Wheel Cylinder Rebuild Issues, Re-use Outer Seals

[UPFINN]

I took the hubs/drums off of the middle axle due to a brake fluid leak. Wheel cylinders appeared to be leaking.

I got two rebuild kits, the Newstar kits which may be made in China, and the Napa UP45 kits which are made in the USA and Mexico, but at least on the Mexico ones the seals say USA. The trouble the the surplus Newstar kits is they do not have springs with cup expanders, but the NAPA kits have boots with a hole too small for the push rod

Cylinder bores have minor pitting after honing. They are small enough that when you look through the bore it is mirror shiny, but when you shine a light inside and look at an angle, you can see tiny pits. They are too small to feel. I honed them for 20 minutes each and they are much better than before. Is this acceptable?

I am also installing a remote brake fluid reservoir, and worried the copper washer might leak under pressure, and a rubber o ring should be used instead? The washer always seemed to seep before. I annealed and cleaned the washer to re-use it but I also got a 1 1/4 ID 1/8 plumbing o-ring.

When I took off the drum I noticed the hub was full of gear oil, and the outer bearing was washed clean of grease. Last Fall (around 600-700 miles ago) I had to adjust brakes and repack bearings. I torqued inner nut to 50ft lbs, backed off 1/4, torqued outer to 130ft/lbs. Hubs never got hot. Yes the cork is in the keyway, but it is old. Outer seals look good. I am trying to figure out if it leaked through the cork, or the outer seal is bad. Has anyone re-used the outer seals and just put gear oil permatex in the keyway with good results? Grease and oil got past the inner seal into the drum, but from what I read the inner seal is meant to keep stuff out from the bearing, not in.

Comparison between Newstar (left) and NAPA (right) kit. Newstar kit does not have cup expanders but has proper end caps. Piston seals have ribs on the sides and feel flimsy, but they are also a tiny bit wider. The NAPA kit has cup expanders and the piston seals are USA made but with smooth sides. The cylinder end caps have a hole too small for the push rod.



Cleaned and annealed copper washer next to o-ring.


Minor pitting on driver side cylinder?


Under bright light pitting is hardly noticeable. Can't be felt. Same cylinder as above.


Passenger side cylinder minor pitting.


Same cylinder as above.



Keyway and seals on leaking passenger side hub/drum.

 

[UPFINN]

Wheel bearing that had grease washed off. Seems to look ok. Just a a small scratch around the entire bearing, but all the bearings on both sides have that scratch.

 

[Floridianson]

As the TM's call for that last 1/4 back off I think that is too much. Every large axle calls for that 1/4 back off and they don't run the grease hubs seals but oil bath. I only back of 1/8 of a turn so as to keep the outer seal tighter. The last Ga. Rally Chris's dad just had the axles serviced before leaving Fl. but one axle leaked. When Gimpy and I worked on it at the Rally the inner nut was more then one complete turn from being even at 50 foot pounds. The thing I like to do is before I loosen the inner nut on R&R is to run it tighter and see how far off the preload it is.

 

[rchalmers3]

20 minutes of honing on a cylinder sounds excessive. But I'd do as you are doing and give them a try.

x2 on the bearing preload. On used bearings I set them at zero lash without worries or issues.

Rick

 

[UPFINN]

20 minutes of honing on a cylinder sounds excessive. But I'd do as you are doing and give them a try.

x2 on the bearing preload. On used bearings I set them at zero lash without worries or issues.

Rick

Half the honing was done using dot5 for lubrication. Does not work very good. I used cutting oil instead and that worked a lot better!

 

[UPFINN]

As the TM's call for that last 1/4 back off I think that is too much. Every large axle calls for that 1/4 back off and they don't run the grease hubs seals but oil bath. I only back of 1/8 of a turn so as to keep the outer seal tighter. The last Ga. Rally Chris's dad just had the axles serviced before leaving Fl. but one axle leaked. When Gimpy and I worked on it at the Rally the inner nut was more then one complete turn from being even at 50 foot pounds. The thing I like to do is before I loosen the inner nut on R&R is to run it tighter and see how far off the preload it is.

Actually now that I think about it, the outer nut on the leaking side wasn't too tight and the inner nut could be turned almost by hand. Perhaps that was the issue after all. The other side was much tighter and the leaking was less severe. I'll go ahead and reuse the seals and torque inner to 50, back off 1/8, then outer to 130-150. Will have to service all hubs to be safe.

 

[Floridianson]

On the last axle service I did on my 939 series just for smitts & giggles after about 20 miles I pulled one axle and checked the preload.
Believe the first 150/200 Flbs. is very important to get the bearing seated and all grease pressed in. Then normal 50 lbs and your back off.
Chris's dad did have the key way corked so that was not the problem.

