Leaky Master Cylinder?
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Fleet Owner
Joined: Aug 2010
Posts: 21,253
Likes: 1,656
From: Reynoldsburg, Ohio
Leaky Master Cylinder?
Not a Blue Oval product, one of those Swedish nightmares, aka '99 Volvo S80. 
(Got it CHEAP, can't badmouth it too much............)
Replaced all four rotors & pads, PO had run them all the way to metal on metal contact----never seen brake parts this bad. Replaced with good NAPA stuff, car was great for a few days--brakes right at the top of the pedal where I like them.
No idiot light but a "Warning: Brake Failure" message appears on a screen alone with another light warning of low brake fluid. Refilled the reservoir (thinking it was just low due PO neglect---all was good for another few days.
Just this morning once again with the warning lights/messages, reservoir low again. There's not one sign of fluid on the ground or underneath the car anywhere.
No noises from the booster---that seems to be working just fine. Any ideas?
Thanks in advance BTW!
(Got it CHEAP, can't badmouth it too much............) Replaced all four rotors & pads, PO had run them all the way to metal on metal contact----never seen brake parts this bad. Replaced with good NAPA stuff, car was great for a few days--brakes right at the top of the pedal where I like them.
No idiot light but a "Warning: Brake Failure" message appears on a screen alone with another light warning of low brake fluid. Refilled the reservoir (thinking it was just low due PO neglect---all was good for another few days.
Just this morning once again with the warning lights/messages, reservoir low again. There's not one sign of fluid on the ground or underneath the car anywhere.
No noises from the booster---that seems to be working just fine. Any ideas?
Thanks in advance BTW!
Postmaster
Joined: Dec 2008
Posts: 3,940
Likes: 8
From: Southern Oregon Coast
Sounds to me like it's sucking the fluid through the booster. I had a van that did that - even though the booster seemed fine. Is there smoke in the exhaust? Do you notice any "spots" on the paint behind where the exhaust dumps out that look like someone splattered oil on the paint? On my van, those spots covered the back doors...
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Sent from my Nexus S 4G using IB AutoGroup
Post Fiend
Joined: Jul 2013
Posts: 11,055
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From: greater cleveland
Finding Brake Fluid Leaks
This might not be as easy as it sounds. Some brake fluid leaks can be downright hard to find. Start with a good inspection of all the brake lines and fittings. If you don't see any leaks there, remove the wheels and inspect the brakes themselves. Pay particular attention to the wheel cylinders. Pull back the dust boots on the wheel cylinders and look for fluid leakage. If you see any, replace the offending wheel cylinder(s). Lastly, check the master cylinder by holding your foot on the brake pedal. Don't push too hard; it's easier to diagnose with just a moderate amount of pressure. If the pedal slowly sinks to the floor, then you likely have an internal leak inside the master cylinder.
This might not be as easy as it sounds. Some brake fluid leaks can be downright hard to find. Start with a good inspection of all the brake lines and fittings. If you don't see any leaks there, remove the wheels and inspect the brakes themselves. Pay particular attention to the wheel cylinders. Pull back the dust boots on the wheel cylinders and look for fluid leakage. If you see any, replace the offending wheel cylinder(s). Lastly, check the master cylinder by holding your foot on the brake pedal. Don't push too hard; it's easier to diagnose with just a moderate amount of pressure. If the pedal slowly sinks to the floor, then you likely have an internal leak inside the master cylinder.
Thread Starter
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Fleet Owner
Joined: Aug 2010
Posts: 21,253
Likes: 1,656
From: Reynoldsburg, Ohio
Thanks guys----I really appreciate your thoughts! I had those same initial ideas based on past experiences and yet thought I might be over looking something. As it turns out it was something far, far more surprising than I ever imagined.
Conversation with a trusted mechanic friend suggested it could be a blown line inside the cabin!
Since no fluid could be seen outside his idea was to feel for soaked carpet, he'd seen it before. Sure enough removing the driver's side factory floor mat there must have been almost a quart of fluid saturating the carpet.
Not a sign whatsoever of the master cylinder or booster leaking into the cabin so it must be a line that runs through the interior.
I called this "cheap" find a Swedish nightmare----its proving to be all that. I'm going to sell it quickly with full disclosure so someone else isn't surprised by this, at least the brakes part.
Thanks again----appreciate the input!
Conversation with a trusted mechanic friend suggested it could be a blown line inside the cabin!
Since no fluid could be seen outside his idea was to feel for soaked carpet, he'd seen it before. Sure enough removing the driver's side factory floor mat there must have been almost a quart of fluid saturating the carpet. Not a sign whatsoever of the master cylinder or booster leaking into the cabin so it must be a line that runs through the interior.
I called this "cheap" find a Swedish nightmare----its proving to be all that. I'm going to sell it quickly with full disclosure so someone else isn't surprised by this, at least the brakes part.
Thanks again----appreciate the input!
Post Fiend
Joined: Jul 2013
Posts: 11,055
Likes: 0
From: greater cleveland
JWA,,,thanks for the learning experience i never would of thought of interior run brake lines,,,but a friend says the car he owns has the battery installed under the seat,,,,good luck and peace
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