Update: '99 OBS CC SWB Brake Issue

[SCOTI]

Originally Posted by Just call me Sean

It all comes back to that Tech2. I would like to have one for mine but since I can't buy one at a store I fumble around without it. So far I've managed fine without it, but it seems things would be easier with one. One of the reasons I prefer OBDI. My special code reading tool is a paperclip. Buying the Tech2 or buying the lines, valve, and master cylinder and the labor of gathering and installing. Sounds like it wouldn't be money wasted since it even holds its value if you wanted to sell it.

If the Tech2 was $250 its close enough I'd call it a draw. $350 or more, what then?

A new aftermarket prop valve is $125 or under. A donor 88-92 prop valve is <$10. Brake lines? Re-use what you can or snag some parts off wrecking yard donors. After that? You're done. Ever have an issue w/the master cylinder failing in the future? Replace it & bleed the brakes like any non-ABS hydraulic system. No need for the computer access.

*EDIT*
I've only had 3 vehicles new enough to utilize a scanner (my old '93 x-DPS Mustang, my old '90 model OBS, & it's replacement Spot).
All my stuff has been older carb'd rides.

[Just call me Sean]

OBDI doesn't need a scanner. The "scanners" available for them don't do anything but show you the codes, which you can read off the check engine light with a paperclip and not waste your money. GM and Ford, paperclip. Dodge is even easier, turn ignition on, off, on, off, on. Codes start flashing.

I'm not trying to change your mind on how you want to fix your truck, just that it probably won't be the last time you need to fix it and the Tech2 may come in handy later. Of course, I still haven't gotten one either though.

I thought the air would eventually work its way out on its own anyways. Like how a pressure tank with a ruptured bladder gets waterlogged. Fluid displaces the air. When I would bleed the clutch on my F150 I couldn't get all the air out, I had to drive it to work out the rest of the air.

[hatzie]

Originally Posted by Boog

Well sure. I'd like to have a tech 2 as well but mainly for the engine performance diagnostics. That's why I've been asking around about a laptop cable and diag program such as Winaldl or Tunerpro or something like that. There are some hand held scanners out there that the listers say they read OBD1 but I've not found one available that I would chance the money on. I've found some OBD1 to OBD2 adapter cables and for cheap but some reviews show they are junk, do not work so I am left still wanting something useable for less than the price of a Tech 2 type.

Your 1991 is the old GM ALDL 8192 baud serial communication protocol with a completely autonomous Rear Wheel ABS system that communicated on a different terminal in the 12 position ALDL jack. There were ABS brake cartridges for the Tech1 but good luck finding one of those in working condition for a price that you can afford. Even the Bosch Mastertech 3100 (basically a Tech1A with a larger screen) isn't cheap anymore... and GM cartridges for your truck will cost you dearly as well. I repaired a Tech1A about a year ago for a Corvette guy and sold it with no cables, no adapters, and no cartridges for a fair chunk of money. They guy that bought it sent me his non working Tech1 for the postage but it was beyond repair... obsolete proprietary part failure.

A Tech2 only begins to be useful on 1993 and newer vehicles. The earlier ECUs are fairly embryonic tech. Not much in the way of bi-directional controls if anything. The Tech2 will not give you much more than WinALDL or TunerPro on a 1992 and will not give you anything on a 1991 or earlier rig whereas the WinALDL and TunerPro will let you view you any data that's available on the serial comm port back to the 1985ish TPI systems.
If you eventually intend to get a 1995-2007 truck I'd keep your eyes open for a Tech2. You can still buy them new from China right now and it'll be something you can sell if you need to.

A T800 Master cylinder is not biased for Disc/Drum brake systems because the T800 brake bias is controlled by the ABS system. It'll work but it won't be quite right.

On a 1994 and earlier truck I'd bypass the ABS pulse motor between the master cylinder and the metering/proportioning valve with a longer piece of brake line and bleed out the system. It'll work surprisingly well after you get all the air out and properly manually adjust the drum brake shoe clearances.

[Just call me Sean]

If you're careful, you shouldn't have to buy anything. The line doesn't have to move far and it should be coiled under the fitting.

