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How does a bad master cylinder act?

I am starting to suspect my MC, as it is the connection between the brakes and clutch which have both been giving me issues since new. Does this stuff sound like an MC issue?


New- won't let me into 1st about 1/10 times at a stop, about 1/5 times it went in it would kick out when release clutch
800 miles- the 1st gear issue got a little better but started having issues with 2nd and 3rd
1200 mile- brakes spungy but got a little better, clutch was ok then started to hang half way down
1500 miles- bled clutch and it was full of muck and the 2nd and 3rd issues went away
2000 miles- started refusing to go into 3rd above 5500 rpm when warm. I figured out how to finesse it in, which almost always works. 1st starts having some issues again
2500 miles- brakes would surge really bad and not slow down the car right - continues until I get it home and have time to rebed the brakes (today). They are about 95% better now as far as the surging after rebedding, but it still wiggles a bit on hard braking which it has done since new.

I kicked on ABS on purpose today, and it did not feel like the surge. The surge does not have the same mechanical feel, for lack of a better way to describe it, and is not as intense. My rear rotors look odd as well, instead of being smooth the surface rust (like all rotors get when the car sits a bit) has been scraped off in a sun's rays type of pattern. Almost like the pads are skipping as they grip.


Does that sound like an MC issue? I have heard rumors of Ford replacing them on a few Bosses. Also one of my bleeders on the Brembo is leaking, from the stains looks like it has been a while. The bleeders on that one were super tight from the factory and had the most air in them.
 
Cali, this is just my 2 cents as a tech. Typically when we have a bad MC the oil is leaking into the booster through the rear piston seal. In a pressurized system if oil can escape, air can intrude. You said your bleeder leaking. Everytime you press the brake and pressurize that bleeder it also experiences somewhat of a negative pressure as the piston is pushed back away from the rotor. (oil goes out, air sucks in) I would say say eliminate this variable and diag from there. Again IMO :)
 
Thanks, I am going to have them take a look at the bleeder when I bring it in for oil/trans fluid. But it was not the only bleeder with air, and it should not affect it all the way up to the clutch.

I had a MC go bad on my Bronco, it was spitting fluid out from where the reservoir rail connects to the main disk. I had it towed in as soon as I noticed it so did not get to feel if it caused any issues with the brakes. This one is not leaking, and there is only a very small amount of leak at the bleeder. After bedding the pads again today it was "moist" around the bleeder, but no actual drips.

I have already had the car in 3 times iirc where I had them check the clutch and asked them to look at the MC, getting tired of bringing it in and getting no results but they keep claiming they can't get it to kick out of gear or do anything else weird. I have a manual with 200k+ miles and done my own prep brakes and prep work on several track cars now with no issues so I really doubt it is a me driving issue. The MC is the only thing that would connect the two.
 
Sorry to hear that Cali. Three times is ridiculous. At my dealer, on the first comeback, we typically keep the car until its fixed. Sometimes this requires extensive driving of the customers vehicle, but this is better than hearing the dreaded phrase "lemon law" that luxury car owners like to throw around alot. Hopefully you can get it worked out :'(
 
I took it to a different dealer the last time, I don't want my money back I just want my car to work right. FWIW both dealers refused to do the TSB for the tranny fluid swap because they said the tranny was acting normally. I finally just told the 2nd dealer to do the fluid and I will pay for it and he said he will talk to his boss about getting it under the TSB since I seem serious... If they don't fix it this time, I am bringing it to a dealer my friend has bough 3 GT500s and a Boss from plus some other cars. He said he would introduce me to his guy and make sure it gets done, but the dealer is pretty far.
 
Smack, I took some pics. The reservoir is leaking, a little bit from the cap and more from where it hits the rail. You can also see the gunk in the fluid, it was nice and clean a few hundred miles ago. No burn outs or anything else that should get that much burned fluid in the MC (at least I think it is burned fluid).

The caliper too, I cleaned it real good when I washed the car, so I could see how much it was leaking in a set amount of driving. It is just a little moist but this is in less than 50 miles in the hills.

Valve cover to show how far the fluid spurted.


I am pretty sure this is not "normal" as the dealer told me ::)

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Great pics. Definately NOT normal. I dont understand why some dealers have such a hard time doing warranty work. ??? This should have been a pretty obvious fix, especially after you explained that air was entering the system. Maybe a call to HQ is order if these sorry dealers cant produce sufficient results!!
The fluid in the resevoir appears to be aerated already. Air contains moisture and brake fluid is designed to absorb moisture. Moisture also lowers the boiling point of the fluid and the snow ball keeps rolling.
 
