please guys help me out. what's the case. early this morning i took the 308 QV out for a drive but immediately after starting i heard some strange kinda slissing sound from somewere in the front after hitting the brakes. everytime i hit the brake the sound can be heard again. Opening the hood defenitely made the sound more clear coming front the boosterarea. at driving the brakes have a very low braking power. at idle and hitting the brakes the revs go slightly up. figured out that appearently there's air going from the booster or boosterline giving the engine more air causing to rev it up a little. my questions: most likely there a hole in the vaccuumline, i will check this now secondly after reading on the forum i came across a malfuctioning checkvalve as probable cause. This seems a good thought but were the hell is this, i can't find it anywere. third. did any had a similar problem? cause?
checked te line, no holes found and checked the checkvalve, works oke while running it seems that there's air continuiing to be sucked out of the booster, as this is leaking. Can this be the case??
Hi Steven, If you hit the brakes and the engine speed goes up, it sounds like you might have a hole in the booster diaphram. This would also not give the brakes much if any boost and would explain the hard pedal/poor braking performance. This is just my first shot at it. Does the car idle normally without the brake pedal depressed? Hopefully one of the tecs that help out here will post an opinion. Good luck, chris
If you get a new booster, or booster/mastercylinder combo, or have yours rebuilt, please let us know where/who you use for sourcing.
after studying quite a lot on internet i've reached the point that i'm pretty sure the booster is the problem so i started this morning getting it out (i'm from Europe so well ahead of most of you in time ) Starting figuring out which way's the best the get the booster out. Finally decided to get it all togeter with the master cylinder and pedalbox ( i did read a story on another tread a guy stating he removed it without removing all the other parts but this seems impossible to me) there's quite some work to do to get this out. Both under the dash and leaning over the fenders in front. Pretty soon i noticed my age, it seems that i'm not 18 anymore nowaday, (when does that happen....) I attached some pictures for anyone to use for future reference next tread i'll continue Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
pretty technical story but move on if you do not like it. (not very good to read due to my English probably, sorry for that too) after getting the complete assy out I removed both the master cylinder and the pedal box. Pretty straight forward job. Then i was left alone with the booster that, i my opinion was the trouble maker. remember: -the car did not have much braking power -there was a hissing sound as soon as i hit the brakes and this kept on going as long as i kept on braking. -the engine's revs slightly increased during the hissing some background on boosters: a brakebooster is normally a small vessel divided by a "wall" creating two "rooms" This wall however is not always closed, there's a "door" in it (important to understand) This door is openen and closed by the driver. What happens in the booster: During driving the door is open and both rooms are sucked out ( this is probably not good English..) of air creating partial vacuum. As you now hit the brake the two things happen, one: the door in the wall closes and two: air from outside (so ambient pressure) is allowed in the room the farest away from the MC. The other room with still has the partial vacuum in it now "moves" the wall to one side of the vessel. This movement is the actual assistance for your brakingpower. Back to my 308 The wall in the 308's booster (and probably some other models as well) is made of a rubber kinda ring which allows the movement and a plastic ( bakelite kind of stuff) centre part. This centre part turns out to be the one causing all this s..t. Althoug not broken there are two really big cracks in it from the centre to 1,5 inch from the outside. see again some pictures. I'll continue in a new tread again Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
so when hitting the brake one room is filled with ambient air creating a pressure difference between the two rooms resulting in a movement of the wall ( which' force, as said, is assisting you when braking) however in my case now this ambient air will also reach the other room! No difference in pressure now in between the rooms and therefore no force helping my to brake. Remember the car was lacking braking power. The sisssing sound is also explained now. As I hit the brakes air was let in but as the crack was making the complete vessel "undivided" the suckting from the engine sucked in ambient air simply through the vessel. As this was sucked trought these small sharp-edge-cracks it sang its song... the revs going slightly up also explained. Fresh air from the outside was sucked into the inlet of the car. This created a extra airflow (probably also lifting the petrol flowcontrolvalve slightly) to the engine. I was giving trottle with my brakes what's next? as i try to fix EVERYTHING myself ALWAYS is will figure out a way the repair the cracked "wall" i'll let you know as soon as i figured this one out. And be sure, I'll will take it seriously as this ARE braking we are talking about. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
after giving it some serious thought i decided to repair the plate with some fabric. As I thought if this yesterday evening I already made a glue test on the plastic plate using Plexes EP225 glue specially for difficult plasics. This glue was harded out this evennig giving me the oppertunity to stengten-test it. It succeeded very well! so i will use this glue for gluing the fabric on the plate. This evening: I happen to have a sheet of woven and than plastified fabric and i think this is perfectly suited for the job. First at the end of both cracks i rilled a hole to stop the crack and than I glue-ed on the fabric. After that i kept all in place using a load of ordinary packingtape. On the other side i filled the two holes and smeared glue into the crack. This will probably do not much but it wound hurt either. See attached pictures to follow the process. first three pictures if the plate with the cracks (quite hard to see) and the drilled holes. Now I leave it all to dry for 2 days and than i'll prepare myselfe for getting it all together and into the fcar again this weekend.