 

[UPFINN]

Is it a good idea to clean out the mix of grease and gear oil for inside the hub between the races when repacking bearings? It is only 700 miles old. Kind of a pain in the butt and have to add new grease.

 

[rosco]

Its also very important when tightening those bearings, is to be rotating the hub, as they are tightened. Rotation allows the cones to climb up on the taper & seat themselves against that shoulder on the race. Failure to do so can lead to the looseness described, as soon as the hub is rotated.

 

[UPFINN]

Did something dumb yesterday afternoon. Washed wheel bearings in purple power/water mix as usual then mineral spirit rinse. Works great, but I left the bearings in the hot sun after washing and they flash rusted in minutes! Vinegar works great for removing light rust, so I washed them a bit and rust disappeared, but then returned. I then repeated purple power/ mineral spirit wash and it cleaned up better, but the bearings became stiff. Shiny before but now gunmetal grey. Had to spin them dry to break free. I proceeded to pack the now moving bearings in grease, but found they are stiff after packing but move good the more you turn them, then stiff again with more packing. Did I kill my bearings? Too much grease? Supposed to be stiff?

You can see the brown rust tint in this pic and they are not shiny like before I washed them.


First set of cylinders has been rebuilt.

 

[UPFINN]

Did something dumb yesterday afternoon. Washed wheel bearings in purple power/water mix as usual then mineral spirit rinse. Works great, but I left the bearings in the hot sun after washing and they flash rusted in minutes! Vinegar works great for removing light rust, so I washed them a bit and rust disappeared, but then returned. I then repeated purple power/ mineral spirit wash and it cleaned up better, but the bearings became stiff. Shiny before but now gunmetal grey. Had to spin them dry to break free. I proceeded to pack the now moving bearings in grease, but found they are stiff after packing but move good the more you turn them, then stiff again with more packing. Did I kill my bearings? Too much grease? Supposed to be stiff?

You can see the brown rust tint in this pic and they are not shiny like before I washed them.
View attachment 629138

First set of cylinders has been rebuilt.
View attachment 629139
View attachment 629140

 

[UPFINN]

Is it normal for the outer seal to move back and forth bout a millimeter in the keyway? I got the bearing torqued to 50ft lbs and backed off 1/8 turn, but at 50ft lbs the seal does not wiggle.

 

[rustystud]

Did something dumb yesterday afternoon. Washed wheel bearings in purple power/water mix as usual then mineral spirit rinse. Works great, but I left the bearings in the hot sun after washing and they flash rusted in minutes! Vinegar works great for removing light rust, so I washed them a bit and rust disappeared, but then returned. I then repeated purple power/ mineral spirit wash and it cleaned up better, but the bearings became stiff. Shiny before but now gunmetal grey. Had to spin them dry to break free. I proceeded to pack the now moving bearings in grease, but found they are stiff after packing but move good the more you turn them, then stiff again with more packing. Did I kill my bearings? Too much grease? Supposed to be stiff?

You can see the brown rust tint in this pic and they are not shiny like before I washed them.
View attachment 629138

First set of cylinders has been rebuilt.
View attachment 629139
View attachment 629140

I have had that happen to me before. You basically took off the surface hardening with the rust. The surface hardening is only a few thousandths thick. The bearings will wear real fast now. Sorry !

 

[UPFINN]

I have had that happen to me before. You basically took off the surface hardening with the rust. The surface hardening is only a few thousandths thick. The bearings will wear real fast now. Sorry !

So any rust removes the hardening? From mechanic/metal working friends I know, they say to remove the hardening would take long acid, water, and rust cycles. Folks who go mudding a lot and have water intrusion into the hubs just soak their rusty bearings in vinegar and re use . As long as it rotates and no scratches it should be fine.

I'll just keep an eye on it and listen for grinding or feel for overheating.

**Edit**

I called a friend of mine who is a blacksmith and worked as a mechanic in the army. He had serviced hundreds of bearings in trucks made from the 50s to the 70s. They would repack the bearings every year. He saw many that were discolored from improper storage, cleaning, and light rust but were still useable as long as they moved and were kept lubed properly. However, on trucks with water/sand intrusion and lack of grease, bearings corroded in the truck and became spalled and scratched, even friction welded onto the spindle.

That is why the TM's say to repack hubs after water crossings. Very important. For that reason I try to avoid mud with my truck. I use it for wood hauling and it is nice to have a vehicle that can get you out of sticky situations, but I try to avoid them in the first place.

