ABS Master Cylinder / Pump Assembly

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brokencase
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Re: ABS Master Cylinder / Pump Assembly

Post by brokencase »

Found the wiring diagrams for the Crown Vic ABS with traction control.
Turns out that we really want the 2000 (maybe 2001) vintage units. The later units added an interface to the engine control to ease up on the engine power for the case when both rear wheels slip. This is not absolutely necessary and I think we Scorpio drivers can avoid that case with our foot.

Sorry my document is pdf, but here is a screen shot...
absconn.jpg
absconn.jpg (116.54 KiB) Viewed 8853 times
schem1.jpg
schem1.jpg (86.3 KiB) Viewed 8853 times
The only question that remains is - How many teeth are on the front and rear ABS rings on a Crown Vic?
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Re: ABS Master Cylinder / Pump Assembly

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brokencase wrote: Mon Nov 29, 2021 5:38 pm The only question that remains is - How many teeth are on the front and rear ABS rings on a Crown Vic?
Answer: 50 teeth front and rear... Now, How many teeth are on the Scorpio hubs?
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Re: ABS Master Cylinder / Pump Assembly

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Is the number of teeth really that critical? Consider...

In the case of ABS operation the computer is only looking for the case where a wheel locks up. So it looks at the majority of the wheels pulse trains and then notices that, during braking, one of the wheels pulse train has slowed down relative to the others. So it starts pulsing the brake pressure on that wheel until it's pulse rate matches the rest. It is relative.

In the case of traction control the computer is watching the two rear wheels during acceleration and if one of the wheels starts spinning faster than the other it starts pulsing pressure on the wheel to slow it down.

So the number of teeth is not critical. Have I missed something here?
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Re: ABS Master Cylinder / Pump Assembly

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I think I found an insurmountable problem that prevents this swap and possibly others.
https://www.youtube.com/watch?v=gfnwdqJupXU

If you change ABS control units on later Fords you have to reprogram the swapped ABS module with the VIN stored in the ECM of the car.
Apparently this information is exchanged across the DLC link when the car starts up.

I say "I think" because I have not found definitively that the 2000 Crown Vic needs this but they say generally that 1997 onwards requires this.
I also don't know if the ABS is disabled in this case or it just constantly issues an ABS error light.

This may mean you can only swap in an abs unit from 96 and earlier.

Stinks. It's not so much as to prevent this swap so much as it only allows ford dealerships (and mechanics who buy into the software) to service the components involved.
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Re: ABS Master Cylinder / Pump Assembly

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Ok, it may still work, but the error light will be lit all the time.

However there may be another initialization sequence that occurs across the link that might prevent the ABS computer from activating, since the Scorpio does not have this data link. But you have to wonder, would they purposely disable the ABS on the car if the data link was down (i.e., like a bad connection)? I think not. The car must be able to stop reliably regardless. The question is - Would they disable ABS/traction control and they allow only the master cylinder to work normally?

https://www.explorerforum.com/forums/th ... ch.449845/

"Replacing the ABS Module is a very tricky job. I bought a used one, the identification/part numbers on it matched my old one exactly, installed it, without configuring it with my VIN number (only the dealers have equipment to configure). Now I have the ABS light ON constantly, and the ABS is setting one code: "Vehicle Identification Number Mismatch". Brakes work fine, vehicle rides fine."
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Re: ABS Master Cylinder / Pump Assembly

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I'm pretty confident that you can swap the units from the CV into other cars.
I say this because, back a while I swapped 95 Cobra brakes to my 89Mustang.
A handful of other people were putting the ABS from the Marquis and CV onto their Mustangs and it was functional.
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Re: ABS Master Cylinder / Pump Assembly

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I think you are right.

