Not Enough Air In My "b"

[martinf]

Hey gang.

Was going to wake up my B-75 (early 60's model) to do some work and I only get 30 lbs of air pressure, not even enough to keep my seat up! before I start digging into it, was looking for some advice...

Doesn't seem like it would be gunked up air intake filter as this one draws thru the engine air intake. And doesn't seem like the compressor would all of a suden go bad (rings or whatever)...what's most likely, governor not operating correctly, stuck intake valves or crappy exaust one-way valve?

Yes, I've checked and I'm not leaking air out the lines or cans or anything as I stopped the engine and listened close everywhere and no hissing anywhere. I'm assuming that'senoeugh of a check to know that the problem is on the air production side, not that there';s a leak so big that the compressor can't build up enough pressure.

Anyways, thanks for any ideas or advice.

~martin

[Rob]

Hey gang.

Was going to wake up my B-75 (early 60's model) to do some work and I only get 30 lbs of air pressure, not even enough to keep my seat up! before I start digging into it, was looking for some advice...

Doesn't seem like it would be gunked up air intake filter as this one draws thru the engine air intake. And doesn't seem like the compressor would all of a suden go bad (rings or whatever)...what's most likely, governor not operating correctly, stuck intake valves or crappy exaust one-way valve?

Yes, I've checked and I'm not leaking air out the lines or cans or anything as I stopped the engine and listened close everywhere and no hissing anywhere. I'm assuming that'senoeugh of a check to know that the problem is on the air production side, not that there';s a leak so big that the compressor can't build up enough pressure.

Anyways, thanks for any ideas or advice.

~martin

Sounds like the air governor has gone bad.

Rob

[Packer]

Som times the parts get gummed in setting that will not let things work as they should.

I have seen trucks that will do the same thing, and as you run them, they self-heal themselves.

Last air gov I bought was $25.00 (or maybe 2 for $25.00)??

Anyway, pretty cheap!

Rob hit it on the air gov.

you might try resetting the gov and see if that gets you going.

Replace first chance you get.

Packer

[Mike]

Hey gang.

Was going to wake up my B-75 (early 60's model) to do some work and I only get 30 lbs of air pressure, not even enough to keep my seat up! before I start digging into it, was looking for some advice...

Doesn't seem like it would be gunked up air intake filter as this one draws thru the engine air intake. And doesn't seem like the compressor would all of a suden go bad (rings or whatever)...what's most likely, governor not operating correctly, stuck intake valves or crappy exaust one-way valve?

Yes, I've checked and I'm not leaking air out the lines or cans or anything as I stopped the engine and listened close everywhere and no hissing anywhere. I'm assuming that'senoeugh of a check to know that the problem is on the air production side, not that there';s a leak so big that the compressor can't build up enough pressure.

Anyways, thanks for any ideas or advice.

~martin

I seen them get gummed up after sitting for little awhile so I just run the engine to get enough heat and finally it will get the suffient amount of air to remedy the problem with the Air govenor. Beats buying them unless your billfold is burning a hole in your pocket. But like Rob said it's a good idea to have a spare since they are rather cheap at this time.

mike

[Mike]

Sorry PACKER,.........got to give you the credit. Rob was slithering.

[martinf]

Som times the parts get gummed in setting that will not let things work as they should.

I have seen trucks that will do the same thing, and as you run them, they self-heal themselves.

Last air gov I bought was $25.00 (or maybe 2 for $25.00)??

Anyway, pretty cheap!

Rob hit it on the air gov.

you might try resetting the gov and see if that gets you going.

Replace first chance you get.

Packer

Thanks, everyone.

Where's the best place to get a governor? And, are these Mack specific or generic?

~martin

[Rob]

Thanks, everyone.

Where's the best place to get a governor? And, are these Mack specific or generic?

~martin

Generic. Ask for a Bendix D2 style governor. Easy to plumb if different from your original and about $12.50 plus shipping on ebay regularly. I've purchased several over the years.

Here is a good, honest vendor to deal with.

http://cgi.ebay.com/...VehicleQ5fParts

Rob

[Rob]

Sorry PACKER,.........got to give you the credit. Rob was slithering.

Damn. I skinned my belly and now it hurts. Will you kiss it and make it well?