Purple power is a alkaline degreaser. Safe to use if rinsed in water, then QUICKLY (seconds!) rinsed in parts washer/mineral spirits, and repacked or oiled. Blacksmith said white vinegar does remove rust, however the acetic acid also lightly etches the steel. The etching is actually so light, it is more of a stain if done for only about a minute or so. In fact, for decorative etching in knife production, it takes too long! If your bearings rust, the staining while cleaning is not as damaging as the rust itself.

The case hardening on Timken roller bearings is about 1mm deep until rockwell 50 hardness. I honed my wheel cylinders for 20 minutes and they are much softer steel and I did not even get close to removing a millimeter of material.

 

[gringeltaube]

.....
....The case hardening on Timken roller bearings is about 1mm deep until rockwell 50 hardness.....

Can agree with that - after having (with the lathe) turned/cut down/modified so many cups and cones to desired shape and size.


G.

 

[rustystud]

So any rust removes the hardening? From mechanic/metal working friends I know, they say to remove the hardening would take long acid, water, and rust cycles. Folks who go mudding a lot and have water intrusion into the hubs just soak their rusty bearings in vinegar and re use . As long as it rotates and no scratches it should be fine.

I'll just keep an eye on it and listen for grinding or feel for overheating.

**Edit**

I called a friend of mine who is a blacksmith and worked as a mechanic in the army. He had serviced hundreds of bearings in trucks made from the 50s to the 70s. They would repack the bearings every year. He saw many that were discolored from improper storage, cleaning, and light rust but were still useable as long as they moved and were kept lubed properly. However, on trucks with water/sand intrusion and lack of grease, bearings corroded in the truck and became spalled and scratched, even friction welded onto the spindle.

That is why the TM's say to repack hubs after water crossings. Very important. For that reason I try to avoid mud with my truck. I use it for wood hauling and it is nice to have a vehicle that can get you out of sticky situations, but I try to avoid them in the first place.

Purple power is a alkaline degreaser. Safe to use if rinsed in water, then QUICKLY (seconds!) rinsed in parts washer/mineral spirits, and repacked or oiled. Blacksmith said white vinegar does remove rust, however the acetic acid also lightly etches the steel. The etching is actually so light, it is more of a stain if done for only about a minute or so. In fact, for decorative etching in knife production, it takes too long! If your bearings rust, the staining while cleaning is not as damaging as the rust itself.

The case hardening on Timken roller bearings is about 1mm deep until rockwell 50 hardness. I honed my wheel cylinders for 20 minutes and they are much softer steel and I did not even get close to removing a millimeter of material.

I don't know who your friends are or what there expertise is but the average depth of hardening on roller bearings is 2.5 micro meters to .75mm on the largest bearings. Most bearings today are alloy combinations like Chromium-Nickel (stainless-steel) and Manganese-Chromium to name a few. These metals use the "Nitriding" process. If you look at the chart I provided you will see the depth of hardening with this process. View attachment Scan0146.pdfView attachment Scan0147.pdf
The other hardening process's are also very thin, in the micro range. That is way a "scratch" you can feel with your fingernail is bad, and the bearing should be condemned. Well rust goes further then a scratch.
I might have slept through some of my classes when I went to trade school but this class on bearings I remember real well.
To sum this all up, rust is bad for your bearings so is using a water based cleaner on them.

 

[Richard D]

I am about to rebuild a wheel cylinder. Is there any tell tale signs that I need to check the hubs as well while I am in there?

 

[Scar59]

Just good preventative maintenance while you have the hub exposed. Any heat damage to hub? Front or rear axle? real easy to pull the cap/axle and inspect condition of bearing/grease. When is the last time you serviced the bearings?

 

[Richard D]

We have three M35A2s(I'm pretty sure that's what they are) of various vintage. We put A/C and power steering on one, but other than that, haven't done much except change filters. I am doing a lot of reading on this great forum to learn about these trucks. I know several guys who used to drive them 30-40 years ago in the military, that does not make them experts even if they thinks they are! I come here to learn from the guys who are currently working on these things with pictures to back it. Thanks for all the help, I'm sure I'll have some specific questions when I get the truck apart, but I'll read the "TM" first. "TM" stands for Technical Manual?

 

[Scar59]

You got it Richard, TM is the acronym for Tech Manuals. I'm and aircraft mechanic by trade, so I encourage individuals to maintain their equipment by the book. Source the manuals for your model trucks. Invaluable information is contained in them. Then get to know your equipment, and their maintenance history. If you cannot establish when something was last accomplished or serviced, make a list and start the maintenance process when time and resources are available. You will have a lot more confidence in the reliability of equipment when you know it maintenance history. Keep a maint. log for each truck. This site and it's member contain a wealth of experience/knowledge and parts availability. All willing to help those who help themselves.
Now pull that axle out and check the condition of the bearing.