Brake problems, puzzeled

[gaboy1]

I've been working to get my rig stopping better. 35" tires, 351w.

I recently replaced the front drums with discs from WildHorses. That install was fine, but the brakes still weren't great. So I have replaced the master Cylinder with a Wilwood unit from Wildhorses, had literally no brakes after that, so I figured maybe the booster itself was worn out. I bought a new unit from WH for that as well, with everything bolted up, my pedal travel is fine, and the brakes do bottom out but it just doesn't feel to me like I am getting much assist. I got the 1 1/8" bore wilwood cylinder. Also, the front discs were a complete kit, including a new prop valve. Everthing is bled, and everything seems to be installed fine, it just feels I have to stand on it a bit to much to get it to stop.

Any ideas? The brake lines all look fine, no pinches, no crimps, and tons of fluid when bleeding. I am going to check the vacuum, but it definitely feels strong with my thumb on the end. It is thick walled 3/8" hose going directly to the back of the carb. Any ideas would be greatly apprecated.

 

[Jkman67]

I had this same problem, did all the things listed that you did....what fixed it for me was moving the vacuum hose off the carb to the manifold. Thats what fixed it.

 

[DirtDonk]

Interesting fix Jkman! I've never heard of that making a difference, but will make a mental note of it now and see if that helps others in the future. Thanks.

Normally that setup works fine for people gaboy. The 35's definitely tax even disc brakes, which are actually only nominally more powerful than drums, but the booster should improve that bit more.

Do you know for sure that you ground sufficient material from the front knuckles for caliper clearance? Can you see at least 1/8" of daylight between the caliper and knuckle when you look down over the tire? If not you may have to do more grinding.
But from the sound of it, what with the good pedal and all, I'd say you did it all correctly.

Are you running the brass combination type proportioning valve, or the single manually adjustable type?
Not that this should make a difference in power, but trying to get all the info while trying to diagnose your issue.

Are your tires and wheels particularly heavy? Something like running Hummer steel beadlocks and Goodyear MTR or BFG Baja T/A's or something like that?

Good luck. Nobody likes lack of braking in these old vehicles!

Paul

 

[blubuckaroo]

Did you "bench bleed" the master cylinder before installing it?
Yes, even though the fluid bleeds out of the calipers and wheel cylinders, you can still have air in the master cylinder.

 

[gaboy1]

Fixed

I found the issue. My buddy who was helping, (unpacking stuff while I was removing the old one), and the guy who was in a hurry to plug up the new one for results gratification, failed to actually replace the check valve. I took it off, and couldn't blow through it either way, and he said, "You think that might be it, the new one came with one, but since that was easier to get in the hose I used it, and it's just an elbow".

So, putting the new one that came with the booster fixed the issue. Could have strangled him, but he was one of the few folks that even offer to help anymore

Thanks guys!

 

[Apogee]

A brake system with good feeling pedal, but high pedal effort required to achieve what feels like low brake torque will typically have either an oversized master cylinder bore size, undersized booster/low vacuum or low CoF brake pads, or any combination thereof. This assumes proper installation, knuckles ground sufficiently, etc.

 

[sprdv1]

LOL, glad you got it fixed up

I found the issue. My buddy who was helping, (unpacking stuff while I was removing the old one), and the guy who was in a hurry to plug up the new one for results gratification, failed to actually replace the check valve. I took it off, and couldn't blow through it either way, and he said, "You think that might be it, the new one came with one, but since that was easier to get in the hose I used it, and it's just an elbow".

So, putting the new one that came with the booster fixed the issue. Could have strangled him, but he was one of the few folks that even offer to help anymore

Thanks guys!