Fluid out of rear brakes

[wanta4runner]

I noticed yesterday that there was some fluid inside the fender well on the back passenger side of my runner. Looks like the drum is leaking and there is also buildup in the rim. Is it worth looking into a disc brake conversion on the rear?

Pics of fluid


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[RikTT]

Axle seals leaking through wheel bearing or brake wheel cylinder. Most likely axle seals. Have a look at the brake reservoir and confirm if it's low but highly not the culprit.

 

[JRZEE2000TR4LTD]

Yes, in all likelihood, the dreaded rear axle seals. Tons of info about that repair on here. Don't forget to change your diff breather.

 

[GJReefer]

I had my Tacoma do the same thing after replacing all the driveline fluids with Royal Purple synthetic gear oil. Apparently our trucks were all made to have conventional oils run in them and the synthetic will slip past the axle seals. Also, is its not the wheel cylinder, check your breather on top of the axle housing. They usually get corroded or stuck closed and will create excess pressure in the rear diff, causing the seals to blow out and leak.

 

[Myrunr2010]

If it's coming from your brakes you ought to feel a difference in your pedal when you stop, at least I could in my f150 when they went bad.

I haven't seen too much info on rear disk brake conversations. I know there are a few companies that sell kits, but you end up losing your e-brake (which is an inspection item in VA), and your ABS I believe.

 

[catrains]

if the brakes work properly then it is the axle seal. first I would check the breather for proper operation as the diff heats up and the breather is plugged up with dirt rust this can create pressure that will cause the leak.

when changing the diff gear oil I always check the diff breather on all my vehicles non toyota also..

brake fluid is like water that looks like oil....

 

[Myrunr2010]

first I would check the breather for proper operation as the diff heats up and the breather is plugged up with dirt rust this can create pressure that will cause the leak.

I know this is commonly accepted as the reason that axle seals go, but I have a real hard time believing it, unless those seals are far more fragile than I think. I really don't think your thermal expansion rates are high enough under normal operating temperatures to cause enough pressure to cause the leak.

 

[JRZEE2000TR4LTD]

I know this is commonly accepted as the reason that axle seals go, but I have a real hard time believing it, unless those seals are far more fragile than I think. I really don't think your thermal expansion rates are high enough under normal operating temperatures to cause enough pressure to cause the leak.

I can 100% say that it is. All my seals, bearing etc were fairly new OEM. No leaks for about 5000 miles. Diff breather new too. Went wheeling and went through some pretty thick mud (which I'm still trying to get of months later) and about 2 weeks later I was dealing with a low brake pedal, which was caused by the same mud in the brakes. (one side was missing the adjustment cover) On a whim I pulled out the ABS sensor and had a sheen of gear oil in there. I pulled that side axle and there was only a slight amount in there. No puddling or anything. I cleaned it all up and looked on the other side and the same thing. I looked at my breather and it was encrusted with mud. Took it out as it was and tried to blow through it and it was stopped up good. I did the diff breather mod, changed my diff fluid and have since driven it about 7000 miles and it is bone dry.
I would suggest to everyone to do the diff breather mod as preventative maintenance not just if you wheel or ford water especially in the climates where rust is prominent.

Also, just to be clear, the diff breather isn't the only reason the seals leak.

 

[thegipper]

I can 100% say that it is. All my seals, bearing etc were fairly new OEM. No leaks for about 5000 miles. Diff breather new too. Went wheeling and went through some pretty thick mud (which I'm still trying to get of months later) and about 2 weeks later I was dealing with a low brake pedal, which was caused by the same mud in the brakes. (one side was missing the adjustment cover) On a whim I pulled out the ABS sensor and had a sheen of gear oil in there. I pulled that side axle and there was only a slight amount in there. No puddling or anything. I cleaned it all up and looked on the other side and the same thing. I looked at my breather and it was encrusted with mud. Took it out as it was and tried to blow through it and it was stopped up good. I did the diff breather mod, changed my diff fluid and have since driven it about 7000 miles and it is bone dry.
I would suggest to everyone to do the diff breather mod as preventative maintenance not just if you wheel or ford water especially in the climates where rust is prominent.

