Go Back   Ford Truck Enthusiasts Forums > Older, Classic & Antique Trucks > 1973 - 1979 F-100 & Larger F-Series Trucks
Sign in using an external account
Register Forgot Password?


1973 - 1979 F-100 & Larger F-Series Trucks Discuss the Dentsides Ford Truck

Welcome to Ford-Trucks Forums!
Welcome to Ford-Trucks.com.

You are currently viewing our forums as a guest, which gives you limited access to view most discussions and access our other features. By joining our community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is fast, simple and absolutely free so please, join the Ford-Trucks Forums community today!





 
Reply
 
LinkBack Thread Tools Search this Thread
  #1 (permalink)  
Old 02-10-2013, 01:27 PM
78FordTruck78's Avatar
78FordTruck78 78FordTruck78 is offline
Freshman User
 
Join Date: Jan 2008
Posts: 42
78FordTruck78 is starting off with a positive reputation.
No Brake Pressure

In my 78 Ford F100 i've noticed i have to really pump the brakes to get any pressure to stop it. If i push on them regularly it goes to the floor. What is the primary reason be for this? Is it the valves under the brake reservoir, master cylinder, or possibly the proportional valve?

Thanks
Reply With Quote
  #2 (permalink)  
Old 02-10-2013, 01:47 PM
montana_highboy's Avatar
montana_highboy montana_highboy is offline
Post Fiend
 
Join Date: Apr 2008
Location: Big Sky Country
Posts: 8,244
montana_highboy has much to be proud ofmontana_highboy has much to be proud ofmontana_highboy has much to be proud ofmontana_highboy has much to be proud ofmontana_highboy has much to be proud ofmontana_highboy has much to be proud ofmontana_highboy has much to be proud ofmontana_highboy has much to be proud ofmontana_highboy has much to be proud of
Sounds like the master cylinder may be giving up the ghost, do you notice a decreasing fluid level inside the reservoir and/or fluid leaking out the rear?
Reply With Quote
  #3 (permalink)  
Old 02-10-2013, 02:13 PM
F-250 WARHORSE's Avatar
F-250 WARHORSE F-250 WARHORSE is offline
Elder User
 
Join Date: Nov 2009
Location: montrose, co
Posts: 955
F-250 WARHORSE is gaining momentum as a positive member of FTE.F-250 WARHORSE is gaining momentum as a positive member of FTE.
It could be a lot of things. I recommend looking at the fluid level close and seeing if it goes down. It sounds like a leak to me. The master cylinder is the easiest thing to replace and cheap too, but you might have a bad slave cylinder in the back, a leak in a line somewhere, a bad caliper, or something. Look high and low for leaks.
__________________
Due to the recent economic down turn, rising energy costs and mandatory labor cuts, the light at the end of the tunnel has temporarily been shut off, sorry for the inconvenience.
Reply With Quote
  #4 (permalink)  
Old 02-10-2013, 02:40 PM
78FordTruck78's Avatar
78FordTruck78 78FordTruck78 is offline
Freshman User
 
Join Date: Jan 2008
Posts: 42
78FordTruck78 is starting off with a positive reputation.
Thanks guys, i just noticed the larger reservoir was a little low, but i've noticed over the last couple of years this is not shocking for this truck. Typically i have to refill both the small and large reservoir. while troubleshooting today the small reservoir is completely full and the larger is low, is that a key to something?

Thanks again
Reply With Quote
  #5 (permalink)  
Old 02-10-2013, 03:39 PM
wilcam47's Avatar
wilcam47 wilcam47 is offline
Senior User
 
Join Date: Feb 2013
Location: Idaho
Posts: 259
wilcam47 is starting off with a positive reputation.
If you are losing quantities you have a leak somewhere...easy way to check is look at the back side of the wheel if it looks wet it most likely a leak...check your lines, also check around where your master cylinder is..and or inside the cab....its a closed system so you shouldnt have any leaks...unless you changed your brakes recently you shouldnt have any fluid loss.
AUTO REPAIR HELP - THE MASTER CYLINDER

Master cylinders used with disc/drum combination brake systems will use a large reservoir for the disc brake portion of the system and a small reservoir for the drum brake portion.
Reply With Quote
  #6 (permalink)  
Old 02-10-2013, 04:42 PM
78FordTruck78's Avatar
78FordTruck78 78FordTruck78 is offline
Freshman User
 
Join Date: Jan 2008
Posts: 42
78FordTruck78 is starting off with a positive reputation.
Alright a bit more troubleshooting and i've noticed around the top of the master cylinder it appears to leak around that seal. That's probably why i lose fluid periodically and need to refill them both. While driving the truck i can pump the breaks multiple times and get great break pressure and it will kick the brake light off. If i don't pump the brakes it will go to the floor not stopping the truck as well, and the red brake light comes on until i start pumping the brakes again. Once again after pumping the brakes i get good pressure and the light goes off. Does this help push me towards a particular problem?
Reply With Quote
  #7 (permalink)  
Old 02-10-2013, 04:47 PM
78FordTruck78's Avatar
78FordTruck78 78FordTruck78 is offline
Freshman User
 
