Author Topic: Bleeding Rear Brakes on a C30  (Read 2384 times)

Offline JIM W

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Bleeding Rear Brakes on a C30
« on: August 03, 2020, 06:02:57 AM »
I just recently bought a 1985 dual wheel C30 dump truck with a 9' plow to plow my driveway. It was a farm truck and hasn't been registered for 8 years or so.  It is very rotted and rusty underneath and only stops with the front brakes.  I found and replaced a leaking brake line under the center of the truck and now the master cylinder will hold fluid.  The rear brakes still won't work until I properly bleed them.

That is the problem.  There is only about one inch of space between the backing plate and the rear spring assembly.  The bleeder and mounting screws for the brake cylinder are located almost up against the springs and about half way down the 9 leaf spring assembly.  There is NO way anyone could get his hand in there. I think I must find a long (12" or so) box wrench that I can then bend to fit flat over the bleeder and then curve it out over the edge of the drum to a spot where I can get a straight pull on it.  Has anyone found a way to bleed these brakes?  GM must make a special tool?

I am afraid the bleeder is so rusted it may just break or round off anyway but I have to try - otherwise this truck will only be good for parts.  If the bleeder does break I thought I would pinch off that line and see if I could get the other side to work although the bleeder is impossible to reach there as well. There are lot of these trucks still on the road so I was hoping someone else has figured out a way to get these brakes working again?

Thank you for any suggestions that you might have.

JIM

Offline zieg85

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Re: Bleeding Rear Brakes on a C30
« Reply #1 on: August 03, 2020, 06:57:15 AM »
New rear wheel cylinders are needed if they are as rusty as you say.  Pictured is one of the specialty wrenches to bleed them
Carl 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
https://www.facebook.com/groups/248658382003506/

Offline JIM W

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Re: Bleeding Rear Brakes on a C30
« Reply #2 on: August 03, 2020, 08:04:13 AM »
Thank you for the quick reply.  I didn't realize these wrenches were so readily available.  I will pick one up asap and see if it is as long as I need.  I assume 1985 still needs 3/8" and is not metric?

I wouldn't know how to hold the cylinder bolts to even get new ones started in a replacement cylinder.  There looks to barely be enough room to unscrew them all the way before hitting the springs.  I hope I don't have to go that far.

Offline zieg85

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Re: Bleeding Rear Brakes on a C30
« Reply #3 on: August 03, 2020, 08:09:00 AM »
Thank you for the quick reply.  I didn't realize these wrenches were so readily available.  I will pick one up asap and see if it is as long as I need.  I assume 1985 still needs 3/8" and is not metric?

I wouldn't know how to hold the cylinder bolts to even get new ones started in a replacement cylinder.  There looks to barely be enough room to unscrew them all the way before hitting the springs.  I hope I don't have to go that far.

It is a tight fit on cab and chassis rear ends but with a little patience you'll get er done
Carl 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
https://www.facebook.com/groups/248658382003506/

Offline JIM W

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Re: Bleeding Rear Brakes on a C30
« Reply #4 on: August 29, 2020, 11:07:41 AM »
Thank you for the encouragement, Zieg, I did get the brakes working.  I had originally replaced a 3’ section of brake line near the center of the vehicle but then had to replace an additional 5’ length back to the axle.  I purchased one of the long 8mm brake wrenches but then had to heat and bend as shown in my photo.  The bleeder was well rounded to begin with so the wrench only grabbed enough for a partial turn before it hit the brake line, springs or axle u-bolts.  There is no chance of getting the bleeder completely out to replace it as there is just no way to reach in and hold it while turning.

The wrench got me a partial turn but then I couldn’t take it off and reposition it as it hadn't turned the bleeder far enough to reach another flat spot.  Extra long vice grips got another partial turn and then the wrench again got just enough to get fluid to flow.  It was slow and frustrating but I did manage to get the driver’s side bled and a pretty solid brake pedal.  I had hoped to also bleed the passenger side rear but I really do not think that is possible.  It’s only a site truck and will never have to pass inspection so we will see how it does plowing this winter.

The next project is the parking brake assembly that is so worn that the pawl won’t hold on the pedal.  I think I will drill out the center pivot and reassemble using a bolt with large washers on each side and then drill the nut for a cotter pin.  Should be interested if I can get it back together and working.

Thanks again for your help and responses.
JIM