Guest the_dj Posted March 5, 2003 Share Posted March 5, 2003 I tried to include ALL relevant information in this post, and minimize the unrelevant (emotionally induced writing). I am posting my current setup first so as to help reduce repeating myself. Current brake setup: Near stock system from 1978 280Z New stock master cylinder New stock brake booster New stock front calipers New front stock (sized) crossdrilled rotors Stock untouched 4-way proportioning valve on firewall Stainless lines at all 4 wheels New front pads and rear shoes (4 types tried up front) Squeak stopper goop on front pads Lines are heat shielded at all points where they are near the exhaust system. What I have already done: Bled, bled, and rebled lines and master cylinder Adjusted brake pedal & booster Adjusted rear shoes Checked for any leaks or weak lines I have not examined my proportioning valve, because I was told for a while that they "rarely go bad". I haven't had time to check it since I decided I wanted to. Funny feeling pedal: Right now my brake pedal feels really wierd. When the car is running the pedal will be really REALLY soft initially (yet still sorta stop the car) and then once it hits a certain point near the bottom of travel get hard as a rock! If I put pressure here, I can bring the brakes to the lock-up point for one so-so 80-0 stop (the tires like to chirp-chirp-chirp on hard stops, and I'm not sure if it's the fronts, backs, or both). Then the pedal is squishy at the bottom and stopping power is scary (weak with not a chance of locking up). After a serious stop (or especially 2), there is a noticeable burnt smell at the front wheels (not sure about back), but I haven't found ANY leaks and the MC tanks stay full. For normal driving around the city, the brakes "work", but the thought of a necessary emergency stop worries me significantly. Squeaky front brakes: The brakes squeak, ALL THE TIME. It's just the front brakes, and until I reach the "hard spot" at the bottom of travel and put pressure there, they squeak with such unbelievable loudness you can hear them twice as far away as my full throttle V8 exhaust. My current plan of action: I have a week to fix the problem. A new proportioning valve is in the mail, but I'm not sure how to install it. Note that it currently has the 4-way proportioning valve on the firewall. What should I do with that valve, and how and where should I connect the new valve? What tools and parts will I need to complete this other than the new valve? What else might you suggest I try? Thank you for any help, Sam Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted March 5, 2003 Share Posted March 5, 2003 Are you sure the brake pedal is even engaging the MC during the first part of the travel? There is an adjustable length rod going from the brake lever to the back of the booster. When I upgraded my 70 240 to a larger MC I had to lengthen this rod by over an inch. The brakes were somewhat like you said. Only spring tension for the first 80% of the pedal travel then BOOM! All the brakes came in with the last inch or so. I had upgraded to stainless steal lines with otherwise stock brakes so a inch of travel is all I really needed. As for stink and squeal, did you get brake fluid or caliper lube on the pads or rotors? Like off your hands? Get the brakes working then see if some of the lube burns off and the squeal dies down as the pads get broken in. Quote Link to comment Share on other sites More sharing options...
Guest the_dj Posted March 5, 2003 Share Posted March 5, 2003 I am sure the pedal is engaging. There is braking power during the first portion of travel and you can tell this, but it is very weak. I am under the impression that only the rears are fully engaging, causing weak braking power (from the drums) and the squeak (from partially engaged but no braking pressure on the front calipers. Then again, I may be wrong. Quote Link to comment Share on other sites More sharing options...
Guest 240hybrid Posted March 6, 2003 Share Posted March 6, 2003 Hey dj....Im having the relatively the same problem too after swapping the MC and booster from my old 75 280z into my 73 240. Brakes seem to function properly and stops the car, but there is no resistance in the pedal like there should be . I also get a sqeak from the brakes, but its the front and not often. Heres a few things I'm planning on doing before replacing parts.....bleeding the brakes (3rd time), checking the rear brakes to see if their adjusted out properly. Also Im gonna check the MC to see if theres any gunk in it thats impeding its function, as I have heard a clog in the reservior cap vent hole, can create a vacuum and cause sponginess. I hope these remeeds work, I'm running out of solutions. Hope one of these ideas helps one of use. Quote Link to comment Share on other sites More sharing options...
