New Wheel Cylinder Issues

[USMC 00-08]

About 3 months ago, I purchased 12 brand new wheel cylinders for my M135 from a reputable military parts dealer online. The wheel cylinders looked great and are very close to the originals that were on the truck. All 12 wheel cylinders were installed and the truck has had less than 100 miles on it since having all new brakes put on.

The problem I am having is that one by one, these new wheel cylinders have begun to leak. Upon disassembling to inspect, I was not happy with what I saw. Here is a picture of the new wheel cylinder internals on the left and the internals of the original military wheel cylinders on the right.


The new wheel cylinder internal is a single machined piece that the cup has to be stretched around to fit into the groove and nothing pressed against the bottom of the cup. The original military is a two piece setup where the lower piece pressed up against the cup and makes it swell when the brakes are applied.

I do not see how the new wheel cylinders are even functional with nothing pressing into the cup to form any kind of seal. Mine are obviously not functional because they are all leaking. I am not happy and wanted to get some opinions. I want to contact the seller and request a refund and also complain about the lack of quality and the safety hazard these pose by leaking so badly.

What should I do?

 

[gringeltaube]

............................The original military is a two piece setup where the lower piece pressed up against the cup and makes it swell when the brakes are applied.

That is not correct: in any case, when you step on the brakes it is the fluid under pressure that forces the lip of the cup against the cylinder wall and makes it seal.
The extra part you see on the right are cup expanders, yes, but the only force applied to them- with brakes applied or stationary- is the action of the compressed coil spring, which is fairly constant.

I do not see how the new wheel cylinders are even functional with nothing pressing into the cup to form any kind of seal.......

On those replacements (with no cup expanders), about the only thing keeping the cups from leaking - while at rest or moving outward that little bit until pressure is built-up - is the resiliency of the slightly compressed rubber part itself.
Now, if for some reason these cups have shrunken and maybe the cylinder surface is not absolutely perfect and smooth, then that may be the cause of your issues.


G.

 

[dmetalmiki]

Most all the older vehicles including jeeps etc have the single rubber seal.(and) it seals by pressure applied. as mentioned before. Seems like those new (old stock?) units would benefit from new seals all round, But then so would the old units have surely?.

 

[Keith_J]

That is not correct: in any case, when you step on the brakes it is the fluid under pressure that forces the lip of the cup against the cylinder wall and makes it seal.
The extra part you see on the right are cup expanders, yes, but the only force applied to them- with brakes applied or stationary- is the action of the compressed coil spring, which is fairly constant.



On those replacements (with no cup expanders), about the only thing keeping the cups from leaking - while at rest or moving outward that little bit until pressure is built-up - is the resiliency of the slightly compressed rubber part itself.
Now, if for some reason these cups have shrunken and maybe the cylinder surface is not absolutely perfect and smooth, then that may be the cause of your issues.


G.

Bingo. Same issue with M35A2 mil spec wheel cylinders. The UP45 rebuild kits from NAPA have expander springs and seal much better.
Another issue is the master cylinder venting. If the vent or check valve clogs and a partial vacuum develops, the wheel cylinders can leak.
Finally, installing a remote reservoir higher up in elevation can help by placing the master cylinder under a bit more pressure from higher fluid level. This additional hydrostatic column won't bother braking action as each foot of elevation is only a bit less than a half PSI but it works.

 

[m1010plowboy]

Wheel Cylinders G749

You deserve a break about now! Usually I break something new while I'm fixing the first broken thing but having new parts go down tops the list of painful hurdles. That would drive me to drink but not drink and drive.
I've always wondered if the pressure applied to the brake pedal is = to the pressure the wheel cylinders feel. If it was just fluid flowing a guy could anticipate pascal's theory but with the air/ hydraulic cylinder, how much pressure hits the wheel cylinders? How do we test this?
I've never had to force the brake pedal on Goose so have you ever had to jump hard on the pedal? They should be designed so a 300lb fat, balding guy can stand on them with 5 tons in the back so having them leak with low or no usage is just wrong.

The Wagner's are set up so much better by the looks of things. Goose is on her 4th year with low miles and frequent/ light usage but seeing extreme ambient temp swings of 130°f.

Your cylinders look like they came out of the NOS manual. When I hunt weepay for wagner I see hundreds of wheel cylinders for $20 or $30 greenbacks and when I get to the 15306....$70.00. Do you think these guys could help us out, if we ask? http://aftermarket.federalmogul.com/en-us/brands/wagner-brake/pages/home.aspx#.VeIwAZerEuc

I'd run WAGNER stickers on the truck and be real happy continuing to promote their product if they'd support our G749 restorations and kick you a few cylinders.
I'll need 36 and a few spares next spring so let's find the promotional department.
http://federalmogul.com/en-US/Contact/Pages/General-Inquiry.aspx

In the meantime I'll get an idea on inventory up here.

 

[USMC 00-08]

I will check the vent on the master cylinder to see if anything is clogged. These are new manufacture cylinders so I did not figure the seals would leak.

