Hello
I think my brake booster is on its way out. Never mind why or how unusual it is I am just led to believe that after years of poor pedal feel on track and a mysterious surging that has plagued the car for longer. I think I have a small vacuum leak out of the booster somewhere. Kind of helps explain both problems. Now a booster is quite expensive considering the bootstrap affair I have with tracking this car.(Plus just found out we are expecting child no. 2). I know I have read that some people are running unboosted brakes. How do you do this mechanically? Do you have to remove the booster and reattach the master? Can you simply plug the vacuum line to it? What do unboosted brakes feel like? This car is pretty much a J prepared racecar with a rollbar. It was getting a cage this coming winter but with baby due in February that probably wont happen. More likely to get comp liscense this fall and maybe catch some co drives next year. Then put my car on the track in '07. Anyway if anyone has input on the brake issue please let me know.
Thanks
Ryan
92 328i TCD TrackTurbo stage 1
02 325iT SportWagon
00 528iT SportWagon
Just unplug the vacuum line, and plug up the fitting on the intake manifold. You could rip out some other stuff probably, but un-plugging it does the trick in about 2 mins.
Edit- I used the word 'plug' a lot, but I'm sure you know what I mean
-Peter
Current toy: none
Past cars: 88 M3, 99 M3 x2, 04 M3, 91 NSX, 06 S2000, 01 911TT, 06 Exige, 00 NSX, 04 GT3
Just unplug and plug . Seriously - it is easy and works well. Pedal effort is pretty increased, but some people like it. Don't try it for 5 minutes - you will hate it. Give yourself a day to form an opinion. Our racecar brakes are between this and a normal boosted setup. When I drive more of a stock type car, I prefer the non-boosted. Way more feel.
For those with no booster issues, you can also put a restrictor in the line to limit boost and increase feel.
Try This
like2short
E36 M3 3.0L Gruppe N
E39 //M5 TiAg/Silverstone
E53 X5 4.4
Sweet, but not prepared legal. Always build toward a race class...
whoops, did not see that is was running prepared....which means # of master cylinders must remain as factory configuration.
If in a 325, try an E36 M3 master which has a slightly larger bore.
like2short
E36 M3 3.0L Gruppe N
E39 //M5 TiAg/Silverstone
E53 X5 4.4
Specter, just sent you a PM.
Have you tried replacing any of the o-rings in the system? Like at the master cylinder connection to the booster?
"And also, let's not forget let's NOT forget, Dude, that keeping wildlife... um, an amphibious
rodent, for... um, you know, domestic... within the city. That ain't legal either."
Tell us more. I have had a similar problem with a low pedal. Not sure, but it seems to be booster related.Originally Posted by mck325is
I have also been considering eliminating the booster but would prefer to have it all working correctly.
Jay
From wannabe to has been in a few short years..... the older I get, the faster I was
I am intrested in this. Where can I find these restrictors? Are they adjustable?Originally Posted by jamesclay
Last edited by Deadphan; 06-06-2005 at 10:48 PM.
If you are pulling the booster, you want a smaller bore for less pedal effort.
R restrictor would be a piece of rod with a hole in the middle to let air flow. Drill a small hole and drill out more until you are happy.
Now I hope I'm remembering this right... did an M3 brake swap into my 325 including the master cylinder. There was an O-ring at the connection to the vacuum booster, and I remember reading that if I didn't seat the o-ring correctly it would allow a slight leak. Also if I improperly torqued the nuts holding the master cylinder on. I am assuming that the O-ring could also age and harden...? and is sure a lot cheaper than other parts of the brake system to do a trial and error replacement.Originally Posted by jayhudson
My PM to Specter was that I have my old 325 master cylinder and the M3 vacuum booster in the garage, not being used.
"And also, let's not forget let's NOT forget, Dude, that keeping wildlife... um, an amphibious
rodent, for... um, you know, domestic... within the city. That ain't legal either."
Thanks. Might be worth a look-see.Originally Posted by mck325is
Jay
From wannabe to has been in a few short years..... the older I get, the faster I was
Well just pulled the line and pluged both ends. I am doing a couple of other things to the car right now but I will be running VIR Grand in two weeks so I will rpeort back then on what it feels like the first time out on track with it. I will also hedge my bets and take the hose with me just in case. But I will drive it in the meantime to see if that little hesitation went away. Just FYI the car is a 92 non-vanos with 183k on it. The last 20k have been mostly autox and track events with lots of to and from.
Ryan
92 328i TCD TrackTurbo stage 1
02 325iT SportWagon
00 528iT SportWagon
Be careful the first time you pull out of your driveway...unless you've driven an unboosted setup before, nothing can prepare you for the amount of effort you'll need just to stop your car from rolling into the street. It's at least 10x harder. But give it a 30 minute session on the track and you may just like it.Originally Posted by Specter325
What did you find as a suitable cap for the ends?