Found this over at the crownvic.net forums.
This guy updated his 2004 to a traction control ABS unit and did not have to do any programming.

https://www.crownvic.net/ubbthreads/ubb ... er=4115786

"My 04 experience might help. I swapped in TCS. Had to change valve block and ABS module. Module was plug and play, no additional programming needed. Swapping module and valve block is easy. Valve block will need to be bled. Drive and trigger ABS and TCS events to get the air bubbles moving. Bubbles will migrate to master cylinder. Apply pedal pressure and crack MC supply lines. Repeat as needed. Again, this is good for 04."
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Re: ABS Master Cylinder / Pump Assembly

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This from the FMS "How to Prepare the Sierra for Motorsport;" don't know if these details apply to the Scorpio Teves, though I imagine they do. Caveat: I don't have electrical schematics specifically for a Sierra RS, so I don't know what the two wires actually control. But, it does address the concern whether the brakes/MC will operate well without ABS. The mechanical unit with accumulator itself stays intact, so it doesn't solve the issue of replacing the ABS unit with a vacuum operated system, nor if disconnecting the ABS sets off warning lights on the instrument panel. Note also that the full race versions use twin MC's with F/R balance bar, no vacuum assist. Naturally, not a lot of fun having to push hard to brake in normal stop-and-go traffic or around town, but certainly much less complicated and less worry about parts availability.

" GROUP N CARS: ... On top of the brake master cylinder reservoir there are two multi-wire connections - one with three wires, the other with two. Permanent disconnection is achieved by breaking one of the two-wire connectors. If the wire is routed into the cockpit, and the break is achieved by an On-Off switch, the gives the driver the choice of having ABS in operation, or out of action.


AFTER GROUP N - THE NEXT STEP: To improve further on a Group N specification, but without converting the car to a full 'works-specification' Group A braking system, the standard brakes should be retained, the ABS system disconnected (see above) and the hydraulic piping slightly modified to eliminate the possibility of front-wheel locking.

The ABS hydraulic installation includes a metal casting in which three brake pipes protrude downwards. On all SIERRA RS COSWORTH models this is mounted on the left side of the engine bay. To re-balance the braking effort the following very minor modifications are recommended:

Blank off the front hydraulic connection.

Leave the central hydraulic connection (to the rear wheels) alone, but remove the pressure restrictor from the rear line. It will be used elsewhere.

Modify the piping to the rear hydraulic connections as follows: Mount the brake restrictor valve to the metal casting, then apply the hydraulic tee-piece to this and route the brake pipes to each of the front wheels.

This does not provide more powerful braking, but it re-balances and reduces braking effort on the front wheels, curing the lock-up problem which may occur once the ABS system has been disconnected."
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Re: ABS Master Cylinder / Pump Assembly

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Yeah, I don't think there is any difficulty disabling the ABS portion on the Scorpio. But you are left with just a basic master cylinder system.

BTW, FreshAirInspector - I am beginning to believe the Frenkit master cylinder rebuild kit I purchased is for the European non-abs master cylinder cars and I am not certain if it will work for the Teve's master cylinder portion. But I have no way of confirming this.

I think a vacuum assist swap would transform the feel of the brakes on the Scorpio. But I must admit I have moved on beyond this basic upgrade, which I believe is very easy to achieve.

I am now more interested in upgrading to a somewhat more modern ABS system from the Crown Vic. Specifically gaining the feature of traction control, and having a more reliable ABS system that does not depend on a very expensive nitrogen accumulator or otherwise very difficult to procure parts in all other aspects.

Let's face it, the Scorpio's open diff makes it a lousy car to drive in slippery conditions.

One time I went to a flea market, The parking was in a field on a raised plateau that was adjacent to a fire station parking lot.
so it was like a 45 degree drop from the field which was about 40 feet up from the parking lot. So I was parked up in the crest of this field...in the hay.

So now it is time to leave. I put it in reverse and all I got is a single rear wheel spinning. I had my father with me. "How are we gonna get out of this?" So I start rocking the car back and forth. Only problem was I had about 2-3 feet in front of me before I go down the 45 degree decent down to the crowded parking lot. I finally got it to catch, but it was very touch and go..

Likewise with the snow. Now, I don't typically drive the Scorpio in the snow, but you never know if you could hit ice or snow on a long trip.

I had often considered installing an MC2Racing limited slip differential. But that is pretty expensive and it takes a lot of work to pull the diff out of the car.

