The Stovebolt Site Forums The Parking Lot Big Bolts Air brake question

I have a 1966 C70 that come with full air brakes. Some time in the past the trailer part was partly removed most still there.

My question is the low pedal hight (this pedal hangs down from the dash)not floor mounted. Also the travel is short . The brakes work but it feels to me there is not the back feed you normally feel in the peddle when applying them.
Could it be it need the trailer part of the brakes air going to it still? . I'm not sure if it does looks to have been removed but I'm still looking it all over.
I'm not sure where the trailer air goes when bob tailing ?
I'm still in the making every thing back to stock and fixing stage . The truck is very drivable but don't want to find a surprise when there is no brakes or brakes applying buy them self.
Any one have a older with air brakes?

There is very little pedal travel with air brakes. You need to picture that unlike hydraulic brakes where you are providing the hydraulic pressure by stepping on the brakes, with air brakes you are merely opening a valve to allow air to go to the brake chambers. When you let off the brakes, air escapes through a quick release valve. The trailer air is controlled by what is called a tractor protection valve. It has 2 outlet ports. The emergency or supply port which has constant air pressure going to the trailer to supply the trailer with air and to keep the trailer brakes released. The service port is the port that supplies air to the trailer brakes when you apply the brakes. Chevrolet was still just a rigged up straight truck and was really not engineered for tractor equipment as were the heavy duty trucks in 1966. Many did not have a tractor protection valve and merely had 2 ball valves to cut off the trailer air when bob tailing. If you have a tractor protection valve, there should be a toggle switch on the dash somewhere. Also you may or may not have a trolly valve on the steering column which you can use for extra braking power to the trailer. In my opinion, the swinging brake pedal Chev used is difficult to use because with floor mounted brake pedal, you rest your heel on the floor and learn to apply braking power with your ankle. With swinging pedals, you have to regulate the pressure with your whole leg and it is easy to apply too much air in a panic situation and wind up in a skid. I guess my main point is that in 66 Chev was not engineered as a truck tractor from the ground up like the heavy trucks. Many were retrofitted with tractor equipment, and air brake principles were poorly understood by most people who installed the tractor equipment and many systems were poorly designed. Probably the best thing to do would be to find some old timer who worked on and understood the systems of that period to find out what you have. If it were mine, I would not worry about staying original, but rather retrofit the brake system with more modern components for safety.

What you have described is normal for an air brake equipped truck. There is no feedback with full air brakes and they cannot be compared to hydraulic brakes in that regard. There is a push button valve on the dash that is for charging the trailer brake system. It will be marked "Emergency" I imagine and be yellow. If your not pulling an air brake trailer it is of no consequence to you. There should also be another push/pull button valve for the parking brake. It is pulled out to engage and pushed in to release.

You claim that the trailer part has been removed. Are you thinking about the hoses and valve at the back of the cab? If so it is still just fine and there would be no air to them. Air is only released to the trailer thru the charging valve located on the dash (assuming it has not been removed also). There is no danger of them applying themselves so not to worry. The air brake system is simple and direct. What is important to undestand is that moisture is the enemy of any air system and your truck is no different so be sure to drain the reservoirs daily. If the sludge that comes out of the tanks contains a lot of oil it is from the air compressor which gets it's oil from the engine so don't let the engine oil level get too low. Adjustment to the brakes is made at the wheel on the slack adjuster/cam if not equipped with wedge brakes. It is possible that your truck does not have any front brakes as a lot of older tractors had them deleted.

I doubt that the truck would be equipped with a yellow emergency button. This did not come out until the 70's. If his truck had a tractor protection valve, and a lot of 60's tractors didn't, it would probably be operated by a toggle type lever. It is the same toggle valve that is used today on sliding 5th wheels, power divider lock and suspension dumps. I think International's first year for the button was on their 4070B model which came out in 74. But it is hard to say what his truck has because it was common to retrofit as newer stuff came out. It is also very unlikely that a 66 model had spring brakes. If it did, it would probably be a chrome plated knob on a BW valve that you push to drive and pull to park.

Yes I suspect your right. I do recall upfitting air brakes trucks with tractor kits in the late 60's and up. I had a 4070A that had the yellow button however. It may have been a late one but being a Cornbinder anything was possible. As the old saying goes "they never built two alike".

