Chevy Impala SS Forum banner

1 - 20 of 20 Posts

·
Premium Member
Joined
·
6,396 Posts
Direct from the FSM:

"Adjustment for both the rear (drum) brake primary and secondary shoe and linings is automatic during reverse brake application."

During service of the rear drum brakes, manual adjustment is necessary to set the initial shoe dimensions (to match the drum) and is described in the FSM.

The automatic adjustment function is controlled by driving habits--if you rarely back up with the intent to consciously apply the brakes hard enough to force the adjuster to actually work, the rear brakes will not be adequately adjusted to compensate for lining or drum wear.

Adjusting each rear brake manually is the other option open to you....there's a stamped slot on the backing plate (typically it needs to be punched out) to insert an adjustment tool.

The adjuster linkage can malfunction, and age will play some part in just how well the "auto-adjust" feature works 15+ years after original assembly--the self-adjusting design was standard on these cars, so there's no need to add it. Some or all of the actuation parts may need to be replaced to restore proper function, however.
 

·
Super Moderator
Joined
·
8,894 Posts
I have always fought with my wagons' rear brakes to get them to self-adjust. On my current wagon, I have switched the ratchet arms from side to side to get better geometry, and that seems to have worked. I disassemble and lube the star wheel every time I'm in there.
 

·
Registered
Joined
·
529 Posts
I've wondered about the self-adjusters as I'm shopping for parts to do my first drum service ever. This is a 92 RMS with unclear service history and brake fluid that (after having allegedly been flushed as ordered and paid for at a shop right after we bought the car last January)
looks like root beer leaning towards root beer float.
Mostly, having previously had rear brake lines rust out, I really just want to flush the fluid in a hurry. Due to the location of the bleeders, corrosion, prices, and while-I'm-in-there, it's obviously bleeding >> new cylinders >> new pads >> new hardware.
But what constitutes the hardware?

I'm looking at Rock Auto, and I'm only slightly unclear on most of the parts I need, but moreso on hardware and the adjusters:
1. shoes for 11x2 brakes (bonded or riveted? Less durable vs. more damage if they wear through?),
2. wheel cylinders (7/8", not 1", because it's a sedan?)
3. drum brake hardware kit, 11x2 (Several brands share the same picture, showing 2 of 5 types of springs, 2 circlips(?), 4 pins, 6 "cups", and 2 plugs also sold by themselves under "self adjuster conversion kit" - except Dorman which shows 4 more pins. Which is right?)

4. Under "self adjuster conversion", the only part listed is the aforementioned plug. Is there nothing else because the only part of this conversion lacking on the cars could be that you get a new backing with the hole not plugged?

5. Under "self adjuster repair kit", there are numourous kits which (by pictures) seem to all contan the same collection of plug, spring, wire hook, 2 different flat metal arms, washer, "cup", star wheel, thing that looks a bit like then end of the star wheel pin.

6. Does this "repair kit" complete the adjuster part? And does the hardware have everything else? All other drum-related parts I've looked at appear to be part of either the hardware kit or the adjuster repair kit. Do I need 4 or 8 ("spring hold-down"?) pins? Did I miss anything? The prices are so good, I'd hate to not get something due to my ignorance and then have to run around the local stores and pay triple for junk when I find out I'm short.

7. Finally, is the hose connection to the wheel cylinder of the banjo type, and thus in need of a new bolt? or a seal? I can't quite tell from the cylinder pictures.


I hate to put up a gigantic "I know nothing, tell me everything" post like this, but while I do have the manuals, they're hard to buy parts by.
And I'd guess that if you know, the answers are a lot simpler than my questions above.
Any help is very much appreciated.
 

·
Super Moderator
Joined
·
6,000 Posts
Was told in "Tech-School" that applying emergency/parking brake keeps them adjusted as well.
Not for GM drums. This does apply to the old rear GM discs, though (70s/80s Cadillacs, Firebirds, etc).

Reverse, roll, stomp brakes, done. As Joel pointed out, clean and lube those star wheel adjusters.
 

