I've been having some strange brake behavior recently (long pedal travel before I get any real brake pressure, spongy pedal feel) and while I was under the car replacing CV axles, I noticed a small drop of brake fluid where the master cylinder mates with the brake booster. Do you think this behavior and the fluid could be indicative of a failing master cylinder? Does anyone know of any tests I could do to possibly corroborate my thought that it might need to be replaced? (The brake fluid level is fine and the brakes were bled when I replaced a wheel cylinder about 8 months ago, so I don't think it's an air issue unless the master cylinder is failing and air was introduced through the piston seal.)
Should I replace my brake master cylinder?
- Thread starter BrotherMichigan
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Nick1994
$100 site donor 2024
I'd replace it. Check around for the leaks to make sure it isn't a brake line connection leaking.
Master cylinders can fail and leak internally you will not see any sign of a leak. Based on your symptoms I would replace it. Usually not hard to do and not too expensive. Make sure if you do it yourself to bench bleed the master cylinder though.
Thanks for all the quick replies. I've been meaning to get after this problem for a while and Rockauto has a master cylinder for my car on closeout for about $25, so I figured I should jump on it if I could get some confirmation.
Thanks again, all!
Thanks again, all!
Originally Posted By: BrotherMichigan
I noticed a small drop of brake fluid where the master cylinder mates with the brake booster. Do you think this behavior and the fluid could be indicative of a failing master cylinder?
Yes it is probably seeping out the back of the master cylinder. My Volvo did the same a few weeks back, and I had to replace it. If I sat at a traffic light for a good bit, the pedal would start dropping to the floor, but one pump would bring it back up. Definitely change yours ASAP before it gets worse.
I noticed a small drop of brake fluid where the master cylinder mates with the brake booster. Do you think this behavior and the fluid could be indicative of a failing master cylinder?
Yes it is probably seeping out the back of the master cylinder. My Volvo did the same a few weeks back, and I had to replace it. If I sat at a traffic light for a good bit, the pedal would start dropping to the floor, but one pump would bring it back up. Definitely change yours ASAP before it gets worse.
Just wanted to come back and say that I finally got the master cylinder replaced and it did wonders for my brake feel. Pedal travel is still a bit long, but the car needs a brake job too, so I'm sure that's part of it.
A tip for anyone who stumbles across this post in the future: make sure your new master cylinder comes with an o-ring to seal the master cylinder to the brake booster or salvage the one of the old master cylinder. It's a pain to get everything all buttoned up and bled only to have to undo it all after because you've got no power brakes.
A tip for anyone who stumbles across this post in the future: make sure your new master cylinder comes with an o-ring to seal the master cylinder to the brake booster or salvage the one of the old master cylinder. It's a pain to get everything all buttoned up and bled only to have to undo it all after because you've got no power brakes.
If you are going to do it yourself, rebuilding it is hardly extra effort and is cheaper and ensures OEM parts. Make sure to use line wrenches on the nuts, not ordinary wrenches.
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