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90 Chev 1/2 ton brake question



 
 
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  #1  
Old September 6th 06, 03:27 PM posted to rec.autos.tech
news[_2_]
external usenet poster
 
Posts: 56
Default 90 Chev 1/2 ton brake question

90 K1500 4x4 10" rear brakes.
(the leading/trailing style with the adjuster at the top)

replaced the rear axle seals yesterday (leaking bad bad bad) and the
rear shoes.

Brakes were working before - just crappily because of all the grease on
them.

Now... the brake light is on, and the pedal pretty much goes to the
floor - not quite as soft as if there was air in there, but pretty darn
soft.

It would appear BOTH rear wheel cylinders are seeping. The only thing I
did as far as the hydraulics was to push the pistons back into the
cylinders so we could get the new shoes on. Is it possible that there
was a bit of corrosion in there that caused my leak? And/or is it
likely I did something wrong with the self adjusters and the leak is
actually just seepage from doing that and it's not really a leak? I
tried bleeding the rear brakes and they seem fine.

The truck has rear wheel abs.

I'm going to replace the wheel cylinders because I'm assuming they're
fubared, but I'm wondering if there's some other trick/something I did
wrong.

Also, the park brake cable is currently not connected - the whole thing
was rusted solid so we pulled it all out and I'll be getting new cables.
The park brake switch was disconnected.

Ray
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  #2  
Old September 6th 06, 04:12 PM posted to rec.autos.tech
Mike Romain
external usenet poster
 
Posts: 3,758
Default 90 Chev 1/2 ton brake question

Normally there is a right and left adjuster. If you got these mixed up,
the brakes might actually be adjusted the wrong way which would give you
an extremely low pedal and could cause the cylinders to leak from being
over extended. The cylinder pistons can actually fall out causing total
failure too.

This could just happen if you didn't manually adjust up the shoes when
installing also. If they are out of adjustment all the way, the self
adjuster won't usually grab them. They need to be manually set up close
or better, exact first.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

news wrote:
>
> 90 K1500 4x4 10" rear brakes.
> (the leading/trailing style with the adjuster at the top)
>
> replaced the rear axle seals yesterday (leaking bad bad bad) and the
> rear shoes.
>
> Brakes were working before - just crappily because of all the grease on
> them.
>
> Now... the brake light is on, and the pedal pretty much goes to the
> floor - not quite as soft as if there was air in there, but pretty darn
> soft.
>
> It would appear BOTH rear wheel cylinders are seeping. The only thing I
> did as far as the hydraulics was to push the pistons back into the
> cylinders so we could get the new shoes on. Is it possible that there
> was a bit of corrosion in there that caused my leak? And/or is it
> likely I did something wrong with the self adjusters and the leak is
> actually just seepage from doing that and it's not really a leak? I
> tried bleeding the rear brakes and they seem fine.
>
> The truck has rear wheel abs.
>
> I'm going to replace the wheel cylinders because I'm assuming they're
> fubared, but I'm wondering if there's some other trick/something I did
> wrong.
>
> Also, the park brake cable is currently not connected - the whole thing
> was rusted solid so we pulled it all out and I'll be getting new cables.
> The park brake switch was disconnected.
>
> Ray

  #3  
Old September 6th 06, 05:12 PM posted to rec.autos.tech
ray
external usenet poster
 
Posts: 90
Default 90 Chev 1/2 ton brake question

Mike Romain wrote:
> Normally there is a right and left adjuster. If you got these mixed up,
> the brakes might actually be adjusted the wrong way which would give you
> an extremely low pedal and could cause the cylinders to leak from being
> over extended. The cylinder pistons can actually fall out causing total
> failure too.
>
> This could just happen if you didn't manually adjust up the shoes when
> installing also. If they are out of adjustment all the way, the self
> adjuster won't usually grab them. They need to be manually set up close
> or better, exact first.
>
> Mike


thanks Mike.

we did one side at a time, so unless they were done wrong before... I
can't have mixed up the parts.