Administrators SuperDan Posted March 6, 2003 Administrators Share Posted March 6, 2003 IMHO 3 things. Pads, shims, proportioning valve. The proportioning valve is very suspect! The car sat for 8 years. There is the chance that the noise could be related to the PowerStop rotors.... not sure though. Dan Quote Link to comment Share on other sites More sharing options...
dmyntti Posted March 6, 2003 Share Posted March 6, 2003 Possibly bad rubber brake lines. I have seen the rubber brake hoses get spongy and balloon to cause a soft pedal. It does not take much expansion to really screw up the brake feel. Also check that the calipers are moving OKon their sliders. This could cause both the squeak and the funny pedal. Quote Link to comment Share on other sites More sharing options...
Guest Your Car is Slow Posted March 7, 2003 Share Posted March 7, 2003 Have the same issue....however I dont have rear brakes on the car...only the fronts are hooked up (I plugged the little valve in the rear before the T fitting) Very spongy and soft until about halfway down..then very firm and the car stops. Im thinking that all the lines/prop valve, and master cyl need replacing (I see brake fluid trails coming from the booster itself. Does anyone know why exactly the line for the rear brakes goes into some sort of valve....then does a 180 and goes into the T fitting...which then goes to the left and right rear brakes? I have no clue what that other valve is for. Ill replace the lines and hardware at a later time when the LT1 goes in. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted March 7, 2003 Share Posted March 7, 2003 If you have the stainless steel brake lines on all 4 corners, then if you are like me you don't get more than about a half inch of movement in the brake pedal. It is the rubber brake lines expanding that let you get an extra couple of inches of travel out of the pedal even after the brakes are fully engaged. The stainless lines get rid of that and after the half inch or inch of travel it is like stepping on a brick. If you are getting that much movement then I would suspect you either have air in the lines or the pedal is not engaging until late and you need to adjust the connecting rod. I am not sure how a proportioning valve works nor what happens when they go bad so I personally can't rule out that possibility. But if everything is working correctly the stainless brake lines will put a very real limit on the amount of pedal travel you will see. Quote Link to comment Share on other sites More sharing options...
Mike C Posted March 7, 2003 Share Posted March 7, 2003 Sounds like a bad booster combined with air in the master? If you are have the car in Austin ever, we can do a brakeline pressure test on it if you want to verify. Your car is slow: fluid from the master can ONLY get in the booster if the master is bad. If you see it INSIDE the car, not only is your master bad, your booster is, too. Leaky mastercylinders will wipe out the booster in record time. You will never get the brakes to feel right with a leaky master. Quote Link to comment Share on other sites More sharing options...
Guest Your Car is Slow Posted March 7, 2003 Share Posted March 7, 2003 nono..not leaking IN the car...the bolts that hold the master to the booster are completely rusted..along with that plate on the back of the booster. Its from this plate (well behind it obviously) that the fluid is leaking...you can see the trail from the booster down to the fender of the car (actaully ate away the paint before I noticed it). Chances are the booster is ok...as it gets good pressure...but the master is most certainly hosed (or perhaps its just a bad/rusted seal) It will have to come off either way. Quote Link to comment Share on other sites More sharing options...
Guest the_dj Posted March 7, 2003 Share Posted March 7, 2003 Sounds like a bad booster combined with air in the master? If you are have the car in Austin ever, we can do a brakeline pressure test on it if you want to verify. This is my Spring Break. If I work on it and things don't change, I might be able to bring it up here for a day. I'll let you know if I plan to do that. Thanks. Quote Link to comment Share on other sites More sharing options...
Guest the_dj Posted March 10, 2003 Share Posted March 10, 2003 I took the proportioning valve off and opened it. It looks clean What exactly am I looking for that could cause a problem? All the seals and such look new. What else can I do? Sam Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 10, 2003 Share Posted March 10, 2003 hook a leaf blower too it, and then run like hell LOL Quote Link to comment Share on other sites More sharing options...
Guest Your Car is Slow Posted March 10, 2003 Share Posted March 10, 2003 I had to blow most of my lines out with compressed air before filling with fluid....some wouldnt even pump fluid through under pressure until the line was blown out backwards :/ Quote Link to comment Share on other sites More sharing options...
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