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Help diagnosing rear brake issues...

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Chet Zerlin

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Hello all,

Hadn't driving my 100-6 BN6 in a while and yesterday I found that the right rear brake was locked up tight. When I tried to loosen the brake adjuster it wouldn't move. Jacked up the rear and checked to see if a clogged brake line was the issue but when loosened brake fluid was not under pressure and flowed freely. So I put more muscle in the brake adjuster and it moved slightly - enough so that the wheel would turn. I noticed that moving the adjuster slightly in either direction would again lock up the brake. I was able to get the brake drum off and found fluid leaking (pic below).

This is my first time dealing with drum brakes (very familiar with disc brakes) so I wondered if anyone can give me some advice on what to do or check first before taking everything apart. Any suggestions or guidance would be greatly appreciated!

Thanks!

Chet
 

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I just put one on my BJ7. AH Spares has TRW. The web page says Girling but they are TRW. Seems like good quality.
https://www.ahspares.co.uk/austin-h...s-BRK159-to-BRK216/WHEEL-CYLINDER-rear-1.aspx

Mine has the plate/spring holding it in place. It's meant to move in the brake plate slot so that the parking brake functions right. If yours is the same as the BJ7 your in for a treat. Meaning a miserable 2 hours removing and reinstalling. I think that Randy Forbes had some good advice/how to.
 
You probably have brake fluid on your brake shoes. That means you will have to replace them too. If you don't have fluid on them, you're lucky.
 
Well I spent all of today riding a steep learning curve with my right rear drum brake. After studying the three (!) workshop manuals I have, I started to get a clearer understanding on how to dismantle and what to look for. Here's what I found:
1) the fluid was not leaking from my brakes but was leaking out from the half-shaft. The front and back of my brake shield as well as the wheel cylinder assembly were completely dry.
2) wondering why the brake was locked up (since a leak from the half-shaft shouldn't stop anything from turning) I discovered that the two tappets (thanks Moss Catalog!) that go into the adjuster (and move up or down with the adjustment screw) did not move easily and the bottom one had to be forced out with a screw driver. So that might explain my "seized" brake and also explain why when I was able to finally move the adjuster screw the brakes came free. However I don't think the adjuster screw is moving in and out completely so I'm planning on removing that assembly and taking a closer look at it after I solve the leak.
3) next I began to tackle the source of the leaking half-shaft. I undid the small screw that holds it on (it came out easily) and pulled the half-shaft out. Luckily the parts I got from the PO included the correct size wrench to undo that huge nut so I was able to get that off and then remove the washer (which has a small slot that needs to be lifted out of a hole in the hub). Then I used a hub remover to pull the assembly off so I could inspect the oil seal that I'm presuming was the source of the leak.
4) However, now I've hit a point that has me stumped. To me the bearing seems to be fine, no binding or other gritty feeling when turning....
I also looked closely at the condition of the oil seal and to me it looks fine too. No sign of wear and tear (at least from what I can see without removing it). Running my finger over it I could find no rough surfaces and nothing that looks like it's warped or otherwise damaged. Before I attempt to remove the bearing and replace that seal I want to make sure that it's needed (and that I fully understand why it leaked). Here's some pictures.
IMG_4073 2.JPGIMG_4076 2.JPG
Does anyone see anything wrong from these pictures. Is there supposed to be a space between the back of the bearing and the front of the seal as shown in the first picture?

I want to be sure I fully understand how this entire assembly seals out the differential oil. If the rear seal was not seated or was worn I can see how that would result in the oil coming out inside the brake assembly (which is what I found). But is that the only way for the oil to leak out where I found it? Is there any other seal or area that might explain it other then this seal?

I greatly appreciate any help!

Thanks!
Chet
 
There are two sealing places:
1) between the hub and the axle housing, which uses the seal you have identified.
2) Between the half shaft and the hub face. There is normally a very thin paper gasket between those faces. Leakage there ends up in the brake drum, so that wasn't it.