The MC is the only thing I could think of that connects all the issues I am having (other than quart/500 miles oil consumption) so I have been keeping an eye on it. It has leaked from the cap a bit before, but not like this. It was just barely enough to notice dripping down the side. I did notice if I pump the clutch, that gunk comes up into the reservoir even just a few days after I bled it. Combined with the clutch getting stuck half way up and pulsating, refusing to go into gear, and grinding. Two separate dealers have said it is normal, but this is bad enough I am assuming they will at least take a real look at it now. Still leaves the oil consumption and the leaky bleeder but if they do anything with the MC I would assume they will bleed the brakes and then if it leaks again they won't be able to deny it is an issue with the caliper. I don't have any proof of the air that was in the brakes from the factory but I have done enough brake bleeds on various track cars that I am sure of it.

I also remembered, sometimes the brake pedal comes back up slower than normal and sometimes it is pretty soft just driving around town.
 
FWIW the reservoir caps are notorious for leaking and can run down the MC and onto your paint. I'm not saying that's what's going on here and I have no idea what's in your reservoir. Mine does not look like that after several track days. And if the dealer gives you shiznit about swapping in DOT 4 just remind them that's what Ford recommends for track prep in the supplement.
 
Will see what they say. I'm also going to have them do the thing where they put a seal on the dipstick so they can measure oil consumption. So far it has only been me bringing it in and them not noticing anything strange, but now there is visible proof something is amiss. Giving them the benefit of the doubt. Worst case I can call that lady at Ford, I don't recall her name, she helped me with the paint issues though I ended up fixing that myself in the end because I didn't want a respray on a new car.
 
Can somebody do me a really big favor and try pushing the brake pedal, then pushing it again while the clutch is on the floor? Is there a dead spot at the top when the clutch is down that is not there when the clutch is up? It is only like 1/4" or so but it is not there when the clutch is not down.

By dead spot, I mean you can wiggle it with a finger and it just bounces around with no resistance at all, not like the normal soft initial part of the sweep. If I hit it with a finger clutch in/out I can hear the difference, and the brake pedal is a little softer.

I have never noticed this phenomena on my other cars, and went and checked my other current manual car and it does not do it, but it is a 1988 BMW and possibly the design is just different. Dealer says everything is normal, so trying to pinpoint specific ways it is not working right.
 
CaliMR said:
Can somebody do me a really big favor and try pushing the brake pedal, then pushing it again while the clutch is on the floor? Is there a dead spot at the top when the clutch is down that is not there when the clutch is up? It is only like 1/4" or so but it is not there when the clutch is not down.

By dead spot, I mean you can wiggle it with a finger and it just bounces around with no resistance at all, not like the normal soft initial part of the sweep. If I hit it with a finger clutch in/out I can hear the difference, and the brake pedal is a little softer.

I have never noticed this phenomena on my other cars, and went and checked my other current manual car and it does not do it, but it is a 1988 BMW and possibly the design is just different. Dealer says everything is normal, so trying to pinpoint specific ways it is not working right.

I will go out and check now for you.

*EDIT* I just went out and checked for you. There is NO difference in feel between the clutch in or not. There is no wiggle at all. It feels exactly the same whether in or out.
 
As far as the bleeder screws leaking, I have that same issue, but much worse than your pics show. Mine will actully run down the caliper slightly. Also, mine only leak when tracking the car. I believe it is due to the heat in the aluminum caliper and the steel beeders screws. Two different rates of expansion.
 
Lindasy, thanks. I have been doing some research on google and found people with other cars that have almost my exact symptoms. A lot of flushing seems to be the fix, as they seem to all think it is air bubbles inside the MC. My friend says he fixed a similar problem last week in a GT by unbolting the MC and leaning it while applying vacuum and pressure alternating.

06mach1, mine does it on the street. The picture is after at most 50 miles, and I had scrubbed it before that. It will have drips running down the caliper after longer drives. It is the only one that is weeping though, which is the biggest worry about it.
 
CaliMR said:
Lindasy, thanks. I have been doing some research on google and found people with other cars that have almost my exact symptoms. A lot of flushing seems to be the fix, as they seem to all think it is air bubbles inside the MC. My friend says he fixed a similar problem last week in a GT by unbolting the MC and leaning it while applying vacuum and pressure alternating.
No worries man. I dont have as much knowledge as most, but that was pretty idiot proof. Hopefully it is just air and not something worse.
 

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