The Stovebolt Site Forums The Parking Lot Big Bolts Hydro-vac vacuum check valve

Looking for the original style check valve for the hydro-vac line for my 1965 VH5000 401 V6. Or what one looks like.

I am going through some of the jury-rigged construction on my new truck. I was told by one of the persons working at the shop where my truck came from that the air tank behind the seat was for the air handlers for the tar tank truck back that was on it. So, I took it out and cut a 1/2 ID line off of it, figuring it was going to the air pump under the hood. Well, took the truck for a ride, no brakes, stuck my finger in the hose and had brakes, in fact, better brakes then before. So, I plugged the line and went for another ride and I have much better brakes. I'm not too sure who told them that you need more volume for the brake vacuum system, but I don't think so, and it may impact how the brakes work. The brakes act much faster now. Just my thoughts.

Anyway, they had just put on a new hydro-vac and the tank was part of the plumbing. Also, they put a white plastic check valve with a third leg, which is plugged, on it. Looks like hell.

I am looking for an original, or original part number or a picture of what its supposed to look like. Thanks.

I did take the air pump out from under the hood. Talk about a hack job. Some people should not be allowed to open a hood, much less turn a wrench. Getting a new belt for the power steering now that the extra pulley is gone.

Thanks for any help,

BaconFarms

The check valve on mine is mounted on the firewall in the engine compartment higher then the carbuerator. 1/2" steel lines run down to the hydrovac under the driver side floor, mine has no vacuum reservoir. It was working a little but leaking brake fluid so for now I have it bypassed.

I can't help with GMC numbers, but Chevrolet used a Bendix 378904 (Chevy 3757922) from 1958-66 and from 63-65 ALL w/ HD Brake Booster used Bendix 2501214 (Chevy 2445987).

I'm betting GMC used the same parts as Chevrolet...

Are you sure the pump you removed was pressure and not vacuum? Chevrolet had vacuum pumps on some trucks in the mid/late 60's...

Hope this helps,

Mike B

Bacon Farm do you have pic's? I'll have to do some digging. But some were I have Part Numbers for a 66 Chevy Hydro-vac from Napa. Bought a Reman a few years back.

Mike,

Thanks for the reply. I tried all four numbers and can't seem to find a replacement , or any of those numbers to come up. Might have to go to the parts store and see if they have a old cross-reference book. The innerweb and GMC Big Bolts don't play well.

The air pump was a vintage Midland, and used for air. The tank was plumbed into the hydro-vac line going from the intake to the hydro. I cleaned that up, but am looking for the correct check-valve and where it mounts, etc..

Thanks for the numbers, maybe I will strike gold at the parts store. I'm sure they will ask if it has air conditioning and power windows, but I'll work through that, LOL..

BaconFarms

Does your truck have a 5/8" hole somewhere in the middle of the firewall above the engine? If so that's where the valve goes.

The valve has a port with external threads that goes through that hole and into the cab for vacuum wipers and or vacuum gauge (if neither are used then it's plugged). A big nut threads onto this port to mount the valve to the firewall.

This may be a junk yard item...you would want the steel lines as well.

There should also be a "fresh air" line to the Hydrovac that connects to the high pressure side of the air chamber with the other end going to the air filter on top of the carburetor. these two lines parallel each other going down the firewall.

Mike B

Mike,

I believe the fresh air intake for my truck is in the cab at the drivers cab corner. I will shoot a picture when I get a chance.

Thanks for the other info, I will look and see what I see regards the firewall.

Thanks,

BaconFarms

Hydrovac master cylinder. Napa #51-8052 http://www.napaonline.com/en/p/NBB518052

Here are some pics http://picclick.ca/Cardone-Industries-51-8025-Remanufactured-Power-Brake-Booster-192586850175.html

BF,

So you have the air breather cap attached to the floor...looks like a valve cover breather cap, right? They were used for normal highway driving (cleaner air). For Heavy Duty use they plumbed it to the air cleaner.

Mike B

Mike,

Yep, thats the one....

BaconFarms