75 that doesnt want to stop..

[potenziata]

hi everyone...got an issue with my v6 75. my brakes are attrocious lately, and its becoming hard to work out why they are so terrible. its kind of hard to explain what its doing, or not doing, but here goes.

it has a weird vague pedal, like a 'wooden ' feel to it, and just has no stopping power. its not like a typical master cyl failure, (theres no real dramatic pedal sinking, etc..), it just feels like it doesnt want to stop. they work reasonably sufficient on light stopping duties, but if you roll on more pedal pressure for harder braking, it doesnt seem to respond to the extra pedal pressure..and it just has a weird, awful feel to the pedal, (which kind of transfers through the whole car), and doesnt want to stop. ive had the front calipers apart, no sticky pistons, ive replaced the front brake hoses too, and the rear calipers i rebuilt maybe a few years ago??? No fluid loss anywhere either, it has decent pads in it, and has near new rotors on it..(it just doesnt seem like a friction material issue either), more like a booster problem (although it does appear to be working ok ), or a hydraulic problem of some sort...???? anyone struck this before?? any thoughts on this rather annoying problem would be much appreciated!!!

[alfahaze]

Sounds like pad material has transfered to the discs - I would try to use the handbrake at lights after extreme stopping to avoid pad transfer onto the front discs for a week or so. What brand front disks are you using? and what brand/compound brake pads? Also, can you actually lock the front wheels during the 'woody' part of the pedal travel if you press really, really hard?

Is this a milano with ABS? were you from?

[potenziata]

Originally Posted by vantasticc

Is this a milano with ABS? were you from?

it has mintex 1144' pads in the front, not sure what rotor brand...??they arent slotted or drilled..just standard replacements that are affordable here in oz...my first thoughts after i got these mintex pads and new rotors, was that the steel was too 'hard' in the discs...so i went back to my local brake supplier where i got them from, telling him it still didnt stop, and he said , look somewhere else, cause it wouldnt be the discs..??? and asured me the mintex pads should make it stop really well......mmmm...if i try real hard after theres a bit of heat in the pads..i suppose i could get it to lock the fronts....but i'd nearly have to use two feet on the pedal!!! and no, it doesnt have ABS....i feel like it could be a hydraulic 'restriction' somehow, it just feels like the pressure you put on the pedal, doesnt equate to the way it stops.......not even close. i remember years ago, it was one of the best braking cars i'd even driven!!they were utterly amazing as a standrd set up!!! i want my glorious alfa brakes back!!!

[potenziata]

Originally Posted by alfahaze

Sounds like pad material has transfered to the discs - I would try to use the handbrake at lights after extreme stopping to avoid pad transfer onto the front discs for a week or so. What brand front disks are you using? and what brand/compound brake pads? Also, can you actually lock the front wheels during the 'woody' part of the pedal travel if you press really, really hard?

mmmm..read the reply that i gave to 'vantasticc' above, that is the reply i sent to you both.......mmmmmmm...any thoughts lads..???

[alfa101]

check your brake limiter is not stuck

[veesix75]

I used 1144's in my race sud with standard discs, they were useless and felt just like you describe...wooden.

They are a semi circuit pad and I wouldn't use them on the road.

They are the worst pad I have ever come across.

For road use, I'd go for a decent Ferodo or Red Line (depending on where you are). For racing I now use Ferodo DS3000. For fast road the DS2500 might work, but you need to get heat into them.

Anything that is designed for track use needs heat, so unless you drive like a maniac on the road, then go for normal pads for road use.

For fear of repeating myself, the 1144's are absolutely terrible, ditch them.

[ally]

Check the one way valve to the brake servo is working and not letting manifold gas into the servo at low engine speeds.

Bet that'll fix it.

[panda4x4]

Try EBC green pads and check out your servo.
When were the flexible hoses last changed? They might be delaminating internally causing restrictions

[ally]

The flexible hoses could collapse but it is unusual for more than one to fail at a time. This would likely cause the brakes to pull (front) or premature rear locking (rear hose). Simply moving the caliper pistons or bleeding the brakes would also highlight that. I'm not dissagreeing with the possibility. I just don't think it is likely.

Good bit of lateral thinking though.