It also had my first and last double breasted Yamaha in it.

my '72 GMC has a black and red button for tractor protection and a red one for parking, it also has the hand valve for controlling the trailer brakes. usually when the brakes apply themselves it is because the air pressure gets too low, most trucks have buzzer that turns on when the pressure drops below 60 psi so you still have some time to stop and wait for the pressure to build back up. you get used to them after a while.

Many of federal safety standards do not apply to to vehicles manufactured before 1975
However, states are at liberty to pass more stringent laws. In Texas for example, we do not have the year of manufacture exemption for brakes. It would be good to check your state laws because a truck tractor falls in the catagory of a commercial vehicle.

Does your '66 C-70 have a steel pedal with no rubber pad on it and the word "Air Brake" embossed on it?

It sounds like your '72 has Maxi Brakes (Spring Brakes). My '71 9500 had Maxi's. I doubt very much too that the '66 would have Maxi Brakes. Not sure exactly what year they started showing up, but I believe it was somewhere around '68 (in Chevy's and GMC's anyway).

Bill

I don't think he has had the brakes to set while he is driving. I think he is worried that he either will have no brakes or that the brakes might set while he is driving. Heavy trucks had spring brakes in the early 60's but I think it was much later when they offered on Chev gas burners. I remember Texas grain haulers with 409s trying to retrofit them but there wasn't enough room with the configuration of the brake spider.

Thanks for all the replies ,

The truck is now just cab a chassy it last use was a road oiler for a county road dept. New it was a small bobtail semi with a 5th wheel. It always was a county road dept truck from new.

I will start with this one and try to explain some. The pedal is steel but looks like is could have had a rubber pad bot no name one it.
It does have brakes on all 4 corners so all good there.
I know there was at least 3 type of air brakes and 1 air over hyd available in 66 : Air pack , Standard air brakes, Stop master (wedge brakes), And DD3 . Mine has the Stop master with what they call "fail safe brake chambers" (Spring brakes).
The parking valve is a black round knob. The trailer Emergency valve is a stop sign looking shape knob.

The trailer emergency valve is hooked up but the charge line was being used for some air Cyl for laying oil on a road .
The Hand control valve is missing and the Breakaway valve and the air lines been removed from the back of the cab.

I am going to try to put all the air lines and controls back.

The foot valve feed back I was trying to explain is what happens on newer air brakes is some of the application air is fed back into the pedal to push back so you have some feel of the amount of air being sent to the brake chambers.
On this foot valve it feels like its only spring presser I feel and the travel is so short it hard to control the brakes and no way of driving in the snow or ice. I guess what I need is a air line schematic the 66 shop manual only show the DD3 air circuit maybe the older books show it?? And nothing on the foot valve.
What I trying to find out if the foot valve is bad or the lines not hooked up correctly.
I hope I explaned my problem without go on and on .

Thanks
Brian

First of all, don't be mislead by the "fail safe". 66 may have well been the first year for Stopmasters. They were appealing because they were compact and therefor fit a Chev and they were lightweight which appealed to bulk carriers. They were only popular with carriers who looked at numbers and not at practicality. Consolidated Freightways was the last carrier that I know of that used them and they were auctioned off in 2001. Parts are very expensive and not readily available any more, and very few techs know how to trouble shoot them. However, the only to retrofit them to cam brakes would probably get different axle housings with cam brakes on them. The plunger gets rusty and sometimes functions, and sometimes not. I have 9 former CF trailers, and I have replaced the axles on all of them. One lot of 4 that I bought in Los Angeles and trip leased them to San Antonio, all 4 arrived with no service brakes at all. However the spring brakes were working. However on a truck as old as yours, there is a very good chance that the springs have rusted and broken The swinging pedal was just not a very good idea to begin with. This is what is standard of the industry now and basicly has been for the 44 years I have owned trucks. http://www.bendixvrc.com/itemDisplay.asp?documentID=2590. If I were to drive a truck any distance at all I would totally redo the brakes using modern components. However, it is simple for me to do because I am a licensed salvage dealer as well as operate trucks and I always have donors sitting around. As for not having a trolley valve, they are not manditory. Schneider National specs their trucks without them to keep drivers from using them as a parking brake. I personally prefer to have them. We have two trucks that came from Schneider, and we added a trolley valve from a donor.

off topic but what do you usually have to do to be a scrap/salvage dealer? my dad and i have been thinking about it.

