Brake Bleeding Issues
 

Hopefully somebody on here can tell me exactly where I am messing up. I had the brake lines off at the MC to remove a T-fitting that an old trailer brake controller was hooked to. To do that I simply bled out all 4 corners before removing the lines at the MC to prevent a mess under the hood, also figured it would be a good time for new brake fluid anyway.

Well, now I've had great success gravity bleeding the rear brakes, but I get absolutely nothing from the fronts, not even a drop. Still nothing when pulling a vacuum on the system at the caliper.

I realize this has something to do with the metering valve, but I see absolutely nothing on the thing that I can push in or pull out. I popped the rubber bulb off of the one side and don't see anything over there, popped the switch out of the top and don't see anything I can do in there.

At this point I am quite lost, maybe the metering valve is stuck and I need a new one. But its probably something quite simple I am missing?

Truck in question is a 1978 GMC C25, 454 engine. Any suggestions would be greatly appreciated!

Re: Brake Bleeding Issues
 

3 Day's and no one has helped you if you are still in need of help i'm gonna say take the proportion/metering valve off take it apart and clean it. it's probably full of sludge from 1978 brake fluid.

Re: Brake Bleeding Issues
 

hadn't seen this...your proportioning valve is tripped it sounds like...youll have to recenter the spool and use the tool that holds it centered while bleeding

Re: Brake Bleeding Issues
 

You can reset the depressor at the end of the valve and give a try, but you can also try this tool. And have some slowly press on brake to bleed. Do not stonp on it while bleeding them like my neighbor🤦*♂️😂

https://images.nationaltoolwarehouse...C/OTC-7853.jpg

Re: Brake Bleeding Issues
 

Hmmm, educational thread. I haven't seen those prop valve tools but they look pretty cool. I always get them centered by driving and stomping on the brakes. I think if you bleed the crap out of the rear lines the prop valve will center itself. I haven't got to try that method yet but it sounds logical to me.

If you would have just cracked the lines at the master you would have lost almost no brake fluid and the lines would still be full when you reconnected them.