New Master Cylinder?
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Senior User
Joined: Jan 2009
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From: Texas
New Master Cylinder?
Okay ... so here's the readers digest version of the problem (1985 Ford F250 Supercab 6.9 Diesel Engine 2x4).
1) I started noticing that when I was braking at very slow speeds the rear left tire would lock up. I didn't know what this mean, so I just watched it and since I was still stopping fine and the brake light wasn't on, I didn't do anything.
2) brake light begins coming on. I notice the braking getting sluggish and I'm nearly to the floor to stop the truck.
3) Checked the brake fluid reservoir. The front compartment was empty (but not dry), so I fill it up.
4) after driving on it for a few days, I finally get the time and bleed the brakes.
5) I filled the reservoir in the front to the brim, and after hooking up my popbottle filled with fluid and hose I pressed the pedal down. A geyser errups in that front compartment (I can see it cuz the hood is up and i'm in the cab. I press a few more times and each time, a shot of brake fluid shot up and hit the hood.
So the manual tells me that this means I need a new master cylinder. Has anyone else had this happen? Any tips when fixing? Most of all, can I just get one from the salvage yard to save some money?
Thanks for the help!
Tim
1) I started noticing that when I was braking at very slow speeds the rear left tire would lock up. I didn't know what this mean, so I just watched it and since I was still stopping fine and the brake light wasn't on, I didn't do anything.
2) brake light begins coming on. I notice the braking getting sluggish and I'm nearly to the floor to stop the truck.
3) Checked the brake fluid reservoir. The front compartment was empty (but not dry), so I fill it up.
4) after driving on it for a few days, I finally get the time and bleed the brakes.
5) I filled the reservoir in the front to the brim, and after hooking up my popbottle filled with fluid and hose I pressed the pedal down. A geyser errups in that front compartment (I can see it cuz the hood is up and i'm in the cab. I press a few more times and each time, a shot of brake fluid shot up and hit the hood.
So the manual tells me that this means I need a new master cylinder. Has anyone else had this happen? Any tips when fixing? Most of all, can I just get one from the salvage yard to save some money?
Thanks for the help!
Tim
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From: Virginia
The geyser is normal, you just have to keep the cap on loosely so you won't make a mess. You are losing fluid somewhere in the rear brakes, that's why you are having to fill it, and why the pedal went down, you lost all the fluid and have been pumping air in the lines.
My guess would be the right rear side that is not locking up is leaking fluid out of the wheel cylinder. It's getting brake fluid all over the brake shoes, and they are not stopping like they should, and that's why the other side is locking up. It could be the other way around, though I only usually have locking problems after I try to re-use the old soaked brake shoes. If your leak suddenly stopped, and they shoes are drying out, then that could be causing the locking problem too.
What I would do is pull both rear wheels and check both sides out. If you have a Dana rear, some of them are a pain to take apart since the drum is not separate from the hub, so you have to pull the hub. It's a bigger job than you would think.
My guess would be the right rear side that is not locking up is leaking fluid out of the wheel cylinder. It's getting brake fluid all over the brake shoes, and they are not stopping like they should, and that's why the other side is locking up. It could be the other way around, though I only usually have locking problems after I try to re-use the old soaked brake shoes. If your leak suddenly stopped, and they shoes are drying out, then that could be causing the locking problem too.
What I would do is pull both rear wheels and check both sides out. If you have a Dana rear, some of them are a pain to take apart since the drum is not separate from the hub, so you have to pull the hub. It's a bigger job than you would think.
Thread Starter
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Senior User
Joined: Jan 2009
Posts: 167
Likes: 0
From: Texas
The geyser is normal, you just have to keep the cap on loosely so you won't make a mess. You are losing fluid somewhere in the rear brakes, that's why you are having to fill it, and why the pedal went down, you lost all the fluid and have been pumping air in the lines.
My guess would be the right rear side that is not locking up is leaking fluid out of the wheel cylinder. It's getting brake fluid all over the brake shoes, and they are not stopping like they should, and that's why the other side is locking up. It could be the other way around, though I only usually have locking problems after I try to re-use the old soaked brake shoes. If your leak suddenly stopped, and they shoes are drying out, then that could be causing the locking problem too.
What I would do is pull both rear wheels and check both sides out. If you have a Dana rear, some of them are a pain to take apart since the drum is not separate from the hub, so you have to pull the hub. It's a bigger job than you would think.
My guess would be the right rear side that is not locking up is leaking fluid out of the wheel cylinder. It's getting brake fluid all over the brake shoes, and they are not stopping like they should, and that's why the other side is locking up. It could be the other way around, though I only usually have locking problems after I try to re-use the old soaked brake shoes. If your leak suddenly stopped, and they shoes are drying out, then that could be causing the locking problem too.
What I would do is pull both rear wheels and check both sides out. If you have a Dana rear, some of them are a pain to take apart since the drum is not separate from the hub, so you have to pull the hub. It's a bigger job than you would think.
So how do I tell if I have a dana rear?
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Joined: Jan 2001
Posts: 56,984
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From: Virginia
If your fill plug is located in the rear cover, you have a Dana. If the rear cover is smooth, and the fill plug is on the front driver's side casting, then you have a Ford/Sterling.
If you have a really bad leak, usually you can see dampness on the backing plate and the tire.
If you have a really bad leak, usually you can see dampness on the backing plate and the tire.
