| Author | Message | ||
| David Feinberg (Fastradio2)
Junior Member Username: Fastradio2 Post Number: 95 Registered: 4-2002 |
Congrats on the feeling! The sense of accomplishment is great, without a doubt... The steady brake pedal, with a long travel would suggest an internal problem with the brake master cylinder itself. Bypassing, I believe would be the correct term. Others may have a "better" testing procedure than I, but here's a quick test that I use to verify the condition of the master cylinder. First, we'll make the presumption that, after the bleedng was done, no air was present in the system. If so: With the engine off, sitting in the car, pump up the brakes...release your foot from the pedal briefly, then apply light, even steady pressure (with your foot) to the brake pedal. If the pedal continues to drop, i.e. long travel...the problem lies within the master cylinder. A quick, firm stab on the pedal should result in a firm pedal... Replacement, or rebuilding of the MC is your next step. Pehaps some of the 308 folks can suggest the least painful (expensive) way to deal with the mc replacement/rebuilding issue. I've got several PhD's in BB parts sourcing and rebuilding connections, but many years since I spent time with the 3-series cars. Best of luck, David | ||
| Don Norton (Litig8r)
Junior Member Username: Litig8r Post Number: 85 Registered: 6-2001 |
Thanks for all your help David. Just as a recap, I did the procedure you described, and I bled the brakes (again). I bled he fronts first because that's what I found in the 308GT4 service manual I ran across. The brakes are better than they were, but steady and long pedal pressure will still sometimes cause the pedal to drop alarmingly. So, still troubleshooting. But I did learn how to bleed brakes so I feel very manly today.  | ||
| David Feinberg (Fastradio2)
Junior Member Username: Fastradio2 Post Number: 93 Registered: 4-2002 |
Dan, Looks like you've found the master. As to the car running, or not...doesn't really make a difference, though I do mine with the car off. When you start the car, the power booster, if you will, will create the illusion of a softer brake pedal... In summary, after you bleed the lines at the master, re-bleed the calipers (starting from the farthest point from the mc), presuming there's no air remaining, you're done! The liklihood of a power booster problem is slim, if when you first start the car...you feel the pedal change. Drive the car to verify the stopping power, versus the perceived pedal feel. As Bruno does on his car...and I on mine, this is a pretty straight forward procedure, and in general...Ferraris bleed quiet easily. Regards, David | ||
| bruno bandaras (Originalsinner)
Junior Member Username: Originalsinner Post Number: 247 Registered: 5-2002 |
I do mine the way David does his.On all my cars. | ||
| Don Norton (Litig8r)
Junior Member Username: Litig8r Post Number: 84 Registered: 6-2001 |
Thank you David - I'm going to try that tonight. If I have the right part, the master cylinder is directly under the fluid reservoir and has 2 fittings attached, which are the ones that I'm going to bleed. Does it matter if the car is running or not when I do it? I have noticed that the pedal fade seems to occur only when the car is running. Might that suggest that it's part of the vaccum assist that's the culprit ya think? That Mighty Vac is pretty cool... | ||
| David Feinberg (Fastradio2)
Junior Member Username: Fastradio2 Post Number: 92 Registered: 4-2002 |
Don, Sorry about the level of discussion...I guess I just take the knowledge I've collected through the years foregranted... OK...I haven't owned a 308 in many years, but believe I can still walk you through the steps. All removing all the visible screws that hold in that fiberglass cover that surrounds the MC, remove the rubber perrimeter moulding as well. Can't remember for sure if there is a "hidden screw" under the spare tire...??? The cover will, with a little persuassion will slide down slightly towards the front of the car, and then can be lifted out. Once the cover is removed, the MC will be in plain view...and you'll see several brake lines going into the cylinder. What we're trying to do here is ensure that there is no trapped air between the master and the rest of the braking system. Just because you got all the air out at the wheels doesn't necessarily mean that there isn't some air trapped in a line near the MC. So, by "cracking a line", I mean simply to loosen and then immedaitely re-tighten each fitting on the MC while your helper HOLDS the brake pedal down. Note that you'll bleed one line on the MC, then tighten the fitting. The helper will re-pump and hold the brake pedal down, and you'll repeat the process for the next line...Be sure to use a flare (line) wrench to loosen these fittings, as they can be quite tight.... Hope this helps a bit more... Regards, David | ||
| Don Norton (Litig8r)
Junior Member Username: Litig8r Post Number: 83 Registered: 6-2001 |
David, could you describe your procedure in a little more detail and take it down a couple of notches for the mechanically-challenged? I did do the brake bleeding procedure (I'm kind of proud of myself) but it didn't help my spongy and fading pedal, so I'd like to also try the master cylinder procedure and use the teflon tape on the bleeder screws and do it again. Could you give a little more detail about what connections on the master to address and how to work on them? I didn't understand when you said to "crack each fitting directly at the master". Also, is there an easy way to remove the fiberglass cover which is over the master cylinder and brake fluid reservoir? It doesn't slide out easily or compress, and I don't want to put too much force on it if there's an easy way to do it. Thank you very much. | ||
| David Feinberg (Fastradio2)
Junior Member Username: Fastradio2 Post Number: 88 Registered: 4-2002 |