Since the bearing seems to be ok, replace the seal. It may be old.

Now, when reassembling the half shaft to the hub, if the new paper gasket is too thick, the bearing outer race wont be properly clamped and will spin. That's not good. The gasket needs to be thin enough so that the bearing spacer (Moss 675-130) clamps the bearing outer race. Measure how much the bearing spacer sits above the hub face, usually about 0.005" IIRC, and you'll see how thin a gasket you'll need. You may also go without the gasket and use a sealer like Hylomar. When you assemble the hub and tighten down that bug nut, plan on tightening it to 70 - 100 lb ft. Tight to clamp the bearing in place.
 
Thanks!

John, forgive me but what does "0.005" IIRC" mean (and exactly how do I measure that?);

I'm still questioning that space between the back of the bearing and the front of the oil seal - is it supposed to be there? If it is then when I replace the seal and press the bearing in how do I know when to stop? Is there a groove that stops the bearing from going any further?

Chet
 
There's a shoulder that stops the bearing.

PS - there's extensive discussion in another thread here about the Moss paper gaskets being too thick and causing the bearings to spin.

If the bearing slips out in your hand, it's probably spun. Heat from spinning ruins the seal. Spun marks on bearing:

BearingSpun.jpg
 
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Thanks Steve!

The bearing is tight and I will need to tap it out but thanks for the picture so I know what to look out for. The paper gasket I have on it now seems to be in good shape so I plan on just reusing it with a small amount of Hylomar just to be sure it seals tight.

I'm still unsure how I accomplish such a small measurement....Can anyone share how they do it?


Chet

 
The back end of my calipers slides out to measure from that end. Would that help you?
 
Or you can lay a straight edge across the bearing and check with a feeler gage set to see if the measurement is correct.
 
Chet Zerlin said:
Thanks!

John, forgive me but what does "0.005" IIRC" mean (and exactly how do I measure that?);

I'm still questioning that space between the back of the bearing and the front of the oil seal - is it supposed to be there? If it is then when I replace the seal and press the bearing in how do I know when to stop? Is there a groove that stops the bearing from going any further?

Chet
Click to expand...

Hi Chet,

"IIRC" means "If I recall correctly". It's a common forum acronym.
 
Good diagnosis.
Double check that bearing. Mine was spun due to the thicker paper gasket used in a repair job 12 years ago.
I suggest a new oil seal & bearing, new large o ring (if used, NA some models).
I needed to use a substance called "Bearing Mount Stick" (like an oversized glue stick) to seat the new bearing in the hub. I suggest sealer only on that flange, no paper gasket. I also replace brake shoes and springs.
Both sides.
Good Luck.
 
Chet

When you removed the half shaft you were presented with a paper gasket - right. Did you come across a large rubber ring as well? I do not have my 100/6 manual any more but I am sure that all the models are the same in this regard - should be a large rubber ring about 1/8" thick.

:cheers:

Bob
 
Bob - I was in the process of reading a number of other postings on the forum and was beginning to notice the same thing ("O" ring? What "O" ring?) :smile:.
Your post was very timely!

The answer is "no" there was no large rubber "O" ring when I took it apart.

Hmmmm....

Now I'm beginning to think that it's not the oil seal but the lack of that rubber ring that's the issue. There's only one way to test that theory.

I just ordered one from Moss Motors and when I get it I'm going to try assembling everything without doing anything to the existing bearing and oil seal. I will put a little Hylomar on that large rubber "O" ring just to make sure.

Then I'll top off the differential oil and give it a go....

If it leaks again at least I will know which is causing it! And now that I know how to take things apart I can certainly accomplish it quickly. I also found this great picture on the forum that shows me how to measure .005":

BearingClearance_Sm.JPG


So now I just need some recommendations on what oil to use in the diff?

Thanks!
Chet


 
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