1976 chevy c50 brake problem
- Thread starter jobo
- Start date
Do you still have good brakes when the pedal gets hard?
That sounds like you're losing your vacuum boost. check all the hoses from the intake manifold to the vacuum tank and to the hydrovac from the tank. could also be that the air inlet on the hydrovac is full of dirt and needs cleaning. I haven't worked on one of these setups for years, but this is what I remember. Oh. somewhere between the intake manifold and the tank is a check valve to keep vacuum in the tank.
And another crosses over to the dark side.
td25c
Well-known member
LOL ! I'm cool with the dark side .
One other item to check is the rubber line between the cab & frame coming from the master cylinder to the booster.
Years ago we had same symptoms on the 1966 chevy C60. Hard peddle , brakes would halfway work .
We put a new booster on & nothing changed . Turned out the inner liner of the rubber line had separated inside itself stopping up the line and yet not leaking on the out side .
Pretty crazy !:bangh
One other item to check is the rubber line between the cab & frame coming from the master cylinder to the booster.
Years ago we had same symptoms on the 1966 chevy C60. Hard peddle , brakes would halfway work .
We put a new booster on & nothing changed . Turned out the inner liner of the rubber line had separated inside itself stopping up the line and yet not leaking on the out side .
Pretty crazy !:bangh
Attachments
I've heard of this happening before but have yet to see it. I heard one case where the deteriorated hose worked like a check valve and wouldn't allow the brakes to release!
td25c
Well-known member
That's pretty much how it was in my case Steve . Rare when it happens but can happen .
You would think the brake hose would blow or at least leak if the inner liner fails and is stopping the flow . Made it tough to diagnose the problem .
We ended up with a new booster and a brake line hose
You would think the brake hose would blow or at least leak if the inner liner fails and is stopping the flow . Made it tough to diagnose the problem .
We ended up with a new booster and a brake line hose
A vacuum hose won't "blow"... Implode maybe, but not blow. That's what makes vacuum leaks so hard to find. One way to find vacuum leaks is leave the engine idle and use small puffs of ether on suspect areas. Another possibility in the OP's case is the check valve between the intake and the vac reservoir isn't holding. It's all kinda coming back to me now.That's pretty much how it was in my case Steve . Rare when it happens but can happen .
You would think the brake hose would blow or at least leak if the inner liner fails and is stopping the flow . Made it tough to diagnose the problem .
We ended up with a new booster and a brake line hose
Truck Shop
Well-known member
I have a policy in the shop {If it doesn't have air brakes we don't work on it}. I worked on juice brakes years ago and there was nothing worse than air over hydraulic.
If it's over 26 GVW it should have air brakes IMO. If the truck is 25 years old then replace every thing, because of liability. And most of those systems require a
pressure bleeder to remove all of the air from the system. If you don't use one on a hydrovac system your just pi$$ing in the wind. IMO.:avid
Truck Shop
If it's over 26 GVW it should have air brakes IMO. If the truck is 25 years old then replace every thing, because of liability. And most of those systems require a
pressure bleeder to remove all of the air from the system. If you don't use one on a hydrovac system your just pi$$ing in the wind. IMO.:avid
Truck Shop
You're preaching to the choir there. I remember driving Chevy tandems at 50-52K with hydraulic brakes, first thing you did was get the coasting RPM as high as possible to get the vacuum to the max, at that point a tad bit of religious faith seemed to help too.
And yes, a serious pressure bleeder was needed for both air or vacuum systems. It's kinda funny, but I remember an old IH L-180 that dad had that seemed to have reverse hydrovac brakes... you would step on the pedal (that would screech on the floorboard) and it went all the way to the floor, as soon as it hit the floor you would have to let up as the hydrovac applied the brakes or she would toss you through the windshield.
And yes, a serious pressure bleeder was needed for both air or vacuum systems. It's kinda funny, but I remember an old IH L-180 that dad had that seemed to have reverse hydrovac brakes... you would step on the pedal (that would screech on the floorboard) and it went all the way to the floor, as soon as it hit the floor you would have to let up as the hydrovac applied the brakes or she would toss you through the windshield.
Truck Shop
Well-known member
td25c
Well-known member
Yeah RZ . Totally agree bro .
What happened on our chevy C60 was the rubber brake line stopped up inside when the inner liner came apart .
The fluid line between the master cylinder and the booster . Has a rubber line between cab & frame . Picture on post #9