On the other hand, if I can possibly swap in the Crown Vic ABS/TC unit. I address the downfalls of the aging Scorpio ABS unit and at the same time get the advantage of "limited slip" the traction control provides....and I don't see it as a lot of work.
I run a separate brake line for each rear wheel. I swap in the Crown Vic ABS/TC unit and master cylinder. need to work out mount for ABS unit. I need a vac power booster and I think I would use the Foxbody Mustang unit we discussed earlier. I then make an adapting wiring harness that goes from the existing Scorpio ABS connector and runs out to the engine bay to the Crown Vic unit...about 12 wires in the harness. Pop in a switch to the dash so you can turn traction control on/off.

The nice thing about this is even if somehow it does not work, like the Crown Vic ABS computer refuses to work or there are other issues that take time to resolve... I still get vacuum power boosted brakes when I am done regardless...
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Re: ABS Master Cylinder / Pump Assembly

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If you can change an axle, you can remove the differential carrier. It's only 2-3 more bolts.
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Re: ABS Master Cylinder / Pump Assembly

Post by john keefe »

I agree that its only a couple more bolts to pull the diff, but getting TC without rebuilding/converting a diff to LSD is very attractive.

In my 5.0 XR, I've got a reworked FMS VLSD (7.5") that works great for now, though they're prone to wearing out, requiring specialized viscous fluid & coupling rebuilds. However, it's on a 3.64:1 gearing. The auto 3.34 gearing would be a LOT more fun and practical with the 5.0L at this weight, but its a PITA to think about taking the existing one apart to fit a different crown and pinion. OTOH, I've got a stock XR 3.34 auto diff sitting around that could be swapped to an Eaton or other LSD, but then there's the problem of sourcing new RS 108 mm stub shafts, as well as obviously gutting the diff carrier to make the Eaton or other fit. If I could get some TC in the Scorpio w/o having to actually do similar diff surgery to get an LSD, but rather minimal mechanical-electrical alterations elsewhere, that's a lot of appeal.
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Re: ABS Master Cylinder / Pump Assembly

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john keefe wrote: Sun Dec 05, 2021 4:15 pm but then there's the problem of sourcing new RS 108 mm stub shafts, as well as obviously gutting the diff carrier to make the Eaton or other fit.
108's not required, stock stubs will work.
There is pretty minimal clearancing of the case to make the Eaton fit. This is based on information from the handful of people I know that have done the conversion, not my personal experience.
My feeling is, if you converted your XR to a 302, then you can probably do the LSD swap in your sleep. :)
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Re: ABS Master Cylinder / Pump Assembly

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my8950 wrote: Sun Dec 05, 2021 5:14 pm 108's not required, stock stubs will work.
There is pretty minimal clearancing of the case to make the Eaton fit. This is based on information from the handful of people I know that have done the conversion, not my personal experience.
My feeling is, if you converted your XR to a 302, then you can probably do the LSD swap in your sleep. :)
Ha! Thanks for the compliment... but of course that was a few years ago. Now it seems like I'm constantly looking for excuses to take mid-day naps. :) :( Having enough motivation/time issues just getting my hydraulic e-brake bracket made, and installed.

I thought the XR 105mm stub shafts were not large enough in diameter to be re-drilled for 108mm? Or, at least not enough meat/mass for a high-performance rear end. Just me, but I don't much care for adapter plates if the "real" thing can be used. Plus, seems in my recollection that my 108mm RS stubs are significantly beefier all around.
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Re: ABS Master Cylinder / Pump Assembly

Post by my8950 »

Yes, more beef, but not necessary.
The stock XR stub shafts slide right into the Differential provided by MC2/Eaton, which I believe is a GM 7.5" posi unit.
No adapter plates required for using the Eaton with stock XR axles.
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Re: ABS Master Cylinder / Pump Assembly

Post by brokencase »

I think that it is worth mentioning that the Traction Control is not so much a performance item as a LSD would be.

It is just useful for those cases where you might get stuck with a single wheel spinning. It is also ads some safety when you hit slippery surfaces at speed.

Granted, removing the diff is not a big deal but I was more referring to the effort for the whole process of converting over to the LSD.
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