Weak brakes...
Thread Starter
|
Freshman User
Joined: Nov 2001
Posts: 29
Likes: 0
From: Mesquite USA
Weak brakes...
Well...I have finally worked out the majority of the my brake problems....(72 disc brake conversion)...and yes, the lines were crossed...
Now the brakes work ok...but I really expected better than ok...
they stop the truck but I can't lock them up....
I haven't touched the rear drums yet (coming up next weekend) but I figured the front drums should lock up when I slam on the brakes at speed...
To detail work so far....
Junkyard disc spindles off a 75 F100, with new discs, rebuilt calipers, new pads, rebuilt master cylinder, added new power brake booster, used distibution block/proportioning valve, new front braided stainless flex lines...no leaks, bled lines, bled master cylinder on truck by loosening lines on the side of the master cylinder untill they leaked, then applying brakes and closing down fittings...
Did not replace any of the hard lines, did nothing to the inside of the prop valve, do not have the brake light hooked up yet...
Any ideas why the poor performance?
Now the brakes work ok...but I really expected better than ok...
they stop the truck but I can't lock them up....
I haven't touched the rear drums yet (coming up next weekend) but I figured the front drums should lock up when I slam on the brakes at speed...
To detail work so far....
Junkyard disc spindles off a 75 F100, with new discs, rebuilt calipers, new pads, rebuilt master cylinder, added new power brake booster, used distibution block/proportioning valve, new front braided stainless flex lines...no leaks, bled lines, bled master cylinder on truck by loosening lines on the side of the master cylinder untill they leaked, then applying brakes and closing down fittings...
Did not replace any of the hard lines, did nothing to the inside of the prop valve, do not have the brake light hooked up yet...
Any ideas why the poor performance?
Thread Starter
|
Freshman User
Joined: Nov 2001
Posts: 29
Likes: 0
From: Mesquite USA
Weak brakes...
The proportioning valve is off the donor truck...I removed the old distribution block that was there and replaced it with the distribution block/proportioning valve combo off the donor truck.
Senior User
Joined: Aug 2001
Posts: 211
Likes: 0
From: Houston, Tx
Weak brakes...
Ok now... Are you saying your brakes don't work well, or you're just wondering why they don't lock-up when you press hard? I did this conversion on my '67 F-100 with '77 parts. I know what you mean when they don't lock up, you would think with all that added braking power they would. But, I just take this as a blessing I love not worrieing about locking up when the roads are wet. And, My brakes still work a hundred times better than the drums, they just don't lock up like the drums did.
If your brakes aren't working good, then I would check out the prop-valve, I had problems with it, but fixed it and it worked great.
Basically, If you're not shouting "THANK YOU GOD.." Then somthings broke.
If your brakes aren't working good, then I would check out the prop-valve, I had problems with it, but fixed it and it worked great.
Basically, If you're not shouting "THANK YOU GOD.." Then somthings broke.
Freshman User
Joined: Dec 2001
Posts: 29
Likes: 0
Weak brakes...
Matt, Can I ask what kind of problem you had with prop vavle?
I am finishing change from drum to disk and I think this junkyard
vavle I have is not doing right. Front works fine but rears are
not doing right is the best way I know how to put it.
Thanks
I am finishing change from drum to disk and I think this junkyard
vavle I have is not doing right. Front works fine but rears are
not doing right is the best way I know how to put it.
Thanks
Senior User
Joined: Aug 2001
Posts: 211
Likes: 0
From: Houston, Tx
Weak brakes...
Manning,
Sounds like you might have the same problem I did.
When I put it on, there was juice going to the front but nothing to the rear. I took it out and blew air in all the holes to see witch ones worked, ( I would suggest you do this to). I found that the rear ones were blocked by something. Turns out it was the little piston inside the prop-valve thats supposed to slide around in it. We sprayed brake-cleaner, B-12 chemtool, and WD-40 trying to unstick that piston. Finally, in a last attempt before going and buying a new one ( about $100-plus) my dad stuck a small drill-bit in the "rear-outlet" hole, and tapped it with a hammer. It slide the piston back in place, and after blowing air in it again, the rear was now getting air. I put it back on the truck, bled the rear first, and its works great now
Sounds like you might have the same problem I did.
