Squishy brake pedal, fluid inside drum, possible axle seal leak or brake fluid leak?

Hello everyone,

I am experiencing some long brake pedal throw and my truck is not stopping as well as it should so I took off my rear drum to inspect and take some pictures.



as you can see it is clear there is some fluid in there my question is, is it brake fluid or axle grease...

more pictures close up:

this is the spring holding the bottom of the shoes. this is the wettest part, the rest of the gunk inside the brakes was a little more hardened from collecting brake dust.

the cylinder doesn't look like its leaking...

And the pads look OK, also the surface of the pads and where they contact the drum was not greasy or wet.


Finally, here is 2 pictures of the backing plate this is how I knew something was wrong. My uncle who is a mechanic said that I had an axle seal leak as soon as he saw the backing plate but we didn't investigate further. I don't have a picture of the other backing plate but it is completely squeaky clean:


Any info would be helpful. I am going to do a brake fluid flush soon to see if that makes my brakes feel any better.

 

Almost certainly brake fluid from a leaking wheel cylinder. If the axel seals were leaking it wouldn't affect pedal travel and the liquid would be very thick (90w gear oil). You'll need to replace both cylinder and shoes.

 

I would flush the brake fluid and do a good bleed job first.

To see if a wheel cylinder is leaking, carefully pull back the rubber boot on the front-end side of the cylinder, then do the same for the back side. Both should be dry. If one is wet, that cylinder is leaking.

Are the shoes themselves dry? Looking at the 3rd photo from the last, it appears to be dry. And looking at the 5th photo from the end, I don't see any signs of leakage. And I've seen plenty of leaky wheel cylinders over the last 60 years.

The stuff on the 4th photo from the top looks pretty dry to me, as if it happened years ago.

Look behind the backing plate where the axle housing connects. You should not see any sign of leakage there either.

If you are thinking about replacing the wheel cylinders, see if you can buy a kit instead. It's a lot less expensive, and the kit for one wheel will consist of a spring, a rubber cup, and a rubber boot, and it's very easy to replace those parts.

 

Ya, the shoes were dry. and the wheel cylinder did not seem to be leaking at all. I did not pull the boot back though...

I will clean up the backing plate and try to see if anything is leaking. there is so much gunk caked on the backing plate that I can not tell if anything is leaking at the axle housing. from what I did see, it was totally dry back there tho.

 

Pull the rubber boots on the wheel cyls. Fluid will collect inside when cyls are leaking. Will be dry inside boots if not leaking.

 

What's it smell like? If it's not brake fluid then it would be gear oil from the axle seal, and the two are very different from one another...gear oil has that very distinct gear oil smell.

 

Does the fluid residue have a smell?

No? It's brake fluid.

Yes? It's diff oil.

Dammit, beat me by 2 seconds haha

 

I will pull the boot and check it out.

 

hahaha, It had a faint smell. but my brake fluid in my reservoir smells?

 

faint smell = brake fluid

"holy hell this shit STINKS" = diff oil

 

haha ok that makes sense.

 

Also, I totally forgot to include this video in my post. not sure if this is totally unrelated or not but it seems like wheel hub as a lot of play in it. not sure if this is normal.

 

Have you been losing brake fluid by chance? If you had that much brake fluid in the rear near the axle I would imagine the reservoir would look pretty low

 

You can also undo bolt and cover (shown in quoted picture) where your ABS speed sensor would go if you had ABS and look down into the axle housing. If you see fluid you have a leaky axle seal.

 

No the reservoir looks fine, I have only owned the truck since March and it hasn't changed since.

 

O ya, I totally forgot about that I should have done that while I had the wheel off...

 

Today I noticed that I had more brake dust on my driver side front wheel than on the passenger. I'm guessing I also have some problem with the passenger caliper, maybe the slide pins are stuck or something wrong with the pistons.