M936A2 service brakes

[charlesmann]

I did a search, might not be using correct word search, and this might have been answered already.

I will start by checking my check valves and abs relays. But for now, id like to go ahead and see if it could be something else.

Got my truck hm today from a job site about 20 miles away. I did my post trip, checked my tires, axles, fluids and so on. I didnt notice/feel it when i got hm, but i needed to get fuel and tobacco products, so i drove it to the local buc-ees, went in for water and cigs, came out and noticed a brake/clutch smell from the L/F steer tire. I checked the hub flange and rim and they were very hot to the touch, so i decided to check the drum and steer knuckle, even hotter at the drum. I proceeded to check the remaining 5 hubs and the R/F steer, both intermediate axle hubs/drums were warm, but nothing more than normal usage warmth. The rear axle hubs/drums were much warmer than the intermediate hubs, but nothing like the L/F steer hub.

I poured a couple bottles of ambient temp water on the steer drum and it steamed and boiled. I limped it home and when i shut it down to check the drums, the l/f was lightly smoking, so as a precautionary, i got the water hose and proceeded to cool the hub down first for about 5 min, then moved to the srum and i could hear the water boiling and steam was so thick, i could see the tire bc of it. After i got it cooled down to the touch, i moved to the rear axle and repeated. Steam didnt roll out like on the front, but there was a small amout of steam, even at the 3rd member.

Im gonna check diff levels tomorrow too, but i know 100%, there was ample gear and lucas oil in all 3 axles but i did notice a weep starting at the output flange seal the faces rearward on the 3rd member. My vent might be clogged, but it was working just fine several months ago when changed over from greased to oil bath bearings on the drive axles.

Thoughts, theories, causes on the service brakes sticking? Maybe need to pull the wedges out and lube them, or maybe a broken return spring?

 

[98G]

How's the front gladhand on the service side?

 

[charlesmann]

How's the front gladhand on the service side?

Installed. Im sure the rubber could need to be replaced, as with the others, but no issues till today

 

[98G]

Installed. Im sure the rubber could need to be replaced, as with the others, but no issues till today

There should be a valve on it. If this valve becomes jammed/clogged, then pressure won't be released when you let off the brakes and the service brakes begin to drag.

 

[charlesmann]

There should be a valve on it. If this valve becomes jammed/clogged, then pressure won't be released when you let off the brakes and the service brakes begin to drag.

Ill check that first thing in the morning and report back.

 

[charlesmann]

There should be a valve on it. If this valve becomes jammed/clogged, then pressure won't be released when you let off the brakes and the service brakes begin to drag.

The only valve i found is on the emerg gladhand, which both fwd and aft valves ar closed. The svc side has a vent/breather plug, which is functioning.

 

[98G]

Vent/ breather plug is the valve I had in mind.

 

[M35A2-AZ]

You need to have this vent on the front service gladhand and if you have a valve on it you need to have it in the open position..

 

[charlesmann]

You need to have this vent on the front service gladhand and if you have a valve on it you need to have it in the open position.View attachment 846198.

See comment #6.

 

[Mullaney]

See comment #6.

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So, now we have a problem.

The yellow painted gladhand has the words "service" typed above the picture.
Your wording says "emerg" in post #6.

I'm thinking one of those statements are wrong. OR the wrong part is on one truck or the other.

 

[charlesmann]

.
So, now we have a problem.

The yellow painted gladhand has the words "service" typed above the picture.
Your wording says "emerg" in post #6.

I'm thinking one of those statements are wrong. OR the wrong part is on one truck or the other.

The only valve i have up front is on the emergency gladhand. On his picture, someone might have installed a valve as well on his truck, or at some point in time, someone removed the valve on mine. Either which way it happened, there is no valve outside or inside of the frame for the service side.

 

[M35A2-AZ]

The only valve i have up front is on the emergency gladhand. On his picture, someone might have installed a valve as well on his truck, or at some point in time, someone removed the valve on mine. Either which way it happened, there is no valve outside or inside of the frame for the service side.

That is the way it should be, the service side should just have a vent on the gladhand, but some trucks like my M923A1 also have a ball valve, (THAT YOU DO NOT TURN OFF) if you do your service brakes will slowly come on.

 

[charlesmann]

Using the L/F service brake chamber as an ex., since i am having an issue with that particular chamber. Which hose is supply when pedal is pressed and which is exhaust once pedal is released? I want to crack the exhaust side to let the air out to see if it fully releases then back track to a possible bad component.

Just curious if an abs failure could cause the issue. My abs light comes on and stays on at times. The other day when i would go to start the tck with mostly charged air, i would hear 4 air pops. I get 4 elec clicks most of the time but 4 times in the past week, i would get the air pops.

 

[Mullaney]

Using the L/F service brake chamber as an ex., since i am having an issue with that particular chamber. Which hose is supply when pedal is pressed and which is exhaust once pedal is released? I want to crack the exhaust side to let the air out to see if it fully releases then back track to a possible bad component.

Just curious if an abs failure could cause the issue. My abs light comes on and stays on at times. The other day when i would go to start the tck with mostly charged air, i would hear 4 air pops. I get 4 elec clicks most of the time but 4 times in the past week, i would get the air pops.

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So it is really strange... Both of my S&S trucks have exhaust vents on the front gladhand covers. My M936 has stamped steel (rather than aluminum) gladhand covers and there are NO vents on those stamped pieces of metal. I went out back to look and took a picture and the back of the gladhand appears that it might have some sort of vent.

 

[charlesmann]

@Mullaney

As pictured in my post, my service g/h does have a vent a d it is open and it does allow air to escape. The problem is between the g/h, the treadle valve and the svc chamber. It might be the treadle valve is bad and not exhausting the air. I might try whacking it with a hammer to see if that might jiggle something around inside and allow air to release.

Im assuming the park/emerg chambers are releasing since the intermediate axle seems to be fine, or the shoes arent adjusted correctly but when i had the hubs apart, i had to build air with the parking brake lever and valve pushed in to get the drums on all axle but particularly the intermediate axle since its the only axle not having an issue.

 

[Mullaney]

@Mullaney

As pictured in my post, my service g/h does have a vent a d it is open and it does allow air to escape. The problem is between the g/h, the treadle valve and the svc chamber. It might be the treadle valve is bad and not exhausting the air. I might try whacking it with a hammer to see if that might jiggle something around inside and allow air to release.

Im assuming the park/emerg chambers are releasing since the intermediate axle seems to be fine, or the shoes arent adjusted correctly but when i had the hubs apart, i had to build air with the parking brake lever and valve pushed in to get the drums on all axle but particularly the intermediate axle since its the only axle not having an issue.

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You might put a few drops of Marvel Mystery Oil in the IN line on the treadle valve. Love Tap might work too, but if it is a rubber o-ring going south a few drops of really thin oil could help.