Bleeding ABS / Snap On MT2500

Have a 94 XJ with the Teves ABS brake system. Does anyone know if the Snap On MT2500 scan tool (with correct cartridge) will bleed the ABS system, or do you have to have the Chrysler scan tool?

No idea - but if you ever decide to part with that MT2500, I'd like to talk to you about it...

I'd have to check, but I've been able to vacuum bleed various ABS systems without any trouble.

They're talking about bleeding ABS brakes in the usual manner (hose and helper stepping on brakes) in the 1994XJ FSM, just with a modified sequence:

1) Master Cylinder (probably not needed, unless you've pulled a line off or there is a bleeder screw on the body.)
2) Hydraulic Control Unit Valve Body, at Fluid Lines (same caveat as #1, I'd think.)
Then the wheels, farthest to closest (RR/LR/RF/LF.)

Interestingly, after going through the bleeding order mechanically, they then mention the following:

"(6) Perform 'Bleed Brake' prcedure with DRB II scan tool. Procedure is described in DRB II software information and diagnostic manual.

...

"(7) Repeat conventional bleeding procesure ..."

Almost sounds like you end up doing it twice. Perhaps someone who has the DRB II manual can chime in here and say just what you're supposed to do with the DRB II in between the first mechanical bleed and the second?

Unfortunately, I don't have a MT2500, but I can borrow one if I need it. That's the procedure I found also, here's the issue:

Both front brakes were dragging, calipers were clearly not releasing all the way. I put new calipers on and bled using normal bleed procedures. The brakes are fine when you start driving after the truck has been sitting a while, but after two or three stops, you can hear them dragging again(it isn't a heavy drag, but you can hear it with the windows down - I jacked up the front and confirmed both are dragging, I've been checking rotor temps and highest is about 130F after a fair drive, this doesn't seem hot enough to do damage for now..).

Anyway, it seems that the brake system builds up a little pressure it can't release after I start driving, but it bleeds off if it sits for a while. I just wanted to make sure I had a complete bleed per FSM before I tore into the master cylinder or prop valve.

Thanks for any help on this.

Oh, I have watched the Snap On scanners on ebay over the years. Prices are kind of soft right now with the economy. I bet you could grab one for $150 or so if you kept after the auctions. I may try to get one for myself given that I now have a 90 XJ and this 94 my 16 year old son just bought. Even after the correct cartridges and cables, I could probably be in for less than 225, which is just about two hours of labor at a garage around here, so not really a bad deal for the scan tool.

OK - if the caliper isn't releasing and dragging slightly, it's not a bleeding problem (that usually causes a "soft" or "spongy" pedal.)

Lift up the front end, take the wheels off, and clean the slide rails on the caliper bracket and the mating surfaces on the caliper casting. Lubricate with dry graphite powder, and burnish some into the metal surface (use a metal rod with a rounded end for that.)

Remove the caliper pins and scrub clean. Clean the bores for same - IIRC, you can use a 9m/m phosphor bronze bore brush there. Lubricate with dry graphite as well (I don't like using grease - too much dust and crud. Graphite has worked well for me for years.)

Reassemble and test.

Ok, I have a DRB Scan tool, and ABS bleeding is in DRB Standalone/Diagnostics/ABS/MISC-bleed ABS

It is only necessary when the complete system was drained - also the ABS pump is without fluid or there is an air in the ABS system.

It works as follows (DRB on-screen menu)

!! Ignition is ON, engine MUST NOT be running!!
1. press and hold the brake pedal
2. DRB opens some valves, you feel the brake pedal falling down slightly
3. release brake pedal
4. this sequence repaetes twice
5. press and hold the brake pedal
6. DRB actuates ABS pump - you feel the pump "kicking" to the pedal
7. DONE

Bleeding ABS via DRB is a simple procedure, i think it could be done also without the DRB, you just need to actuate some electricaly controlled valves and ABS pump.
I can have a look to the wiring diagrams to find out what/where/when is actuaded.

But i am not sure if 94 has an ABS bleed feature via OBD. I think it is only for OBDII capable cars, form 96+

SKJeep said:

Ok, I have a DRB Scan tool, and ABS bleeding is in DRB Standalone/Diagnostics/ABS/MISC-bleed ABS

It is only necessary when the complete system was drained - also the ABS pump is without fluid or there is an air in the ABS system.

