Particles in the brake fluid

[Martin Evans]

I'm surprised to hear that. I've looked around and all I could find was one negative review on this forum regarding the NBS MC swap. I haven't had good luck with my current MC right now and even panic stops aren't great. I'm a pretty cautious driver and it ****** a lot of people off so I've rarely needed to panic stop and I've mostly done it when testing my brakes after bleeding the fluid.

I know there are scan tools out there that bleed this module. Does manually bleeding work too. I've seen a YouTube video on bleeding the ABS via a valve on the side.

xc_hide_links_from_guests_guests_error_hide_media

I have an '89. I can't get rid of the spongy pedal. New master cylinder, new wheel cylinders, new hoses (except for the center rear hose), new pads and shoes, bled the brakes like 10x and it still doesn't feel right. I don't have the 4-wheel anti-lock brakes, so the tip from the video won't help me. I will probably try the GMT800 MC later when I have some extra money.

 

[Schurkey]

I have an '89. I can't get rid of the spongy pedal. New master cylinder, new wheel cylinders,

Does "wheel cylinders" include the calipers up front?

Did you THOROUGHLY bench-bleed the master cylinder? It's REALLY common to not get the air out of them, and if the master cylinder is tipped "up" in front when it's installed, it's essentially impossible to get the last of the air out of them on-the-vehicle. Sometimes a person can raise the rear of the vehicle enough to tip the master "down" in front, and then tickle the brake pedal so the air gets pushed into the reservoir via the ports in the master cylinder. Otherwise it has to come off the booster STILL ATTACHED TO THE BRAKE TUBES, forced "down" in front flexing the tubing some, and then the pistons are lightly stroked--tickled--until the air bubbles into the reservoir.

Have you manually adjusted the horse-shiit rear drum brakes that are PERPETUALLY out-of-adjustment because no one uses the park brake regularly--and that's what keeps the rear brakes adjusted?

new hoses (except for the center rear hose), new pads and shoes, bled the brakes like 10x

Including the bleeder screw on the RWAL?

I will probably try the GMT800 MC later when I have some extra money.

That is insane, if you retain the low-drag front calipers. Low-drag calipers need the three-chamber "Quick Take-Up" master cylinder.

Adjust the rear brakes.

Bleed the master as described previously. Also bleed the ABS. Does the ABS actually work? Do you hear it/feel it pulsing in the brake pedal on hard stops on low-traction (ice, gravel, dirt) roads?

Verify that the caliper pistons aren't sticking/seized, and both calipers are free-floating on the steel sleeves 'n' O-rings.

If EVERYTHING else checks-out, you've maybe got a stuck-open accumulator valve in the RWAL. Possible, not likely.




For the record--If your '89 has JN3 brakes like my '88, they're the crappiest, weakest power brakes ever put on a GMT400. They're so bad that GM quit using them in the early 1990s.

 

[Martin Evans]

Does "wheel cylinders" include the calipers up front?

Did you THOROUGHLY bench-bleed the master cylinder? It's REALLY common to not get the air out of them, and if the master cylinder is tipped "up" in front when it's installed, it's essentially impossible to get the last of the air out of them on-the-vehicle. Sometimes a person can raise the rear of the vehicle enough to tip the master "down" in front, and then tickle the brake pedal so the air gets pushed into the reservoir via the ports in the master cylinder. Otherwise it has to come off the booster STILL ATTACHED TO THE BRAKE TUBES, forced "down" in front flexing the tubing some, and then the pistons are lightly stroked--tickled--until the air bubbles into the reservoir.

Have you manually adjusted the horse-shiit rear drum brakes that are PERPETUALLY out-of-adjustment because no one uses the park brake regularly--and that's what keeps the rear brakes adjusted?


Including the bleeder screw on the RWAL?


That is insane, if you retain the low-drag front calipers. Low-drag calipers need the three-chamber "Quick Take-Up" master cylinder.

Adjust the rear brakes.

Bleed the master as described previously. Also bleed the ABS. Does the ABS actually work? Do you hear it/feel it pulsing in the brake pedal on hard stops on low-traction (ice, gravel, dirt) roads?

Verify that the caliper pistons aren't sticking/seized, and both calipers are free-floating on the steel sleeves 'n' O-rings.

If EVERYTHING else checks-out, you've maybe got a stuck-open accumulator valve in the RWAL. Possible, not likely.




For the record--If your '89 has JN3 brakes like my '88, they're the crappiest, weakest power brakes ever put on a GMT400. They're so bad that GM quit using them in the early 1990s.

Thanks for the reply! I think I replaced the front calipers also, but I don't remember. I also think I bled the system at the RWAL bleeder screw, but again, I don't remember for sure. I'm pretty sure that I bench bled the master cylinder when I installed it and also at the fittings. Rear drums were adjusted to slight drag. It was at least 5 years ago and probably more like 6 or 7. Someone lit the inside of my truck on fire shortly afterwards and I haven't driven it since. I literally drove it one time for about 20miles after going through the brakes. I'm still in the process of rebuilding it. I'm not sure which brakes I have, I gutted the interior and my dash, including the glove box and sticker came from from my local u-pull-it. I may still have the original glove box insert and sticker.

 

[Martin Evans]

You must be registered for see images attach

Does anybody know if I can get a replacement glove box sticker? I had a cab fire and gutted the interior. The replacement dash/glove box/sticker came from my local u-pull-it

 

[df2x4]

Does anybody know if I can get a replacement glove box sticker? I had a cab fire and gutted the interior. The replacement dash/glove box/sticker came from my local u-pull-it

Not sure about a replacement sticker, but if you plug your VIN into compnine.com and spend $5 they'll give you a list of all the options/RPO codes on the truck.

 

[someotherguy]

Not sure about a replacement sticker, but if you plug your VIN into compnine.com and spend $5 they'll give you a list of all the options/RPO codes on the truck.

Yep, then just make your own, print it up and laminate it so it'll last.

When I built the 3500HD I made a SPID label that would have otherwise been an impossible combination, like an L29 Vortec 7.4 in a 1994 model. (truck was originally a 6.5td)

Richard

 

[Boots97]

Reviving another thread:

Shoutout to @df2x4 for the recommendation on the Classic Tube StopFlex brake hoses. I got them installed today (about time) and they look awesome.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

Braking has improved as well. I didn't think something like this would work so well out of the box, but I was wrong. Can't wait to do some other brake mods in a few years once my old stuff wears out.

EDIT: Also, no more brake particles in my lines either. All I need now is a scan tool for my ABS module and I'll have perfect brakes!

 

[df2x4]

Shoutout to @df2x4 for the recommendation on the Classic Tube StopFlex brake hoses.

I think it was @Schurkey who originally posted those somewhere else, so I'll give him the real credit for that recommendation.

Glad they worked well for you!

 

[Schurkey]

I learned about them from someone else. I've posted them several times, but the original credit is not mine.

 

[Boots97]

Reviving thread #2:

After driving for a week, I didn't like how the brakes were, so I ended up reflushing the fluid again yesterday and WOW. These brakes stop on a dime now. I just used cheap FVP DOT 3 brake fluid from Menards and went through 3 quarts to get what I wanted. Now I REALLY feel the benefit of these braided stainless steel brake hoses and wish I would've installed them sooner.

Can't wait to install some 2500 wheel cylinders and calipers one day. These brakes are going to be awesome!