Also, just to be clear, the diff breather isn't the only reason the seals leak.

Exactly what he said ^

A clogged breather is not the only reason why they can leak but it is certainly one of them.

 

[Myrunr2010]

Coorelation is not necessarily causation is all I'm saying. I have not seen any empirical evidence to say that is the cause. I can't find the coefficient of thermal expansion for gear oil to be able to do the calcs.

 

[TheDurk]

Coorelation is not necessarily causation is all I'm saying. I have not seen any empirical evidence to say that is the cause. I can't find the coefficient of thermal expansion for gear oil to be able to do the calcs.

The expansion of the air above the fluid is more likely the major driver of the pressure rise. Plenty of air space to raise pressure with a decent ∆T from ambient temp, not running temp..

 

[shahsmerdis]

you do have rust on your frame. I assume it came from the salt belt? You should give it a good scrubbing down there and a coat of fluid film. check your rear diff breather as everyone said.

 

[JRZEE2000TR4LTD]

Coorelation is not necessarily causation is all I'm saying. I have not seen any empirical evidence to say that is the cause. I can't find the coefficient of thermal expansion for gear oil to be able to do the calcs.

Hmmm, I pretty much proved that the leak was caused by the breather as it was the only think I fixed given that everything else was baselined being new and not leaking before or after. Empirical enough for me.

 

[alumarine]

Hey OP check your brake fluid level.
It might just be leaking brake wheel cylinders.

 

[wanta4runner]

I'll check the fluid level. I did stop by the place that installed my lift and replaced the wheel bearing on that side. They said it's got a warranty on it so I might be in luck if that's it and only pay for the drivers side to get fixed if that's the problem.


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[thegipper]

The expansion of the air above the fluid is more likely the major driver of the pressure rise. Plenty of air space to raise pressure with a decent ∆T from ambient temp, not running temp..

Plus, why would they even put a breather in the differential if the temperature rise would never cause a seal to fail? Isn't that the whole point of the diff breather, to release excess pressure?

And by "fail" I mean, not keep the fluid from leaking out. It's not like the seal itself becomes damaged or disfigured.

Many of us have had trace amounts of fluid on our ABS rings but after doing the extended diff breather mod (essentially fixed a clogged breather with a much better design) the fluid has completely disappeared.

Again, it is not to say that is the only reason why they "fail". I'm sure some just get worn out and don't keep the fluid back. Slop in the wheel bearing will also absolutely cause the seals to fail.

 

[nevada]

Hmmm, I pretty much proved that the leak was caused by the breather as it was the only think I fixed given that everything else was baselined being new and not leaking before or after. Empirical enough for me.

I think he was talking about synthetic being the cause of it leaking.

edit: oh geez MY BAD. never mind. that isn't what he was saying.

 

[ZionXIX]

The expansion of the air above the fluid is more likely the major driver of the pressure rise. Plenty of air space to raise pressure with a decent ∆T from ambient temp, not running temp..

Your "delta T" is giving nightmare flashbacks to Physics and Chemistry courses

 

[thegipper]

When I changed my fluid I specifically didn't use synthetic because of the stories I read on here and guys who used it having leaks shortly thereafter. You can probably run synthetic if you have a fresh set of bearings and new seals.

I figured I don't want to take the chance and just used some cheapo diff fluid.

 

[shahsmerdis]

When I changed my fluid I specifically didn't use synthetic because of the stories I read on here and guys who used it having leaks shortly thereafter. You can probably run synthetic if you have a fresh set of bearings and new seals.

I figured I don't want to take the chance and just used some cheapo diff fluid.

I dont think synthetic actually causes the leak, just makes a borderline seal more apparent.