I didn't adjust them at all, I usually just do the backup/stop thing.

The wheel cylinders are only like $20 so I'm going to change them as a
preemptive thing (wife is picking them up today while I'm at work), and
I'll be sure to adjust the brakes as per the shop manual.

Ray
  #4  
Old September 6th 06, 05:34 PM posted to rec.autos.tech
anumber1
external usenet poster
 
Posts: 77
Default 90 Chev 1/2 ton brake question

ray wrote:
> Mike Romain wrote:
>
>> Normally there is a right and left adjuster. If you got these mixed up,
>> the brakes might actually be adjusted the wrong way which would give you
>> an extremely low pedal and could cause the cylinders to leak from being
>> over extended. The cylinder pistons can actually fall out causing total
>> failure too.
>>
>> This could just happen if you didn't manually adjust up the shoes when
>> installing also. If they are out of adjustment all the way, the self
>> adjuster won't usually grab them. They need to be manually set up close
>> or better, exact first.
>>
>> Mike

>
>
> thanks Mike.
>
> we did one side at a time, so unless they were done wrong before... I
> can't have mixed up the parts.
>
> I didn't adjust them at all, I usually just do the backup/stop thing.
>
> The wheel cylinders are only like $20 so I'm going to change them as a
> preemptive thing (wife is picking them up today while I'm at work), and
> I'll be sure to adjust the brakes as per the shop manual.
>
> Ray


Your gonna have to adjust the rear shoes before they will "self adjust".
The self adjustment mechanism is meant to compensate for the wear of the
shoes and the adjustment needs to be set after replacing the shoes.

Spin the "star wheel" with a adjusting tool or a flat screwdriver until
you feel a slight drag when spinning the wheel. The low pedal is
probably caused by the rear shoes being so far out of adjustment.
  #5  
Old September 6th 06, 06:19 PM posted to rec.autos.tech
ray
external usenet poster
 
Posts: 90
Default 90 Chev 1/2 ton brake question

anumber1 wrote:
> ray wrote:
>> Mike Romain wrote:
>>
>>> Normally there is a right and left adjuster. If you got these mixed up,
>>> the brakes might actually be adjusted the wrong way which would give you
>>> an extremely low pedal and could cause the cylinders to leak from being
>>> over extended. The cylinder pistons can actually fall out causing total
>>> failure too.
>>>
>>> This could just happen if you didn't manually adjust up the shoes when
>>> installing also. If they are out of adjustment all the way, the self
>>> adjuster won't usually grab them. They need to be manually set up close
>>> or better, exact first.
>>>
>>> Mike

>>
>>
>> thanks Mike.
>>
>> we did one side at a time, so unless they were done wrong before... I
>> can't have mixed up the parts.
>>
>> I didn't adjust them at all, I usually just do the backup/stop thing.
>>
>> The wheel cylinders are only like $20 so I'm going to change them as a
>> preemptive thing (wife is picking them up today while I'm at work),
>> and I'll be sure to adjust the brakes as per the shop manual.
>>
>> Ray

>
> Your gonna have to adjust the rear shoes before they will "self adjust".
> The self adjustment mechanism is meant to compensate for the wear of the
> shoes and the adjustment needs to be set after replacing the shoes.
>
> Spin the "star wheel" with a adjusting tool or a flat screwdriver until
> you feel a slight drag when spinning the wheel. The low pedal is
> probably caused by the rear shoes being so far out of adjustment.


thanks. I usually do the adjustment, but these were such a PITA to
install and it was 11:30pm when I went for the test drive...

I'll try adjusting them properly first.

