Hyd Brakes

[Moose]

I believe these photos are of my hydraulic brake system. Not sure what is what?

I have a vairly strong leak as you can see and getting ready to take it on the road. Good size spot under after repositioning bus.









Thanks for any ideas or help

[Rameses]

That's your master cylinder.

I can't really see where it's leaking from in the pictures, but it doesn't look like it's leaking out the end of the piston.

That doesn't leave many other options. I'd check the two lines coming out the side of the master cylinder and the pressure switch (that's what has the wires plugged into it, it turns your brake lights on) to make sure they're all tight.

Is there anything wrong with the way the brakes feel when you step on the pedal?

[Robin97396]

Have you checked your slave cylinders for signs of leakage? Usually that's where a wet braking system has problems because as the lowest point in the system the slave cylinders collect water and chorode/rust.

I also am not seeing the leak on the master cylinder. Perhaps you cleaned off the master cylinder before taking a picture? I'm not seeing the leak.

How much, and how often, are you having to add brake fluid?

[Rameses]

Originally Posted by Robin97396

I also am not seeing the leak on the master cylinder. Perhaps you cleaned off the master cylinder before taking a picture? I'm not seeing the leak.

In the second picture, I thought it looked wet in a couple places.

[Moose]

All leakage seems to be on what I think is the backup pump. in the 3rd and 4th pictures. Master was not wiped down

[Robin97396]

I saw the wet spots on the first two pictures. That looked like a wet spot from a spill while filling what looks like a new master cylinder. That's some fresh looking cast.

On the second two photos I didn't see any indications of a leak on the attached mechanism. That kind of looks like a windshield wiper motor but it's to small. It's got to be some kind of power assist, and from the design I don't believe it should contain any brake fluid. I believe it's a brake energizer of some sort, but I'm not familiar with it.

How much brake fluid are you having to use and how often?

[Moose]

Not driving yet on relocating in yard. But worried by leak. Found this on the hydraulic break system

http://www.centralstatesbus.com/2006...c%20Brakes.pdf

looks like what I have except fluid reservoir is behind drivers seat

[Robin97396]

The good news is you're going to be an expert on your entire bus, including the master cylinder in the near future. It sounds like you haven't had to actually replace any fluid in your brake fluid reservoir yet. Watch the fluid level and take it out for a drive. I'm not trying to be a smartass. I'm just not seeing the leak. Wet spots yes. Likely from the last time it was filled, or overfilled. On the other hand I could have missed some of the points you've mentioned. You mention there was a puddle of brake fluid on the ground?

I have a truck that has two master cylinders, just to make things confusing. The first one is normal but the second one is power assist. Seems redundant.

If your brake fluid reservoir is still full you're likely ok. You've never mentioned having to refill it, and that is where most of us first notice a leaking brake system. Even if it does leak you'll be ok as long as you keep the reservoir topped off. Brake leaks are generally pretty slow.
You also mentioned that you had not wiped off the master cylinder. How about you fill the reservoir, then wipe everything down before simply applying pressure to the system from the driver's seat. If you can pressurize the brake system for several minutes, after wiping down the master cylinder, you should be able to see new signs of leakage.

[BlackJohn]

That drop of fluid is probably sitting at the low point and is residue left from sloppy fill, otherwise it looks clean enough to eat from.

[Robin97396]

When you do move it around in your yard are your brakes working alright?

If the brake fluid reservoir isn't noticeably dropping I don't think you've got a problem. At least carry brake fluid to be safe and check the reservoir level when you pull over until you trust the reservour level isn't dropping. If the brakes are spongy you might have bubbles in your brake lines. Has anyone done brake work on that vehicle lately? That is one new looking mastercylinder.

[Moose]

What I have learned from the doc I posted.

The hyd brake system is run on one of two hyd power sources. Either the power steering pump or the electric booster pump. I believe my leakage is associated with the booster pump. Last time I relocated that pump was running most of the time. and the leakage everyone was looking for is on my driveway about 12" or so stain.

Also while reading the manual I learned the two reservoirs split the system into front and rear brakes.

brake system DOT 3 and power steering is power steering fluid correct

[Robin97396]

Power steering fluid and brake fluid are not the same. It will cause you a lot of problems if you get them mixed up.

They seem similar because they both perform a hydraulic function, but they are not the same and mixing them is not a good thing.

[Moose]

There seems to be a wide range of approved power steering fluids with the warning not to mix different fluids but to drain and refill. What did others do

[Robin97396]

I got a turkey baster and took out the old fluid, twice. It took two changes to get clear looking, probably because of the fluid in the hoses.