[potenziata]

mmmm..thanks fellas, im going to change the rear brake hose first, (still original i think..oops..), then make sure its all good hydraulically, from the master cyl back.....then if that checks out...im going in for a look at the booster assembly, then all things brake related, no matter how small!!! i bet what ever it is thats causing this...will be soooo laim...as it always is!!!!!! little things on these cars make or break them...in every department!!!!! its testimony to how precise they are....if everything is not working the way it was designed to, they arent worth driving, not even around the block. but when everything is right....there is no car on the planet that offers a more adranalin pumping, amusing, and rewarding drive......im ramblin now....better go.........

Originally Posted by veesix75

I used 1144's in my race sud with standard discs, they were useless and felt just like you describe...wooden.

They are a semi circuit pad and I wouldn't use them on the road.

They are the worst pad I have ever come across.

For road use, I'd go for a decent Ferodo or Red Line (depending on where you are). For racing I now use Ferodo DS3000. For fast road the DS2500 might work, but you need to get heat into them.

Anything that is designed for track use needs heat, so unless you drive like a maniac on the road, then go for normal pads for road use.

For fear of repeating myself, the 1144's are absolutely terrible, ditch them.

What he said, I use DS2500 pads on my 75 (and scoob) and think they are very good but need to be warmish (is that a word) good luck mate

[alfahaze]

One quick question , I don't mean to offend, but you did clean the discs VERY VERY VERY carefully with brake cleaner when you replaced the pads and discs? If not, it can take ages for the pads to bed in, and you get that woody feel, and no matter how hard you press you will never lock the fronts- they just judder you to a stop.

The best brake pads I ever tried on any alfa were the original Asbestos / Metallic Alfa ones. Green stuff were quite good, but I found them to lack bite at high temperatures, and first thing on wet mornings - very kind to the discs though.

-Hazel

[potenziata]

Originally Posted by alfahaze

One quick question , I don't mean to offend, but you did clean the discs VERY VERY VERY carefully with brake cleaner when you replaced the pads and discs? If not, it can take ages for the pads to bed in, and you get that woody feel, and no matter how hard you press you will never lock the fronts- they just judder you to a stop.

The best brake pads I ever tried on any alfa were the original Asbestos / Metallic Alfa ones. Green stuff were quite good, but I found them to lack bite at high temperatures, and first thing on wet mornings - very kind to the discs though.

-Hazel

no offense taken!! im always really anal with cleaning friction surfaces before and during assembly, so i would doubt it would be that.

and you know what? i couldnt agree more on the whole pad thing. those original asbestos alfa pads were the most phemonenal pad ive ever used too. they were on the car when bought it ten years ago, and ive tried just about every kind of off the shelf pad since, and they have all been utter garbage! i winge to every parts supplier i get new pads from, saying 'i just want it to stop like it used to when it had the alfa pads in it, how hard is it to get the friction material right..for @##@'s sake!!!
Even the expensive designer 'street/ track' pads havent got a patch on those early factory pads...they were perfect for fast road use. perfect. near impossible to make a 75 stop the same without them!!!!!! gota keep on searchin i suppose....
ive even contemplated putting monster brakes on it, to get the same stopping efficiency i used to get with the standard set up!!! crazy. thanks for the tips anyway. Rick.

[ally]

The best brakes I ever had on any car- until I drove a TVR Chimaera, was my old 1.6 116 Giulietta. I had standard Ferrodo pads- medium compound front and soft compound rear. They worked over a large enough temperature range to have all the discs glowing (about the same colour of street lamps) and were still effective. That was probably 1992.

I still think it is the non return valve on the servo hose on your car, Potenziata.

[alfahaze]

The Nurburgring 75 guys use Pagid Red on the front, and Ferodos on the rear - and they insist on original ATE discs all round. On my previous Montreal the brakes were rubbish, and I tried all sorts of pads - rebuilt all the calipers, proportioning valve, new disks, new master cylinder, new one-way valve, stainless hoses - they were still rubbish when I finished - the only thing I didn't replace was the Vacuum servo - as they were not available. The only change that made them feel less 'woody' was a change to the idle setting - go figure.

[ally]

Exactly, because there is less inlet manifold depression whilst idling, there is less servo effect. This will happen more if the one way valve that I've been harping on about is defective.

