CUCV Brakes Question (M1009)

[RickTheEngineer]

Okay I'll be sure to do that. I'll vacuum the lines and everything to make sure as much of it is as removed as possible. The guys over at summit have been telling me to spray brake cleaner in the lines and then blasting it out with compressed air. Only reason why I was a stickler was because I was worried that there would be unforeseen residue from my seals wearing out that can only be removed with a solvent. I'll follow up with how it goes asap

 

[Ilikemtb999]

Dot 5.1 is NOT silicone based like dot 5. It's still glycol based but has a higher boiling point than dot 3/4

 

[RickTheEngineer]

Well, the brakes have been flushed, and I replaced the fluid properly, and now I got a rock hard pedal, which is awesome! However, a friend of mine accidentally spilled brake fluid (dot 3+4) on the frame and by the time I noticed all the paint has gunked up and is just melting off. I am guessing this is the point of no return... What can I do? I am thinking paint stripper and then just getting it down to bare metal and painting the frame? The problem is that it's the part of the frame by the wheel well so there's "stuff" that gets in the way (lines, hoses etc) what would you guys do?

 

[cucvrus]

At this point. I would remove the frame send it out and have it sand blasted. Have it hot dipped in a zinc rich primer and powder coated. You have opened up Pandora's box and all the creepy evil things are going to happen now. This K5 here I spilled a bottle of brake fluid on the frame. Poof. The frame dissolved in 2 weeks. Engine driveline and all. 2 weeks after this picture was taken I picked up all the fiberglass parts. Even the plastic had dissolved. I think all will be well. Just clean the area dry it and recoat it. No harm done. All in fun. Good Luck.

 

[RickTheEngineer]

what was amazing was after cleaning off the surface with denatured alcohol, I found the original bottom enamel was perfect. And I mean completely perfect. The gunky mess was the Rust-Oleum that I used over top of that layer! So I cleaned her up and have her a fresh coat of paint! Good as new!

 

[86m1028]

Your upper shock mount is on backwards.
Spacer goes to the inside.

 

[RickTheEngineer]

Hey all, I looks like there has been a little bit of a situation. So I decided to do a little aggressive brake tests and I find that the rear locks up before the front, which makes me feel like I have reduced brake power compared to in the past. Also the parking brake indicator light stopped working, which makes me fear that something might be wrong with the proportioning valve. I'm guessing a good place to start is to try bleeding the front some more? Brakes don't feel spongy in the slightest, however. I would also like to add that if I am at a complete stop, with the truck running, and I press the brakes progressively harder and harder, there will come a time when I hear a slight hissing noise, almost as though fluid is moving around in the master cylinder. Could this be residual air? A faulty master that is not providing enough power to the front? Keep in mind, I did switch to DOT 4. I did flush the proportioning valve with brake clean and denatured alcohol. only thing that has changed was I realized that one of my parking brakes was not working on the passenger side, so I reattached the line to the parking brake mechanism. Any thoughts?

 

[cucvrus]

Are the rear drums is great shape? many are bell shaped at this point and get grabby when new shoes are introduced to the rear drums. Also was the rear drums saturated with gear oil and did you replace the axle seals while you were rebuilding the brake system. I doubt proportioning valve. I think the switch on the e-brake or the printed circuit board/light on the instrument cluster need to be looked at and ruled out. Do you have the brakes adjusted up on the rear drums? These are my sight unseen help and diagnosis. It is an unseen opinion only. Good Luck and have a great day. It is 70 degrees here and I am going to take full advantage of it. I am going to work.

 

[RickTheEngineer]

The rears were in Nice shape actually, and I took some time to adjust the brakes with care and precision. I have a lot of experience with these adjustments so I decided to take the time to do it right. All clean, absolutely no oil on any of the brakes for sure. The light has always been functional and I remember when the brakes were failing the light would come on sparatically (probably due to the wrong pressures front to rear). After the brake job was finished this happened. My guess is the front could have some air hidden in those lines and is not triggers the the switch and causing the rear to lock up early. Can't tell though. I will bleed the front yet again to see if I get results, although I was very confident in the work I did. I'll follow up! Have a great day yourself! It's gonna be beautiful here as well!

 

[HelluvaEngineer]

The rears were in Nice shape actually, and I took some time to adjust the brakes with care and precision. I have a lot of experience with these adjustments so I decided to take the time to do it right. All clean, absolutely no oil on any of the brakes for sure. The light has always been functional and I remember when the brakes were failing the light would come on sparatically (probably due to the wrong pressures front to rear). After the brake job was finished this happened. My guess is the front could have some air hidden in those lines and is not triggers the the switch and causing the rear to lock up early. Can't tell though. I will bleed the front yet again to see if I get results, although I was very confident in the work I did. I'll follow up! Have a great day yourself! It's gonna be beautiful here as well!

Just saw this while searching for brake info. Some other GMs with rear drum brakes came with a special proportioning valve that I believe also applied a slight delay to the front or rear - I think it applied drum first because they are slower. I don't see one on my 1009 but just throwing that out there.

Sent from my VIVO XL using Tapatalk

 

[tremonttruck28]

hey, quick question for you. I have about a quart of dot 3 contaminating my otherwise dot 5 brake fluid. I'm planning on using a vaccum pump to get all the bad stuff out then replace with clean dot 5. is it ok to drain the master cylinder completely before adding clean dot 5? the reason I'm thinking I should do that is because I'm worried that if I just add the clean fluid to the top of the reservoir then it will continue to cross contaminate with any amount of dot 3 that might be in there. what do you think? any advice appreciated. thanks! p.s. truck is m1028

 

[sneekyeye]

You can vacuum it out if you want. Once you fill it up and then bleed the whole system, you should have a complete fluid change.

I can tell you what I did though. When I purchased my truck what was in the master cylinder was a mess of unknown mix. I vacuumed out the master cylinder and cleaned all the gunk out of it then flushed the whole system with dot4 fluid. I used dot4 only because I still have something like 40 quarts of it.
I still need to flush it again to see if anything else has cleaned itself out in the meantime.

 

[cucvrus]

Mixing Dot 4 with Dot 5 brake fluid - Page 1 - General Gassing ...

https://www.pistonheads.com/gassing/topic.asp?h=0&f=23&t=748824

1. Cached

Sep 18, 2009 - 6 posts - ‎5 authors
While it's permissible to mix DOT 3, DOT 4 and DOT 5.1 brake fluids, DOT 5 Silicone fluid cannot be mixed with any other type. If the system is not completely purged before conversion, the mixture may gel and result in very poor braking.

NEVER MIX BRAKE FLUIDS. THAT IS WHY SO MANY CUCV BRAKE SYSTEMS ARE FILTHY AND CONTAINATED. DOT 5 ONLY.