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BJ8 Rear Wheel Cylinder leaking

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AUSMHLY

AUSMHLY

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I noticed a leak, below the right wheel tire. Took off the drum, the wheel cylinder is leaking.
Brake/clutch reservoir is low.

Why do the wheel cylinders start leaking? When replacing it, should the other side be replaced at the same time, or only after it starts leaking. These can go years without a problem, right?
The brake pads have some oil on them, seem thick enough to last a while longer. OK to clean them with brake cleaner and keep them?

Local parts store doesn't sells these wheel cylinders. Moss sells two models. What's your thought on $15.99 vs $59.99.
Do I need the brake assembly rubber grease? If so, where do I put it?
Moss only sells Dot 4 Castrol brake fluid. Thought BJ8 should be Dot 3?

I have always had a mechanic work on my brakes, this time I thought I'd give it a try


021-151 BN7-BJ8 Wheel cylinder, 3/4” bore, Rear, aftermarket $15.99


021-161 BN7-BJ8 Wheel cylinder, 3/4” bore, Rear, TRW brand $59.99


220-443 Brake Assembly rubber Grease $2.59


What fluid, Castrol brake fluid DOT 3 or DOT 4
 
So many questions ...

1) Why do the wheel cylinders start leaking? Normal wear, or a piece of grit/rust roughs up the seal, crappy fluid, ...

2) When replacing it, should the other side be replaced at the same time? IMO, no (unless you really want to). The other might last another 50K miles, and the new one might leak in 50. But, see answer #2.

3) The brake pads have some oil on them, seem thick enough to last a while longer. OK to clean them with brake cleaner and keep them? If the pads have just a teensy bit of fluid on them, you might be able to sand/clean/sand/clean them. I've not had any luck with that; the material might as well be made of sponge (I'd think I had one cleaned off, but it would ooze fluid overnight). If there's fluid on the pads they will not perform properly and, obviously you should replace them. If this is the case you might end up doing both sides (you'll be up on jackstands--right?--and have your tools out, and you're making an order to Moss anyway ...). Check the drums; if they have ridges you might need new (unless you can find someone to turn them; I never could).

4) What's your thought on $15.99 vs $59.99? I installed one of the 'cheap' ones a few years ago. Haven't pulled the drum off lately, but my brakes work fine and I'm not losing fluid. Quality was fine, a logo isn't worth $44 to me.

5) Do I need the brake assembly rubber grease? If so, where do I put it? Can't hurt; put a very thin smear on the seal. In a pinch, use your brake fluid of choice (note the cylinder will probably come with a small packet of grease; don't buy it separate).

6) What fluid, Castrol brake fluid DOT 3 or DOT 4? What do you have in there? Best to stick with what you have, IMO, but AFAIK 3 and 4 can be mixed. If you haven't bled your system in a while now's a good time (up on jackstands, etc.). DoT 4 is fine and can be used without a thorough cleaning of the system--if you didn't have it in there already--but so is DoT 3 (which is used in many ABS systems). DoT 4 has a higher boiling point.

Two things you never want to half-ass: brakes and suspension/steering.
 
Thank you Bob.

So many questions ...

In reading Norman Nock's "Teck Talk" Technical Article Book, I read this under Brake Adjusting.
"Note: if the brake fluid is dirty, the seals in the hydraulic system are deteriorating, and the hydraulics should be completely rebuilt."

My left rear cylinder is leaking, is that because it's deteriorating or maybe just a bad part? The fluid on the ground does look brown, not clear.
Once I replace the cylinder and brake pads, I'll bleed it till I get clear fluid with no air. That takes care of the defective cylinder.

Being I'm replacing the left shoes, I think it would be prudent to replace the right shoes too.

How do I determine if I should replace all associated brake system parts that have rubber for fear of deteriation?
I can bleed all four wheels till clear fluid come out. At least that clear the system of dirty fluid.
If I should replace things, what list of parts?
Thoughts?
 
Brake seals deteriorate after long-term exposure to fluid that has absorbed moisture. That's why the advice is to change it every year or so Most people don't bother, but British cars seem to be especially sensitive to this. If your brakes are working fine, the only way to tell the condition of the seals would be to take the cylinders and calipers apart and inspect them. At which point, you might just as well throw new seals at them. If the brakes are working well, I'd probably replace both rear cylinders and shoes and bleed the system. If your front calipers aren't hanging up, you're probably good. Personally, I'd spend the extra bucks for the TRW brand. Read about their quality control and try to guess how it would compare to an off-shore unbranded part: https://www.trwaftermarket.com/us/import-program-pc/drum-brake-systems/Wheel-Cylinders/ Your driving probably an $80k car with a single circuit braking system Brakes are probably not a good place to go cheap
 
You might get away with a rebuild kit on the brake cylinder. Pull it, take it apart and inspect the bore; if it's not worn a kit should do it.

