I want to take the cruise control system out of the vacuum loop due to broken parts, and checking for vacuum leaks as the brake light shows up when driving. So I disconnected its hookup off the plastic t vaccum branch and capped it.

That also takes the bean tin can looking thing out of the loop on the drivers side which was hooked up to the cruise control servo system.

I thought I had read that the tin can is needed for the brake system? If so, how do I plumb this back into my system?

Thanks!

 

The factory vacuum canister is only needed for the cruise control, whoever tells you otherwise is quite misguided. Pull the hose for the tin can from the vacuum tree and cap the vacuum tree port off.

 

The can is NOT needed. When I first got my truck the can was rusted out so I just plugged the lines into eachother and everything worked fine, including the cruise. I also have no vacuum leaks.

 

If the can wasn't needed it wouldn't be there from the factory. You get to slide cause your vacuum pump works good, but once that starts to weaken you'll quickly see what the can was there for...

 

Ok I have taken my cruise control system off the vacuum tree where its capped but have some more questions.

1. If the ball on the passenger fender is the vacuum reservoir, how can I make sure it is doing its job? For example I can let the truck idle for just a bit and turn it off, then come back to the truck later and I can get a couple pumps of the brake with just the key on, before the brake light comes on.

2. Would this system benefit from a bigger reservoir like the drivers side can size or even bigger?

3. I am wondering if my vacuum is working good. I measure 25 with a vacuum gage when its idling. If I pump the brakes it drops down about 3 on the gage with each pump in succession. I can get about 7-8 pumps in a row before the brake light comes on.

If I pump the brake and hold the pedal down, it slowly goes to the floor and the gage will hold the same unless I let go of the pedal, and the vacuum recovers in 10 seconds, or I pump the brakes some more and it continues to go down on the same scale mentioned earlier.

4. What is the guuussh guuuush noise at the brake pedal inside the cab when you pump the brakes?


Thanks!

 

1. there's no vacuum reservoir for the brakes of these trucks, the brake booster itself is the vacuum reservoir - so pumping the brakes will not test your vacuum canister. If you do wanna test it hook up a vacuum gauge on its output port, then run the truck and after you shut it off watch the gauge, it should stay stable. But all this would confirm that your cruise has vacuum reserve to smoothen its operation, again it does nothing for the brakes.

2. Definitely could use a larger reservoir, but I mean large, something like 5 gallons or so (you can mount that on the frame rail, as there ain't no way it fits in the engine bay) - you disconnect the main vacuum line off the brake booster and run it to the large vacuum tank instead, then run another large vacuum line from the tank to the booster. This will give you a huge reserve for operating your brakes should your vacuum pump go out or you throw a belt, but it will take a while to "fill" the tank right after you fire up the truck at first before you can get full brake assist.

3. 25" is good, but there was something about flow too, I'd think 7-8 quick pumps would be alright performance if the truck is just idling. The pedal slowly sinking to the floor is a master cylinder issue tho, a new one is like $30 so you wanna consider replacing it.

4. The cruise control has a vacuum dump valve that purges the vacuum from its chamber every time you step on the brake pedal. The booster itself sometimes hisses like that...

 

LOL It is telling you to get a master cylinder quick. If it bleeds down while you hold it , it is not going to be long till you need it and it goes to the floor, and it is always at a bad time.

 

If you end up replacing the master cylinder I would get one with the brake fluid reservoir already attached. I changed mind not long ago and it was a bear to get the reservoir off the old one. I finally got it off without breaking it but I swore I would never do it again for the few extra bucks to get one with it already one there.

 

His '85 should be an all-metal one-piece thing, not the two-piece unit the bricknose and newer trucks have with the plastic reservoir.

 

If you can get 7/8 good pumps your doing very well.........

If your pressing hard on the pedal at a stop and it is sinking that is normal. If you find the pedal does NOT sink at normal pedal pressure to hold the truck still after a stop........ that is good.