When I put it on, there was juice going to the front but nothing to the rear. I took it out and blew air in all the holes to see witch ones worked, ( I would suggest you do this to). I found that the rear ones were blocked by something. Turns out it was the little piston inside the prop-valve thats supposed to slide around in it. We sprayed brake-cleaner, B-12 chemtool, and WD-40 trying to unstick that piston. Finally, in a last attempt before going and buying a new one ( about $100-plus) my dad stuck a small drill-bit in the "rear-outlet" hole, and tapped it with a hammer. It slide the piston back in place, and after blowing air in it again, the rear was now getting air. I put it back on the truck, bled the rear first, and its works great now
Junior User
Joined: Jun 2001
Posts: 71
Likes: 1
From: North Alabama
Weak brakes...
I have a '75 w/disc brakes & it doesn't sound like it stops any better than yours. My brake guy says everything is okay. Maybe just the nature of the beast? It's still better than my '90 Bronco, that locks the fronts up any time you have to stop in a hurry. However, if the system has to come apart any time in the future, I'm sure gonna check out that piston in the proportioning valve. Thanks for the tip.
John
John
Trending Topics
Senior User
Joined: Mar 2002
Posts: 271
Likes: 0
From: La Canada, CA
Weak brakes...
I optimized my disc brake conversion on my 1967 F100 by tossing the proportioning valve.. This finally gave me some rear brake lockup. I then installed an adjustable Wilwood valve ($40 from JEGS)in the rear with 2 turns adjustment. Now have great brakes but no lockup. Yes, it's the nature of the beast.
I had used all new parts in my conversion. I made the mistake of using a 1 1/8" master clinder at first, which is too large resulting in a hard pedal. Replacing with a 1" cured that and improved the braking a lot, but not as much as removing the proportioning valve.
I had used all new parts in my conversion. I made the mistake of using a 1 1/8" master clinder at first, which is too large resulting in a hard pedal. Replacing with a 1" cured that and improved the braking a lot, but not as much as removing the proportioning valve.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 10 Fords at 2026 Carlisle Ford Nationals
Joe Kucinski
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Senior User
Joined: Aug 2001
Posts: 211
Likes: 0
From: Houston, Tx
Weak brakes...
I would of used one of those Wilwood Valves, but with my setup it was easier to just use the '77 prop valve, since I got the brake lines off the donor, and all I had to fab was the rear line.
Personaly, even though my brakes don't lock, I don't think it afects the braking ability, it may even increase it. All I know, is I got into my Moms '98 Camry the other day and said,"wow, these brakes don't seem as good as my 67's!" I had to press them harder to stop than I do with my truck, and it has a manual master-cyl. Her car is in tip-top condition, so its not because of them being worn out.
In my research, I have come to beleive that '73-'79 F-100's are heavier than the little 67-72's. The fact that my truck only weighs about 3,700#s and now has 12" disc's up front would make it true that it may stop better than most car's.
Just some thought's from My point of veiw.:7
Personaly, even though my brakes don't lock, I don't think it afects the braking ability, it may even increase it. All I know, is I got into my Moms '98 Camry the other day and said,"wow, these brakes don't seem as good as my 67's!" I had to press them harder to stop than I do with my truck, and it has a manual master-cyl. Her car is in tip-top condition, so its not because of them being worn out.
In my research, I have come to beleive that '73-'79 F-100's are heavier than the little 67-72's. The fact that my truck only weighs about 3,700#s and now has 12" disc's up front would make it true that it may stop better than most car's.
Just some thought's from My point of veiw.:7
Thread Starter
|
Freshman User
Joined: Nov 2001
Posts: 29
Likes: 0
From: Mesquite USA
Weak brakes...
Well...finally tracked down and solved my brake problem....
turns out my rear flex line was completly dry-rotted...it was probably balloning when I hit the brakes...
So, with a new flex line, new calipers and drums....all four wheels lock up when you stand on the brakes...
I am happy....now to go on to find new problems........
Doing the headlight relay conversion next.
turns out my rear flex line was completly dry-rotted...it was probably balloning when I hit the brakes...
So, with a new flex line, new calipers and drums....all four wheels lock up when you stand on the brakes...
I am happy....now to go on to find new problems........
Doing the headlight relay conversion next.
