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I decided to post another thread since this will be a diagnosis thread.
I am about to order master cylinder and reservoir from FCP Euro pending the comments I receive here. I thought about buying 2nd hand from ebay but I am no a risk taker when it comes to safety-related components.
Last edited by DLB_Adelaide; 06-01-2023 at 03:20 AM.
Update: just found B34 is actually master cylinder output data. Now just have to figure out what the “acceptable” values are for full foot brake applied. Pic below shows model w163??
The GL is pretty much the same as the ML and when I purchased mine in 2007 (first year of GL) the magazine road tests of the time noted poor brake pedal feel. So did I, but I’m used to it by now.
The GL is pretty much the same as the ML and when I purchased mine in 2007 (first year of GL) the magazine road tests of the time noted poor brake pedal feel. So did I, but I’m used to it by now.
That might be a possibility. I am used to great pedal feel from my previous cars.
That might be a possibility. I am used to great pedal feel from my previous cars.
My ML has what I thought was a soft pedal and I did need to get used to it. But there's nothing wrong with it after 120k it's still the same and never given me an issue. If you want me to compare readings from mine let me know.
My ML has what I thought was a soft pedal and I did need to get used to it. But there's nothing wrong with it after 120k it's still the same and never given me an issue. If you want me to compare readings from mine let me know.
That will be heaps helpful if you could. Grab the B34 max value when you depress the brake pedal.
Last edited by DLB_Adelaide; 04-06-2023 at 04:49 AM.
Engine ON so the vacuum helps to achieve MAX value. I just did a test again. Brake pedal able to reach the floor and achieved 140Bar of pressure at B34
Agree with the above. My GL is spongy on the brakes. When I put on new downgraded rotors and pads I’m going to do a full bed in cycle and see if this helps.
That will be heaps helpful if you could. Grab the B34 max value when you depress the brake pedal.
You'll have to show me which part of the icarosft program you were in as I have the same scan tool and couldn't find anything on the metrics shown on your screenshots. Let me know where to access them and ill do it early tomorrow.
Agree with the above. My GL is spongy on the brakes. When I put on new downgraded rotors and pads I’m going to do a full bed in cycle and see if this helps.
I’m not optimistic.
The pedal might be soft (plenty of comments on this in the forum) but i still reckon the brakes are great. Mine has the 350mm rotors so that could make a difference but mine stops on a dime.
Thanks all for the input. I graphed the B34 pressure over time. I would say I am not satisfied. Although the pressure reaches 140Bar, it takes a while to reach operating pressure. So there might be some truth to an internal leak on the master cylinder. I would have expected a sharper slope on my graph. The 140Bar is the result of pressure equalisation inside the cylinder. So my true B34 reading is somewhere 98Bar as I originally posted. In the old W163 brake, there are two sensors for B34 (master and slave). It would have been easier to diagnose with two sensor readings.
I might be wrong but these are my observations so far.
The test is in:
Diagnostic
Manual scan
ESP selected
Further select ESP
Tick B34
Last edited by DLB_Adelaide; 04-06-2023 at 09:05 PM.
Ok, so below is the result of testing on my ML500/550 with the 350mm brake package. Note pads and rotors due for change havinh done about 80,000km.
Yep, that's the IDEAL graph curve I was looking for. Sharp and vertical. Notice the difference between my graph. My graph reaches at 75% mark then starts to curve. Definitely something wrong with my brakes.
Yep, that's the IDEAL graph curve I was looking for. Sharp and vertical. Notice the difference between my graph. My graph reaches at 75% mark then starts to curve. Definitely something wrong with my brakes.
I cant say I understand the pressure difference or what the proper scale might be, but there's a fair difference (92 v 147). Make sure you post the solution and what the 'normal numbers' should look like.
04-05-2023, 07:51 AM
