OBS to NBS Master Cylinder Question

[Royal Thunder]

I have a 1998 Chevy K1500 Z71 extended cab with brake code JB5. I rebuilt the whole brake system except for the ABS unit (lines, calipers, rotors, drums, shoes, pads, parts kit, wheel cylinders, brake booster and NBS MC #18M1159). I had a shop bleed the brakes and the pedal still goes almost to the floor. The pedal travels half way before it starts grabbing.

I read through alot of threads here and on other sites bouncing between needing a residual valve and not needing one. I also read that I should have went for a newer mc as the one I bought is from a disc/disc setup not what my truck has.

So what did I do wrong?

A few notes:
When the shop did the bleeding they said they adjusted the drums all the way off (max distance between drum and pads) and that it will adjust out to where it should be. I also told them to bleed the ABS too which I am not sure they did.

When the truck is off the pedal is rock hard and when the truck is on it is soft till about half way. When the pedal stops you can actually push the pedal more. Like when there is air in the lines.

Truck is almost 100% stock. No lift or huge tires.

 

[dave_erald]

Bleed the abs system, and adjust to brake shoes up to almost touching the drum. Idiots. And if you have a disc/disc master on a disc/drum system you will either need a residual valve, or better idea yet would be just grab a 99-07 MC that is disc/drum. I got that on my hydroboost with a 88-94 proportioning valve and it works mint.

 

[Royal Thunder]

I am having a hard time finding the correct part numbers or would this one fit? http://www.dormanproducts.com/p-44911-m630453.aspx

Also should I order the MC then have the shop rebleed or have the shop rebleed and then see if that fixes the problem?

 

[Rparsh]

I am having a hard time finding the correct part numbers or would this one fit? http://www.dormanproducts.com/p-44911-m630453.aspx

Also should I order the MC then have the shop rebleed or have the shop rebleed and then see if that fixes the problem?

I personally would not trust that shop (the shop that backed off the rear shoes before bleeding the brake system) to do any brake work.

 

[Royal Thunder]

This is the first time they have done something stupid and I think it was because they let a new guy do the work. I am now having a clunking sound from the rear and what sounds like a pelican when I am backing up slowly and applying the brake.

I ordered the MC I posted as no one said it was wrong. I am also going in on Friday to talk to the owner of the shop to get this straightened out. The shop has gone above and beyond for me in the past and their rates are not a rip off. Not to mention they are the only shop within 25ish miles that is any good. I have tried all the shops in the area and they all suck. I actually took one to court because of the ****** work they preformed. So I am hoping it was due to a new guy and the fact that the work was done July 3rd.

 

[dave_erald]

I think you've got the right one ordered. I looked last night on rockauto for awhile. Forgot that some of them actually list for rear drum applications specifically.

And true, if you've found a good shop then go back, just chew out the mechanic that worked on your truck. They'll learn

 

[Royal Thunder]

Well I have a new problem. I order the mc and got it today. Found out that the outlets are m12x1.00 and not the standard 1/2x20. I was thinking of doing the residual valve but I would have to make lines for that too. So I am thinking of just going back to an OBS MC unless someone can point me in the right direction.

 

[magimerlin]

They make brass adapters for that situation... the part numbers are in one of the MANY threads on this topic... sorry I can mot remember which on though..

Sent from my SAMSUNG-SM-G891A using Tapatalk

 

[dave_erald]

Yeah not sure what the part numbers would be. When I did mine I made all new brake lines and just bought the proper fittings for the master cylinder instead of having to use adapters

 

[Royal Thunder]

I went to AGS and I think the other is Edelman and neither make a 9/16-18 inverted to m12-1.00 inverted or a 1/2-20 inverted to m12-1.00 inverted. They also don't make the adapters for the valve but I was able to get lines that have the ends I need as long as the threads at the abs unit are 9/16. If they aren't I suck at flaring and will have to make leaky lines. I also looked around to see if I could find the lines with m12 and standard, no luck.

The fitting mentioned in the other threads is the AGS BLF-21C - Female(9/16-18 Inverted), Male(1/2-20 Inverted)

Also the m12 line fitting is either for 6mm or 8mm diameter line. The 9/16 is 1/4 (6.35mm) diameter and the 1/2 is 5/16 (7.93mm).