Join Date: Jan 2008
Posts: 42
78FordTruck78 is starting off with a positive reputation.
Thanks wilcam, that is a nice article and makes me wonder if my problem is one of the pistons in my master cylinder is bad. maybe the fact that i pump the brakes i get it to respond, or possibly a bad seal. still troubleshooting the system...any thoughts or recommendations is greatly appreciated.
Reply With Quote
  #8 (permalink)  
Old 02-10-2013, 05:56 PM
devino246's Avatar
devino246 devino246 is offline
Post Fiend
 
Join Date: Mar 2011
Location: Lynchburg, VA
Posts: 8,457
devino246 has a superb reputationdevino246 has a superb reputationdevino246 has a superb reputationdevino246 has a superb reputationdevino246 has a superb reputationdevino246 has a superb reputationdevino246 has a superb reputationdevino246 has a superb reputationdevino246 has a superb reputationdevino246 has a superb reputationdevino246 has a superb reputation
Quote:
Originally Posted by 78FordTruck78 View Post
Thanks guys, i just noticed the larger reservoir was a little low, but i've noticed over the last couple of years this is not shocking for this truck. Typically i have to refill both the small and large reservoir. while troubleshooting today the small reservoir is completely full and the larger is low, is that a key to something?

Thanks again
No fluid loss is acceptable. You should never have to top off your brake fluid. If the smaller (rear brake) reservoir fluid level changes, you have a leak that needs attention. The larger (front brake) reservoir fluid level will lower as the brake pads wear. Don't top off the reservoir unless the level becomes excessively low; doing so will cause fluid to overflow when the pads are replaced and the pistons are retracted.

Quote:
Originally Posted by 78FordTruck78 View Post
Thanks wilcam, that is a nice article and makes me wonder if my problem is one of the pistons in my master cylinder is bad. maybe the fact that i pump the brakes i get it to respond, or possibly a bad seal. still troubleshooting the system...any thoughts or recommendations is greatly appreciated.
If you're sure that you're losing fluid at the master cylinder and not elsewhere in the system, rebuild or replace the master cylinder.
__________________
Devin- 1979 F150, 351m/C6

Licensed Virginia Safety Inspector
Quote:
Originally Posted by dustybumpers View Post
I'm cheaper than Devin
Reply With Quote
  #9 (permalink)  
Old 02-10-2013, 07:21 PM
78FordTruck78's Avatar
78FordTruck78 78FordTruck78 is offline
Freshman User
 
Join Date: Jan 2008
Posts: 42
78FordTruck78 is starting off with a positive reputation.
Thanks everyone, i'll again for leaks or anything that looks out of the ordinary. If i dont see anything i'll go after the master cylinder.
Reply With Quote
  #10 (permalink)  
Old 02-10-2013, 07:54 PM
montana_highboy's Avatar
montana_highboy montana_highboy is offline
Post Fiend
 
Join Date: Apr 2008
Location: Big Sky Country
Posts: 8,244
montana_highboy has much to be proud ofmontana_highboy has much to be proud ofmontana_highboy has much to be proud ofmontana_highboy has much to be proud ofmontana_highboy has much to be proud ofmontana_highboy has much to be proud ofmontana_highboy has much to be proud ofmontana_highboy has much to be proud ofmontana_highboy has much to be proud of
Quote:
Originally Posted by 78FordTruck78 View Post
Thanks everyone, i'll again for leaks or anything that looks out of the ordinary. If i dont see anything i'll go after the master cylinder.
Sometimes a leaking master cylinder won't reveal itself with the tell-tale signs of brake fluid running down the booster, often times the fluid will be sucked directly into the booster, pull the boosters vacuum hose and check for brake fluid coating the inside of the hose.
Reply With Quote
  #11 (permalink)  
Old 02-11-2013, 01:48 AM
crownver crownver is offline
Junior User
 
Join Date: Mar 2006
Location: B.C. Canada
Posts: 84
crownver is starting off with a positive reputation.
I'd pull the rear drums to see if the wheel cylinders are leaking and check that the self adjusters are working. If the rear shoes are grossly out of adjustment, you would get the light coming on until you build up pressure in the rear lines.
Reply With Quote
  #12 (permalink)  
Old 02-18-2013, 01:57 PM
78FordTruck78's Avatar
78FordTruck78 78FordTruck78 is offline
Freshman User
 
