550: I'm having a clunk sound when depressing the brake pedal at roughly 1/2 pressure/halfway travel. It's independent of movement and vacuum/engine on. Can be heard both inside and out. Listening with a stetoscope, it seems to come from the T at the brake pressure sensor. Local dealership says that's not it, but blames the master/slave cylinder. I've bled these as well as driverside front wheel. No change. Sounds use like something of metal gives/moves at a certain pressure and can be felt through the pedal. I have no leaks and all bolts seems to be tight. Anyone experienced this or have some idea of how to proceed without just replacing parts with new.
Not sure what the dealership is on about with slave cylinders on a brake system...do the brakes perform as expected?
Interesting. A faulty brake pressure sensor has been known to cause a knocking sound on the F355. https://www.ferrarichat.com/forum/posts/146952841/ (first page of this thread only... It digresses after that) Sounds like identical symptoms.
This would be the equivalent switch on the 550 (Item 7) Image Unavailable, Please Login Since the switch is for the suspension system, your brake system should be relatively normal (if this is the cause). It's just to prevent dive when braking. Changing that switch first would sound like a good first DIY step to me. Eurospares has these for U$24 (21 Euro) https://www.eurospares.co.uk/parts/ferrari/550-maranello/brakes-wheels/brake-system-not-for-gd-19861 For info, the switch has the same part number as the one on the F355.
Wow! Thanks! That is the exact description of my issue. It also comes to the same conclusion I got to with a 3$ stetoscope and a girlfriend stamping the pedal. Suspension system? Really? I thought it would go to ECU monitoring brakepressure for safety. The sensor sits on a line going from the master cylinder to the ABS system. i'm guessing the signal could be used as input to the active suspension (which i cant seem to feel any function of, except traction control not kicking in constantly). The part no is the same and yes, it is cheap. Would probably need to bleed the whole system again after replacing it though.
The wiring diagrams show the sensor is wired into the Suspension ECU only. As I said, the sensor is for anti-dive. When you stomp on the brake pedal, the front of the car will tend to drop. The suspension ECU tells the shock aborbers to firm up. I'm not sure what this does to the car dynamically. Perhaps it maintains the geometry of the suspension for better handling. Looking forward to the update. I don't know if bleeding is required. Experts? I assume there is no pressure in the line until you push the brake pedal, but I guess fluid may leak out when you remove the switch. I would clean up everything near the switch so you can do a fast swap. Use lots of rags to protect the paintwork.
Makes sense yes. I think you are spot on in regards to geometry. Also, weight transfer is preferably to be avoided. Braking into a corner, with a heavy V12 hanging over a single front tire, is asking for understeer. I'll try to test the 'sport' function when braking, if there is a noticable difference. As mentioned, I haven't found any change in firmness with sport on/off. I thought something might be off in my system, due to age/lack of use from original owner. But again, this must be one of the first active suspension systems.. My thoughts are the same. The T junction can be loosened a bit to get a rag under there, depending on how much flex I have in the brake lines going down there. But should be doable. If nothing comes out, all is well. But it any air in there is too much. Especially as the line goes to the ABS system and I don't know how that would react. What brake fluid is Ferrari recommended for the 550? I only have Castrol SRF, and that is wasted on this in my mind.
Not sure what you mean by "wasted on this". Remember the fluid is used for the clutch, too (same reservoir). What does your handbook say? The WSM says Shell Donax UB Brake Fluid Dot4 Ultra. http://triska-uploads.s3.amazonaws.com/1480499938-TDS_Brake_and_Clutch_Fluid_DOT_4_Ultra.pdf https://oilgrease.co.in/brake-and-clutch-fluid-dot-4-ultra-shell/ I know I always have trouble finding the right fluid for my F355. I think I ended up using Motul RBF600. I see the sensor has a pressure value printed stamped on the side. Perhaps it's a switch rather than a sensor? Image Unavailable, Please Login
I mean that SRF have an extremely high boiling point, being expensive but quicker at absorbing moisture, hence must be changed more often. Hence this being a track oriented fluid. Use it on my GT3. I'll have a look for the Shell Donax. I should have checked the manual. I'm still getting used to how great Ferrari are at giving relevant info in their manuals, as opposed to almost everyone else. I wouldn't think of that. Makes sense. It must have some kind of moving part to make that sound. Also looks like a regular oil pressure switch from my old 205GTI.
Sadly no. I got the part home, and would replace it, but the whole assembly feels too delicate to force, and it is really stuck on there. I decided to asked Ferrari to do it, when it goes on for a service