Thanks for the reply,
I don't think its all doom and gloom with wedge brakes. Lots of truck still running them. Yes I also don't like stop master wedge brakes.
But if they was maintained they still should work and this truck was a county truck and had good maintenance and the brakes still work. I will look and keep looking for a other axle with normal air brakes . I think my 3rd member with the 2 speed should fit in newer axles maybe. But until then what I have will do.
The foot valve is one thing that need fixing. If mine is not serviceable any more I will go with the link you posted new or look for a good used E 12 ,15 or ?. I may need 1 more air tank to retro fit an newer system to my truck. It has what makes out to be 3 tanks now but I need to look some more at it.I know one tank is a duel compartment type.
Do you have any good used foot valves for sale?

Just to add a little extra, my '62 GMC 6500 had Air Brakes with the swinging pedal. That's the truck that had the steel pedal with no rubber pad and the word "Air Brake" on it. I am far from an expert as far as the mechanicals go, but that truck (as long as the brakes were adjusted correctly) always stopped just fine, empty or with a full load (32,000 GVW). I also had no trouble with controlling the amount of pressure with the swinging pedals, whether I applied pressure directly or when the heel of my foot was on the floor. My '67 GMC 7500 also had swinging pedals, altho that one had a rubber pad, and again no problems, but my '71 9500 did have the foot pedal and I have to say I did like that one better, but the difference was not enough to matter much, to me anyway.

The time I would have trouble with brakes were those IH 1600's and 1800's that had power hydraulic brakes. After driving the GMC all day and then jumping in an IH, I almost always left 4 rear wheel patches of rubber on the road. Those brakes were extemely touchy. I think those trucks would stop even if you breathed on the pedal.

Bill

I got the opportunity to drive a 90's ford-chassis school bus when I moved to Wisconsin. It had Bendix air brakes with a swinging pedal.... I absolutely LOVED those brakes.... I'd put air brakes on my truck in a heartbeat if it weren't for the gray area about needing a CDL to drive it.....

The valve that your swinging pedal controls could probably be retrofitted with a later style valve. If you have never driven a treadle type and learn on this one, you will probably be ok. I have driven an 18 wheeler several million miles in my life and it would scare me in a panic situation because I am used to the treadle type. We had a Chev for a yard mule back in the 70's and it seems like the pedal operated a valve much like modern valves. We didn't care about brakes because we never got over 10 mph. Maybe you can get a late style valve to fit in the place of what you have now. Schematics always show 3 tanks but in reality it is usually a single and duel compartment tank. I would recommend new or good used tanks. There is no way to get the rust out of old tanks and rust will eat up your valves. If you know a truck salvage dealer that isn't greedy, you should be able to pick them up for practically nothing. I throw them in the scrap iron pile. The wedge brakes will work, but they are certainly not the system of choice. Make sure that the plungers are free and the brakes are adjusted properly

I will look to see if it can be retrofitted to a newer valve.
Looking over my tanks so far I just found 1 duel compartment tank I thought I saw 2 tanks the other day but it was getting dark out today so tomorrow going to look the air system over good. I'm going to get a 63 truck manual I think it should show more on my air system as the 66 truck manual that come with the truck keeps refering to the 63 book. What I would like to see is in side photo or something in the manual showing where the air control valves should be located at. Right now both are on the far left side below the dash. I don't think thats where they should be. I should have most of the day tomorrow to play with the truck.
Thanks for the help.

Brian

Brian,

Are you sure the manual that came with your truck is for the new series truck. It very well could be possible that they have the air brake system of the '63's, but the truck that you have is a whole brand new design. In '66 there were probably more models than any other year. They still made the '60 to '66 conventional style trucks, cab overs, believe they still had the series "B" and series "L" as well as the new style.

