PD4106 park brakes won't release...

[busenthusiast]

I've reached another cross road and don't know what direction to take. I've used the search button and have found multiple entries on park brakes that won't release, but none that seem to correspond to a 4106. When I bought this bus the other day, we had some trouble getting the park brake to release, but it eventually did. The guy I bought it from really didn't use it at all......he may have put 5 or 600 miles on it in 10 years. I'm pretty sure that these park brakes aren't original since the the GM manual refers to hand brakes. This being said, I'm not sure if I have DD3 or spring brakes. I've tried several time to get them to release. I'm using my air compressor in the garage (helps recover the pressure quicker) along with the on-board compressor to build to the max, then dumping the park brake valve and then applying a 10 to 20 second service brake to get it to unlock, but then trying to put her in reverse keeps yielding a stuck park brake. It I hold the service brake pedal down too long the park brake valve pops back up. Anyone got any pointers?

[luvrbus]

If no one has changed the brakes you have ICC brakes bleed all the air off they should release,those are called chaser brakes air pressure leaks off you chase the bus down the road that was the reason for the hand brake,what is written on the park valve 

good luck

[robertglines1]

try holding foot brake before and during parking brake release.

[busenthusiast]

Luvrbus, the park brake valve is just a standard valve (I guess).....pull to set, push to release. Is there anyway to tell what type brakes I have?

Bob, I'll give your recommendation a try first thing tomorrow.

[robertglines1]

prob biggest problem with your bus is lack of use.  Air relays and ck valves become dry and tend to stick or bind from lack of use. Back feeding with shop air sometimes will release a stuck valve or relay. Again feeding with both sources at the same time can confuse a relay or valve including ck valves or you air compressor governor. Experiment with different combos.  make sure your brake cams/shafts are greased and not binding.  Just a few things to look for on a bus that hasn't been used much.

[wildbob24]

Billy,

The only way to determine which brake chambers you have(If the PO can't tell you) is to look.

You could have Mini Max chambers, or DD3s, or spring brakes.

The Mini Max chambers were often used on the 4106 because they could be installed without modifying the mounting bracket. They are easily identified because the relatively short chamber is made from cast aluminum. They will have 3 hoses attached.

DD3s and spring brake chambers are larger and made from steel.  The mounting bracket has to be cut and relocated for these to be installed. They are different in appearance, but the easiest way to tell the difference is the DD3 will have 3 hoses attached, while the spring brake will only have 2 hoses attached.

Bob

[RJ]

Billy -

WAIT!

Before you try what Robert suggested, take a look at your rear brake cans.  There are two different types of parking brakes used on buses, DD3 and Spring.  Spring brakes were not an option on 4106s, but DD3s became optional long about mid-year of 1963 production.  A previous owner may have installed either type, so you need to determine what you've got, because the release procedure is different between the two types!

How can you tell what you've got?

Simple - look at the rear brake cans.  How many air lines do you have coming off the cans - 2 or 3?

If two, you have spring brakes.

If three, you have DD3s.



Release Procedure - Spring Brakes

1.  Build coach air pressure up to governor cut-out (approx 120 psi).

2.  Lightly cover service brake with foot - do not apply, just cover.

3.  Push in on parking brake knob until it seats.  Wait 3 -5 seconds.

4.  Put coach in gear and away you should go.


Coach should roll after #3.  If not, then pull knob back out to reset brakes and repeat steps 1 - 3.  If coach still doesn't roll when put in gear, something is wrong and needs to be looked at.  Make sure coach wheels are properly chocked, preferably front and rear, before doing any investigative work.


Release Procedure - DD3 Brakes

1.  Build coach air pressure to governor cut-out (approx. 120 psi).

2.  Lightly cover brake pedal - do not apply, simply cover.

3.  Push in parking brake knob to release parking brakes.

4.  AFTER pushing in knob, apply a FULL service brake application (FLOOR IT) and hold for 3 - 5 seconds.

5.  Release service brakes, coach should roll when put into gear.

6.  If coach doesn't roll, lightly cover service brake again (do NOT apply - just a light touch).

7.  Pull knob to reset parking brake.

8.  Repeat steps 1 - 5.


As stated above with spring brakes, if the coach doesn't roll after steps 1 - 5 are repeated, there may be a problem that needs investigation.


