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mpbronso
Dodge Dakota
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8/04/2006
17:20:34
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 Subject: Brake Master Cylinder and Booster
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2000 4.7l CC, 5-speed manual, 4x4
Took the truck into the stealer today on an unrelated issue. Calls back and said the brakes felt funny (I had to agree), they looked into it and said that the master cylinder and booster are both shot and need to be replaced; he mentioned the cylinder was "bypassing" the booster or vice-versa.
Obviously I'm not going to let them do the work on it at $90/hour. I may try and do it myself...but how do I tell if it's really both the booster and cylinder? Or is it common that both go? How do you diagnose each part?
Also, I have been meaning to post for some time because every time I start the truck cold (mostly in the morning) I get a loud thud, seemingly from underneath the truck towards the front (maybe driver's side) after about 5-10 seconds of the engine running. It's happened both when moving and when still.
Is that sound related to the braking issue, or is this something ELSE?
Incidentally, the guy at the dealership tried to suggest that maybe it was time to trade it in. I about blew a gasket. Nobody's taking my truck from me!
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shatto
Dodge Dakota
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8/05/2006
03:32:30
|  RE: Brake Master Cylinder and Booster
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Can't blame them for asking.
Did they say why the brakes became bad?
Any chance this could be partly covered as a safety item. They might help.
Don't go cheap. Lives are at stake.
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Tfw
Dodge Dakota
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8/05/2006
17:00:19
| RE: Brake Master Cylinder and Booster
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Have you had to add any brake fluid recently ? If the master cylinder is leaking into the booster you will need to replace both of them. Don't think your noise is related.
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mpbronso
Dodge Dakota
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8/05/2006
19:20:04
| RE: Brake Master Cylinder and Booster
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Picked the truck up today.
Brake fluid is normal and I've never had to add to it in all 115,000 (mostly highway) miles of having the truck. And I check regularly...
I used the information in my Haynes manual to perform the self-diagnostic tests on the brake booster. Everything checked out.
Anything I could be missing? Incidentally, the tech's notes on my invoice only mentioned the BOOSTER, not the cylinder. I gotta think these guys are full of it. My brakes feel great to me, I think maybe I was succombing to the power of suggestion...
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mpbronso
Dodge Dakota
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8/07/2006
12:01:18
| RE: Brake Master Cylinder and Booster
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FOLLOW UP:
The tech said the seal between the master and the booster was bad, and the way to tell is by pulling the vacuum port off the booster and sticking something in there to check for fluid.
I did that, used a piece of electrical wire (long, flexible, and won't poke through rubber diaphragm), sure enough there was brake fluid--not a lot, but a little. Also, I noticed wet greasey material and dirt accumulating on the bottom edge of the booster where the two halves are machined together.
I think my booster is still good, but I'm guessing it's got to go sooner or later with the corrosive brake fluid being in there.
I can't help but wonder if the vacuum line isn't sucking some of that fluid back into the engine.
Looking forward to learning how to do this job...
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Kowalski
GenIII
8/07/2006
15:16:59
| RE: Brake Master Cylinder and Booster
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Brake fluid is not corrosive, unless it's been contaminated by water. Anything but dot 5 will dissolve paint; but that's not corrosion.
Lead, follow, or get out of the way
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RaZoR1
Dodge Dakota
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8/08/2006
18:12:41
| RE: Brake Master Cylinder and Booster
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I've been having a problem with my brakes for over a year now. I've replace front flex line calipers pads rotors. My front brakes are BOTH locking up. it only seems to happen when the truck is hot. The pedal starts to get really hard and the front brakes start to seize up. shut the truck off for a few minutes and all is fine, drive fro some more and it happens again. II'm pissed because I'm afraid to take my truck any long distance. I'm starting to wonder if it's the booster or the master. It seems like I'm losing booster vacumn(hard pedal) but why would that APLY the brakes?? Then i think must bwe the master, but I just don't know which to start with. Any suggestions???? 2000 4.7 auto.
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daddio
Dodge Dakota
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8/08/2006
18:31:33
| RE: Brake Master Cylinder and Booster
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did you flush the old fluid out and fill with new? brake fluid will absorb moisture and if there is enough moisture in the fluid when it gets hot it will try to "cook" that water out. that would make the calipers seize.
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RaZoR1
Dodge Dakota
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8/08/2006
19:23:52
| RE: Brake Master Cylinder and Booster
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I am going to try that first.
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Forseti
Dodge Dakota
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8/09/2006
22:31:22
| RE: Brake Master Cylinder and Booster
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Its possiable that the booster is bad. There is a diaphragm inside the booster the pushes a rod that goes into the master cylinder to apply the brakes.. The diaphragm might be getting stuck and not returning to the proper place after you take your foot off the brake thus keeping the master cylinder in the "brake" position
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RaZoR1
Dodge Dakota
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8/11/2006
17:27:58
| RE: Brake Master Cylinder and Booster
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I thought about that but would that situation not make my pedal "soft" as opposed to hard??
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RaZoR1
Dodge Dakota
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8/14/2006
15:41:21
| RE: Brake Master Cylinder and Booster
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Swapped out the fluid this weekend. Man i hope this solves the problem!!!! the fluid looked a little dirty. I'll post back after i take her for a long drive.
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