M35A2 Brake Service Questions

[Brownac1983]

Hey guys, I've been looking for a long time and it seems I've finally found a deuce. It's a 1970 AMG M35A2 with 1995 overhaul tags. It's in pretty nice shape, but the guy I'm buying it from has the brake line blocked off to the rear axle because of a right rear wheel cylinder leak. There's a new wheel cylinder included but he never got around to installing it.

Now, I'm wary enough of the single circuit brake system, but if I'm stuck with it for the time being I really have to know that it's 100%. Here's where my questions come in. I plan on tearing the whole system apart and rebuilding it all with fresh rubbers and DOT-3 fluid (I'd rather be able to buy it locally even if that means flushing it yearly) and installing a remote reservoir.

1. Are there good and bad wheel cylinder rebuild kits, or are they all about the same? I see them on eBay, vendors, and all sorts of different places and the prices vary by about 100%. Is there a cheap version of these and a good version? If so, how do I tell the difference?

2. If they won't hone out, are there good and bad wheel cylinders out there? I've been reading some threads that mention that they are almost all imported now. Are they as good as a rebuilt USGI cylinder?

3. Is there a maximum acceptable I.D. for the wheel cylinders after honing?

4. Are all the air pack rebuild kits the same quality? Are the ones that are for sale at some of the vendors as "new" of the same quality as a NOS surplus kit?

5. Are shelf life issues common on NOS parts? Would I be able to depend on the rubber goods in an NOS kit of unknown age?

I appreciate any input. The last thing I want to do is a whole lot of work just to have a failure because I chose the wrong parts. Thanks in advance.

-Drew

 

[Valence]

I can provide a tiny bit of help here, so I apologize as I'll skip the numbers I can only answer with "I don't know" (which is most of them).

Q: 1. Are there good and bad wheel cylinder rebuild kits, or are they all about the same?
A: You absolutely want the rebuild kits with the springs with "cup expanders" on the ends. If it's just a regular straight spring, then that is the inferior kind and will allow the cup seal to fail sooner.

See pictures & part numbers here:
http://www.steelsoldiers.com/showth...on-the-Deuce&p=1688001&viewfull=1#post1688001


As far as switching to DOT 3 brake fluid because of the availability of DOT 5, I disagree. Yes it is more expensive but all 3 auto parts stores near me sell DOT 5 in at least 11 OZ bottles (Auto Zone, O'Reilly's, and CARQUEST - CARQUEST had the 32oz bottles)

Member peashooter has excellent information on the cheapest DOT 5 sources:
http://www.steelsoldiers.com/showth...-LINE-REFERENCE-GUIDE-(Sizes-lengths-fittings)

 

[SteveKuhn]

I've driven mine in a pinch blocked as you describe. I carry the plugs as an emergency kit. That said: Take it easy, no load, leave lots of room in front, and hope another one doesn't blow. Get someplace to do the work and fix it. There's a big difference when 33.3% of your brakes ain't there.

Steve

 

[Brownac1983]

I can provide a tiny bit of help here, so I apologize as I'll skip the numbers I can only answer with "I don't know" (which is most of them).

Q: 1. Are there good and bad wheel cylinder rebuild kits, or are they all about the same?
A: You absolutely want the rebuild kits with the springs with "cup expanders" on the ends. If it's just a regular straight spring, then that is the inferior kind and will allow the cup seal to fail sooner.

See pictures & part numbers here:
http://www.steelsoldiers.com/showth...on-the-Deuce&p=1688001&viewfull=1#post1688001


As far as switching to DOT 3 brake fluid because of the availability of DOT 5, I disagree. Yes it is more expensive but all 3 auto parts stores near me sell DOT 5 in at least 11 OZ bottles (Auto Zone, O'Reilly's, and CARQUEST - CARQUEST had the 32oz bottles)

Member peashooter has excellent information on the cheapest DOT 5 sources:
http://www.steelsoldiers.com/showth...-LINE-REFERENCE-GUIDE-(Sizes-lengths-fittings)

Thanks Valence. That's good info, I was very close to buying the kits without cup expanders. I found the DOT5 brake fluid as well. For whatever reason, they keep the big bottles in the back at the commercial desk, that's why all I was seeing were the little motorcycle sized bottles, so it is available locally after all. I appreciate the info.

 

[Brownac1983]

I've driven mine in a pinch blocked as you describe. I carry the plugs as an emergency kit. That said: Take it easy, no load, leave lots of room in front, and hope another one doesn't blow. Get someplace to do the work and fix it. There's a big difference when 33.3% of your brakes ain't there.

Steve

Thanks Steve. I'll definitely keep the plugs just in case, but we won't be transporting it that way. I'm buying it from a friend so we can fix it before I take it home.

