Is this squirting brake fluid from the wheel cylinder normal?

257 Views 3 Replies 3 Participants Last post by Treegrower, 13 d ago

MartyMcfly121

Discussion Starter · 14 d ago

Clearly it’s not normal but hear me out. I was changing my back brake shoes and drums because I was hearing a grinding / squealing and figured the brakes needed to be changed.

Once I got the drum off, I noticed there was a bit of leaking fluid from the rubber part of the wheel cylinder and I gently pressed on it and more fluid came squirting out.

This made me want to see what happened when I pressed on the brakes. The pedal bottoms out to the floor which is not how it acts when driving. theres maybe an inch or two I can depress. So I’m thinking that with the drums off, the pedal is allowed to go to the floor, and puts a lot more pressure through the brake line causing it to squirt out.

I’ve been driving the pat for 4 years and If it was leaking this much brake fluid, i’d be out in less than a week so it must be that it acted this way since I had the drums off, but can anyone confirm / deny this for me ? I have two wheel cylinders coming Monday to replace them , but I’d really like to hear from more knowledgeable people if they think this looks bad or other opinions. Also, the shoes seem thinner at the bottom than the top - I’m not sure if these are super low or not.

May 20, 2023

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mr_et2

· #2 · 14 d ago

The brake cylinder is only supposed to have a certain amount of travel on it. Too much and the piston inside can get ejected and seals can get damaged. When the brakes are assembled and the drum is on, the shoes pressing on the drums is what limits how far the piston in the brake cylinder can travel. Remove the drum though, and there's nothing to stop it. When you press the brake pedal without the drum in place, the piston comes out of the cylinder, seals and boots get damaged, fluid squirts all over, and air get into the brake line.

You're going to need to replace that brake cylinder and bleed the line. If there was fluid leaking out before you removed the drum and pressed the brake pedal, then it needed to be replaced anyway, as it was already leaking.

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MartyMcfly121

Discussion Starter · #3 · 13 d ago

mr_et2 said:
The brake cylinder is only supposed to have a certain amount of travel on it. Too much and the piston inside can get ejected and seals can get damaged. When the brakes are assembled and the drum is on, the shoes pressing on the drums is what limits how far the piston in the brake cylinder can travel. Remove the drum though, and there's nothing to stop it. When you press the brake pedal without the drum in place, the piston comes out of the cylinder, seals and boots get damaged, fluid squirts all over, and air get into the brake line.

You're going to need to replace that brake cylinder and bleed the line. If there was fluid leaking out before you removed the drum and pressed the brake pedal, then it needed to be replaced anyway, as it was already leaking.

Thanks very much for this information. That all makes sense.
I agree with your thought that it needed to be replaced regardless as it was leaking fluid prior to stepping on the brake after removing the drums.

I’m going to just flush the system on every line while I’m at it- The fluid looks very dark and I doubt the previous owner ever changed it.

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Treegrower

· #4 · 13 d ago (Edited)

I agree with mr_et2's assessment - you can see the right piston overextended. I'm doing my rear drum brake shoe replacement today. It is important when installing the shoes, springs, etc. to keep the wheel cylinder pistons from over extending in either direction. Someone posted here that some aftermarket shoes don't have the brake shoe material extend far enough on the metal, so be aware of that possibility. It is normal for the shoes to wear thinner on one end because of the way they engage the drum.

I found this YouTube video to be one of the best for rear shoe replacement, except he admits he should replace the severely rusted drums/hardware:

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May 20, 2023

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