Join Date: Jan 2008
Posts: 42
78FordTruck78 is starting off with a positive reputation.
Ok, so I've went out and bled the brakes. No change. I can still pump the brakes and get really good pressure and keep it until I let off the brake. Once I let off the brake and go to press it again, it's if I have no brakes. I looked everywhere for leaks, and I didn't see any evidence at all, that I have a leak. Do you believe it is the rear shoes horribly out of adjustment, and that this can all of a sudden happen? Do I aim at the master cylinder being the problem now? Do I attempt a rebuild on it, or replace it? Thank you all for the continued support and troubleshooting tips.
Reply With Quote
  #13 (permalink)  
Old 02-18-2013, 02:02 PM
AK FORD GUY's Avatar
AK FORD GUY AK FORD GUY is offline
Posting Guru
 
Join Date: May 2009
Location: Eagle River, AK
Posts: 1,401
AK FORD GUY is gaining momentum as a positive member of FTE.
I would adjust your rear brakes and check the operation again.
__________________
GPBFD Pyromaniac
Under Construction:
1974 F100 4x4 on 8-Luggers
360/NP435/NP205/HP D44/10.25
SOLD 68 F100 2wd, 97 F350 Diesel
SOLD 1976 F250 Ranger XLT 2wd
Reply With Quote
  #14 (permalink)  
Old 02-18-2013, 02:23 PM
montana_highboy's Avatar
montana_highboy montana_highboy is offline
Post Fiend
 
Join Date: Apr 2008
Location: Big Sky Country
Posts: 8,244
montana_highboy has much to be proud ofmontana_highboy has much to be proud ofmontana_highboy has much to be proud ofmontana_highboy has much to be proud ofmontana_highboy has much to be proud ofmontana_highboy has much to be proud ofmontana_highboy has much to be proud ofmontana_highboy has much to be proud ofmontana_highboy has much to be proud of
Quote:
Originally Posted by 78FordTruck78 View Post
I looked everywhere for leaks, and I didn't see any evidence at all, that I have a leak.

If the master cylinder is leaking internally you won't find a leak, it's bypassing the piston seals inside the master cylinder and no external leaks would be noted.
Reply With Quote
  #15 (permalink)  
Old 02-18-2013, 02:24 PM
crownver crownver is offline
Junior User
 
Join Date: Mar 2006
Location: B.C. Canada
Posts: 84
crownver is starting off with a positive reputation.
Did this happen suddenly? Don't think you mentioned that.

-Is your parking brake working correctly? If not, your rear shoes are possibly out of adjustment.
-You have a hard pedal when pumped up so I doubt there is air in the lines. Plus you've ruled that out by bleeding the lines.
-It could be your master leaking internally, but I think you'd lose pressure gradually as you push on the brake pedal. One way to check is to remove the brake lines from the master and plug the inlets. You should now have a very hard pedal. If it leaks down slowly then you have a leaking master. Another thing is to check the linkage under the dash to the master. Everything connected and straight?
-Slightly low fluid in the disc brake side is normal as the pads wear. Nothing to worry about there. Doesn't sound like you're losing fluid.
-Run out on the discs can push the pads back to where you get low pedal, but your case seems extreme. Something to check though. Do you get vibration when you brake?
-Weak, bulging soft brake lines would cause a soft pedal, but again something to check.
-If it happened suddenly, it could be something amiss in the rear brake shoe linkage. That's where I would start, I think. Pull the drums, make sure everything is connected properly, maybe clean and lube the adjusters. Then manually adjust the shoes through the backing plate to just where you have a little drag. Try the brakes then.
Reply With Quote
Old 02-18-2013, 02:24 PM
Reply

Go Back   Ford Truck Enthusiasts Forums > Older, Classic & Antique Trucks > 1973 - 1979 F-100 & Larger F-Series Trucks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
78 proportioning valve 78fordguy 1973 - 1979 F-100 & Larger F-Series Trucks 3 08-08-2014 10:33 AM
78 Ford Brake Issues jdeanjunior 1973 - 1979 F-100 & Larger F-Series Trucks 10 04-04-2014 03:23 PM
ABS Hydralic control valve barkfarm 1987 - 1996 F150 & Larger F-Series Trucks 0 02-08-2014 09:18 PM
brakes lynn s 460 1973 - 1979 F-100 & Larger F-Series Trucks 3 08-31-2013 09:40 AM
'70 vs '78 Proportioning Valve Location? MavSprint 1967 - 1972 F-100 & Larger F-Series Trucks 7 02-19-2013 04:49 PM



All times are GMT -5. The time now is 06:56 AM.


Powered by vBulletin® Version 3.7.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Advertising - Terms of Use - Privacy Statement - Jobs
This forum is owned and operated by Internet Brands, Inc., a Delaware corporation. It is not authorized or endorsed by the Ford Motor Company and is not affiliated with the Ford Motor Company or its related companies in any way. FordŽ is a registered trademark of the Ford Motor Company.

vbulletin Admin Backup