 

[Valence]

Thanks Valence. That's good info, I was very close to buying the kits without cup expanders. I found the DOT5 brake fluid as well. For whatever reason, they keep the big bottles in the back at the commercial desk, that's why all I was seeing were the little motorcycle sized bottles, so it is available locally after all. I appreciate the info.

No problem-o. Anyway, after thinking about it I do have a comment on the following:

Q: 3. Is there a maximum acceptable I.D. for the wheel cylinders after honing?
A: I do not think this is an item you need to worry about. The cylinders will either hone out smooth or be obviously pitted and just need replacing. The rubber cups at either end of the spring should make up the difference.

(I suppose it is theoretically possible to repeatedly rebuild and hone out a wheel cylinder enough to be unusable but I can't imagine that happening for any of us.)

These cut-away views of the wheel cylinder parts may help:



The boot keeps the external push rod (not pictured) in place on the piston and debris from entering the cylinder. The piston provides the hard, flat, metal surface to push against while the rubber cup inside is actually what seals against the cylinder wall. So the piston does have a little play. Obviously honing out the cylinder will increase that play but again, I wouldn't worry a bit about it. If you need to hone out that much material I hope you'll just replace the whole wheel cylinder. Make sure you use a liberal amount of oil on the honing stones.

When I rebuilt my wheel cylinders I could see scratches in the piston sides and cylinder wall from crud that got between the cylinder and piston but the piston wall was still smooth and round and honing took care of the cylinder. If there is obvious wear or flat spots, replace. I am unaware if you can just buy the pistons separately, though I wouldn't be surprised if they only came with a whole new wheel cylinder.

Also notice that the second diagram is an excellent illustration of how the "cup expanders" on the ends of the springs would help keep the cup sealed and in place (though I think the diagram is just showing a straight spring).


Q: 5. Are shelf life issues common on NOS parts? Would I be able to depend on the rubber goods in an NOS kit of unknown age?
A: I've only read about shelf life on Air-assist-steering, but I can image there being similarities -> rubber. Rubber ages even if still in a box, but there are many factors probably mostly centered around how it was stored (temperature, humidity, sun exposer and etc). So I would say to myself: "Self, NOS is a gamble, are you willing to gamble it?" I would then answer "Depends on the part and price. I wouldn't bother buying NOS for the wheel cylinder rebuild kits though, since you can order them new for about $12.00 each from NAPA.". Or such was my experience. I do not have experience to speak of regarding the Airpack, but personally I would tend to go with an NOS USA made kit over new rubber made in China.

----

Anyone able to answer his other questions?

2. If they won't hone out, are there good and bad wheel cylinders out there? I've been reading some threads that mention that they are almost all imported now. Are they as good as a rebuilt USGI cylinder?

4. Are all the air pack rebuild kits the same quality? Are the ones that are for sale at some of the vendors as "new" of the same quality as a NOS surplus kit?

 

[rustystud]

I would stay away from any military venders wheel cylinders and rebuild kits. They all are made in China now and their seals are junk ! You can buy new wheel cylinder seals from NAPA. Just tell them you need generic 1-3/8" wheel cylinder seals. I bought over 24 for spares. They come in packs of 8 for the bulk buy. They also are new manufacture made right here in the good old U.S. of A. ! If your wheel cylinders are too pitted after honing, go ahead and buy the venders cylinders but take out the crappy seals and replace them with the NAPA seals.
As far as the air-pac rebuild kits go, most seem to be OK. I have bought over 8 for the long style and 4 for the short style. Of course the short style are much newer. The only problem I have found is that some gaskets shrink in the long style rebuild kits. This is especially true for the air cylinder end cap gasket. You can stretch it by warming it up (hair dryer works fine) and slowly working it on to the end cap. I also use some silicone grease as I do this. The rubber seals have been sealed so there was no exposure to air which causes rubber to age. Also if you stay with DOT 5 silicone brake fluid you will have an added benefit as the silicone actually lubricates the seals. Most of my long style kits where bought from "Eriks" . On the honing part, if you have to spend more then a couple of minutes honing out a wheel cylinder then it is too worn out to use. On an average rebuild I'll hone for just about 20 strokes. If it is more then that I replace the unit. I'm using a medium grit hone.

 

[treva2]

NAPA wheel cyl. rebuild kits

I really wouldn't want to leave it up to the NAPA to give me exactly what you bought. Would you happen to have a part number for the bulk buy? Thanks for the tip.