·
Premium Member
Joined
·
6,396 Posts
1992 BUICK ROADMASTER 5.7L V8

Brake/Wheel Hub : Brake ShoeRelated Parts
RAYBESTOS Part # 462PG {#462NR} 11.00 X 2.00 Professional Grade
Rear B
$24.79 $24.79

Brake/Wheel Hub : Drum Brake Self Adjuster Repair KitRelated Parts
RAYBESTOS Part # H2578 {#H25782} Wheel Kit Professional Grade [Wholesaler Closeout -- 30 Day Warranty] (Only 1 Remaining)
Rear Left D
$4.09 $4.09

RAYBESTOS Part # H2579 {#H25792} Wheel Kit Professional Grade [Wholesaler Closeout -- 30 Day Warranty] (Only 1 Remaining)
Rear Right D
$4.09 $4.09

Brake/Wheel Hub : Brake Shoe Hold Down (Combination) KitRelated Parts
RAYBESTOS Part # H4003 {#H40032} Professional Grade
Rear C
$3.70 $3.70

Brake/Wheel Hub : Wheel CylinderRelated Parts
WAGNER Part # WC56406 {#F56406}
7/8" Bore; Rear; Limited; Base Model A
$8.16 $16.32

RAYBESTOS Part # WC37080 {#2037080} Professional Grade
Rear C
$4.59 $9.18

Subtotal $62.17

I think that ought to do it....rear disc is a little simpler, but.....note that I stayed with one brand, except for an optional wheel cylinder, since the Raybestos part does not spec the size.

The only thing I'm really uncertain about is the combination hold-down kit--typically that describes a kit for the axle (both sides) but you MAY need 2 of these kits.

As far as your questions:

1. Does not really matter--stay with a national brand is my approach
2. Wagon wheel cylinder is larger because the weight bias of the wagon means the rear brakes will be doing more work, thus larger WC
3. Again, stick with the brand-name
4. Plug is included in the service kit, it appears. The backing plate already has a knockout stamped into it for the access port where the plug goes--you can do the initial adjustment through the access port, then let the self-adjusters do their thing after that--you can also adjust for wear manually in the future, even if the self-adjuster setup is still in place
5. See #3
6. I think I've spec'd all you will need
7. Hard line connection is compression, not banjo style
 

·
Registered
Joined
·
2,321 Posts
To get the best from cars this age I recommend replacing all the hardware and springs. Clean and lube with brake lube. Use the high end brand name parts.
Manually adjust the brakes upon installation. Then once the shoes arc into the drums use the self adjusting technique for a final adjustment.
Initial manual adjustment can be made with a brake spoon through the knock out slot on the backing plate or by taking the drum on and off and adjusting the star and rotating the drum to get the desired fit.
One last thing is if you are manually adjusting the brakes, have both wheels off the ground and the car in neutral.
 

·
Super Moderator
Joined
·
8,894 Posts
Just to follow up almost two years later, I continue to find that the self adjuster star wheel likes to freeze up on a regular basis (keep in mind that this is Syracuse, extremely high moisture environment). At least once a year, I disassemble the star wheels, clean them, wirebrush the threads, apply a very light coat of lube on, and reassemble them. They work for awhile afterwards.
 

·
Registered
Joined
·
5 Posts
For the last few years my car was just giving its very best on brakes and now since for the last few months its braking is not really good and my tires are sipping so i m planning to change the rear brakes so any info will be highly appreciated.............
 

·
Super Moderator
Joined
·
8,894 Posts
Start reading the brake section. It's all here. Every question you could possibly ask, already answered. Just read and search.
 

·
Registered
Joined
·
529 Posts
That sounds like a good shopping list. What doesn't seem to be included anywhere (unless they come with the new cylinders) are replacement mounting bolts for the cylinders, which would likely need replacement at this point as well. But regardless of whether I have to get them separately (standard hardware store stuff, I would assume)
-
what are my chances that the brake line compression fitting and the two cylinder mounting bolts aren't at least as stuck as the bleeder?

The fact that all these cheap parts should be replaced at this time still stands, but for just getting the ancient hydrophile DOT-3 out of there before it rusts through the lines, is replacing the cylinders (etc.) perhaps not the easy way around probably-stuck bleeders that I thought it was?

(I ask this while still not done with the front brakes, due to weather and other stuff. So I haven't yet tried undoing any of the above rear wheel hardware, yet.)
 

·
Premium Member
Joined
·
10,064 Posts
Regardless of how much crap I replaced in the wagon's rear drums I found it was still better to just get under there and manually adjust the damn things every 3-5 months. The so called self adjustment feature is ****. Utter ****.
YRMV.
 

