'44 Chevy CMP C15 Master Cylinder

[Craig McKelvie]

Has anyone successfully found a rebuild kit for a Chevy C15 brake master cylinder? (Preferably in Canada) Mine is leaking from the rubber dust boot end and assuming it will need new piston cups.

[Grant Bowker]

If you don't think it is safe to drive now (and I think you are right to be concerned) you could take it out of the truck, plug the lines, disassemble the master and inspect whether the cylinder is pitted. If it is pitted, you will probably have better luck getting it sleeved and rebuilt/remanufactured by someone like John Stuart http://www.johnstuartpowerbrake.com/...-Sleeving.page in Stoney Creek. A new kit put into a pitted cylinder will wear and leak much sooner than new seals in a good bore. The master used in most of the Chev CMPs is a pattern that isn't readily available. Similar looking style exist, but not in the needed 1-1/4" size.
If only a kit is needed, this auction has ended on ebay but the seller regularly has CMP parts.
Based on a quite comprehensive Wagner Brake Catalog HU-400 dated September 1947, the master cylinder used on CMPs is probably a FD-4388 in "Wagner speak" based on shape, mounting pattern and bore. If this is correct, it is listed as taking a Wagner FC-3630 kit. The FC-3630 number in turn goes back to GM part number 603646, which is one of the repair kit numbers given in the C15A parts list. I don't know what the difference between this kit and the ones listed as superceding it are. GM part number 5450260 doesn't appear in the Wagner cross-Index, but it isn't one of the "unique to CMP" part numbers according to the parts list.
The FD-4388 seems to have been used in some GMC trucks late 30s to mid 40s.

[cletrac (RIP)]

Farm oriented auto parts stores quite often have stuff for 40s trucks that will work. I got a kit from Great West Auto Electric in Swift Current a few years ago. They even had wheel cylinder kits on the shelves.

[Maurice Donckers]

Dodge WC series have the same rebuilt kit , it is just a standard 1 1/4 kit .

[Grant Bowker]

Another source that might help you are long established heavy truck repair shops, probably better if they are independent - not a dealer, that make their living by keeping customers trucks on the road, not selling new ones. Avoid anywhere like Canadian Tire where the kid at the counter can't even sell you a 12V 7" sealed beam headlight bulb without knowing what vehicle it fits to find the stock number in his computer.

You probably already know that the wheel cylinders are as used on Ford trucks of the period (and probably others too) and are still readily available new. Ford master cylinders are also still available new. New replacement and NOS Chev master cylinders are rare (even used ones on ebay are rare, but the master for early C60X are a whole different breed of rare. I have never seen a new or NOS of that style. They may exist, just I've never seen one that wasn't already on a truck and I've seen cases where they were neatly robbed from the C60Xto keep something else running. I suggest to folks that any CMP Chev master cylinders, safe to use or not, that aren't already on trucks be saved unless the casting has failed beyond the ability to repair by sleeving.
I agree with Maurice that in that period, parts were less vehicle specific. For a small production vehicle like the C60X, you don't design a new part if something already in production by one of your suppliers can do the job.
The Wagner catalog I referred to did list the same repair kit for several different master cylinder housings but all were GM.

[Harry Moon]

I bought the one that was new manufacture, Argentina, and it was off by a couple mm's as it was obviously manufactured to metric specs, took some work to install on the C60. I would buy the rebuild that requires a core.

[Grant Bowker]

Originally Posted by Harry Moon

I bought the one that was new manufacture, Argentina, and it was off by a couple mm's as it was obviously manufactured to metric specs, took some work to install on the C60. I would buy the rebuild that requires a core.

My C60 manual says the master cylinder assembly is part # 5450260 (same as the C15A). The only master cylinder I see today at Chevs of the 40s that looks to be the same general shape as CMP master is part # 5450257, listed as fitting cars. I thought most cars and pickups had 7/8" or 1" master cylinders rather than the 1-1/4 usually found on CMPs.

Is more information available about you got and how close it was to the CMP master cylinder?

Chevs of the 40s do sell kits, but todays catalog seemed to be for 7/8 or 1" master cylinders.

[Harry Moon]

Originally Posted by Harry Moon

I bought the one that was new manufacture, Argentina, and it was off by a couple mm's as it was obviously manufactured to metric specs, took some work to install on the C60. I would buy the rebuild that requires a core.

A follow up on this master cylinder. It failed before I got on the road. There is a outlet at the end for the brake sensor and when you rotate the push rod to install or adjust the seal cuts itself on that opening. no way to avoid rotating the push rod. in addition it is a one inch bore which required a longer stroke or travel to the pedal. seemed to work fine but after adjusting it it started to fail. I recall the same damage to a similar later master cylinder adapted to another truck, same 1 1/4 master with the mounting holes on the side and I think back then the culprit was the same outlet on the side ripping the seal when it was being adjusted. So I have taken Grants suggestion and sent an original one off to Stoney Plain for sleeving and a Rebuild.

[rob love]

Originally Posted by Grant Bowker

Avoid anywhere like Canadian Tire where the kid at the counter can't even sell you a 12V 7" sealed beam headlight bulb without knowing what vehicle it fits to find the stock number in his computer.

He will also need to know the engine size before he can look anything up for you, as if that would make a difference on the majority of body parts.

A good parts counterman has to have some years of experience, and should not give you a puzzled look when you ask for something like a vacuum advance.

[cletrac (RIP)]

Like I told my daughter, when you go to a parts store, Always ask for the OLD GUY!