I have a need to get an old 1951 GMC 2.5 ton side-dump farm truck running for a few errands. This truck has been parked out behind the barn for about two years now.
My question is about a part in the brake hydraulics system. When I started the project, there was no brake pressure. A several minute search brought me to the master cylinder that is located under the driver's position floorboard. Pulled a plug from the floor and found where the reservior is (it is actually the body of the master cylinder itself).
Following the hydraulic line from the master cylinder brings me to the part in question. This is a large cylindrical device about six inches in diameter with a narrower neck coming off the front of it. The neck feeds into a rubber tube that ends at a breather of some sort mounted on the firewall. There is a bleeder for the brake system in the narrow neck as well, and the brake lines come off of there too.
There is also a feed from this device to the hydraulic pump for the dump bed on this truck, but I don't believe that the system shares the fluid between the brakes and the dump hydraulics.
I got the brakes working well, but I'm still baffled by the purpose of this rather large device in the middle of the system.
Any ideas?