it and added a remote reservoir ran into the cab. The reservoir is a small motorcycle reservoir, I wasn't comfortable using the one that vented directly to the atmosphere.

 

[Barrman]

OK. That eliminates the airpack vent blowing brake fluid from your master cylinder out of the master cylinder.

Just 299 more things to check and cross off….

Seriously. It reads like your brake fluid is rushing back into the master cylinder when you release the pedal with a lot of force. Now that the airpack vent is out. Have you done a full major and minor brake shoe adjustment at all 6 corners.

 

[davidb56]

OK. That eliminates the airpack vent blowing brake fluid from your master cylinder out of the master cylinder.

Just 299 more things to check and cross off….

Seriously. It reads like your brake fluid is rushing back into the master cylinder when you release the pedal with a lot of force. Now that the airpack vent is out. Have you done a full major and minor brake shoe adjustment at all 6 corners.

What he needs to check is if the fluid does it on a "push" down of the brakes, or a release. Both without any air pressure in the system. to eliminate (mostly) the master cylinder as the problem.

 

[Barrman]

You are correct. As I wrote, 299 things to go.

Pedal on or off does come before my thought. Which with the shoes out of adjustment has fluid getting pushed back by long traveling shoes getting pulled back by springs.

 

[banditt1979]

Its when the pedal is released. But I haven't gotten back out there to check it without air in the system. Had some family events this evening. I'll definitely check that tomorrow.

I've adjusted the front wheels and one mid axle one one side, minor adjustment, so I have 3 more drums to adjust. I'll add that in the summer after I did the work that I had a pedal that would stop about halfway. Yesterday when I fired her up it was about 1 inch to the floor. No visible leaks anywhere and fluid didn't seem to have dropped.

 

[banditt1979]

Also should add that all the shoes looked very nice and thick like they were serviced before the previous owner bought the truck.

 

[banditt1979]

I just went out and pumped the brakes with no air pressure in the system and no fluid spraying out of the reservoir no matter how hard or how many times I pump. I will add that when I last worked on and power bled the brakes a few months ago I had about a half pedal. When I checked today and Tuesday it was about 1" before it hit the floor. I pumped the pedal and got it back to about halfway. Firm too not spongy. Thinking I need to do some brake shoe adjustments?

 

[banditt1979]

Can someone post the tm that details how to do a major brake adjustment? I've searched and come up short. Thank you

 

[davidb56]

have you lost fluid level in the system, but not on the ground or dribbling down the brake plates?

 

[banditt1979]

The fluid dropped after I pumped up the pedal with no air in the system. Thinking the shoes stayed moved out closer to the drum? No leaks at the wheels.

 

[davidb56]

The fluid dropped after I pumped up the pedal with no air in the system. Thinking the shoes stayed moved out closer to the drum? No leaks at the wheels.

I was wandering if you are actually losing fluid somewhere, as in having to top it off a few times.

 

[M37M35]

I have completely rebuilt my entire brake system...

...NOS air pack...

I just went out and pumped the brakes with no air pressure in the system and no fluid spraying out of the reservoir no matter how hard or how many times I pump.

I'd be suspicious of the NOS airpack. Remember it's been setting on a shelf somewhere for 30+ years...

The fluid dropped after I pumped up the pedal with no air in the system... ...No leaks at the wheels.

Unhook the vent line off the airpack and see if it blows brake fluid out.

 

[banditt1979]

I'd be suspicious of the NOS airpack. Remember it's been setting on a shelf somewhere for 30+ years...

Unhook the vent line off the airpack and see if it blows brake fluid out.

While there's air pressure in the system? Or wait til it bleeds down?

 

[gringeltaube]

Can someone post the tm that details how to do a major brake adjustment? I've searched and come up short. Thank you

http://www.steelsoldiers.com/upload/M35/TM9-2320-209-20-3-2.pdf

Chapter 13, pages 63-72

 

[banditt1979]

http://www.steelsoldiers.com/upload/M35/TM9-2320-209-20-3-2.pdf

Chapter 13, pages 63-72

Thank you! The adjustment doesn't seem too bad. Hope I can get a couple days on a weekend that aren't too hateful and get this done.

Right now I seem to have about half a pedal that doesn't sink. Maybe the adjustment will give more pedal and stop the backflow of brake fluid out of the reservoir. And I may need to get a larger reservoir than the tiny motorcycle one I have now.

 

[banditt1979]

While there's air pressure in the system? Or wait til it bleeds down?

Unhook the vent line off the airpack and see if it blows brake fluid out


Good idea. I will attempt this tomorrow, today would have been nice but more family events......1 year old great niece birthday party lol. Thank you for the suggestion