Brake pedal goes to the floor
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Joined: May 2004
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From: Fergus Falls, MN
Update:
I finally got to pull the truck into the shop. When I pulled the cover the resivor was empty. Soooo, I'm going to fill that up, bleed the brakes again and make sure there's no leaks. Once that's done I'll be better able to asses the brake problem. I still think my master is junk, but time will tell. I fell like a fool for not checking something so simple first.
I finally got to pull the truck into the shop. When I pulled the cover the resivor was empty. Soooo, I'm going to fill that up, bleed the brakes again and make sure there's no leaks. Once that's done I'll be better able to asses the brake problem. I still think my master is junk, but time will tell. I fell like a fool for not checking something so simple first.
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Joined: Apr 2008
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From: Palmyra, Nebraska
Not at the moment.
My comment was a general statement, based on experience with the older Mopar cars and light trucks.
The "Diesel" MC is a 1-1/8" bore.
I have found that there are some later Dodge ones with 1-1/4" bores and one from a Chevy application with 1-5/16" bore, but they will not mount to the brake booster without some bolt spacing mods and possibly a small spacer between the master and booster.
If you can't increase the master size, decrease the slave (wheel cylinder) size instead.
Mark.
My comment was a general statement, based on experience with the older Mopar cars and light trucks.
The "Diesel" MC is a 1-1/8" bore.
I have found that there are some later Dodge ones with 1-1/4" bores and one from a Chevy application with 1-5/16" bore, but they will not mount to the brake booster without some bolt spacing mods and possibly a small spacer between the master and booster.
If you can't increase the master size, decrease the slave (wheel cylinder) size instead.
Mark.
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Joined: Dec 2010
Posts: 6,838
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From: Land of the Toxic Avenger
It is probably your master cylinder, if you apply the brakes, the pedal is hard at first then sinks to the floor under your foot there is an internal leak and needs to be replaced.
When you get a replacement, try and get a new one and not a re-manufactured but if you must then when they bring it out to you, first pop the cap and make sure the sealing surface to the reservoir is sharp and flat, if it is dull and looks banged up then tell them to bring you another one.
If this surface is not sharp and flat, the fluid will leak out from under the cap and eventually cause rust to eat everything it touches.
I just went through this problem with a master cylinder and booster I got from NAPA.
As good as everyone think NAPA is, these parts are from A1-Cardone the same vendor used by Auto Zone and most small Auto Parts stores.
Oh BTW the first NEW master Cylinder I got from them was also defective, probably nicked the seal on the piston when it was assembled, pedal went right to the floor.
Jim
When you get a replacement, try and get a new one and not a re-manufactured but if you must then when they bring it out to you, first pop the cap and make sure the sealing surface to the reservoir is sharp and flat, if it is dull and looks banged up then tell them to bring you another one.
If this surface is not sharp and flat, the fluid will leak out from under the cap and eventually cause rust to eat everything it touches.
I just went through this problem with a master cylinder and booster I got from NAPA.
As good as everyone think NAPA is, these parts are from A1-Cardone the same vendor used by Auto Zone and most small Auto Parts stores.
Oh BTW the first NEW master Cylinder I got from them was also defective, probably nicked the seal on the piston when it was assembled, pedal went right to the floor.
Jim
Before I tackled my replaced master cylinder issue, I read this post and followed your advice.
I couldn't buy a "new" master anywhere, that's why I put a reman one on last week. Since then the reman one failed. I went to the local Napa and found one there that was new. The reservoir was flat and machined clean as you had said to look for. I thought I was good.... but the new one was bad. 8 hours in 15-20 degree weather sucks.
I put it in, after bench bleeding as in the instructions, and bled the brakes all the way around including the modulation valve in the rear of the truck. Had a great pedal.... for about 30 seconds, then it went right to the floor. Spent several hours, bleeding then re bleeding and wasting 2 quarts of fluid.... all for nothing. Brakes feel good, then go right the floor. The fluid levels in the master reservoir do not change, and there is no leaking anywhere in the system. Not one drop.
I called the Napa and they said they would replace it with another NEW one tomorrow.... and that from time to time the new ones are defective... but very rare. I guess I'm just lucky.
Would you get this "Hard pedal, then nothing" if that rear valve was bad ? I don't see how, as it only affects the rears..... in theory, the fronts would still work, right ? Am I thinking logically here?
Hopefully the NEW replacement will work this time. 2 days in this weather doing this kind of work is enough for me. .... Keeping my fingers crossed.
If it doesn't work, i'll be having a bonfire in my driveway, so all of you guys are welcome to bring marshmallows or hot dogs on sticks. One old dodge will be torched if this doesn't work.
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Joined: Apr 2008
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From: Palmyra, Nebraska
NJTman, here's a simple test to check for internal leaks:
Remove the brake lines from the master and put plugs in the line ports and see if it acts the same as it does now.