two pictures of the repair, in progress now I just have to wait. Obviously I gave the risk-factor some thought too but in the end all that can happen is a similar problem as which started all this in the first place. The fabric can either crack (not likely as it is very tough material) or the glue can get loose. In both cases the original crack will re-appear, with the same effect. Nothing more and nothing less. In fact the worse thing that can happen to me is that in that case I have to do all the work again...... Image Unavailable, Please Login Image Unavailable, Please Login
"Both under the dash and leaning over the fenders in front. Pretty soon i noticed my age, it seems that i'm not 18 anymore nowaday, (when does that happen....)" Thats the way I got my stroke last year.... Enzo52
booster is rebuild with the self-repaired part. the testdrive revealed no more problems! another 2K saved i guess!
Steven, I have to agree with 2NA - the brake system is not the system to try to save money on by repairing parts with glue or whatever. Yes, it's true that if it fails again, the worst thing that can happen is that you loose boost. But if this occurs at the wrong time, it could certainly cause an accident. Example: you are in routine traffic and you are slowing to stop behind a car. You are applying the amount of brake force that you know will stop you appropriately. The booster fails, suddenly and dramatically increasing the pedal force necessary to provide that same stopping power. Before you can react, you've hit the guy in front. I'd really suggest you "do it again" with the correct replacement part... I am worried about you a little bit but, of course, I am more worried about a Ferrari getting hurt! Just kidding about that last part.
My guess would be if its cracking anwhere it will not stop & a new booster should be installed. I would imagine this post would be a trial lawyers dream... Fate may have this fail in a dire situation when you needed the assist & it fades - someones life could hang in the balance over a few dollars.. Besides the tragic outcome, you will forever live with it. Replace with a new booster. Unless you are related to Fred Flintstone.... My 2 cents-
I do not agree with the you, sorry, first: it's never my intention to cut corners, owning two F's i'm more than capable to pay for a new part, any part. the problem in this one is caused by a combination of age and probable a slight slip of spec of material or productiontemperature. The problem can ( and read the treads on this subject) and will occure quite frequently with all the older cars. I bet none of you will change his booster now reading (and thereby knowing) this..... As a certified Mechanical Engineer I do happen to know all about glueing stuff. You can take my word for it that the now repaired part is indeed stronger than the original, the tension is gone and the strenght is actually increased. In the end it's now safer than it was before. (and that mean also saver than all old boosted cars on the road....
Steven, c'mon... as a mechanical engineer you know that there is now a greater chance for failure at the point where the glued "patch" transitions to the area where it meets the original material. It is the same "problem" that exists with boats and marine wiring. solder connections are NOT used on boats in areas where there is vibration. This is because the vibration causes the joint to break right at the solder joint. The joint itself doesn't break but wire breaks at the point on the wire where the solder ends. The soldered portion of the wire is brittle compared with the rest of the wire. Your glued/epoxied/whatever joint is exactly the same. It will probably work fine for a while but it will eventually either fail on it's own or induce failure in the area adjacent to the repair.
Improving on the original design or materials (or both) of an old Ferrari is in more than one case not that hard i think....... comparing a glue-joint with soldering is not the best one to make. some of the current glueing process's are amongs the best possible ways of bonding different materials together. Glue ( we like to call them adhesives) are widely used in modern cars on parts to withstand both static and dynamics forces as well as visual important parts. The (non commercial avaiable) glue I used for this repairment as wel as the fabric are better materials than available at the time Ferrari build my 308... The way I fixed the booster may superficially seems silly, a lawsy way to save a buck or just plain stupid. Non of this is the case. The part is in any aspect more mechanically sound than it was ever before. Furthermore (and for my among the greatest joys of working on cars,) i've got the excitement of fixing it myselfe!