Rob

[Mike]

Damn. I skinned my belly and now it hurts. Will you kiss it and make it well?

Rob

Yes......I've been needing a good human roast with carrots and potatoes. Or maybe since it's friday p.m. some good human ears with a warm blood sauce and wine would be fine.....fine as wine. Thanks for the offer my slithering friend.

mike

[Packer]

Just hit the local 'Car Quest' store.

They have a sale on air govenors for $10.00 each.

I guess the last I bought were $12.00 each (or two fre $25.00)

And all is forgiven!!!!

Packer

[bullhusk]

you could try turning the screw on the back of the air gov.in- clockwise (under rubber plug)1 full turn should do it. if pressure goes up change the gov.

BULLHUSK

[Rob]

you could try turning the screw on the back of the air gov.in- clockwise (under rubber plug)1 full turn should do it. if pressure goes up change the gov.

BULLHUSK

This is true, however my experience is that if you don't replace it at the first sign or trouble, (as presented), it will happen again. Not a real self healing type of unit.

Rob

[martinf]

This is true, however my experience is that if you don't replace it at the first sign or trouble, (as presented), it will happen again. Not a real self healing type of unit.

Rob

Okay, got the governor taken care of. Now I noticed that I lose some air when hitting the brakes and sourced the leak to the air brake cans on the middle axle. Not the spring locking, just the regular. Got them off and apart and I see that they're pretty rusty insode with some pitting. How picky are these units to get a reasonable seal? Do they need perfecty smooth side walls or can you even clean them up with a cylinder hone and some sandpaper? And, is replacing the lockheed wagner rubber seals advisable or can I get a way with reusing them if they look fairly decent? What's a good source for getting those rubber seals? I would imagine that a complete new brake unit is spendy, but can you get just a new can?

And when rebuilding them should I use oil or grease?

Thanks for any advice. I want to get them to not leak, of course, but my budget is pretty tight these days and I only use the truck a few times a year so it's not like I have to get it perfect for full time road work.

~martin

[Rob]

Okay, got the governor taken care of. Now I noticed that I lose some air when hitting the brakes and sourced the leak to the air brake cans on the middle axle. Not the spring locking, just the regular. Got them off and apart and I see that they're pretty rusty insode with some pitting. How picky are these units to get a reasonable seal? Do they need perfecty smooth side walls or can you even clean them up with a cylinder hone and some sandpaper? And, is replacing the lockheed wagner rubber seals advisable or can I get a way with reusing them if they look fairly decent? What's a good source for getting those rubber seals? I would imagine that a complete new brake unit is spendy, but can you get just a new can?

And when rebuilding them should I use oil or grease?

Thanks for any advice. I want to get them to not leak, of course, but my budget is pretty tight these days and I only use the truck a few times a year so it's not like I have to get it perfect for full time road work.

~martin

Most likely you have roto chambers as they are original and very expensive to work with these days. Just the diaphrams are over $50.00 each anymore and it sounds like you have one blown. Replacing the unit complete is about $300.00 or so. Most of the original sizing was for a type 20 diaphram so a type 24 will work well. I would replace all of them with type 24 spring brake chambers if you have either 34, or 38,000 rears. They will fit without much problem, (just bolt on and replumb). Of course you may be able to find a used rotochamber also should you want to go that route.

Rob

[martinf]

Most likely you have roto chambers as they are original and very expensive to work with these days. Just the diaphrams are over $50.00 each anymore and it sounds like you have one blown. Replacing the unit complete is about $300.00 or so. Most of the original sizing was for a type 20 diaphram so a type 24 will work well. I would replace all of them with type 24 spring brake chambers if you have either 34, or 38,000 rears. They will fit without much problem, (just bolt on and replumb). Of course you may be able to find a used rotochamber also should you want to go that route.

Rob

Thanks for the info. Mine don't have a rubber diaphram that goes across the entire chamber, like some air brakes I've seen. Mine are just a metal piston with a rubber sealing lip and expander spring kinda like a large hydaulic brake master cylinder rubber cup. There's also a felt ring in a large grove in the piston side. Is that a roto chamber, or something else?