A rear wheel cylinder leaking by the cup seals CAN act the same way as an internal master cylinder leak.
You'd be surprised how much brake fluid the dust seals over the ends of the wheel cylinder can hold before they leak.
I'm inclined to believe it's the master, though.
Mark.
Remove the brake lines from the master and put plugs in the line ports and see if it acts the same as it does now.
A rear wheel cylinder leaking by the cup seals CAN act the same way as an internal master cylinder leak.
You'd be surprised how much brake fluid the dust seals over the ends of the wheel cylinder can hold before they leak.
I'm inclined to believe it's the master, though.
Mark.
Registered User
Joined: Dec 2010
Posts: 6,838
Likes: 1,683
From: Land of the Toxic Avenger
NJTman, here's a simple test to check for internal leaks:
Remove the brake lines from the master and put plugs in the line ports and see if it acts the same as it does now.
A rear wheel cylinder leaking by the cup seals CAN act the same way as an internal master cylinder leak.
You'd be surprised how much brake fluid the dust seals over the ends of the wheel cylinder can hold before they leak.
I'm inclined to believe it's the master, though.
Mark.
Remove the brake lines from the master and put plugs in the line ports and see if it acts the same as it does now.
A rear wheel cylinder leaking by the cup seals CAN act the same way as an internal master cylinder leak.
You'd be surprised how much brake fluid the dust seals over the ends of the wheel cylinder can hold before they leak.
I'm inclined to believe it's the master, though.
Mark.
I just put all new brakes, whl cyl's, spring kits, steel lines in the rear. I just can't imagine the new cylinders are leaking, but anything is possible.
Once i put the new new replacement master on, I'll know Otherwise, look for the smoke, and you'll be able to find me in no time
Thanks again..
T.
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Joined: Jul 2009
Posts: 5,311
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From: Phoenix AZ
Jim,
Before I tackled my replaced master cylinder issue, I read this post and followed your advice.
I couldn't buy a "new" master anywhere, that's why I put a reman one on last week. Since then the reman one failed. I went to the local Napa and found one there that was new. The reservoir was flat and machined clean as you had said to look for. I thought I was good.... but the new one was bad. 8 hours in 15-20 degree weather sucks.
I put it in, after bench bleeding as in the instructions, and bled the brakes all the way around including the modulation valve in the rear of the truck. Had a great pedal.... for about 30 seconds, then it went right to the floor. Spent several hours, bleeding then re bleeding and wasting 2 quarts of fluid.... all for nothing. Brakes feel good, then go right the floor. The fluid levels in the master reservoir do not change, and there is no leaking anywhere in the system. Not one drop.
I called the Napa and they said they would replace it with another NEW one tomorrow.... and that from time to time the new ones are defective... but very rare. I guess I'm just lucky.
Would you get this "Hard pedal, then nothing" if that rear valve was bad ? I don't see how, as it only affects the rears..... in theory, the fronts would still work, right ? Am I thinking logically here?
Hopefully the NEW replacement will work this time. 2 days in this weather doing this kind of work is enough for me. .... Keeping my fingers crossed.
If it doesn't work, i'll be having a bonfire in my driveway, so all of you guys are welcome to bring marshmallows or hot dogs on sticks. One old dodge will be torched if this doesn't work.
Before I tackled my replaced master cylinder issue, I read this post and followed your advice.
I couldn't buy a "new" master anywhere, that's why I put a reman one on last week. Since then the reman one failed. I went to the local Napa and found one there that was new. The reservoir was flat and machined clean as you had said to look for. I thought I was good.... but the new one was bad. 8 hours in 15-20 degree weather sucks.
I put it in, after bench bleeding as in the instructions, and bled the brakes all the way around including the modulation valve in the rear of the truck. Had a great pedal.... for about 30 seconds, then it went right to the floor. Spent several hours, bleeding then re bleeding and wasting 2 quarts of fluid.... all for nothing. Brakes feel good, then go right the floor. The fluid levels in the master reservoir do not change, and there is no leaking anywhere in the system. Not one drop.
I called the Napa and they said they would replace it with another NEW one tomorrow.... and that from time to time the new ones are defective... but very rare. I guess I'm just lucky.
Would you get this "Hard pedal, then nothing" if that rear valve was bad ? I don't see how, as it only affects the rears..... in theory, the fronts would still work, right ? Am I thinking logically here?
Hopefully the NEW replacement will work this time. 2 days in this weather doing this kind of work is enough for me. .... Keeping my fingers crossed.
If it doesn't work, i'll be having a bonfire in my driveway, so all of you guys are welcome to bring marshmallows or hot dogs on sticks. One old dodge will be torched if this doesn't work.
Check your rear adjustment...veeeery important...Mark
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