Ray
  #6  
Old September 6th 06, 10:18 PM posted to rec.autos.tech
ssggbroot
external usenet poster
 
Posts: 1
Default 90 Chev 1/2 ton brake question


On your truck, you are right in that when you pushed the pistons in- you
probly rode over some junk. but also pushing the wheel cylinders in may
have caused some air to be sucked into the cylinder.
If you haven't installed the new ones yet, try bleeding each one till
you get a good steady drip.
And as the other guy stated, adjust your brakes up with the adjuster,
backing up will never bring them up to where they should be.
Extend the adjusted a few clicks and try to slide the drum on, if its
still loose-adjust alittle more. once they are adjusted properly you
will hear the shoes just rubbing against the drum-but will be able to
turn the drum freely.
If after all of this, the pedal is still low and the brake light/abs
light is still on, you may have a baddump valve. the chey trucks are
famous for this valve going out for the slightest reason. I've replaced
many over the years, I'm a brake and front end mechanic.


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  #7  
Old September 7th 06, 05:32 AM posted to rec.autos.tech
news[_2_]
external usenet poster
 
Posts: 56
Default 90 Chev 1/2 ton brake question

ssggbroot wrote:
> On your truck, you are right in that when you pushed the pistons in- you
> probly rode over some junk. but also pushing the wheel cylinders in may
> have caused some air to be sucked into the cylinder.
> If you haven't installed the new ones yet, try bleeding each one till
> you get a good steady drip.
> And as the other guy stated, adjust your brakes up with the adjuster,
> backing up will never bring them up to where they should be.
> Extend the adjusted a few clicks and try to slide the drum on, if its
> still loose-adjust alittle more. once they are adjusted properly you
> will hear the shoes just rubbing against the drum-but will be able to
> turn the drum freely.
> If after all of this, the pedal is still low and the brake light/abs
> light is still on, you may have a baddump valve. the chey trucks are
> famous for this valve going out for the slightest reason. I've replaced
> many over the years, I'm a brake and front end mechanic.
>
>

readjusted the brakes, felt better, but still one wheel cylinder was
leaking a bit, so replaced them. then had to replace the lines because
they're all rusted and busted... I'm still not done - now I need the
flex line because one of the hard lines snapped off flush while removing it.

$10 in oil seals becomes $300 in brakes. (shoes, park brake cables,
wheel cylinders, brake lines, what feels like 10 gallons of brakleen...)

Whee.
  #8  
Old September 13th 06, 03:01 PM posted to rec.autos.tech
ray
external usenet poster
 
Posts: 90
Default 90 Chev 1/2 ton brake question

ssggbroot wrote:
> On your truck, you are right in that when you pushed the pistons in- you
> probly rode over some junk. but also pushing the wheel cylinders in may
> have caused some air to be sucked into the cylinder.
> If you haven't installed the new ones yet, try bleeding each one till
> you get a good steady drip.
> And as the other guy stated, adjust your brakes up with the adjuster,
> backing up will never bring them up to where they should be.
> Extend the adjusted a few clicks and try to slide the drum on, if its
> still loose-adjust alittle more. once they are adjusted properly you
> will hear the shoes just rubbing against the drum-but will be able to
> turn the drum freely.
> If after all of this, the pedal is still low and the brake light/abs
> light is still on, you may have a baddump valve. the chey trucks are
> famous for this valve going out for the slightest reason. I've replaced
> many over the years, I'm a brake and front end mechanic.
>
>


ok, I replaced both wheel cylinders, both hard lines, and the flex line
to the frame. bled them and bled them and still have a soft pedal that
pumps up. The master cylinder went dry when I ran out of parts and it
sat overnight, so we cracked the lines and bled it too. Didn't bleed
the dump valve - according to the manual it should have a bleeder, but
it doesn't. Do I need to have this thing pressure bled or something?

There are no more leaks, and the truck was stopping fine (well at least
as good as it could with grease soaked brake shoes.)

