Re: 1998 Suburban K2500 - Brakes


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Posted by Chuck (24.175.95.24) on 16:22:02 03/06/08

In Reply to: Re: 1998 Suburban K2500 - Brakes posted by Chuck

I pryed the rubber end caps off the old combination valve and it looks like the metering rod is visible / accessible. I pressed on the rod and it did move down --- probably no more than 1/4".

I had tried to pull the rubber end caps off the NEW valve when I was installing it -- at the time they didn't seem to want to come off so I didn't force them. Next step is to get those off and do another bleed procedure while keeping that rod depressed.

Here is a picture of the old valve - rod is visible. The end shown here is the one towards the left front wheel:



Here is a picture of the other (right) end -- this end is towards the master cylinder.



Here is a picture of the new valve before I installed it:







: Thanks for the info Ben. Some additional comments to your suggestions below.
:
: : Yes,pushing the MC rod in too far can damage the piston seals. The bore into the MC 'some times' is not finished all the way down to the bottom (cost reduction), as they know the pedal does not go that far in normal usage.
: :
: : A new or rebuild kit (haven't seen a rebuild kit in decades....seems no one does that anymore).
:
: Ok - that's what I thought. My wife was helping me bleed the brakes and I don't think she was pushing the pedal down too far. But just looking at all possibilities.
:
: :
: : Did you bench bleed the MC? That is to get the bubbles out of the piston area that is next to impossible when the lines are hooked.
:
: I replaced the MC last year but it was not part of this work. The only thing I did on the MC was remove the front brake pipe (which goes to the rear brakes) so that I could get to the combination valve.
:
: :
: : [IMG]http://img.photobucket.com/albums/v77/bentoy/Brake/09120021_MC_bleedr_3.jpg[/IMG]
: : [IMG]http://img.photobucket.com/albums/v77/bentoy/Brake/09120018_MC_bleedr_2.jpg[/IMG]
: :
: : I've never touched a proportioning valve (combo valve) before, so of no help there. Here is a cross section of one I found on the net loooong ago. Might help you some what.
:
: Thanks for the picture. My combination valve looks quite different. I noticed your picture shows the metering valve --- I need to look at mine again. The comment in the manual indicating it needs to be pressed during bleeding still has me concerned. Wonder if I could have some air trapped in there.
:
:
: : [IMG]http://img.photobucket.com/albums/v77/bentoy/Brake/02040011_rdcd_combo_prop_valve.jpg[/IMG]
: :
: : Bleeding the ABS system requires a scan tool that will hold hope the ABS valves, which are normally closed to the rest of the braking system.
: :
: : Other potential causes of the pedal going to the floor:
: :
: : The brake hose banjo fittings require a 'new' copper washer. Copper because they are supposed to crush and deform to the machine marks to seal. If you re-used the old copper washers, they have work hardened and will NOT seal. You can re-use them like Steve of Id does. He torches them cherry red to anneal them (soften them).
:
: Yes - I used new copper washers on the brake hose where it connects to the caliper.
:
: :
: : The caliper bled screws might not be seating if you are re-using or bought after market that had rusty seats. This is from folks who leave off the bleeder screw boots and water gets in there. Once that seal is broken open to bleed that caliper, it will most likely never seal right again.
: :
: : as for the slop, it depends how much. I've done brakes on driveways with an incline and don't think it would matter too much, unless severe incline.
: :
: : Over at #1 Son's place there are many, many threads on the HOW2s of DIY brakes.
: :
: : Be sure to keep any brake fluid from the friction material. Not a good thing for them.
:
: Thanks for the tips.
: Chuck




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