·
Registered
Joined
·
529 Posts
1992 BUICK ROADMASTER 5.7L V8

Brake/Wheel Hub : Brake ShoeRelated Parts
RAYBESTOS Part # 462PG {#462NR} 11.00 X 2.00 Professional Grade
Rear B
$24.79 $24.79

Brake/Wheel Hub : Drum Brake Self Adjuster Repair KitRelated Parts
RAYBESTOS Part # H2578 {#H25782} Wheel Kit Professional Grade [Wholesaler Closeout -- 30 Day Warranty] (Only 1 Remaining)
Rear Left D
$4.09 $4.09

RAYBESTOS Part # H2579 {#H25792} Wheel Kit Professional Grade [Wholesaler Closeout -- 30 Day Warranty] (Only 1 Remaining)
Rear Right D
$4.09 $4.09

Brake/Wheel Hub : Brake Shoe Hold Down (Combination) KitRelated Parts
RAYBESTOS Part # H4003 {#H40032} Professional Grade
Rear C
$3.70 $3.70

Brake/Wheel Hub : Wheel CylinderRelated Parts
WAGNER Part # WC56406 {#F56406}
7/8" Bore; Rear; Limited; Base Model A
$8.16 $16.32

RAYBESTOS Part # WC37080 {#2037080} Professional Grade
Rear C
$4.59 $9.18

Subtotal $62.17

I think that ought to do it....rear disc is a little simpler, but.....note that I stayed with one brand, except for an optional wheel cylinder, since the Raybestos part does not spec the size.

The only thing I'm really uncertain about is the combination hold-down kit--typically that describes a kit for the axle (both sides) but you MAY need 2 of these kits.

As far as your questions:

1. Does not really matter--stay with a national brand is my approach
2. Wagon wheel cylinder is larger because the weight bias of the wagon means the rear brakes will be doing more work, thus larger WC
3. Again, stick with the brand-name
4. Plug is included in the service kit, it appears. The backing plate already has a knockout stamped into it for the access port where the plug goes--you can do the initial adjustment through the access port, then let the self-adjusters do their thing after that--you can also adjust for wear manually in the future, even if the self-adjuster setup is still in place
5. See #3
6. I think I've spec'd all you will need
7. Hard line connection is compression, not banjo style

So I've slowly done other things with the car and put this off, and now, as the car is suddenly fixing to be out of my reach and going to be driven quite a bit, I'm told by the local repair shop that one rear shoe is cracked. (I gave them the car to give me an estimate for fixing the slight power steering leak, as that's just out of my reach: The cost of not having a lift to do this simple diagnosis and fix is $160 more than the high pressure hose would cost me at NAPA. I also asked them to flush the brake fluid because I obviously hadn't gotten to the rear bleeders yet, thinking I'd pay a few bucks for convenience - I was lucky that they put that on the estimate instead of doign it: $95!! And probably done as honestly as the last place I asked to do that, and with DOT-4 fluid nobody bothers to stock...)
I don't know why they decided to dig in deep enough to find a cracked brake shoe. (I should have just stuck to "do it later" when I told them to only do the power steering hose, rather than the brakes, the known-baddish rear shocks, and other stuff they totalled up to $1000+. Instead, I volunteered that I'd have to do some of it myself, so if they were lying, they've likely now reached in and broken the shoe. Otherwise, this would have been interesting to investigate...)

But assuming they're right, I now need to do the rear brakes in a hurry. No time for Rockauto shipping after all. I may end up doing only the shoes for the moment, but any part that has to come out anyway should obviously be replaced with a fresh one.

Because of a squeak (that's probably the AC compressor, based on recent experience) being diagnosed as the tensioner (and needs a new belt - but that's good prevention anyway), I read around here and ended up looking at house-branded Gates belt and tensioner from NAPA. (Otherwise, if the parts look OK, I'm looking to buy at Autozone to work off a large store credit I have due to a loaner tool fiasco.)
Are NAPA Ultra Premium parts anything special?

If the bleeders are too stuck, I may end up needing to replace wheel cylinders.
The above list has a 7/8" bore type. NAPA only has 1". (Autozone has both.)

Would getting the larger size (to avoid a potentially iffier AZ part) be OK, or do I end up with less rear brake movement due to the larger bore (and brake valve set up for the smaller bore)?