[hatzie]

Originally Posted by Just call me Sean

If you're careful, you shouldn't have to buy anything. The line doesn't have to move far and it should be coiled under the fitting.

Thanks for the refresher.
IIRC you have to change the ferrule on the end of the coiled brake line because the ABS pulser has a different diameter and thread pitch from the Combination valve.

Still pretty darn easy and non intrusive.

[Just call me Sean]

Originally Posted by hatzie

Thanks for the refresher.
IIRC you have to change the ferrule on the end of the coiled brake line because the ABS pulser has a different diameter and thread pitch from the Combination valve.

Still pretty darn easy and non intrusive.

I was thinking the same thing after I posted. Might need an adapter, union the two lines together, or cut swap fittings and reflare.

[SCOTI]

Originally Posted by Just call me Sean

If you're careful, you shouldn't have to buy anything. The line doesn't have to move far and it should be coiled under the fitting.

Originally Posted by hatzie

Thanks for the refresher.
IIRC you have to change the ferrule on the end of the coiled brake line because the ABS pulser has a different diameter and thread pitch from the Combination valve.

Still pretty darn easy and non intrusive.

Originally Posted by Just call me Sean

I was thinking the same thing after I posted. Might need an adapter, union the two lines together, or cut swap fittings and reflare.

So.... I don't have an official plan but I secured parts for Plan-B today. This was removed from a set-up similar to what @Just call me Sean attached in post #29.

[Boog]

Is that like what's on a 91 model? So, at most, you may possibly need an adapter for the rear tube?

[SCOTI]

Originally Posted by Boog

Is that like what's on a 91 model? So, at most, you may possibly need an adapter for the rear tube?

It's like what @Just call me Sean posted in #29. I pulled the parts I posted from a '92.

My '99 has the big Kelsey-Hayes ABS set-up. But if you remove all of the KH stuff until the master cylinder, the earlier stuff can be integrated by simply splicing a 'T' in for the fronts & connecting to a diff location for the rear line vs. where mine is.

I got as much as I could to have the xtra fittings. Will prob have to make some new lines so things can be spliced where it will be easiest under the hood.

[Just call me Sean]

I tried to get a decent picture of my 99 so everyone can see what you're dealing with.

[SCOTI]

Originally Posted by Just call me Sean

I tried to get a decent picture of my 99 so everyone can see what you're dealing with.

Bingo!

You were successful w/your attempt so TY for sharing the image. I took pics of mine as well but it was cold, dark, & raining outside when I did so the JY parts images were decent but the under-hood shots were less than usable.

[Hart_Rod]

Old thread, but how did this turn out Scoti? I have a 93 that I just did a L86/8L90 conversion on and I would like to remove the RWALS. Can I unplug just the module or do I have to delete the solenoids? The current master cylinder is leaking at the seals between the reservoir and the base. Can these be replaced or do I need to buy a whole new setup? Thanks for the help.

Rob

[SCOTI]

Originally Posted by Hart_Rod

Old thread, but how did this turn out Scoti? I have a 93 that I just did a L86/8L90 conversion on and I would like to remove the RWALS. Can I unplug just the module or do I have to delete the solenoids? The current master cylinder is leaking at the seals between the reservoir and the base. Can these be replaced or do I need to buy a whole new setup? Thanks for the help.

Rob

I got the earlier model lines & that's where it ended. I kept digging for info but was not gaining any real insight.

On NYE, I went over to my buddy's place to see the LS swap updates on my old '90 & to help w/some exhaust routing solutions. Conveniently, he still had the core support out which made it easy to again see/visualize the line routing up front (under the motor + where it connects each side @ the flex lines) as well as the placement of the factory unions for a '90.

This thing is scary when braking on irregular surfaces (railroad track crossings & ginormous asphalt road patches) when anything beyond an easy/soft pedal effort braking is used.

We discussed my lingering issue & about the latest 'upgrade' guys are doing for the OBS brake systems (GMT800 series & later master cylinder swaps). So that's going to be my plan moving forward. I'll replace the original OBS master cylinder w/a fresh GMT800 (or newer) unit, plumb the lines to a bias adjustable prop valve, make new connecting lines up front, & dial in rear bias once everything is in place & purged/bled. We'll simply delete the ABS alarm in the gauges as a start.