Master Cylinder weeping????
Thread Starter
|
Senior User
Joined: Aug 2010
Posts: 217
Likes: 0
Master Cylinder weeping????
1974 F250 Power Drum Brakes.
The master Cylinder is weeping and I can't find out why. You can see in the photo that the entire MC is wet. The truck has been sitting in the garage for a couple of weeks after I power washed it. That cleaned the MC and it dried.
Now it came back. Today a drop of brake fluid fell on my arm, but I can locate the leak.
Also, take a look at the MC fitting is that correct. It looks like the PO changed the MC and adapted fittings to work with the existing brake lines.
The master Cylinder is weeping and I can't find out why. You can see in the photo that the entire MC is wet. The truck has been sitting in the garage for a couple of weeks after I power washed it. That cleaned the MC and it dried.
Now it came back. Today a drop of brake fluid fell on my arm, but I can locate the leak.
Also, take a look at the MC fitting is that correct. It looks like the PO changed the MC and adapted fittings to work with the existing brake lines.
Lead Driver
Joined: Apr 2011
Posts: 6,399
Likes: 40
From: El Dorado, Arkansas
The seal under the cap could be bad (may need replacing).
The wire bail that holds the cap onto the MC may not have enough tension to tightly seal the lid/seal to the top of the MC casting.
There's also a small vent in the top of the cap. Make sure it's not blocked.
IF fluid is leaking out the back of the MC (where it bolts to the booster), it means the secondary seal of the primary MC piston is bad. IF it's leaking here, the MC will have to be replaced. If it's leaking here and has leaked brake fluid over into the booster, the booster will have to be replaced too. --brake fluid will attack and deteriorate the diaphragm of the booster.
The wire bail that holds the cap onto the MC may not have enough tension to tightly seal the lid/seal to the top of the MC casting.
There's also a small vent in the top of the cap. Make sure it's not blocked.
IF fluid is leaking out the back of the MC (where it bolts to the booster), it means the secondary seal of the primary MC piston is bad. IF it's leaking here, the MC will have to be replaced. If it's leaking here and has leaked brake fluid over into the booster, the booster will have to be replaced too. --brake fluid will attack and deteriorate the diaphragm of the booster.
Thread Starter
|
Senior User
Joined: Aug 2010
Posts: 217
Likes: 0
I don't think it's the hold down clamp, that was my first thought since its weeping from the top down, but it's tight. Maybe the breather hole.
In the picture, you can see moisture at the bottom of the booster. If leaking from behind the MC the fluid maybe going to Booster. In order to take off the MC, what are the steps?
Does just pull out OR does the push rod on the other end have a circle that goes around a rod that connects to the brake pedal???
Let me know the procedure on this. Thanks!
In the picture, you can see moisture at the bottom of the booster. If leaking from behind the MC the fluid maybe going to Booster. In order to take off the MC, what are the steps?
Does just pull out OR does the push rod on the other end have a circle that goes around a rod that connects to the brake pedal???
Let me know the procedure on this. Thanks!
Lead Driver
Joined: Apr 2011
Posts: 6,399
Likes: 40
From: El Dorado, Arkansas
A MC on a power brake booster doesn't have a small retaining clip, on the tip of the booster output rod, like you would find on the tip of an input rod on a manual MC.
A vacuum booster will have (2) rods; an input rod from the brake pedal to the back of the booster and an output rod from the front of the booster to the MC.
To remove the MC from the vacuum booster, you would just simply take the (2) MC nuts loose from the booster studs, take the (2) brake line fittings loose from the MC ports and slide the MC off.
Of course, unplumbing/opening the hydraulic system means the entire system will have to be bled out after the MC is mounted back to the booster.
A vacuum booster will have (2) rods; an input rod from the brake pedal to the back of the booster and an output rod from the front of the booster to the MC.
To remove the MC from the vacuum booster, you would just simply take the (2) MC nuts loose from the booster studs, take the (2) brake line fittings loose from the MC ports and slide the MC off.
Of course, unplumbing/opening the hydraulic system means the entire system will have to be bled out after the MC is mounted back to the booster.
Thread Starter
|
Senior User
Joined: Aug 2010
Posts: 217
Likes: 0
I'm gonna replace the MC because I think just buying a cap and seal is wasted money, besides another good reason to replace it is to look at the Power Booster, I'm hoping the brake fluid didn't corrode it.
Elder User
Joined: May 2004
Posts: 836
Likes: 2
From: Shreveport, LA
Trending Topics
Cargo Master
Joined: Dec 2008
Posts: 3,217
Likes: 322
From: SW PA
My first thought was just condensation if you don't have the truck in a temperature controlled environment and recently saw a large temp swing.
Since you say it is definately brake fluid - it has to be from teh seal under the cap. I have found some rubber seals are better than others. I ended up with the most expensive one from Advance but forget the manufacturer.
Since you say it is definately brake fluid - it has to be from teh seal under the cap. I have found some rubber seals are better than others. I ended up with the most expensive one from Advance but forget the manufacturer.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
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
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
Hotshot
Joined: Feb 2004
Posts: 10,809
Likes: 2,605
From: The Shenandoah Valley
I put a F350 master cylinder and booster on my '77 F-150 in 2013 and the MC came with a new cap and gasket ..... and for the life of me, I could not get it to stop splash-leaking until I took the old rusty cap and still very pliable soft OEM gasket/diaphragm that was on my '77's original MC (and cleaned caps surface rust and painted it on outside, inside the oem was as clean as the new one) and swap them onto the new MC .... no more splash leaks. The oem had never shown signs of leakage. I found that the oem was thicker gage steel.
Thread Starter
|
Senior User
Joined: Aug 2010
Posts: 217
Likes: 0
I power washed the engine compartment before it sat for 3 weeks in the garage. During that time, I noticed how the MC and booster looked dried, then this past week I noticed it was all soaked as in the above picture. I didn't drive it so splash leaking is not the problem. I could be either the top rubber seal (I've noticed rust around the rim) or a hair line crack some were. I did bleed the brakes a few weeks ago and topped it off, so the fluid is at the very top. In fact today it's still at the top and the MC is soaked.
Thanks to all for trying to help me figure this mystery out.
To be safe I'll buy another MC. A rebuilt one at Autozone is $16.99, almost the same price for a cap.
Thanks to all for trying to help me figure this mystery out.
To be safe I'll buy another MC. A rebuilt one at Autozone is $16.99, almost the same price for a cap.
Hotshot
Joined: Feb 2004
Posts: 10,809
Likes: 2,605
From: The Shenandoah Valley
Fluids expand with increases in temperature. Like ultraranger said, about 1/4" below lip is proper.
Mine has always been that tight .... always have had to use a lever of some type to pop it loose.
Thread Starter
|
Senior User
Joined: Aug 2010
Posts: 217
Likes: 0
The PO stated that he found one side of the MC empty after is sat for a while.
I figured, just buy a new MC and be done with the problem. It only cost $16.99.
I put a new MC in today!
I'd have to say this thread is done and I thank all for their support
I figured, just buy a new MC and be done with the problem. It only cost $16.99.
I put a new MC in today!
I'd have to say this thread is done and I thank all for their support