Thanks.
 

·
Registered
Joined
·
529 Posts
I'll try again without the long story:

1992 BUICK ROADMASTER 5.7L V8
Brake/Wheel Hub : Wheel CylinderRelated Parts
WAGNER Part # WC56406 {#F56406}
7/8" Bore; Rear; Limited; Base Model

$8.16 $16.32
Is the 7/8" bore wheel cylinder required for a 92 RMS Limited? NAPA lists only a 1" type. (Autozone lists both.)

Would a 1" bore type be an allowable upgrade, or just the wrong part?

thanks.
 

·
Premium Member
Joined
·
6,396 Posts
Not sure I would categorize the 1" WC as an "upgrade" - it will change brake bias somewhat, to the rear, I believe. That's not a bad thing--and the greater braking force would be countered by ABS if there is any increased tendency toward rear lockup.

Pedal feel may change somewhat, as well as pedal travel before "takeup" as rear shoes get further out of adjustment (from wear).

Ultimately you might need to look at a MC change or even pedal & booster change to make everything "happy", though I would only see that possibility if you were chasing a problem with excessive pedal travel after making the change in WC size--not likely, but you never know.
 

·
Registered
Joined
·
529 Posts
I see. I was afraid it would take brake force away from the rear as the same fluid now has to fill a larger bore => less extension of the piston.
If it really adds brake force to the rear, that does not sound benign.

However, I have the car back now, and the bleeders look fresh (so they were probably replaced when I asked for a flush 2 years ago) and open easily, so I will address whether the brake line and the 2 mounting bolts can be undone to change the cylinder another time.

After wasting much time yesterday trying to get a rear wheel (235/70/35) out between hub and fender, I managed that today putting the jacking point at the apex of our driveway, and the rear wheels over the sharp dropoff towards the gutter.

I only had time to do one side, so I looked for the "cracked shoe" that a shop diagnosed, and did it. After looking at a number of online procedures that lay out the order of (***)assembly for GM truck drums, I looked at the FSM and found that it's rather too different. (I also found that when armed only with a 91 Caprice FSM, Roadmaster brakes are exactly of the "wagon, police/taxi sedans" variety.)

I didn't look back at how the more detailed amateur pictorial guides show this, but the FSM is wrong in one crucial point:
If you assemble the 2-piece adjuster arm in place with its spring against the shoe first, it is then utterly impossible to place the rod arm from the pivot pin to the hook of the adjuster - even with the spring against the shoe fully compressed and the hole arm angled upward-inward so its bottom isn't restricted by the show, you just can't get the not at all springy rod on there. I had a feeling this would be hard when during disassembly, forcing the rod off the adjuster caused that spring to be forced out of the mechanism, being shot away rather dangerously.
But given that the spring took some effort to insert first already, I followed the instructions and tried, for some time, to put the rod on second. When I finally gave up and pulled the spring out, the rod went on almost easily, and the spring, while requiring great force, went on in about 20 seconds.
20 years with these cars, and that was the first time I looked into a drum brake.
 

·
Registered
Joined
·
529 Posts
I've got some questions about buying shoes. It's a bit late because I've put one side on already, but if what I got is no good, I could certainly put on better shoes when I replace the cylinders:

NAPA "Ultra Premium" shoes is what I got. I noticed they have a core charge, and no mention of new vs. rebuilt. (For contrast, Autozone's say "100% New Steel, 100% New Friction, No Core Charge".)
Does that mean they are necessarily rebuilt? They look OK, as little as I can judge that, and I noticed some matching stamped letters that I interpreted as "matching, therefore manufactured together" - it didn't strike me that during rebuilding, those might have been stamped.
...and if they are rebuilt, is that bad?


Also, I asked about returning the cracked shoe to get the core charged back, and NAPA said they obviously wouldn't want those.
But it turns out that only the friction material is cracked. That should, just as obviously, be OK for a core return, right?

Finally, with a crack in (through, really) the friction material on a rear shoe, such that 1 1/2 pairs of rivets remain in the lower fraction (which is pulled towards the other when braking while going forward) and all the other rivets remaining in the higher fraction,
- how much of a risk, of what sort of problem would this have been? Would this just pull off one day while backing up, and then roll forward and bind the brake with disastrous results?
 
1 - 20 of 20 Posts
Top