Spongy Brakes

wyshyvanuk · 11-13-2023, 12:41 PM

Just came back from a 600 mile road trip during which my 2008 Z4M developed a spongy brake feel. No obvious fluid leaks and the master cylinder is full. Any ideas as to cause? I'm in Tucson and the car never gets close to any rain. I'll pressure flush with new fluid, but I'm curious about the cause. Any insight would be appreciated. Thanks!!

3002 tii · 11-13-2023, 02:28 PM

When was last time you did flush? What kind of pads are you running?

wyshyvanuk · 11-13-2023, 03:02 PM

Flushed about five years/2500 miles ago. I've never changed the pads, but, based on the brake dust, they are probably OEM. I've added about 3200 miles to the car. Yeah....limited use.

86Zed · 11-13-2023, 03:19 PM

Time to flush that brake fluid. I do mine every other year or so, annually if tracking the car. What color is the fluid when you open the reservoir cap?

wyshyvanuk · 11-13-2023, 03:25 PM

Color = very light tan/yellow. Just discovered that I'd lent my flush kit to my grandson in Phoenix. Replacement on the way.

pungo · 11-13-2023, 03:56 PM

AZ heat can be brutal on the rubber hoses, I'd give them a close look, replace them with some stainless ones.

wyshyvanuk · 11-13-2023, 05:19 PM

Will do!!

wyshyvanuk · 11-15-2023, 02:21 PM

Report from the front: Checked the pedal feel again this morning (totally cool temp) and it's mostly normal. It "compresses" a bit but not enough to alarm me, and certainly much less than on the trip. I also checked the four rubber brake lines. Although leak-less, they appeared to be harder than my arteries. Does anyone know if these OEM lines are braided with something underneath the rubber, or does the stiffness indicate that they are toast and need to be replaced? Thanks!!

11-13-2023, 12:41 PM	#1
wyshyvanuk Second Lieutenant 449 Rep 229 Posts Drives: 2008 Z4 MR Join Date: Apr 2018 Location: Tucson AZ iTrader: (0)	Spongy Brakes Just came back from a 600 mile road trip during which my 2008 Z4M developed a spongy brake feel. No obvious fluid leaks and the master cylinder is full. Any ideas as to cause? I'm in Tucson and the car never gets close to any rain. I'll pressure flush with new fluid, but I'm curious about the cause. Any insight would be appreciated. Thanks!!
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11-13-2023, 02:28 PM	#2
3002 tii Lieutenant General 2288 Rep 12,565 Posts Drives: Z4 M, X5, GX460 Join Date: Apr 2008 Location: CT iTrader: (99) Garage List F15 X5 xDrive35i [8.75] E86 Z4 M [10.00] F10 550i (Retired) [9.17] F25 X3 xDrive35i (R ... [9.43] E82 135is (Retired) [9.50] E85 Z4 M (Retired) [9.41] E90 328i xDrive (Re ... [9.25] E86 Z4 3.0si (Retired) [9.24]	When was last time you did flush? What kind of pads are you running? __________________ Follow for latest mods
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11-13-2023, 03:02 PM	#3
wyshyvanuk Second Lieutenant 449 Rep 229 Posts Drives: 2008 Z4 MR Join Date: Apr 2018 Location: Tucson AZ iTrader: (0)	Flushed about five years/2500 miles ago. I've never changed the pads, but, based on the brake dust, they are probably OEM. I've added about 3200 miles to the car. Yeah....limited use.
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11-13-2023, 03:19 PM	#4
86Zed Get off my lawn 932 Rep 1,159 Posts Drives: 6MT Join Date: Sep 2015 Location: USA iTrader: (7) Garage List 2023 GR Corolla [0.00] 2022 BMW X3 M40i [10.00] 2007 BMW Z4M Coupe [0.00] 2002 BMW 325xiT [0.00] 1991 BMW 318is [0.00]	Time to flush that brake fluid. I do mine every other year or so, annually if tracking the car. What color is the fluid when you open the reservoir cap?
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11-13-2023, 03:25 PM	#5
wyshyvanuk Second Lieutenant 449 Rep 229 Posts Drives: 2008 Z4 MR Join Date: Apr 2018 Location: Tucson AZ iTrader: (0)	Color = very light tan/yellow. Just discovered that I'd lent my flush kit to my grandson in Phoenix. Replacement on the way.
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11-13-2023, 03:56 PM	#6
pungo Colonel 880 Rep 2,547 Posts Drives: Z4MC-X3-35i-525i, Corrado G60 Join Date: Nov 2007 Location: MD iTrader: (5) Garage List 2011 BMW X3 x35i [0.00] 2001 BMW 525i [0.00] 2007 BMW Z4 M Coupe [8.76]	AZ heat can be brutal on the rubber hoses, I'd give them a close look, replace them with some stainless ones.
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11-13-2023, 05:19 PM	#7
wyshyvanuk Second Lieutenant 449 Rep 229 Posts Drives: 2008 Z4 MR Join Date: Apr 2018 Location: Tucson AZ iTrader: (0)	Will do!!
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11-15-2023, 02:21 PM	#8
wyshyvanuk Second Lieutenant 449 Rep 229 Posts Drives: 2008 Z4 MR Join Date: Apr 2018 Location: Tucson AZ iTrader: (0)	Report from the front: Checked the pedal feel again this morning (totally cool temp) and it's mostly normal. It "compresses" a bit but not enough to alarm me, and certainly much less than on the trip. I also checked the four rubber brake lines. Although leak-less, they appeared to be harder than my arteries. Does anyone know if these OEM lines are braided with something underneath the rubber, or does the stiffness indicate that they are toast and need to be replaced? Thanks!!
	Appreciate 0 Quote