Don, With very rare exception, brake master cylinders do not have bleeders on them. To eliminate the spongy pedal, you'll need to recruit a helper. Here' how to bleed the master. Before you start, verify that there is some free play in the brake pedal before it actually engages the master cylinder push rod. Only a tiny amount is needed, but zero is not acceptable, as the master cannot function properly if there is even the slightest amount of pre-load. Presuming the above is OK, have your helper pump the brakes, slow and hard a couple of times...making sure that they allow the pedal to briefly return to the very top of its travel...and then hold the pedal down firmly. At this point, with a flare wrench...carefully just crack each fitting directly at the master. (Your helper will comment that the pedal is dropping-OK). Do one fitting on the master at a time. Close the fitting and have your helper pump up the brakes, again...and you do the next master fitting....and so on. (Protect near-by paint surfaces...) Now re-bleed the brakes, starting from the farest point from the master...Re-check rear pad to rotor clearance. I beieve you'll find that this will bring the pedal up to your liking. I've used this procedure on my BB for many years...and the pedal is like stepping on a rock. Regards, David | ||
| Don McCormick (Dandy_don)
New member Username: Dandy_don Post Number: 26 Registered: 2-2002 |
I reinstalled my 1979 308's rear brake calipers last weekend and bled the brake system (twice) using a Mighty Vac tool (also putting the teflon tape on the bleeder screws). No more air comes out of any of the bleeders. I still don't think I have it right though as the brakes still don't feel hard enough to me. I bled the calipers in order starting with the furthest from the master cylinder, but have not bled the master cylinder itself because I can't find a bleed screw on it. Any thoughts, guys on how to get rid of these spongy brakes??? By the way the bleed screws on the 308's rear brakes are 7mm and fronts are 9mm. Use a closed end wrench and make sure you don't strip the bleeder putting it back in. Don | ||
| phil hooper (Wolftalk)
New member Username: Wolftalk Post Number: 18 Registered: 5-2002 |
hey don, The bleed screw is on the back of the caliper near the top, and is normally covered with a rubber cap. On the 308, I think the bleed screws are different sizes on the front and back calipers. They are somewhere in the 8-10mm range. Use a closed end wrench or a deep well socket to loosen them. I used the hand vac that mitchell referred to. It's usually called something like "single person brake bleeder kit". It's just a container with a couple hoses - one hose goes to the vac pump, the other onto the bleed screw nipple. The one problem is that air tends to want to seep in around the bleed screw threads, so it was necessary to remove the bleed screw completely and wrap the threads in nylon pipe tape (or maybe use anti-seize compound on the threads...anything to seal them up). The one hassle on using the kit is the container is too small, so when changing the fluid, you have to stop and dump it out a couple times per wheel. | ||
| Lawrence Coppari (Lawrence)
Junior Member Username: Lawrence Post Number: 113 Registered: 4-2002 |
Positive pressure bleeders work well too. These are attached to the master cylinder. Pushing the brake pedal to the floor pushes the piston past areas that it does not normally pass. If there is any corrosion or buildup of material on the walls, you can damage the piston. | ||
| Steve Magnusson (91tr)
Member Username: 91tr Post Number: 836 Registered: 1-2001 |
I'd add a couple of things to Mitchell's list (if your goal is to change the brake fluid rather than just get some air out of relatively fresh brake fluid): 2a. Using a "turkey baster" (US term?) suck most of the old fluid out of the master cylinder reservoir. 2b. Refill the master cylinder reservoir with fresh fluid. It's not actually required to jack the car up or even remove the wheels -- but it's a lot easier if you do. I've been happy using the MightyVac hand vacuum pump to suck the fluid out at the bleed screw, but like Greg/Ed said there are many acceptable methods/tools. | ||
| Edward Gault (Irfgt)
Intermediate Member Username: Irfgt Post Number: 1568 Registered: 2-2001 |
If you simply recruit an assistant you can bleed the brakes for the price of the fluid without all the fancy expensive equipment. Just get the assistant to hold the brakes while you release the valve and then close it while the pedal is on the floor. | ||
| Greg Owens (Owens84qv)
Member Username: Owens84qv Post Number: 481 Registered: 10-2001 |
There is a device called a Motive Power Bleeder that several of the FC people have used and liked. I was actually getting ready to get one as my brake fluid needs changing also. | ||
| Don Norton (Litig8r)
Junior Member Username: Litig8r Post Number: 82 Registered: 6-2001 |
Oh yeah, one other thing - is the bleed screw easy to find (never done this before)? None of the schematics I've seen have shown it and it's not addressed in the Owner's Manual. | ||
| Mitchell Minh Le (Yelcab1)
Junior Member Username: Yelcab1 Post Number: 218 Registered: 11-2001 |
One wheel at a time is fine. And you can get a handpump specifically designed to bleed brakes and clutch cylinders at almost any PepBoys type of stores. | ||
| Don Norton (Litig8r)
Junior Member Username: Litig8r Post Number: 81 Registered: 6-2001 |
Thanks for the fast response Mitchell. Do you need to completely jack up the car to start or can you just jack up the wheel that you're working on? And any special fitting required or will any pump do? Thanks muchly. | ||
| Mitchell Minh Le (Yelcab1)
Junior Member Username: Yelcab1 Post Number: 217 Registered: 11-2001 |
1. Jack up the car 2. Open the hood and get access to the master cylinder 3. Get a hand pump unit for bleeding brakes 4. Remove furthest wheel from the brake master cylinder 5. Unscrew the bleeding screw (9mm I think) 6. Hook up a small hand pump to the bleed screw and pump away to suck out old fluid. Stop every so often to top off the master cylinder 7. When you notice clean fluid coming out, tighten the bleed screw You are now done with that one wheel. Move on to the next furthest wheel. | ||
| Don Norton (Litig8r)
Junior Member Username: Litig8r Post Number: 80 Registered: 6-2001 |
Greetings - I'd like to do a brake fluid change on my '78 308. I did do my part and research for a simple procedure description here, and though I learned a lot, I couldn't find a nice concise description of how it's done. It seems that most peeps think it's a simple procedure (which is very good for me). So could someone help me out and post a little how-to? Thanks!! |