I'll think you'll need new shoes and, if so, do both sides.
 
Bob_Spidell said:
You might get away with a rebuild kit on the brake cylinder. Pull it, take it apart and inspect the bore; if it's not worn a kit should do it.

I'll think you'll need new shoes and, if so, do both sides.
Click to expand...
I concur. In the old days, (American and foreign cars) it was customary to just buy the wheel cylinder kits (rubber seals and boots) do a clean-up hone on the cylinders and put them back together. Last I looked__not recently__you could still get the rubber kits, but that was when we were much less of a disposing society, and rebuilt, rather than replace.

Unless you have a bonafide reason to suspect them, I'd leave the calipers alone. Oh sure, check pad thickness, and include them in the bleeding process, but don't take them apart if you don't have to. I find that it takes several attempts at bleeding the system to truly purge them of ALL the air.

Rick makes a very good point about refreshing the brake fluid periodically; following BMW's recommended interval, I try to do it every two (2) years (though I do tend to fall behind occasionally...). Doing a refresh is a lot easier than bleeding after working on the circuit, as there's really no air trapped, just let it keep flowing until clear fluid comes out. I'm sure that everyone knows this, but it's the left rear wheel that's farthest from the master cylinder, so start there, and at least on my BN6, the right front is the shortest pipe run, so that'd be the last point to bleed (trivial matters, both, imo).
 
I would do both the shoes (if contaminated) and rear cylinders or cylinder kits. I had brake fluid on a rear shoe and had SEVERE lockup on that wheel. New shoes, as suggested to me on the forum, restored normal braking. Of course I explored other alternatives before I accepted that brake fluid contamination, even though it looked minor, virtually caused the the rear end of my BN7 to skid.
 
Until a few years ago ATE supplied their brake fluid in both clear and blue, which made flushing a very simple job as it merely required draining/adding until you saw the color change. Then DOT promulgated that Dot 3, Dot 4 and Dot 5.1 brake fluids (all of the non-silicone formulations) be "clear or amber" in color (https://www.law.cornell.edu/cfr/text/49/571.116) and the ATE SuperBlue fluid is no longer legal in the US. I assume there is some logic behind this decision though it escapes me, but in any case it gave the 86 to a handy asset.

Being of a contrary nature I must wonder why I could not safely dye brake fluid on my own and I wonder if there are any thoughts or knowledge on this. This can seemingly be done: Go to https://www.youtube.com/watch?v=dMOUFVv4bo8 to see a video that seems to make sense, but with no disrespect to its author Paul I wonder if there is more to it than he says.

Reid: I hope--sincerely--this post does not run afoul of any BCF rules. I am not condoning criminality but enquiring minds just want to know.


 
Bob_Spidell said:
6) What fluid, Castrol brake fluid DOT 3 or DOT 4? What do you have in there? Best to stick with what you have, IMO, but AFAIK 3 and 4 can be mixed. If you haven't bled your system in a while now's a good time (up on jackstands, etc.). DoT 4 is fine and can be used without a thorough cleaning of the system--if you didn't have it in there already--but so is DoT 3 (which is used in many ABS systems). DoT 4 has a higher boiling point.
Click to expand...
I have Castrol GTLMA now. Bottle doesn't say Dot3 or Dot4 specific. (Says, "exceeds dot 3 & dot 4 specs")
None of the local auto stores (Walmart, Napa, Autozone, O'Reillys, Petboys) carry Castrol brake fluid.
Why is this brand recommenced?
I believe Castro doesn't sell this white bottle GTLMA anymore. I think only Castrol Dot 4 in a black bottle.
Can I go with another brand? One that is Dot4.
I'm assuming I should bleed all 4 wheels to get the old fluid out. And best to do so if replacing with a different brand. How many fluid oz do you think that will take?


IMG_2262.jpg
 
Ausmhly also wanted to know about how much fluid it would take to do a complete change--a good question to which I don't know the answer, and it is hard to know when all of the old fluid is expelled without some visual cue.

I am way overdue for a brake fluid flush and ran out of ATE Superblue last year. Since it is no longer available I have decided to make some tracer-laden brake fluid of my own along the lines of Paul Yaw's very colorful and entertaining video (see my post #9 above).

I verified with Bright Dyes that their 506250-R solvent dye is compatible with ester-based brake fluid and ordered 4 ounces of the red from Grainger. At a ratio of 1 oz. dye to 100 gallons fluid I will undoubtedly have a supply that will last into my grandson's lifetime, but that is the least I could get.

In any case I will try to measure how much old fluid comes out of all four corners when I do the flush and will report back.
 
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