Here's a good test. Engine off, press footbrake repeatedly until servo is exhausted. Put left foot on brake with normal stopping pressure. Start engine. Pedal should be sucked down within 1-2 seconds, and then not move further. With right foot on throttle, raise engine speed to between 1500 and 2000 rpm. If the brake pedal moves any further, this can suggest a servo valve or servo fault. The next thing to do is to remove the valve from the servo and hopefully, with breath, air will only move back to the engine and you cannot suck air from the inlet manifold. If you can, the valve is U/S. If not, suspect a weak brake servo.

[downunder]

I can agree with everything that has been said so far.... my brakes are currently weak, I have tried all the things mentioned, and I am waiting for someone to reproduce the old Alfa pads. I thought the Lucas pads were good, but recently the brakes have required too much pedal pressure.
My problem is that I have already cleaned and checked the one way valves on both the booster and the manifold, and it hasn't helped.

I'm wondering if there isn't a blockage in the piping around the MC, or maybe the proportioning valve.

Any more ideas?

[scaligeri]

I have green pads on mine no idea who makes them,but sometimes when you hit the brakes pedal goes hard and she keeps rollin,makes ya poop if you forget

[ally]

The proportioining valve can seize, but that just tends to allow extra pressure reaching the rear brakes, and can cause premature rear brake locking.

I really though it was the valve, but as it's not, I think the servo is possibly weak. I had a Giulietta once and it simply had poor brakes. I checked everything, changed brake linings as necessary but nothing worked. It was sorted when I changed the servo over from my older car. The car had not been bumped or anything, so I just put it down to being faulty. I have noticed other cars with apparently varying servo effect. Is there anyone local to you how could help with a comparison on this one?

Just before I completely overlook it, are you sure the servo hose does not leak? THis may be indicated by the engine idling slightly differently of late. Are you sure there are no wheezing sounds when the brake pedal is activated? This could indicate a servo leak.

[downunder]

If I run the car to ensure that vacuum is available, then shut it off, and then begin to remove the one way valve on the booster, there is a lot of vacuum that is released before the valve comes out. I'm guessing that means there is vacuum available. It doesn't however, tell me whether it is enough! I wonder what appropriate leak-down is? Maybe if I wait 30 minutes and see if there is still vacuum.

The proportioning valve still worries me. If it is biasing to the back brakes, that would greatly reduce the stopping effect, because the fronts take something like 80% of the force. At the track, I can alway stop the car really well, with no front or rear lock ups, it is just that the pedal effort is too high, and very different to what is was several years ago.

[alfa101]

If is not servo i have replaced master cylinders on 75 s befor the brake had much more bite. I have just done this to my 75 for mot major improvement with all standard discs and aftermarket pads

[ally]

Another way to check the valve (which I now think is ok) is to disconnect the valve out of the servo. Hook it up to a vacuum guage, note the depression, switch off the engine and note the rate of decay. It should hold vacuum without a significant drop for a couple of minutes. Likewise, when the engine is revved, it should hold maximum depression value and not fall back when the engine idle returns to normal.

I'd wouldn't worry about the limit valve for the rear brakes. If you brake hard, and the rear locks up, it is faulty. Another way of checking this is to remove the rubber rear cover. Have someone press the brake pedal with engine running. The center piston in the valve should be felt to move out slightly when the brakes are applied harder than normal braking force. At that poiint, no further fluid pressure reaches the rear brakes.

I always felt the limit valve was set up too conservitively on the 75. I got an adjustable one, it broke, so I ended up modifying the standard valve to gain a little more rear brake bias to really make my 75 stop quickly.

[downunder]

It's not that long ago (2 years) that I installed a new MC. I remember it just bolted on, and nothing seemed a problem. Is there some sort of adjustment that I was meant to do while installing it?

Also, what is everyones favorite brand? Are there any to steer clear of?

[alfahaze]

This website is useful :

http://www.kfz-tech.de/Engl/Bremskraftverst.htm

It shows the two extra valves inside the servo body. One valve and the spring is to ensure the brakes don't lock on, but the other one will meter the the amount of fresh air let in through the filter by your foot. I summise that if gone bad (clogged/stuck etc) it might reduce your pedal effort to MC rod transfer ratio. I like the animation too!

-Hazel