I'm planning on removing the line this weekend for an upcoming track day next week. Any particulars to look out for?
I would like to go the restrictor route, but probably need more time to make/find a suitable restrictor.
Drive Safely,
Raza
Current:
2016 Porsche 911 Carrera GTS
Past:
1994 E36 BMW Dinan 3
1998 E36 BMW ///M3/4
2000 E39 BMW ///M5
2002 E46 BMW ///M3
2008 E60 BMW 550i M-Sport
Steel rod from any metal supplier or Lowes/etc. Drill a hole to allow air to pass.
I'm not sure how much it matters, but it seems to me that if you put a plug at the booster you will be creating air pressure inside the vacum booster. I don't know how much this would increase pedal effort. But I think I would put a plug at the intake manifold and some sort of filter at the booster.
I ended up buying a plumbing pipe valve (most similar thing I could find locally to a Grainger-type valve) to allow me to control the amount of air flowing through the line.
It has firmed up the pedal somewhat and feels much better. We'll see how much more I like at my track day at Sears Point this weekend.
Drive Safely,
Raza
Current:
2016 Porsche 911 Carrera GTS
Past:
1994 E36 BMW Dinan 3
1998 E36 BMW ///M3/4
2000 E39 BMW ///M5
2002 E46 BMW ///M3
2008 E60 BMW 550i M-Sport
any more updates on this? interesting...
In an unboosted setup, how hard is it to heel-and-toe? If the effort is 10x, I think I might have a hard time with my wimpy middle-age leg and foot to put down enough brake force and still blip. Comments?
Interesting thread, especially the part about reducings, but not eliminating, the boost.
You get used to the feel of the unboosted setup. I did and it is not even an issue anymore. The increased brake pedal effort forces you to heel toe correctly. Ball of the foot on the brake pedal and heel blips the throttle. Most people learn to heel toe with the sides of the front of the foot. This works fine for the first little bit but then as your skill and speed increase you need more brake pedal travel than will work with the side of the foot heel toe. Once you reach this point you are kind of SOL with the side of the foot method. You cannot brake any harder because then you cannot downshift or you have to let up on the braking to make the downshift. Either way you are loosing time. Also makes for really funny leg contortions in the effort to brake hard and downshift. Mcclaskz tried this two weekends ago at Road Atlanta and liked it quite a bit. He said the pedal effort was high but the feel and ability to modulate the brakes was much better. And he will get used to the effort. I make the transition from my E36 to the Suburban in a minute or two when hopping back and forth. Try it you will like it.
RB
Ryan
92 328i TCD TrackTurbo stage 1
02 325iT SportWagon
00 528iT SportWagon
I'm still able to use the side of my foot in every E36 that I've driven. It's more of a "what's comfortable for you and your feet" type thing. The only car I've ever had to use my heel in is my wife's Saab.Originally Posted by Specter325
I think I like the unboosted feel, but I am still going to try to solve the problem. I have replaced booster, front wheel hubs, and master. This is a stock setup with rebuilt calipers, brass guides, ss lines and now running GS610 fluid. My next step is to see if cylcing the ABS does anything and if not, then bypass the ABS w/ a T fitting (34-34-1-111-435) (thanks Rob @ BW) for the front, and directly connect the rear. If that solves it, then maybe it is the ABS module itself. The plumbing fitting is a great idea. I bought a 3/8 metal dowel to make restrictors, but i think the valve might be easier. Unboosted, the feel is great and you can really tell right before ABS kicks in. When the pads are cold, the pedal is really tough to push, it does get better as they heat up, but I didn't really get to a point where I was confident at Road Atlanta. On turn 10a, I would brake at ~150 at ~135+mph and that was usually too early.
Cold Tires + Wall = Suck
After doing some more track days and playing around with the pipe valve, I don't think it has done much to satisfy me. There was a slight change, but I still have a pedal at the track where is sinks so low that I have to use the top of my foot to heel-toe, which is very inconvenient. And even though I know that the pipe valve is completely shut (meaning I should have completely unboosted brakes), I can't tell much of a difference when the valve is all the way open.Originally Posted by mcclaskz
The pedal is just too low for me at maximum braking, usually requiring me to lift pressure a good amount just to blip the throttle, no doubt making me lose a ton of time in the braking zones.
I've resigned myself to the fact that I'll have this pedal problem with stock, floating calipers. Everyone I've talked to with aftermarket fixed, calipers (StopTechs, APs, Brembos, etc.) have all said that they haven't had this problem.
Is there a way to adjust the height of the brake pedal on the stock, factory setup?
Drive Safely,
Raza
Current:
2016 Porsche 911 Carrera GTS
Past:
1994 E36 BMW Dinan 3
1998 E36 BMW ///M3/4
2000 E39 BMW ///M5
2002 E46 BMW ///M3
2008 E60 BMW 550i M-Sport
We had the problem when we were running Brembo's on our car with the stock booster, etc.Originally Posted by RUddin3
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