And now here' a total newbie question: SInce I only had 30 lbs of air in the system (because my governor wasn't working right), is it possible for the sealing lips to not spread out enough and, therefore, lots of air leak by? I ask because it seems kinda crazy that, last fall, the brakes were working okay (a little leakage, but not much) and then now, firing it up the first time this Spring, when I press the brakes, BOTH these air brake chambers leak like crazy.

thanks for the help, Rob and all

~martin

[Rob]

Thanks for the info. Mine don't have a rubber diaphram that goes across the entire chamber, like some air brakes I've seen. Mine are just a metal piston with a rubber sealing lip and expander spring kinda like a large hydaulic brake master cylinder rubber cup. There's also a felt ring in a large grove in the piston side. Is that a roto chamber, or something else?

And now here' a total newbie question: SInce I only had 30 lbs of air in the system (because my governor wasn't working right), is it possible for the sealing lips to not spread out enough and, therefore, lots of air leak by? I ask because it seems kinda crazy that, last fall, the brakes were working okay (a little leakage, but not much) and then now, firing it up the first time this Spring, when I press the brakes, BOTH these air brake chambers leak like crazy.

thanks for the help, Rob and all

~martin

If those rotochambers leak at all, they are unsafe and need replaced. I wouldn't recommend you learn a very expensive lesson of procrastination here. If that truck will move, it needs to stop 100% of it's capacity, without margin.

Rob

[martinf]

If those rotochambers leak at all, they are unsafe and need replaced. I wouldn't recommend you learn a very expensive lesson of procrastination here. If that truck will move, it needs to stop 100% of it's capacity, without margin.

Rob

Yep, good point and I won't mess around with compromised brakes.

How about my question about if my air chambers are the roto type you mentioned? WOuld like to know aboutthat. As I had mentioned, mine are the kind with a metal piston and a rubber sealing lip and a felt ring a bit lower on the piston side. Are these roto's or are rotochambers the kind with the rubber diaphram fully across the chamber? Boy, those seem like an improvement in terms of sealing reliability....

~martin

[Rob]

Yep, good point and I won't mess around with compromised brakes.

How about my question about if my air chambers are the roto type you mentioned? WOuld like to know aboutthat. As I had mentioned, mine are the kind with a metal piston and a rubber sealing lip and a felt ring a bit lower on the piston side. Are these roto's or are rotochambers the kind with the rubber diaphram fully across the chamber? Boy, those seem like an improvement in terms of sealing reliability....

~martin

Your description sounds like rotochambers. If your truck is a tandem of the vintage you mention, it would have been factory equipt with rotochambers. Wagner, or Wagner-Lockheed was the main supplier for rotochambers. Post a photo and we, or I can tell you for sure. Also rotochambers of the size used on trucks use a single air line plumbed directly into the center of the chamber at the rear opposite the yoke that attaches to the brake cam. Pancake type diaphram brakes have the air inlet at the side of the cannister that is behind the pancake or diaphram.

Rob

[martinf]

Your description sounds like rotochambers. If your truck is a tandem of the vintage you mention, it would have been factory equipt with rotochambers. Wagner, or Wagner-Lockheed was the main supplier for rotochambers. Post a photo and we, or I can tell you for sure. Also rotochambers of the size used on trucks use a single air line plumbed directly into the center of the chamber at the rear opposite the yoke that attaches to the brake cam. Pancake type diaphram brakes have the air inlet at the side of the cannister that is behind the pancake or diaphram.

Rob

Yep, mine have the air inlet in the center back end and definately are not pancake diaphram, so I bet they are roto chambers. I looked for sources for new 24's and came up with this. I'm surprised how inexpensive these are...definately not worth re-building my roto chambers if I can substitute these. Would these do the trick? They are the right bolt size and bolt spacing.

http://shop.easternmarine.com/index.cfm?fuseaction=catalog.prodInfo&productID=8502&categoryID=471

Thanks again, Rob, for all your assistance. I'm learning as I go here!

~martin

[Mike]

Martin, the 24's in the picture are for the front normally or single unit each side. The rear called spring brakes are 24/24 double chambers. They are a must for parking and service. You'll be glad you got them.

mike

[Rob]

Yep, mine have the air inlet in the center back end and definately are not pancake diaphram, so I bet they are roto chambers. I looked for sources for new 24's and came up with this. I'm surprised how inexpensive these are...definately not worth re-building my roto chambers if I can substitute these. Would these do the trick? They are the right bolt size and bolt spacing.

http://shop.easternm...&categoryID=471

Thanks again, Rob, for all your assistance. I'm learning as I go here!