Setting Spring Brakes for Parking

1.  Once parked, lightly cover service brake sufficiently enough to just keep coach from rolling.

2.  Pull parking brake knob to set brakes.

3.  Release service brake - coach should not move.

4.  If coach will move with parking brake set, have brakes looked at immediately!


Setting DD3 Brakes for Parking

Procedure is basically the same as for Spring Brakes, but the critical point here is that you LIGHTLY hold the coach with the service brakes before pulling the knob to set the parking brake.  You should ONLY apply enough service brake to keep the coach from rolling, no more.  The harder you have the service brakes applied, the more difficult it will be to release the DD3s. 


FWIW & HTH. . .

 

[robertglines1]

Was hoping a more experienced Gm guy would give correct procedure for your coach. I have tried many procedures when things are sticking hoping to get them to correct them selves.I didn't know the correct procedure before now  Bob

[papatony]

Billy here comes another comment on brakes I have a 64 4106 and the flip switch is not a parking brake but a bad weather brake change it will not lock the braakes down.  you have a hand pull brake between the drivers seat and left wall.  Some times when not used much the break pads will stick in the drum. take a 2 or 3 lb. hammer and tap around the housing . also trying to put back presure on them.

[busenthusiast]

Well it's 24 here in South Carolina....brrrrrr. I put on my coveralls made sure the wheels were chocked and squeezed underneath the bus to get a look at the brake cans....here they are...





I'm assuming, by the reading RJ's very detailed post (thank you so much by the way), that I have the DD3's installed, or I could have the Mini Max chambers referred to by wildbob24. Not really sure.....If I do have the DD3's then I may have a problem. I may have already tried what robertglines1 suggested yesterday (applying service brakes while releasing park brake). If so, how hard is it going to be to get them to release now. Is there an alternate method of getting them to release if the proper procedure is not followed.

papatony, I don't have a flip switch or a hand brake between my driver's seat and the left wall....I can only assume that this was removed by the previous owner....

P.S. if you take a close look at the lower photo, the hose to the right is showing signs of damage to the outer hose covering, need to get that replaced..... which brings up a good question....where can you get OEM replacement parts for these old coaches?

[brando4905]

Billy,

Like RJ said, make sure you push in the knob before applying brakes. I have DD3s also, I had problems releasing parking brakes too until I started doing it the right way per RJ.

Brandon

[wildbob24]

Billy,

Those are definitely DD3s, so RJ's procedure should work for you.

It's possible the internal locking mechanisms are gummed up and cycling through RJ's procedure a few times will help free them up.

There is a zerk fitting on each chamber whose purpose is to periodically lube the lock mechanism (one or 2 squirts only; it's easy to use too much). If it hasn't been done in over 10 years, it may be time for a brake chamber overhaul.

OEM parts can be hard to come by. The most likely source is Luke at US Coach: 1-888-262-2434.

Bob

[Rick 74 MC-8]

    What is the air psi when the parking brake knob pops back out. Sounds like you may be loosing air and the brakes apply for safety That's what they do if there is not enough

                                                                                   Rick 74 MC-8

[busenthusiast]

Rick, the valve pops back out at 90 psi....this happened because I was holding the foot brake down for like 20 secs (saw it on a post somewhere and was giving it a try) and the pressure dropped to what I guess is the low pressure pull in for the compressor.

wildbob24, where is the zerk on the the chamber....I felt all around...top, bottom, front, back....I see don't see any fitting on the chamber itself. There are two fittings back by the slack adjuster. I gave them a few squirts....but don't see any others...

Is it still OK to use external air to help build the pressure quicker, or should I only use the on-board air?

And is there a possibility that I've done something to make releasing the park brakes worse by not following the proper procedure....and if so, is there a way to remedy it?

[robertglines1]

wouldn't think you hurt anything by not using by the book procedure. I can assure you allot of drivers never new proper procedure. Just start and point. I apparently didn't and have been driving truck cranes and lowboys  for 40yrs. buses for 15 now. I just shared what had worked for me when brakes wouldn't release. Normal operation I put foot on pedal lightly and release parking brake. If it sticks I stroke a couple times.Have never been past that. A brake problem caused the fire in the coach I'm rebuilding now. Parking brake valve is normally set to pop back out on low air around 60 lbs. some replacement valves set at 45 lbs. 90 is  about where air compressor should cut back in.and off around 120. the grease zerts are on back of backing plate (brake)and lube the shafts that must move freely to release and apply brakes.  Good luck   Bob   PS I learn something new ever day!