M37 Brake Wheel Cylinders

[mkcoen]

Today TexAndy, Keith_J, and I started rebuilding the wheel cylinders on my M37. It turns out that they needed it in a serious way. There was quite a bit of corrosion in all 4 cylinders and we actually had to pull the shoes away from the cylinders then cycle them to get 2 of the pistons out. On two of the cylinders we had to take a socket and the bench vise to get them out.

After honing the housings we cleaned up the the pistons with some 800 grit wet sandpaper and acetone. A couple of the bleeder valves were also clogged so had to ream them out with a bit of wire then flush them out.

Unfortunately on the last wheel we found a rotten brake line and will have to wait until tomorrow to see if we can pick it up locally or I'll have to order it and wait until next week.

Pics -
1 & 2 - corrosion in housing
3 - piston before cleaning
4 - one clean piston and one before cleaning

 

[Ferroequinologist]

Angie has just started doing this to her M37, she wanted to know if it was better to rebuild or replace- I said, it is easier to just replace, but cheaper and more 'fun' to rebuild them. She just gave me this look... so we will see what happens.

 

[zout]

An ole lesson I learned years ago from folks as old as PB and Wm - when you reassemble a component - always use the same liquid or lube that component operates in.

 

[mkcoen]

Angie has just started doing this to her M37, she wanted to know if it was better to rebuild or replace- I said, it is easier to just replace, but cheaper and more 'fun' to rebuild them. She just gave me this look... so we will see what happens.

I've always been curious as to how things work so enjoy rebuilding them to see. Of course it helps having someone around that's done it before so you don't screw it up, especially with brakes.

 

[vtdeucedriver]

Rebuild kits are Common. What is not is pistons. They corrode bad when water gets trapped by the rubber boots. When you hone them out to remove the pitting. Go by the manual and stay within the gap limits between the piston and wall. If excessive you may get a spongy pedal feel or worse a blown seal early with a hard brake application. I have overhauled many for the m37 with no problems

 

[WarrenD]

When it comes to brakes, I prefer the replacement route. Wheel cylinders for these seem cheap enough and I can spend the time doing something that pays better. Time value of my labor, etc.

 

[EMD567]

Having seen the inside of a left front wheel cyl on a M37 on the side of a road, I can see that regular checking of the wheel cyls is a must. I am also glad to see that I am not the only one that uses KROIL penetrating oil.

 

[NDT]

The bores have to be free of pits or the wheel cylinder will fail again.

 

[pwrwagonfire]

When it comes to brakes, I prefer the replacement route. Wheel cylinders for these seem cheap enough and I can spend the time doing something that pays better. Time value of my labor, etc.

Same here!

When it comes to my brake components, I'd rather not take any chances of having to do it again in the future...I just replace the cylinders. Remember if you hone them out and re-build them too many times they won't be operating efficiently/correctly

But I am preaching to the choir on this one!

 

[vtdeucedriver]

Well after having put a offshore one on my m151 and it did not fit right and another that was bored wrong. There is something satisfying knowing that my brakes have Lockeed made in USA. They can be rebuilt and I will continue to do so until they fall outside the OVH limits.

 

[mkcoen]

Well after having put a offshore one on my m151 and it did not fit right and another that was bored wrong. There is something satisfying knowing that my brakes have Lockeed made in USA. They can be rebuilt and I will continue to do so until they fall outside the OVH limits.

I had the same issue with my deuce. Everyone said just replace it instead of rebuilding. Now I have 1 bleeder valve that is metric.

This M37 is a parade ride and nothing else. I intend to make sure it is safely drivable but not worried about hitting the highway with it or lasting another 50 years. I have no doubt the rebuild will last as long as I (or the wife) own it.

 

[TexAndy]

Keith is the brakemeister. I mostly watched and drank beer.

 

[mkcoen]

After rebuilding all the wheel cylinders we still had a mysterious leak issue that was finally tracked back to the master cylinder. This time I opted for the replacement versus the rebuild. I'll hang on to the old master and rebuild it as a spare or trading material but for $100 figured a completely new unit was worth it.

Once again Keith_J was the man that did the majority of the work while I handed tools and told him what an outstanding job he was doing.

The unit obviously hadn't been touched in decades and we had a couple of interesting moments getting it out but in the end overcame.