Bill

Bill,

Good point but from what I see in the 66 book it does say new for 66 is .... and it also say some things unchanged from 63.
It does show the new Stopmaster (Wedge Brakes)but does not show any change to the air lines. It also shows a up dated DD3 brake system.
What I'm thinking is the new Stopmaster was added to the standard air brake system that the 66 book say was unchanged from 63. So I have no idea.
The brakes work OK on my truck . Pump out all the air and at 60 PSI or so they apply in emergency like they should.
I don't believe it has a duel air brake system like the newer trucks.
Also I don't know what may have been updated on my truck or changed . What I do see is the Stopmaster brake air chambers look to be the newer style type. So at least thats better for finding parts.
I plan over time to up date it all. I hoping to find a newer donor truck in a salvage yard for tanks and some parts.
1st on my list is the low air light and buzzer not working or not there. Fix the brake pedal. Then install a tank auto drain and maybe a air dryer.
Replace all the air lines to plastic.

It will be a never ending project.

Any one know do they make a air over electric brake controller for pulling a trailer with electric brakes using a truck with air brakes?

Brian

yes i have seen a air controlled brake controller but why not just use the normal electric kind, they're a whole bunch less expensive. here's a link to one.
hhttp://www.southwestwheel.com/store/p-45-hayes-airelectric.aspx

My thinking on the electric ones is any time the brake on the tow truck is pushed and it sends the power the the controller .
The controller will start sensing the amount of deceleration and I'm thinking if Jake brakes and engine braking alone it will add trailer brakes more then needed. I could be wrong?
One thing I was thinking is if on ice or snow and you don't get the tow vehicle to slow because of sliding wheels you get less deceleration and then the controller will give you less trailer brakes.
But it may just work fine.
$65 or $199 for the air over electric A little more costly.

My head is spinning now

Brian

there are some that are timed so when the brakes go on the controller sends power gradually until full breaking. that's the kind i have in most of my trucks and haven't had any problems with them, i also have one that is hooked into the brake line on the truck to control the electric trailer brakes it works good too.

47Chevy6400, in answer to your question, it is a state issued license and requirements very greatly. The back ground check I had to go through was just as thorough as when I was a director of a bank. This is because Texas with its close proximity to Mexico and sea ports, is home of many "chop shops". Also, If I hadn't became licensed dealer years ago, I would probably not make it through the neighborhood protest period. I am not very active in the business but I must be licensed in order to buy salvage units from insurance companies. The actual fee is only $80 per year.

Motelcambodia, the controllers are not for full air. If you want better brake control on ice, this would require anti-lock. However this would be a whole new can of worms to install. It is doable. We have done it in our shop, but then you need hubs with something like a starter ring gear for the sensor to count. If had a choice between anti-lock and a treadle type brake pedal, I would take the treadle type pedal. If you re do your brake system like the schematics, it will automatically put less braking power on your brakes when you are bobtailing. Full braking power when bobtailing is what causes drive tires to lock up and then you switch ends. You are on the right track thinking about Synflex or vinyl brake lines. The old copper ones were a night mare. Be sure you replace all of the rubber hoses. When this truck was built, the life expectancy of these hoses was 2 years, now it is 20 years. Going to more modern valves will give you 3/8 pipe port instead of the old 1/4 pipe thread which will be compatible with todays replacement hoses. I guess a lot of all your decisions depend on what you really intend to do with the truck. It is rather unclear to me what you expect out of it when completed.

I do agree 100% about updating the brake system. What I expect out of it is mostly what I do with any of my cars trucks is to first bring it back to 100% working cond making every thing works as was originally built. And then as I find Newer or updated parts up grade to more modern but is stock is still safe I may leave it that way . This truck I will in time up grade it.
Then I should be able to like any one my car trucks is jump in and take it cross country.

Mostly I just want to bring it back to what it was when new and be able to pull a large 5ht wheel. And use it a flat bed and to push snow around . It something I don't need but I like older trucks and Detroit diesels.

Brian

With that in mind, I would get new air valves because the ones you have are obsolete and probably will cause trouble if they are not already bad. The schematics from Bendix will work with your wedge brakes. The system you have now does not have the feature to limit braking power. All trucks of the 60's were a nightmare to bobtail even on wet pavement. But we did it because nothing better was available. The newer systems restrict braking power when you bobtail to prevent over braking. Also the synflex lines are a must. Copper lines rub holes and crack. I carried a butane torch and acid core solder in my tool box. I don't recommend steel braid or Aeroquip either. It is fine in airplanes, but water gets in the steel and it rusts. If your fifth wheel trailer has electric brakes, all you need is a brake controller like I have on the dash of my pickup. If it has air, you will be equipped for it.