Ray
  #9  
Old September 13th 06, 03:33 PM posted to rec.autos.tech
Mike Romain
external usenet poster
 
Posts: 3,758
Default 90 Chev 1/2 ton brake question

ray wrote:
>
> ssggbroot wrote:
> > On your truck, you are right in that when you pushed the pistons in- you
> > probly rode over some junk. but also pushing the wheel cylinders in may
> > have caused some air to be sucked into the cylinder.
> > If you haven't installed the new ones yet, try bleeding each one till
> > you get a good steady drip.
> > And as the other guy stated, adjust your brakes up with the adjuster,
> > backing up will never bring them up to where they should be.
> > Extend the adjusted a few clicks and try to slide the drum on, if its
> > still loose-adjust alittle more. once they are adjusted properly you
> > will hear the shoes just rubbing against the drum-but will be able to
> > turn the drum freely.
> > If after all of this, the pedal is still low and the brake light/abs
> > light is still on, you may have a baddump valve. the chey trucks are
> > famous for this valve going out for the slightest reason. I've replaced
> > many over the years, I'm a brake and front end mechanic.
> >
> >

>
> ok, I replaced both wheel cylinders, both hard lines, and the flex line
> to the frame. bled them and bled them and still have a soft pedal that
> pumps up. The master cylinder went dry when I ran out of parts and it
> sat overnight, so we cracked the lines and bled it too. Didn't bleed
> the dump valve - according to the manual it should have a bleeder, but
> it doesn't. Do I need to have this thing pressure bled or something?
>
> There are no more leaks, and the truck was stopping fine (well at least
> as good as it could with grease soaked brake shoes.)
>
> Ray


Did you manually adjust the rear brakes? You cannot get a solid high
pedal with the rear brakes unadjusted. You will have to pump them up.

Does the emergency brake work now?

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)
  #10  
Old September 13th 06, 03:49 PM posted to rec.autos.tech
ray
external usenet poster
 
Posts: 90
Default 90 Chev 1/2 ton brake question

Mike Romain wrote:
> ray wrote:
>> ssggbroot wrote:
>>> On your truck, you are right in that when you pushed the pistons in- you
>>> probly rode over some junk. but also pushing the wheel cylinders in may
>>> have caused some air to be sucked into the cylinder.
>>> If you haven't installed the new ones yet, try bleeding each one till
>>> you get a good steady drip.
>>> And as the other guy stated, adjust your brakes up with the adjuster,
>>> backing up will never bring them up to where they should be.
>>> Extend the adjusted a few clicks and try to slide the drum on, if its
>>> still loose-adjust alittle more. once they are adjusted properly you
>>> will hear the shoes just rubbing against the drum-but will be able to
>>> turn the drum freely.
>>> If after all of this, the pedal is still low and the brake light/abs
>>> light is still on, you may have a baddump valve. the chey trucks are
>>> famous for this valve going out for the slightest reason. I've replaced
>>> many over the years, I'm a brake and front end mechanic.
>>>
>>>

>> ok, I replaced both wheel cylinders, both hard lines, and the flex line
>> to the frame. bled them and bled them and still have a soft pedal that
>> pumps up. The master cylinder went dry when I ran out of parts and it
>> sat overnight, so we cracked the lines and bled it too. Didn't bleed
>> the dump valve - according to the manual it should have a bleeder, but
>> it doesn't. Do I need to have this thing pressure bled or something?
>>
>> There are no more leaks, and the truck was stopping fine (well at least
>> as good as it could with grease soaked brake shoes.)
>>
>> Ray

>
> Did you manually adjust the rear brakes? You cannot get a solid high
> pedal with the rear brakes unadjusted. You will have to pump them up.
>
> Does the emergency brake work now?
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 88 Cherokee 235 BFG AT's
> Canadian Off Road Trips Photos: Non members can still view!
> Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
> (More Off Road album links at bottom of the view page)


I manually adjusted the rears until there's a bit of drag with the drums
on. The pedal is just really soft - just resting your foot on it will
cause it to sink to the floor.

The ebrake doesn't work because I changed all the cables but have not
yet had the time to adjust it. I haven't driven the truck either other
than testing the brakes around the block - I just don't like the pedal
feel. Been too busy trying to get the race car ready for the last race.
(broken axle + cam swap.)

Maybe I'll pull the drums again and double check the rear adjusters,
it's just it feels like there's air in there or something.

Ray
 




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