1994 International 4700 Conversion Begins

[scooter421]

Went to the meet up with folks in Hell and fortunately made it back out! Had a nice time, the beer was cold, food was good and the company was better. Thanks to some Aussie hospitality, I somehow managed to pick up a little bling for the truck while I was there too!


During this little road trip, no brake issues at all. I doubt there is a clog in the lines either, every time I've opened a brake line the fluid gravity flows rather quickly from each line. I did notice previously (some time ago, and I guess I've forgotten about this) when I filled the reservoir to the line and after a bit of driving it would begin to expand leak out the fill caps and begin to apply the brakes. I've since kept the fluid level below the line to allow for expansion. Now, my intentions have always been to keep fluids simple so I could find them on the road if needed and avoid mixing. However, perhaps all brake fluids are not created equally. The reservoir is labelled DOT 3 and I am using the Super Tech stuff from Walmart. That should not really matter though, as they all have to meet the DOT 3 specifications.

 

[dwh]

That much expansion sounds like air in the system. The fluid shouldn't expand enough to cause an overflow.

I hate to say this but...are you sure you are bleeding correctly?

DOT 4 has a higher boiling point than 3.

 

[scooter421]

That much expansion sounds like air in the system. The fluid shouldn't expand enough to cause an overflow.

I hate to say this but...are you sure you are bleeding correctly?

DOT 4 has a higher boiling point than 3.

No worries, I certainly don't know everything and learn something new everyday. As far as I know, unless I've been doing it wrong all these years, I sure hope not! LOL....I've done each caliper multiple times until no air comes out, the pedal is held down while I tighten the bleeder. The brakes feel great, It's only after driving and everything is hot the issue arises. I don't ride the brakes or anything; hell, I keep my foot off the brake as much as I can! Why in the world the transmission temp would have anything to do with it I don't know....but. It seems to happen when the transmission has been pushing 220 deg. for a while. Stop and go traffic increases the trans temp (and brake usage) and often the brake starts to drag at that point. I can slam on the brakes or hold the pedal down hard when it has not been "hot" for a long period of time and no issues. It will idle going up hill when everything is "cool". Maybe I need to double check my brake line routing? Maybe there is a section sitting really close to the exhaust or transmission? Then again, it's probably the brake dragging keeping my transmission temp up.

 

[dwh]

Yea, checking to see of something external is cooking a brake line sounds like a good idea.

 

[scooter421]

Well, I have no idea how hot the area is getting but there is a section about 18 inches long above the muffler about 4 to 6 inches away. It's also sitting inside the frame which puts a pretty good piece of metal between it and the muffler. I would think it's far enough away but sitting in traffic the heat might build up enough. It is a bit of a boxed in area. I'll have to check the temp the next time I am out and about. Interestingly, it appears the exhaust had to be re-routed to accommodate the built in PTO Generator. Otherwise the exhaust would have been on the other side of the frame away from the brake line.

 

[Jeep]

I had the exact same issue under the same conditions you are describing with my F650, same brake system too. It got so hot the first time it happened that it caught the rear calipers on fire, I replaced EVERYTHING calipers, rotors, pads, hoses, at all 4 wheels, and the same thing started to happen when running hard, I then replaced the master cylinder and still suffered the same problem. I had to crack the rear bleed screws to make it home, was a little on the cautious side that day. I replaced the brake booster and noticed that the pushrod started to compress the piston in the master cylinder a little more than I thought it should so I machined the pushrod to a "zero clearance". It has worked flawless since, so I'm not absolutely positive if the booster replacement or the pushrod "adjustment" was the cure. Many older hydroboost vehicles have an adjustable pushrod and I just set mine up as you would something older.

 

[dwh]

I had the exact same issue under the same conditions you are describing with my F650, same brake system too. It got so hot the first time it happened that it caught the rear calipers on fire, I replaced EVERYTHING calipers, rotors, pads, hoses, at all 4 wheels, and the same thing started to happen when running hard, I then replaced the master cylinder and still suffered the same problem. I had to crack the rear bleed screws to make it home, was a little on the cautious side that day. I replaced the brake booster and noticed that the pushrod started to compress the piston in the master cylinder a little more than I thought it should so I machined the pushrod to a "zero clearance". It has worked flawless since, so I'm not absolutely positive if the booster replacement or the pushrod "adjustment" was the cure. Many older hydroboost vehicles have an adjustable pushrod and I just set mine up as you would something older.

Well, if the old booster pushed a bit on the master cylinder piston (like the new booster before you machined the pushrod) and if that was causing the problem, then the problem would have been there since day one, no?

