I recently acquired an older GMC C6500 with a Chevy 350 fairly cheap but it was vandelized and is missing a few items. The local talent stole the radiator, what I assume was an electric air compressor for the breakes and started tearing down the engine. I am familar with the drive train but have never really got to know an air over hydraulic system that well. All of the plumbing past the firewall is in tact, air lines to the booster under the driver's door, the air tank ect. but no compressor. Can anyone provide a picture of where the air compressor should be and how it is wiredl/plumbed into the splitter on the fierwall? And no it (the compressor) was not belt driven off the engine since all of the pulleys are used and no further braketry can mount near the engine, at least what I can tell. Thanks in advance for any advice.
I'm guessing its a vacuum assist system
I whish it was vaccume assist. There is only a small master cylingder bolted/rusted to the firewall that feeds a large breakbooster under the cab. The booster has vent mufflers and a 3-4 gal resevoir tank, I can plumb this into the manifold but doubt the old 350 will pull enough vaccume to get the air gage in the cab to move.
Any chance of a couple pictures? One of master, one of what ever is under cab on frame and one of the gauge in dash. Like they say one picture is worth 1,000 words so post three and that is better than 3,000 words! I'm voting for vacuum booster system, don't ever recall an air over hydraulic system on an over the road truck, not saying they don't or never existed just never seen one in person! I had lots of experience in the past with them on off road equipment however.
I realize the delema, when I get off work I willtake some pictures and post them. Like I said the engine bay was ransacked so I can plumb any of the pipes to whatever will work.
Any chance this truck was cobbled together before it was "deconstructed"? I don't doubt your air brake situation, you see it and we're just reading some kook on the internet. Also something I've never seen on a truck, but there's a first time for everything.
Air over hydraulic boosters existed but would only be half the size or less of a normal vacuum booster, vacuum only gives you the effect of about 7 or 8 psi on a good day, that's why you need a big diaphram to give you good brakes. Does the booster and/or the tank have like a 3/4" hose coming off of it that's not connected to anything?
Here is a picture of a vacuum booster from under the drivers step of my old International You can just barely see the vacuum reservoir on the bottom of the picture. This one is like a giant coffee can but on some trucks they seemed to use a normal air tank, maybe for parts commonality.
I now believe it is all vacuum, just new to me: Air Tank Master + Vacuum distribution in engine bay Brake Booster under driver door The remaining parts in the cab are lines that go nowhere and the Air gauge was hacked in through the floor to the back of the truck. Presumably since the thing was owned by a roofing company for three decades, they had an air compressor on-board at one time and ran the lines for air tools.
I can see where seeing that tank would have made one think "air brakes" but like Birken Vogt says probably used it as they had then on the shelf from another application, no sense in reinventing the wheel or tank in this case.
I will put on a new intake manifold raidiator and carb, then see if the old smallblock will move the truck and post if the breaks work in the next day or so. As an aside where would be the best place to get modle specific parts for these older medium duty trucks?
In the case of my International the answer was that you can't get them, but it has been many years since I cared and since it is just a yard machine it does not need brakes anyway so I can't really help you other than to say I remember it being nearly impossible to find anything.
Start with NAPA, then look for a good truck parts company, there are tens of thousands of old farm trucks still running and most of the brake stuff was generic, at least for the rear axles. I used to deal with a company in Portland, Oregon called Brake Systems and if it was made they could find it or rebuild it, you may have some similar brake parts company in your area.
Another outfit to try is: Precision Rebuilders http://precisionrebuilders.com/about_us.html Our local heavy equipment brake shop has dealt with them for many years.
Try AutoZone for part # 51-8051. Should be it or close. Master cyl will have a casting number on one side. Take that number to a NAPA store. Price a kit, and the cylinder. Unless you are good, have done it before several times, get the cylinder. Get needed length of new vacuum hose and install all. Fill m/cyl with fluid, bleed down at the booster, then farthermost wheel. Should be good go on this portion. Truck is basically same as a 78 C60 Chevy with a 350 in it.