Brake Problem on Cat 950

[Makensmoke]

Here is my latest stumper question.

A 950 cat wheel loader, early 80's i'm guessing its a C series. Brakes are air over hydraulic. Replaced the master cylinder and all the caliper seals last winter while troubleshooting brakes that don't work well. While removing the right rear caliper it was damaged beyond repair and replaced with new parts because of it. Now that caliper has blown its seals out and released all the systems oil again. Any ideas as to why this loader won't stop?

Brand new to this site, I really appreciate anyones help with this!

 

[Squizzy246B]

Welcome to Heavy Equipment Forums. I'm sure there is a few people here who can help with your problem...probably more than few .

 

[Countryboy]

Welcome to Heavy Equipment Forums Makensmoke! :drinkup

 

[zlssefi]

cat brakes

I dont know a whole lot about cats imparticular, but two things come to mind when you say its blowing the seals out of the caliper. My first instinct, as simple as it may be if your linings are worn too far down the caliper will over travel past the seal on the oring of the piston and blow out. Second, is it possible that your air governor or pressure release valve are inoperable causing too much pressure to be applied to the brakes?

 

[John C.]

I believe an early eighties machine would be a "B" model unit.

The calipers on those machines usually could be rebuilt maybe twice. The inside of the bores would get sloppy and not hold the seal and you would be blowing fluid all the time. If you bought a rebuilt caliper it is more than likely the bores are shot and the rebuilder is at fault. If you put a new caliper on then I would also have a sit down with the supplier and talk about future business.

There is no pressure limiter on the brake fluid side. The air side has a governor on the compressor and a pop off on the tank if there is too much air pressure. If the fluid side of the system is good you can't hurt it with too much air pressure.

Another issue might be water in the fluid side of the system or using the wrong type of fluid or seal. As I recall those systems used brake fluid but some calipers came set up for using hydraulic fluid. The seals are not mutually compatible. You might bring this up with your supplier.

Good Luck!

 

[Makensmoke]

The linings are in very good condition, I don't think the piston is over extending. I will check into that caliper wether it was purchased as a new or rebuilt. It was purchased from a pretty reputable Cat dealer, allthough nowadays that doesn't mean what it used to. Also if that brake fluid we've been putting into the reservoir is what the seals are designed for.
They did put new seals in the "new" caliper a couple days ago now and it has since seen about 12 hours of plowing. Seems to be holding together so far. When and if it fails again i'll check the tolerance in the bore.
I appreciate all the help!

 

[steve931]

Brakes 950

Here is my latest stumper question.

A 950 cat wheel loader, early 80's i'm guessing its a C series. Brakes are air over hydraulic. Replaced the master cylinder and all the caliper seals last winter while troubleshooting brakes that don't work well. While removing the right rear caliper it was damaged beyond repair and replaced with new parts because of it. Now that caliper has blown its seals out and released all the systems oil again. Any ideas as to why this loader won't stop?

Brand new to this site, I really appreciate anyones help with this!

You need to put a pressure guage to the incoming side to each caliper and see if you have equal pressure on all four calipers.It is possible that all the pressure is going to one or two calipers instead of equal pressure on all four.

 

[Makensmoke]

I will check that as well, so too high of pressure on the oil side will blow the seals? I didn't know if things were made to the extreme on brakes that they could handle the worst of things that were given to it.

Plowing on ice, none of the tires lock up early when slowing to change direction, I guess my GUT feeling is they are all pretty close anyhow...?

Is there a trick to hooking up the guage you want to share? Do you use the bleeder port?

 

[John C.]

Steve 931,
I don't know where you came up with this idea and I don't want you to think I throwing rocks at you, but there is nothing to be gained by hooking up pressure gauges in this type of brake system.

On the 950B air is used to push a diaphragm which applies pressure to a piston which pushes oil which forces another piston or multiple pistons against pads. There are two sets of power boosters on this machine, one for the front axle and one for the back axle. The two systems are only hooked together by the source of air to apply them. The fluid sides have no connection at all.