It works as follows (DRB on-screen menu)

!! Ignition is ON, engine MUST NOT be running!!
1. press and hold the brake pedal
2. DRB opens some valves, you feel the brake pedal falling down slightly
3. release brake pedal
4. this sequence repaetes twice
5. press and hold the brake pedal
6. DRB actuates ABS pump - you feel the pump "kicking" to the pedal
7. DONE

Bleeding ABS via DRB is a simple procedure, i think it could be done also without the DRB, you just need to actuate some electricaly controlled valves and ABS pump.
I can have a look to the wiring diagrams to find out what/where/when is actuaded.

But i am not sure if 94 has an ABS bleed feature via OBD. I think it is only for OBDII capable cars, form 96+

Click to expand...

OK - so it sounds like it's purging/bleeding the ABS core components, and not the wheel cylinders/calipers or master cylinder.

My previous advice does stand tho - it doesn't sound like a hydraulic issue. It sounds like a "dirt/mechanical" issue, and the hardware could probably stand a vigorous cleaning.

I probably will take the calipers off again and make sure everything is free. We did clean and lubricate the rails the pads ride on, and also the slide pins/bolts, though we used grease and not graphite.

What's bugging me is that both fronts are dragging, which makes me lean more toward a "system holding pressure" problem than a "mechanicals are hung up" problem. I guess the ultimate diagnostic for that is to throw pressure gauges on the ends of the hoses where they would connect to the calipers and actually see what the pressures look like, though I don't know that I have specifications for what's correct, nor do I have gauges that would match up to the fitting, probably. Maybe I need more tools!!!

There are two things that would cause residual pressure in the lines.

1) A residual pressure valve. These are typically used in racing cars with underhung master cylinders (below the floorboard/bottom of the pedal,) and the RP valve is to keep fluid in the lines. Not typically used on production vehicles - the have "overhung" m/cyl units and keep the lines filled by gravity.

2) A "flapper" in the hoses (rare, but possible.) What happens here is that the rubber hose delaminates inside, and you end up with a one-way valve in the hose. If you want to see more or less what it looks like - , except it is usually one flap, not two.

Just Checked my Snap-On SOLUS, and it does have an ABS bleed. I would say that the MT2500 will too with the right cartridge. My 94 doesn't have ABS so I can't tell for sure.

If it works like the Fords do, it just "buzzes" the actuators to shake off any bubbles on the internal surfaces. Then it will tell you to crack open a bleeder, and then it will run up that actuator to force out the fluid, and then it tells you to close the bleeder. It does this with each wheel, in the correct order.

** Thread Hi-Jack **

5-90, I thought that the RENIX system had no diagnostic capabilities? The SOLUS has a connector expressly for the RENIX Jeeps. I have never personally worked on a RENIX system, so I can't confirm if it works or not.

This is what the connector looks like: http://cgi.ebay.com/ebaymotors/Snap...6?IMSfp=TL0901261510007r7340#ebayphotohosting

bhorn said:

5-90, I thought that the RENIX system had no diagnostic capabilities? The SOLUS has a connector expressly for the RENIX Jeeps. I have never personally worked on a RENIX system, so I can't confirm if it works or not.

This is what the connector looks like: http://cgi.ebay.com/ebaymotors/Snap...6?IMSfp=TL0901261510007r7340#ebayphotohosting

Click to expand...

That looks a lot like the Jeep-1 adapter for the MT-2500. The RENIX doesn't have any conventional diagnostic capability (like the OBD systems,) but it does have the ability to present realtime driveability data using the correct interface - like the MT2500, and apparently the MODIS/SOLUS, the DRB-II, the M.S.1700, and a few other high-dollar tools. That's why I've been after an MT2500 for so long - I could use that and a crated-up compleat RENIX system I've got handy to see about making a simpler adapter, something that could give data on, say, a PalmOS device or a laptop, perhaps. It's serial data out, so it's just a matter of sorting out the encoding and all. I think.

Knowing what results you are supposed to get makes it easier to figure out how to get those results to begin with.

5-90 check your PM's