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Ih s1900 brake problems


ryangpayne

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I have a 1984 IH S1900 grain truck I’ve been trying to haul wheat with. It has hydraulic disc brakes. After I made the first load and got home the front brakes were trying to lock down so hard it was hard for the truck to push them. I decided the calipers were probably stuck from the truck sitting around. It needed new rotors anyway so I put new rotors on it, wire wheeled and greased up the slide rails and put new rubber brake lines that go to the calipers. Reused the calipers and pads because the pistons pushed in fine it seemed in order to remount them  

Took it for a few mile test drive and they still got what seemed very hot very quick. Took the lines off the master cylinder and looked over the proportioning valve and it was stuck and one line coming out of it was bone dry. So to get running again I put the master cylinder, steel lines and proportioning valve off a s1700 winch truck I have onto it and had new rubber lines made that go to the proportioning valve.
 

I just took it for about an 8 miles test drive and with my temp gun I get 560 degrees on the rotor on the drivers front, 400 on passenger. 500 on one rear rotor and 400 on the other. Are these acceptable or normal temperatures? The elevator is about 35 miles away so I’m just trying to get everything fixed so I’m not broke down on the side of the road. These temps are with 400 bushel of wheat on it, single axle truck. Thanks for any help!-Ryan

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Do the brakes release when any particular line is loosened? I’m guessing residual pressure caused by the stroke of the master cylinder not going all the way to the end and restricting the bleed hole, or the check valve at the outlet of the M/C , designed to hold 1 psi in the system. Our heavy machinery with hydraulic disc brakes ( Michigan) stated in the shop manual to omit these check valves at overhaul; the bigger the pistons, the less pressure it takes to make them drag. Did this problem happen suddenly or was this an ongoing thing? Have any free play at the pedal? What kind of booster? On the fire wall or under the cab?

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The brakes haven’t completely locked up on me again since that first time. I will have to try cracking the lines to see if that makes them quit dragging. There is some free play at the pedal, it feels like it always has really. On my last test drive it doesn’t feel like they are locking down, just seem to be dragging just enough to get things hot. I will have to see if I can locate that check valve on the outlet of the master cylinder as well. 
 

Here are a couple pics of the system. I dont know a whole lot about them but I would say it is some type of electric booster mounted below the master cylinder. When you turn the key on it buzzes and the pressure light comes on until the motor starts then it goes off. This truck has a 466 motor. 
 

the first time they tried to lock down was the first time this had happened in the 20 years we’ve had this truck. And I had just got home from about a 60 mile trip. Although the last 9 years this truck has just been used to plant out of and hasn’t been over 10 miles from home so they could’ve been dragging some and we just never noticed it. The old rotors were worn heavily on the outside and had cracks in them. 87E57FB6-569D-4A74-BD42-5E66F15AA0BA.thumb.jpeg.67fbfdaccfa70c962d84d22af53a78cf.jpeg34E2C995-AD46-4B52-BEDC-0E8D8F1E6AB9.thumb.jpeg.d4db0f93a543d6898c95e5048e97d7b7.jpeg

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Now that I see it that system has no check valve. I should have known that when you mentioned the proportioning valve but I missed that somehow. Does it stop? I mean, does the booster seem like it’s working?

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I had to re-seal the calipers on my S1700 dump truck -- even tho the piston pushed back, there was still some binding -- the phenolic pistons were egg shaped, used some 360 to sand them back round -- the bore on one caliper was tapered toward the bottom, and the piston would stick in there without the seals

The truck works fine now, has the same system as yours -- my rotors only get warm, not hot -- I can still touch them without a burn

I suspect your calipers are dragging

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Thank you very much to both of you guys for the responses and help. 
 

HydroTek- I will dig into those calipers tomorrow, thank you for the idea. I couldn’t think of where to look next. And didn’t know how hot was normal. It sure tells me I have a problem if yours you can still touch. 

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Uses a hydraulic booster at the master cylinder, ran off the power steering -- and an electric pump as a backup

As long as the master cylinder is returning to the home position, there should be no problems -- pretty basic braking system

The valve block -- I did not take either of them apart when I swapped cabs, but seems to only function to operate the brake loss warning switch -- I replaced all of the brake lines on the truck since they were rusty

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That 500 degrees and less can be residual heat from braking.

There is a lot of iron there that takes time to cool.

It is the thousands of degrees that causes the problems.

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17 minutes ago, Diesel Doctor said:

That 500 degrees and less can be residual heat from braking.

Only way to tell for sure would be to drive around without using the brakes and coast to a stop. If it's still 500+, I'm thinking there's still excessive drag. 500 is where steel turns dark brown during tempering, and above that you get purples and blues.

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I got the front wheels took off today.  I will include a pic of the heat mark on one of the rotors. I could turn the wheels by hand but there was a slight dragging. But it had also sat all night so that might have let some pressure off of it. 
 

My local napa had a couple reman calipers so I got those put on. I took it for the same test drive as before and the highest reading I got off my temp gun was 380 in the middle of one rotor, but most readings were in the 320-340 degree range. I’m not sure if it’s 100% or not but I feel like it is considerably better than it was before the new calipers when it was 560 degrees. I believe I will head to town with a load of wheat tomorrow and check it a few times and see how it goes. I appreciate everyone’s help and will post back tomorrow. 8E265678-B4EE-421F-BE32-79D8C3FC9740.thumb.jpeg.4f21d7e4080b95cf9c14105ce54347bc.jpeg

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Made 2 trips to the elevator today with no problems. Temps stayed in line with where they were yesterday even with going 30 miles or so each way. Got 800 bushel hauled off. It was a good day, thanks to everyone again!-Ryan

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Are your wheel bearings snug, but not over tight ?  Seen them tightened way too much and make heat -- just looking for zero clearance when locking the nut

Also too lose where there is slack can cause the brakes to drag and heat

Looking at the hub in the pic -- mine have the oil caps -- I don't see that on yours -- are the bearings in good shape, lubed ?

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Somewhat related to this thread, maybe it could help someone down the road with these hydraulic brake systems for the IH MDT trucks. 

No affiliation with this company, but he gave me advice by phone once.  They have all the parts to repair these AC Delco brake booster units.  https://www.powerbrakeservice.net/acdehybrasan.html

I converted a 1986 s1900 from that AC Delco Hypower system to a Bosch Hydromax, that were used on later IH trucks.  The bolt patterns and actual master cylinder are pretty much interchangeable. 

The electric emergency booster pump on mine had died (expensive).  For $300 I had a more modern Bosch unit from a relatively new, retired school bus.  

 

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