The other item is the idea of over presurizing one caliper is not possible at all in these systems. Whatever pressure is applied from the power piston will be the same on both calipers. That is a basic tenent of physics.

Makensmoke,
Those calipers are supposed to be able to handle any amount of pressure that the power boosters can apply to them. So if the caliper leaks, there is something wrong with the caliper. Don't waste your time making the problem more complicated than it is.

 

[steve931]

Brakes

Steve 931,
I don't know where you came up with this idea and I don't want you to think I throwing rocks at you, but there is nothing to be gained by hooking up pressure gauges in this type of brake system.

On the 950B air is used to push a diaphragm which applies pressure to a piston which pushes oil which forces another piston or multiple pistons against pads. There are two sets of power boosters on this machine, one for the front axle and one for the back axle. The two systems are only hooked together by the source of air to apply them. The fluid sides have no connection at all.

The other item is the idea of over presurizing one caliper is not possible at all in these systems. Whatever pressure is applied from the power piston will be the same on both calipers. That is a basic tenent of physics.

Makensmoke,
Those calipers are supposed to be able to handle any amount of pressure that the power boosters can apply to them. So if the caliper leaks, there is something wrong with the caliper. Don't waste your time making the problem more complicated than it is.

HAVE YOU EVER HEARD OF A COLLAPSED OR KINKED OR BLOCKED BRAKE LINE.STEVE931

 

[Squizzy246B]

HAVE YOU EVER HEARD OF A COLLAPSED OR KINKED OR BLOCKED BRAKE LINE.STEVE931

Lets be clear on this. Posting in "ALL CAPS" is considered yelling. By all means continue your discussion but All Caps posts will be deleted.

 

[wrench2556]

Hi, Lets start from the beginning. First what is the machine serial number? There should be a tag or stamped i.d. number in the cab or on the loader frame. You say you have changed the master cylinder. There are 2 master cylinders, 1 for the front and 1 for the rear. I will asume you changed them both. Were they leaking? Are the brake linings good on all four wheels? How much air pressure do you have on the gauge?Does the foot valve on the right side feel hard or spongy? Do you hear air exhaust when you hit the pedal and release it? Do you have any kinks or bent lines? When you bleed the brakes , Is there good fluid pressure when you open the bleed screw? What type fluid did you use? Did the new caliper start leaking around the seals or actually push the piston out far enough for it to come past the bore seals? It is a pretty basic and simple brake system, But if you can answer these questions we can get to your problem.

Get me your machine serial number,
Check these things out and get back to me, And I will try to help you with your problem if you have not fiqured it out already. Have a merry christmas Billy:drinkup

 

[EUC-B30]

Fluid

Is there any chance that you have a FLUID / SEAL compatability problem.

Is the caliper you bought to be used with BRAKE FLUID and your are using mineral oil ? Can EAT the seals up QUICK !


-KenB

 

[awhitten88232]

We have been trying to adjust the brakes on a 950C cat. There are 2 separate adjusters for each wheel. Which way are they supposed to be turned, clock wise or counter clock wise? This loader hasn't been maintained very well, and they seem to be rusted stuck. Can the brake drums be removed with the removal of the tires without removing the final drive? I have read the other links for brake questions for the 950, and the answers were helpful and interesting. We look forward to your responses, thank you.

 

[Cmark]

We have been trying to adjust the brakes on a 950C cat. There are 2 separate adjusters for each wheel. Which way are they supposed to be turned, clock wise or counter clock wise? This loader hasn't been maintained very well, and they seem to be rusted stuck. Can the brake drums be removed with the removal of the tires without removing the final drive? I have read the other links for brake questions for the 950, and the answers were helpful and interesting. We look forward to your responses, thank you.

My SIS doesn't show a 950C. What's your serial number?

In the absence of a serial number, I've yet to see a Cat drum brake arrangement where you don't have to remove the final drives in order to remove the drums.

If your machine's as old as I think it is and you want good brakes, you'll have to resign yourself to stripping and overhauling all four corners along with the rotochambers. Time consuming and potentially expensive I'm afraid.