~martin

The link posted is for a pancake type service brake chamber. These would work as acceptable replacements for the existing rotochambers but like I'm doing with my B67, go with 24/24 spring brake service chambers so you will have something better than the driveshaft brake drum holding the truck. However if the original driveshaft brake serves you fine the service chambers will be an easy swap. If your truck has heavier than 38,000# rears the 24/24 chambers will not fit without modifications to the mount(s) due to clearance issues.

Rob

[martinf]

The link posted is for a pancake type service brake chamber. These would work as acceptable replacements for the existing rotochambers but like I'm doing with my B67, go with 24/24 spring brake service chambers so you will have something better than the driveshaft brake drum holding the truck. However if the original driveshaft brake serves you fine the service chambers will be an easy swap. If your truck has heavier than 38,000# rears the 24/24 chambers will not fit without modifications to the mount(s) due to clearance issues.

Rob

My furthest back axle has spring brake chambers on it, and I don't think I have a driveshaft brake.

If I can ask yet another question...how do I tell if my rears are 38,000# or ?

Here's a couple of pics, in case that'll help.

Again, thanks,

~martin

[HK Trucking]

My furthest back axle has spring brake chambers on it, and I don't think I have a driveshaft brake.

If I can ask yet another question...how do I tell if my rears are 38,000# or ?

Here's a couple of pics, in case that'll help.

Again, thanks,

~martin

Those are 44,000 rears.

.

[HK Trucking]

Thanks for the info. Mine don't have a rubber diaphram that goes across the entire chamber, like some air brakes I've seen. Mine are just a metal piston with a rubber sealing lip and expander spring kinda like a large hydaulic brake master cylinder rubber cup. There's also a felt ring in a large grove in the piston side. Is that a roto chamber, or something else?

That sounds to me like it's one of those piston type chambers that were popular in the B model days. It is about the same external dimensions and appearance as a rotochamber but instead of the circle of studs & nuts on the end plate circling the pushrod, the piston type has a flat endplate and screws (usually philips head) around the circumference of the can which hold the endplate to the can.

And now here' a total newbie question: SInce I only had 30 lbs of air in the system (because my governor wasn't working right), is it possible for the sealing lips to not spread out enough and, therefore, lots of air leak by? I ask because it seems kinda crazy that, last fall, the brakes were working okay (a little leakage, but not much) and then now, firing it up the first time this Spring, when I press the brakes, BOTH these air brake chambers leak like crazy.

thanks for the help, Rob and all

~martin

I have indeed seen those type of chambers leak at low application pressures and then "seal up" if the brake pedal is slammed to the floor, however if it's not working perfectly right, fix it. Your life or somebody elses could depend on it.

Another thing I've seen happen on those horizontally mounted piston type chambers is where the suspension gets sloppy and the rears move sideways in a turn, the chamber can strike the frame and get dented slightly causing the rubber seal on the piston to not seal perfectly against the inside of the can due due the dent.

[Rob]

Herb is correct. Those are heavy rears. You can tell by the type of trunion stand, and axle caps that are tapered. The axle shafts are actually two piece units that you can't see. I'd be interested to see the spring brake chamber mounting arrangement if you could post a photo of the area(s).

On the rear rear housing looking at the rear of the truck, just to the rt. side of centerline of the housing bowl, there is a number such as SWD58XXXX stamped, (the X's will be numbers) and these will be the suspension numbers. Anyone with a book can decode these for you.

I don't remember what year you said your truck was but the trunion stand shown is the same as the ones in my 63, and 64 year model B series trucks. These also have the piston type brake cans as Herb mentioned. Rotochambers actually have the rear of the can, (nearest the air inlet fitting) "necked" down about an inch total where the piston type do not. Wagner supplied most of the piston type, with combination of both Wagner, and Bendix-Westinghouse supplying the rotochambers. I've also seen a combination of both installed on the same truck however I doubt they were original to the truck in that fashion.

Rob