We went ahead and replaced the hard line from the master to the frame rail as it had considerable pitting. It's a heavy line so was probably okay but was easy enough to bend a new one and change it so we did. We also replaced all the rubber lines while we were at it. Now the only thing that has to survive without replacement is the steel lines.

Pics:
1) Wrenches on in process of taking old unit out
2) Both units side-by-side
3) From above - some slight differences in the 2 units
4) New unit installed with new hard line
5) Old hard line
6) Pitting in old line
7) New rear brake line

 

[pwrwagonfire]

I could be mistaken; HOWEVER It appears that the MC which you took OUT of your M37, is the MC for a civilian power wagon...I'm sure they are all the same thing minus the angled top; we have 2 WM300s at work, and the MC in them is mounted at a weird angle in front of the fire wall (inconvenient spot) I believe the angled top is to make it easier to fill and etc from that spot


nice job! Looks good

 

[mkcoen]

I could be mistaken; HOWEVER It appears that the MC which you took OUT of your M37, is the MC for a civilian power wagon...

I'm not sure about whether it was original to this 37 but the filler cap on the old one is the same size as the cap on a deuce where the new one is smaller. The other differences are 1) new mc has an opening on top for what I assume is a vent line 2) new one has threaded port for a brake light switch whereas original brake light switch is inside the frame rail.

Either way the new one works great and adds a little peace of mind to the wife driving it.

We also started doing some of the body work but then that'll have to be covered under a different thread.

 

[Ferroequinologist]

The whole thing holding us up with the MC reinstall is the push rod is frozen on the yoke, I can not get it to free up or to get the pin out to open the yoke up and clean it up. I'll probably pull out the whole pedal assembly, to drive that pin out on a bench. I want to replace all the lines while I'm at it, make sure it lasts another 50 years.

 

[mkcoen]

The whole thing holding us up with the MC reinstall is the push rod is frozen on the yoke

That was one of our problems today. We wound up taking the master out first then locking the yoke in the bench vise and using a box end wrech (and lots of Kroil) to break it free. What happened was there was a spot of rust that kind of fuse welded them together and it took some real torque to get it broken free.

edit:

After re-reading your post I guess I was thinking more of the pushrod coming apart not the actual clevis yoke. Any way to get a drift in there to drive it out? After cutting the cotter pin we were able to drive mine out and then cleaned it up good and added a little grease so it won't be freezing up again.

 

[IGALL1]

Replace!

I've had my 1960 M37 for ten years and I love everything about it except for the brakes! However, when everything is prim and proper they work exactly how they are supposed to. I've rebuilt the wheel cylinders and master cylinder multiple times. The rebuilds usually hold out for a few months but the leaks come back. I eventually started buying replacements from a professional supplier as they went out. This is the way to go. The only thing I found in one of the wheel cylinders I purchased was that the cups behind the pistons were in backwards (assembly man had a bad day). So check new ones for that and be sure there is not a speck of dust or debris in the cylinder. I also run my M37 in the mud almost every week and this is hard on wheel cylinders. If you do as I do, it's good practice to pull off the (massive!) drums and clean everything out. The best alternative to these troublesome cylinders (if you arent worried about keeping it stock) is a disc brake conversion! My buddy did this to his and he loves it! Contact me if you want to know how.

 

[mkcoen]

Turns out I am going to have to replace the wheel cylinders. Front left is leaking already so instead of messing with them I'm just going to replace them all.

I had a disc brake set up and sold it. This is the wife's truck and she wants it original so that's the way it's going to stay. It'll never see any mud unless she drives through a puddle.

 

[Keith_J]

IMHO, glycol based brake fluid causes problems when it isn't changed regularly. Silicone DOT 5 is much kinder to brake cylinders since it doesn't absorb water.

When glycol becomes saturated with water and then the temperature drops, the water comes out of solution and settles on the bottoms of the cylinders where it causes corrosion.

I have never seen a deuce wheel cylinder that couldn't be restored with only 30 seconds of honing. And most deuce wheel cylinders lack the expanders on the springs, causing them to leak a bit with atmospheric pressure changes when the breather in the master cylinder sticks.

If you want to totally solve the problem, just give these folks a call: Karps Brake Service-sleeving

304 stainless sleeve will work well with the aluminum pistons.