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  #1  
Old May 8th, 2011, 06:53 PM
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Neill Thornton
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Brakes - bad MC?

OK folks, latest issue for today...

My brakes have been getting progressively shittier on the 90 since I bought it a few months ago. They were to the point that I would put the pedal to the floor and come to a stop from 45 in about 50-75 feet with no more pedal travel to be had.

Since it seemed to be a gradual thing I figured I had gotten air in from somewhere, and went about bleeding the brakes. I have now done the regular 2-person bleeding 3 times with no change.

So I figure maybe its time to do a fluid flush and do a very thorough bleed. I get a Mityvac power bleeder and start by sucking all the nasty fluid out of the reservoir and re-fill with DOT 3 which is what the book says to use. I notice small floaties in the reservoir which have me worried, but I decided to carry on anyways. I have a feeling this was a mistake.

I start by going to the driver's side wheel first as the workshop manual says. I try to use the mityvac and nothing will come out, to the point where I am just sucking in air from around the threads of the bleed valve. I decide "screw this" and get inside and pump the brake pedal. Fluid does come out, and I flush out that line. I tighten that fitting up and move to the front right. I am not able to vacuum out anything again, but this time I can't get anything out with the pedal either, and mind you the fitting is clearly loose. The pedal became rock hard, even with the engine running for vacuum.

Now I am worried. I decided to check out the back right and I have the same problem.

So I can't get fluid to at least 2 of my wheels, so both brake circuits have issues. This makes me think that the M/C has problems. It looks original. I don't know what kind of fluid was in it before, but it was serviced at Falconworks in Tuscon and they seem to have their shit together.

I took it for a short drive up the street and I still have some brakes, about what I had before. It doesn't pull to one side or the other, just doesn't stop.

Does this sound like a MC problem? Could some of those black floaties in the reservoir been master cylinder bits? I am worried I sucked some of that into the system and it's now in a line somewhere.

Ideas? I tried searching but nothing came up with this kind of problem.
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  #2  
Old May 8th, 2011, 07:14 PM
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Jason England
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I wonder if the floaties are from a flexihose that collapsed under vacuum and swells under pedal pressure
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  #3  
Old May 8th, 2011, 07:16 PM
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Neill Thornton
1984 D90 300 Tdi / 1965 Series IIA
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Good question, I hadn't thought of that. I didn't see any obviously deformed flexihoses. I will have to wait until I have an assistant and check and see if anything is bulging under pressure.
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  #4  
Old May 8th, 2011, 07:40 PM
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John B.
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Vacuum bleeding is kind of crappy. Pressure bleeding is a better way to go.

You may have something bad in the system like bad hoses or a cylinder. What pads are you using?
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Old May 8th, 2011, 08:44 PM
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Ze
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Hey Neil. My Defender takes DOT4. You might want to check what type of fluid it requires again.
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  #6  
Old May 8th, 2011, 08:56 PM
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John B.
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DOT3 or 4 won't matter. It will still function the same.
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Old May 8th, 2011, 08:57 PM
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Ive always bled brakes with the nipple furthest from the MC. RPS RDS FPS FDS for a LHD truck, it has always worked for me. Id look to the brake hoses aging, I had issues with the clutch flex line on my 90. Seems vacum bleeding recirculates the bullshit. When I did the lines on my Classic they appeared to have the fluid from 1991, it was pretty bad. I concerned that I would have loosened something up and caused a caliper or MC to fail, bleeding the brakes has been the best thing Ive done to it.
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Old May 8th, 2011, 09:49 PM
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Neill Thornton
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Hey Ze, yeah I went all back over it and it says DOT 3. But some googling says DOT 3 and 4 are pretty much the same stuff except the boiling point. The danger is DOT 5 which is something else entirely.

It could just be that DOT 4 didn't exist in 1984 when they built the thing, or wrote the workshop manual.

Red90 - Not sure what kind of pads are on it, it's whatever the PO had on it.

Also, regarding the flexihoses, this whole truck was rebuilt just a year or two ago, so if the hoses didn't get replaced I would be very suprised. They didn't look bad just glancing at them during the bleedings.
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Old May 8th, 2011, 10:15 PM
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I don't know about drum brakes would a wheel cylinder cause problems
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Old May 8th, 2011, 10:29 PM
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Neill Thornton
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I guess I should add that these axles are, from the best guesses out there, from a Disco 1. Disc brakes all around.
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  #11  
Old May 8th, 2011, 11:00 PM
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John B.
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You cannot really tell hose condition from the outside as there are layers. It is not "normal" for people to replace hoses, so a rebuild does not mean anything.

I'd get a set of braided teflon hoses regardless. They are cheap and better. Get a pressure bleeder for flushing. You will never know what you did without one.

http://store.motiveproducts.com/euro...-0100-p34.aspx
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Old May 8th, 2011, 11:07 PM
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Neill Thornton
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Quote:
Originally Posted by Red90 View Post
You cannot really tell hose condition from the outside as there are layers. It is not "normal" for people to replace hoses, so a rebuild does not mean anything.

I'd get a set of braided teflon hoses regardless. They are cheap and better. Get a pressure bleeder for flushing. You will never know what you did without one.

http://store.motiveproducts.com/euro...-0100-p34.aspx
Is that the right bleeder? I am going to buy one right now if it is.
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  #13  
Old May 8th, 2011, 11:48 PM
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John B.
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Yes, or you can get the 0109, http://store.motiveproducts.com/blac...-0109-p21.aspx with the aluminum adapter.
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  #14  
Old May 9th, 2011, 12:20 AM
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Neill Thornton
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Thanks man, ordered.
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  #15  
Old May 9th, 2011, 05:50 AM
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Ian Gregory
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I've run into the problem of a bleed nipple or caliper drilling being blocked as well a number of times. Most times its just the nipple that's blocked in which case just clean it out with a small bit of wire or just get new ones. Last time I bought some I got them from Checker/O'Reilly and it was a ford appllication (sorry, can't remember which). I just matched the thread.

If they didn't replace the hoses or rebuild the calipers and the systems full of crap there is also the chance the passage behind the bleed nipple has some crap in it and/or may be blocked. I've had it where you can completely remove the nipple and stand on the brake pedal and nothing comes out.

Since you're bleeding the brakes anyway. Just remove the nipple and run a drill bit down the caliper drilling by hand then flush some fluid through it to clean out the crap. If its really bad then you can always split the caliper and do it from the back side as well.

Pressure bleeder is the way to go. Work from furthest to nearest from the MC as has been said but make sure all the bleed nipples are flowing before you do the final bleed.
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  #16  
Old May 9th, 2011, 08:11 AM
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kevin
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Back to the original problem, could you be more specific about the condition of the fluid in the mc? Was it completely contaminated or discolored? Any rust present?
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