Maybe I should run a hone through them and replace with NAPA seals?? Maybe reuse the pistons out of the old original wheel cylinders? The bore in the originals was too pitted to salvage.

 

[USMC 00-08]

Plowboy....I was at the end of a 22+ hour day when I read your post last night and missed a few things. I have not had to get on the brakes hard at all. Just normal braking from normal cruising speed. Would be nice if Wagner could be a little more reasonable on those cylinders. I think $70 is a bit outrageous.

Gerhard, thank you for making sense of that for me. I like the idea of having the expander behind that cup. Seems that when the brakes are at rest, the pressure from the brake return springs and the spring in the wheel cylinder would keep that cup slightly expanded and prevent leaks. Is my thought process on that correct?

I'm seriously thinking about lightly honing the wheel cylinders and putting them back together with the old style pistons out of the original wheel cylinders and new cups from NAPA.

 

[gringeltaube]

..........Seems that when the brakes are at rest, the pressure from the brake return springs and the spring in the wheel cylinder would keep that cup slightly expanded and prevent leaks. Is my thought process on that correct?...

Almost: the brake(shoe) return springs do exactly that: pull the shoes back against their regulators, after braking.
While at rest, those return springs do nothing to keep those cups expanded.

I'm seriously thinking about lightly honing the wheel cylinders and putting them back together with the old style pistons out of the original wheel cylinders and new cups from NAPA

That is what I would try if the replacement cups you can get had the lips chamfered, to more or less follow the angle of the original expanders. (Think of two wedges moving towards each other...)

After blowing-up your pic in post #1 it seems those cups have straight cut, non-chamfered lips...?


G.

 

[Another Ahab]

I will check the vent on the master cylinder to see if anything is clogged. These are new manufacture cylinders so I did not figure the seals would leak.

Well, of course that's the whole reason you went to the trouble to get new, right!?

 

[USMC 00-08]

After blowing-up your pic in post #1 it seems those cups have straight cut, non-chamfered lips...?
G.

That cup in the picture is what came off of the new wheel cylinders. I just slid it on the old piston while trying to figure out the leaks. I will have to look at the NAPA cups that I have. Before I bought new wheel cylinders, I rebuilt the original wheel cylinders on the front. They were salvageable. They did not leak at all. Only decided to buy all new wheel cylinders when all of the original back ones were too pitted to rebuild.

Well, of course that's the whole reason you went to the trouble to get new, right!?

Pretty much.

 

[m1010plowboy]

G749 wheel cylinders

Plowboy....I was at the end of a 22+ hour day when I read your post last night and missed a few things. I have not had to get on the brakes hard at all. Just normal braking from normal cruising speed.

It's all good little buddy, I was picking corn, chasing thieves and pretending to drop a 350 in a deuce. The G749 team don't need no stinkin' sleep. I found another flavor of 15306 from 1982 without the 'wagner lockheed' title on it so it gives me some hope that these were NOS and there are more.

Even if you settle for putting those back in, we need a price and an inventory count from the NOS kids so I'll try and make calls over the next couple days.



I should have loaded the following pictures on your other thread but I'm done already so I'll chase a few more matching number trucks another day.

I managed to get to one truck and check for the top of frame stamp....and thar it is....matching numbers on the 12-8-52 GMC. I heard the G749 veterans mention it but never thought much about it. This will allow me to get the correct numbers on the doors and dash on future builds, very cool.

 

[USMC 00-08]

How did the 350 install work out in your mind?

I should have put the 15306 on this truck but will try to make due with what I have by changing out the pistons and seals. The Napa cups are identical to the military cups out of the original wheel cylinders. Maybe if a bunch of us went together and bought a large order of 15306 from Wagner, they would work out a deal with us. I could use 21. Picked up 3 of them for $9 each on a closeout awhile back. 3 was all they had or I would have bought more.

Check your email. I may have found a very useful part to add to our list. Need your thoughts.

 

[jasonjc]

What napa cups are you using? One of my trailers use the wheel cylinder as the GMC. I rebuilt them with cups from napa and they are so tight after sitting for a few months (with dot 5)I had to pound them out. They would not move other wise. I'm watching this to see what you find out.

 

[jasonjc]

Just checked Oreilys has these in there brake best brand for 42.99.

 

[USMC 00-08]

I am using Napa 14451. Is that what you used?

I hope to start on the wheel cylinders this weekend, but probably won't finish all of them. One wheel cylinder is already done.

 

[jasonjc]

I just checked they are 14451's.



Are you go to the KAMO rally next month???

 

[USMC 00-08]

Well crud...I hope these cups work.

I am wanting to go to the rally if I can get my truck to cooperate. Are you going?

 

[jasonjc]

Well crud...I hope these cups work.

I am wanting to go to the rally if I can get my truck to cooperate. Are you going?

I have too go , I've got the MKT and have to make breakfast Saturday. I think the 14451 cups would work with the one piece.

 

[jasonjc]

One thing I just thought of the 14451 cups are 1 1/4" and the 15306 cylinders are 1 3/8".

 

[USMC 00-08]

Yes. The new cylinders I got are 1 1/4". Next ones I get are going to be 15306.