Brake Master Cylinder
03-18-2018, 04:14 PM
#1
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Brake Master Cylinder
Quick question. Still getting squishy brakes after a brake flush. Did pads and rotors and a flush. Is there a definitive way to determine whether the brake master cylinder is faulty? The reason I’m asking is that I cannot stand my dealer. Everytime I take it there I get “not able to duplicate” excuse. I’ve driven this thing for 6 years and know that the brake feeling is getting worse. I was looking at alldata.diy and there is something that needs to be done after changing it out through PIWIS. Not sure if my Indy can do this? I would DIY but again with the software requirement, i’m at a loss. Just want to be as prepared as possible. Thanks!
03-18-2018, 04:50 PM
#2
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There is typically a function to activate the ABS/PSM modulator - since air can get trapped in some of the pump passages. That shouldn't happen if a flush is done in a manner so no air is introduced to the system. If what you did was actually a bleed of the system - it's possible air did get in.
The other "gotcha" on doing a flush at home - is if you do it by pumping the brake pedal - you can move the pistons in the master cylinder down into parts of the cylinder they've never been in before, and that can damage the seals of the master cylinder pistons. The way to avoid that is to tape a block of wood - perhaps 2-3" thick - to the back of the brake pedal so when it hits the floor the pedal isn't going down any further than it would in normal braking. That can all be avoided by doing a power flush like the dealer does - where the master cylinder reservoir is pressurized and automatically topped up by a pressurized container of DOT-4 and a special reservoir cap.
FWIW - I thought about doing it myself - but when I called the dealer they told me $200 to do it - and it takes about an hour and two techs.. so I just had them do it. I now have a firmer pedal than I did before.
FWIW-II - some aftermarket scan tools such as the Durametric and iCarScan will have a function to activate the ABS/PSM modulator - just like the PIWIS does. If you're going to be doing DIY stuff on a modern car - a good diagnostics tool is really a critical tool to have.
The other "gotcha" on doing a flush at home - is if you do it by pumping the brake pedal - you can move the pistons in the master cylinder down into parts of the cylinder they've never been in before, and that can damage the seals of the master cylinder pistons. The way to avoid that is to tape a block of wood - perhaps 2-3" thick - to the back of the brake pedal so when it hits the floor the pedal isn't going down any further than it would in normal braking. That can all be avoided by doing a power flush like the dealer does - where the master cylinder reservoir is pressurized and automatically topped up by a pressurized container of DOT-4 and a special reservoir cap.
FWIW - I thought about doing it myself - but when I called the dealer they told me $200 to do it - and it takes about an hour and two techs.. so I just had them do it. I now have a firmer pedal than I did before.
FWIW-II - some aftermarket scan tools such as the Durametric and iCarScan will have a function to activate the ABS/PSM modulator - just like the PIWIS does. If you're going to be doing DIY stuff on a modern car - a good diagnostics tool is really a critical tool to have.