Another Braking Thread
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Senior User
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Another Braking Thread
Have some spare time, so pulled the 79 F250 4wd out of storage. (16 months)
The fronts are disc w dual cylinder calipers, The rears are drums
On first drive, found out the brakes hit the floor. On inspection I found the large reservoir was empty.
I thought for sure the large reservoir should be connected to the rear drums, but they are connected to the front discs.
Been reading the many posts for the last several hours to see where to start.
I did a full 4 wheel bleed tonight and will drive it tomorrow.
Two questions.
#1: I want to verify the drums and disks are plumed to the correct reservoir in the MC.
In one post I see "smallerreservoir is always the disc one"
In another post "On a drum - disc dual master cylinder the bigger reservoir feeds the disc" .."drum" for the small reservoir and "caliper" for the large reservoir..."Drums have small slave cylinders, discs have large pistons,"
#2: When pumping the brakes w/o the MC cover in position, should the fluid create a 3-4" fountain in the M/C? I read you can only look for bypass in the M/C by plugging the M/C outlet ports. Is this correct?
tks
The fronts are disc w dual cylinder calipers, The rears are drums
On first drive, found out the brakes hit the floor. On inspection I found the large reservoir was empty.
I thought for sure the large reservoir should be connected to the rear drums, but they are connected to the front discs.
Been reading the many posts for the last several hours to see where to start.
I did a full 4 wheel bleed tonight and will drive it tomorrow.
Two questions.
#1: I want to verify the drums and disks are plumed to the correct reservoir in the MC.
In one post I see "smallerreservoir is always the disc one"
In another post "On a drum - disc dual master cylinder the bigger reservoir feeds the disc" .."drum" for the small reservoir and "caliper" for the large reservoir..."Drums have small slave cylinders, discs have large pistons,"
#2: When pumping the brakes w/o the MC cover in position, should the fluid create a 3-4" fountain in the M/C? I read you can only look for bypass in the M/C by plugging the M/C outlet ports. Is this correct?
tks
Moderator & parts slinger
Joined: Feb 2007
Posts: 50,132
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From: S/W Missouri, Polk county
As I understand it on the drum or disk brake front end, the small (front) resevoir on the master cylinder goes to the rear. The larger (rear) reservoir goes to the front brakes.
And yes with the master cylinder lid off, the pressure from pushng the pedal (which causes the piston in the master cylinder to move) will fountain fluid all over and up. Have your bleeder helper PUSH SLOW on the pedal, hold it, then you open the bleed valve. Helper calls "pedal at the floor", you shut bleeder. With the cap off the helper can keep and eye on fluid level. You do NOT want it to run dry.
And yes with the master cylinder lid off, the pressure from pushng the pedal (which causes the piston in the master cylinder to move) will fountain fluid all over and up. Have your bleeder helper PUSH SLOW on the pedal, hold it, then you open the bleed valve. Helper calls "pedal at the floor", you shut bleeder. With the cap off the helper can keep and eye on fluid level. You do NOT want it to run dry.
Laughing Gas
Joined: Feb 2011
Posts: 995
Likes: 317
Correct Large reservoir is for the front discs. The dual piston caliper requires significantly more volume than the small wheel cylinders for drum brakes. If there was no fluid in the reservoir, you have a leak in the front plumbing or calipers. Storage is horrible on brake systems. Not sure how long it was in storage and how long before that the brake system was serviced but if you are planning on driving it, you should consider a full brake system rebuild.
Lead Driver
Joined: Oct 2018
Posts: 7,840
Likes: 2,347
You guys in higher moisture areas really should change over to DOT 5 fluid. being silicone it repels water rather than absorb it .
Some say it won't mix with DOT 3, this it true it's like oil and water but it will work with it just fine they're both brake fluid should you not get it completely out. others say it has a spongy feel to the brakes, not true .
I switched all my classic vehicles to it mainly because it won't harm paint . no more fear of getting DOT 3 paint remover damage. I've been using it for 15 years now and if there's a downside I haven't found it yet.
Some say it won't mix with DOT 3, this it true it's like oil and water but it will work with it just fine they're both brake fluid should you not get it completely out. others say it has a spongy feel to the brakes, not true .
I switched all my classic vehicles to it mainly because it won't harm paint . no more fear of getting DOT 3 paint remover damage. I've been using it for 15 years now and if there's a downside I haven't found it yet.
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