Makes me think the new booster was the fix rather than the modded pushrod. But yea, no way to be sure at this point.

 

[Jeep]

The problem started right around 70 000 miles so my conclusion was the same, got to try the brakes out REALLY good a couple weeks ago and they worked pretty good! I wish I had a dash cam for that one.

 

[Ozrockrat]

I am not sure I can buy into the "heat causing expansion" makes a single caliper drag theory. Even if something is heating up the fluid causing expansion it would affect both calipers on that circuit. Here are a couple of things I would consider.

1- check and see if a caliper from another position will fit on there. (Maybe the front one is the same) then swap them over to see if the problem moves.
2- Prove that you have a drag problem. Get it to the failure point and jack it up and spin the wheel. Check cold to hot and also check side to side.
3- is the heat coming from the caliper or is the heat coming from the hub and transferring to the caliper. Running a few checks with an infrared thermometer will help see where the temp rise is starting from.

If you need to do a full rebleed I have one of those air powered bleeders if you need it.

Also buy your infrared thermometer from Amazon. Cheaper than Hated Freight and you don't get tempted by all the other goodies in the store.

 

[scooter421]

Thanks for the feedback folks, I've been rather busy with other vehicle issues and had a hard time getting a response in.

Jeep: Your situation sounds all too familiar! I've contacted some manufacturers regarding DOT 4 and of course they recommend their products! I was asking about fluid compatibility and they've all said no problem. I did some research on brake system temperatures. From what I've read, it does appear normal driving situations (city streets) do produce temperatures pushing regular DOT 3 brake fluid to it's upper limits. Adding mountain roads to the equation can easily push the fluid over it's boiling point. I think I am going to try the DOT 4 just to see if the problem goes away, it's a low cost venture and no harm done if it does not work.

OZ: I have not checked as to whether or not another caliper will fit and it's a great idea. If the DOT 4 does not solve the problem, I will have no choice but to tear into it again. Not fun!

I've done exactly what you describe in #2 and when everything is cold nothing drags. When things get hot both rear brakes have dragged in the past but not at the same time. It usually is the passenger side rear. It appears the heat is coming from the caliper; however, I do plan on doing some driving and testing with an infrared thermometer.

I may take you up on the bleeder, I am going to try the DOT 4 just because. Up to this point I've not been able to find anything wrong with the system.

Thanks guys!

Scooter...

 

[rlrenz]

Its possible that you may have a caliper piston hanging up - that's what we found on my ambulance. After exercising them (longer stroke), the problem went away.

Another option is silicone brake fluid -- DOT 5. When the military switched their vehicles to it, they found some GOTTCHAS to avoid.

Silicone fluid will NOT mix with anything else - it will form a separated layer, like oil and water. They found that the only solution was to fill the system with alcohol (hardware store methanol), drain it, then blow out the system with compressed air. This should be repeated 2-3 more times. Silicone fluid can then be added. This is the procedure that the USAR used here at Fort Snelling with success,

Since it won't mix with water, any water that gets into the system will work its way to the lowest point in the system - wheel cylinders. As a result, they may freeze in cold weather if any moisture gets into the system. You may have to bleed the system before winter sets in.

The military has put a shelf life on silicone brake fluid. As a result, it's often available as military surplus in gallon jugs, usually for less than $40 per gallon.

I did this on an M-series 2 1/2 ton truck years ago. The changeover worked perfectly when I was done.

 

[red EOD veteran]

You mentioned earlier that you lost alot of power when you changed tire size and were thinking of regearing, why not just increase the engine performance instead? These motors have alot of room for reliable performance increases for a cheaper price than regearing.

 

[scooter421]

Hi Bob, I would not rule out a piston or two hanging up as it is certainly possible. I've rebuilt all 4 and the problem has bounced from side to side. It has not been easy to pin on one particular problem. Eventually, I will get it straightened out. If I had drum brakes I'd be more inclined to tear into it on the weekends. The disc brakes make for a lot of work.

When you switched to DOT 5, what was the reason behind the fluid change?

 

[scooter421]

Well, I know it can be done. I figured I would get the gearing closer to a factory set up with this tire size before I start boosting the engine output. I am not so worried about the engine as I think it will hold out well even if giving it a little boost later. I am trying to protect the transmission as best I can. It's working hard with these tires.

 

[Ozrockrat]

Have you worked out what axle you have at the back. The guy at AZ RV Salvage on 7th (not sure if it's Ave or St) had a few of the sterlings and also has a bunch of RV axles. Also American Truck may have something. If you pull the axle code I can point you in the right direction.