I would stay away from any military venders wheel cylinders and rebuild kits. They all are made in China now and their seals are junk ! You can buy new wheel cylinder seals from NAPA. Just tell them you need generic 1-3/8" wheel cylinder seals. I bought over 24 for spares. They come in packs of 8 for the bulk buy. They also are new manufacture made right here in the good old U.S. of A. ! If your wheel cylinders are too pitted after honing, go ahead and buy the venders cylinders but take out the crappy seals and replace them with the NAPA seals.
As far as the air-pac rebuild kits go, most seem to be OK. I have bought over 8 for the long style and 4 for the short style. Of course the short style are much newer. The only problem I have found is that some gaskets shrink in the long style rebuild kits. This is especially true for the air cylinder end cap gasket. You can stretch it by warming it up (hair dryer works fine) and slowly working it on to the end cap. I also use some silicone grease as I do this. The rubber seals have been sealed so there was no exposure to air which causes rubber to age. Also if you stay with DOT 5 silicone brake fluid you will have an added benefit as the silicone actually lubricates the seals. Most of my long style kits where bought from "Eriks" . On the honing part, if you have to spend more then a couple of minutes honing out a wheel cylinder then it is too worn out to use. On an average rebuild I'll hone for just about 20 strokes. If it is
more then that I replace the unit. I'm using a medium grit hone.

 

[cattlerepairman]

"5. Are shelf life issues common on NOS parts? Would I be able to depend on the rubber goods in an NOS kit of unknown age?"

I recommend to get the brake hose kit that a member on this site offers. I did mine before these were available and have been suspiciously eyeing my Asian rubber brake hoses ever since. So far, so good, but I would prefer the North American made kind, especially since they are metal mesh sleeved.

I

 

[rustystud]

"5. Are shelf life issues common on NOS parts? Would I be able to depend on the rubber goods in an NOS kit of unknown age?"

I recommend to get the brake hose kit that a member on this site offers. I did mine before these were available and have been suspiciously eyeing my Asian rubber brake hoses ever since. So far, so good, but I would prefer the North American made kind, especially since they are metal mesh sleeved.

I

I totally forgot about brake hoses ! Yes buy the PTFE stainless steel hoses from "peashooter" (Aaron) . Totally worth it ! He also sells trailer hoses too !

 

[rustystud]

I really wouldn't want to leave it up to the NAPA to give me exactly what you bought. Would you happen to have a part number for the bulk buy? Thanks for the tip.

I'll go and look for them tomorrow. I have them stored away for future use.

 

[oboyjohn]

Another possibility for the wheel cylinders that are pitted and cannot be honed out ( if you had the coin to do it) is to have the inside bore machined out and insert a stainless steel sleeve with the origional inside diameter. Yes it would be more expensive that just replacing the whole assy, but for someone who has access to a machine shop, this could be another route to go.

 

[M813rc]

And yes, absolutely install a remote reservoir! You will NOT regret that.

There are several options for location, all work equally well. Personally, I like mine on the firewall on the drivers side. Easy to open the side flap to visually check fluid level (which you need to do often, because that fluid wanders off), easy to refill. If you spill any, it isn't in the cab. If you have a vented cap, you can do away with the vent line.

Whoever thought putting the master cylinder under the floor of the cab, usually with a frame above it, was a sadist. And I don't imagine it inspired the troops to check it scrupulously every day.

One of the members here (several?) sells a complete kit that has everything you will need, at about the cost of gathering it all yourself at the parts store. I don't recall their name, but I was very satisfied when I dealt with them.

Cheers

 

[rustystud]

Another possibility for the wheel cylinders that are pitted and cannot be honed out ( if you had the coin to do it) is to have the inside bore machined out and insert a stainless steel sleeve with the origional inside diameter. Yes it would be more expensive that just replacing the whole assy, but for someone who has access to a machine shop, this could be another route to go.

We do that to heavy equipment that you can no longer buy parts for. In the long run it is so much cheaper then trying to retrofit something into it's place, and it will now out last the truck !
"Treva2" I tried to look up the part numbers for the wheel cylinders but I threw out the boxes ! Sorry I can't help you. Still you should be able to get them. Just ask for generic 1-3/8" wheel cylinder seals. Any parts guy "worth his salt" should be able to look this up.

 

[VPed]

Finding a parts guy worth his salt these days is the real trick!!!

 

[SteveKuhn]

from:

http://www.steelsoldiers.com/showthread.php?82427-Deuce-Parts-Quick-Reference-Spreadsheet

2530-00-529-4209 NAPA Wheel Cylinder Kit n/a 45

Other stuff in that thread too.

 

[rustystud]

from:

http://www.steelsoldiers.com/showthread.php?82427-Deuce-Parts-Quick-Reference-Spreadsheet

2530-00-529-4209 NAPA Wheel Cylinder Kit n/a 45

Other stuff in that thread too.

You don't need the whole kit just the seals. Usually the spring is in good shape as are the outer boots, you just need the good made in America seals.