I know this is an old thread, but I just pulled the Booster last night and it really wasn't all that bad to get out... Steven's photos above are great. I wrote up my steps: 1. Remove the two nuts that secure the bracket that the resistor and heating lines are mounted to. Remove the three wires attached to the resistor. 2. Remove the top plate (four nuts) on the top of the petal assembly under the bonnet (in the photo below he didn't do that. Not sure how he then got the booster decoupled...) The cotter pin it at the top so super hard to get to from underneath in the cabin. 3. Then separate the brake lines and level sensor wires. I used a turkey baster to pull as much fluid as possible and stuffed a rag under it to catch the dribbles. 4. Remove the four bolts holding the brake pedal cluster in (two in the cabin, two under the bonnet). 5. Remove the cotter pin and remove the coupling pin at the end of the booster attached to the brake lever bellcrank. 6. Loosen the four nuts holding the booster to the pedal assembly (two in the cabin, two under the bonnet). They are hard to see from inside the cabin, but will be easiest with the pedal assembly still in place. They may need to be loosened a bit more later, but too much and you risk damage to the booster plunger Bakelite snout (ask me how I know this...). 7. Next, remove the bonnet latch mechanism. Note any adjustments. (I took several photos...) 8. Remove the vacuum hose from the booster. 9. The booster sits in a little valley so what you have to do is to swing the MC end out over the brake lines and over the AC plumbing far enough to clear the valley. Then remove the nuts from the attachment to the pedal assembly and you are home free. It is a bit fussy, but is actually easiest if you remove the spare tire and sit in the well. That will save you leaning over the front wings as well. All in all, not bad. None of the bolts/nuts were actually on very tight and it didn't take any crazy tools to get them off. It *may* have been possible to separate the MC from the booster and sliding the booster to the driver's side, but I couldn't get the bottom back bolt off without removing a bit more. The AC plumbing is kind of in the way. Maybe, but I didn't want to damage the brake lines. I then covered them with the fingers of a rubber glove to keep crap out of them. I am boxing it up and shipping it off to Karp's. "Booster Dewey" in Oregon isn't doing these any more. Karp's quoted $325 for the booster and I'll be having the master cylinder done at the same time for $150 (providing the bore is still good). The MC seems fine (small weeping from the reservoir), brakes were just fine, just a strong hissing from the brake pedal. After looking at the plunger end of the booster, the "O" ring is ripped in half so I'm guessing that is what is causing the fuss, but in for a penny, in for a pound... Thanks Steven for the super helpful photos! (Oh, my car is an '85 Euro QV and it looks very similar to Steven's above as far a component placements) Franny
Franny... I sent mine off to Ray Cook at Power Brake of Pompano in Florida. He did a superb job rebuilding the booster and had a very good turn around time. I believe it was also 325 including shipping. He gave me great tips as well on bleeding the system afterward. Helpful hint is to place a 2X4 or something to prevent the pedal going to the floor during the bleeding. This stretches the diaphragm and could cause issues with a tear or something of the sort. Anyway, I should have had my master rebuilt at the same time. About a year or so after replacing the booster, my brake pedal began to feel "funny". After a while of noticing this I decided to do my research. My symptom was that I could apply pressure, then release a bit and reapply pressure. Doing this would allow the pedal to travel further. After a bit of time, I could get it all the way to the floor. Turns out it was pitted and seal rebuild would not do the trick. I just replaced my master as it was a costly part. Had I done it back then, well possibly could have saved some bucks. Anyway, make sure you put a small amount of silicon lube on the reservoir bibs and grommets to prevent breaking the tips when you reinstall it. Finally, make note of the length of the shaft inserted between the booster and master. Too long will cause your brakes to work when you don't want them too. Too short and you will have a deep pedal. I had to readjust mine a bit with the new master as it was about 1 mm longer. Funny how much that affected the result. Had I not done that, I would have basically had to redo the entire job. While I was waiting to get the booster back I decided to rebuild my calipers. This was a great idea because I did not know I had 3 seized pistons. PMB Performance was a great help there and I would strongly recommend calling and talking to them. They will know what you need to order, and believe me, you will need parts. They stock everything. Good luck and take care. Scott.
A quick update to this thread. I just got off the phone with Steve at Booster Dewey and they are rebuilding these boosters. $150 +50 for plating if it needs it. Power Brake Exchange quoted $300 (no plating) and didn't seem as knowledgable about the Ferrari boosters as Booster Dewey did. Karps hasn't gotten back to me yet. Also, I removed mine quite easily without removing the pedal box: Unscrew the pedal box top plate, remove one clevis pin, shine a light through the pedal box to see the two nuts inside the car, then from the inside remove the two nuts, remove the two nuts on the outside. I drained the brake fluid from the master using my Motiv bleeder, removed the lines, then pulled and twisted the whole booster / master unit out. Took about 30 minutes.
