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7.3L IDI Diesels (Not Power Strokes) Technical discussion of topics related to vehicles powered by the 7.3 Liter In-Direct Injection Navistar engines.

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Old 06-01-2005, 09:28 AM   #1 (permalink)
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Bypassing RABS valve, good idea?

I am having the usual brake problems. After changing pads, shoes, wheel cylinders, brake hardware and adjusting the rear brakes up I am still getting a low peddle. I am about to change the front hoses, as a suggestion by a friend and their old too. Having read much on this wonderful site it seems there is a lot of problems with the RABS valve. What kind of braking capacity would I lose if I simply bypassed it? I know the brake system on these trucks isnt that great so maximizing the braking is important.

Thanks,

Aaron
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Old 06-01-2005, 09:43 AM   #2 (permalink)
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Re: Bypassing RABS valve, good idea?

Aaron,
As I mentioned in another post here, I bypassed mine and my brakes work great now. No fade, can get them to lock up now (not a problem- I learned to drive BEFORE ABS was invented). Got the fittings at Pep Boys and never looked back.

Keith
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Old 06-01-2005, 09:56 AM   #3 (permalink)
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Re: Bypassing RABS valve, good idea?

There are NO normal brake problems with our trucks, I've owned mine 12 years with never as much as a hiccup in my brake system.
If you buy top quality brake pads and turn the rotors and drums correctly and not below the size minimum stated on them they work fine. if you have a vacuum problem do the test on my gallery.

Check these out.........

http://www.asashop.org/autoinc/dec99/techtips.htm

http://www.federal-mogul.com/fmeconn...loads/3404.pdf

1997 and earlier diesel trucks equiped with vacuum power brakes--Low/creeping pedal:
Many owners have complained of a low or creeping brake pedal on their trucks, often mistaken for a bad master cylinder or Rear ABS valve. If the condition occurs after the vehicle has come to a stop, and no other brake concerns are found, (worn or out-of-adjusted brakes, cocked pads, or hydraulic problems) the condition is normal and the result of the vacuum pump replenishing the vacuum inside the power booster. Ford has developed a Zero-Loss Travel brake booster to correct this condition if the customer finds it unacceptable. This part is only for use on diesel-equiped trucks--P/N F5TZ-2005-CA--and is not a service replacement; it must be ordered by the part number, not vehicle application.

This condition is similar to the low brake pedal concern on all 1995 F-series that required a larger-diameter master cylinder:

Trucks without cruise control:


F6TZ-2140-AB
F-250 Gas 4X2; F-350 DRW, SRW Gas 4X2, SRW 7.3 4X2 168" WB
F6TZ-2140-EB
F-250 4X4, 7.3 4X2; F-350 SRW 4X4, SRW 7.3 4X2 133" WB

Trucks with cruise control:
F6TZ-2140-BA
F-250 Gas 4X2; F-350 DRW, SRW Gas 4X2, SRW 7.3 4X2 168" WB
F6TZ-2140-FB
F-250 4X4, 7.3 4X2; F-350 SRW 4X4, SRW 7.3 4X2 133" WB

These part numbers are from TSB's 96-25-19 and 98-5A-34, and are not normal service-stock replacment parts.
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Old 06-01-2005, 10:09 AM   #4 (permalink)
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Re: Bypassing RABS valve, good idea?

Good info, thanks for suggesting it. I am using fleet rated pads and shoes. What I meant about normal problems was those being exprienced by others on this site. Any hydraulic system should work well so long as is functioning properly.
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Old 06-01-2005, 01:02 PM   #5 (permalink)
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Re: Bypassing RABS valve, good idea?

If by some bad luck your involved in an accident and your insurance company discovers the rabs has been by-passed there is a good chance they wont cover you.We all know they dont need much of an excuse to get them off the hook.Also,in a fatal accident you may be charged with neglegence or some other crazy charges.When the system is up to par it works pretty good.
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Old 06-01-2005, 04:22 PM   #6 (permalink)
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Re: Bypassing RABS valve, good idea?

I tell ya what, I used to have an '02 F-350, the only time that truck ever felt dangerous was when the rear ABS started working. The truck would simply loose braking power.

If you have to bypass it, bypass it. Most of us here have driven vehicles that were built before ABS was around. And when the wheels started locking up, we just let off of the brakes a little.

Of course, teh best solution is to replace the RABS valve. But bypassing it is better than not stopping.
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Old 12-09-2011, 02:46 PM   #7 (permalink)
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I have been experiencing similar problems with 88 7.3. Replaced master cylinder twice and with ford bench bleeding master is mandatory. replaced and calibrated the break boost with a used one then with a new one. I was stumped no leaks and I bleed the system many times. I have not looked into the rabs valve I will do that now. However i was told by a fleet owner of tow trucks that I could put it in four wheel drive this should by pass the rabs valve and if the problem goes away then i know it was the rabs valve. I tried this but nothing changed. I have nothing left to try so I will try to replace the rabs valve

thanks for all the feedback

Last edited by styles; 12-09-2011 at 07:29 PM. Reason: added question
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Old 12-09-2011, 07:31 PM   #8 (permalink)
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on a f250 88 7.3 is there a screw that can be removed from the proportioning valve to by pass anti lock ?
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Old 12-09-2011, 09:19 PM   #9 (permalink)
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if you disconnect the electrical connection at the rear axle plug for the aba it will stop the abs from being activated the only thing is the light for abs will be opn to tell you its not working have been doing this for a lot of years never had problem but lots of thanks for this simple solution
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Old 12-09-2011, 09:30 PM   #10 (permalink)
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Quote:
Originally Posted by gmoncion View Post
if you disconnect the electrical connection at the rear axle plug for the aba it will stop the abs from being activated the only thing is the light for abs will be opn to tell you its not working have been doing this for a lot of years never had problem but lots of thanks for this simple solution
BUT if you have an E4OD transmission, it will throw it into "limp mode" and cause harsh shifting and possible tranny damage.
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Old 12-09-2011, 09:37 PM   #11 (permalink)
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if you have just rear wheel anti-lock it won t if your not sure it is easy to unplug it try it if you don t like it just plug it back in hope this helps
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Old 12-09-2011, 11:27 PM   #12 (permalink)
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In that case, if you're going to disconnect something, you disconnect from the RABS module. the VSS goes to the RABS and the PSOM at the same time. I would rather repair the system, though.
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Old 12-10-2011, 09:39 AM   #13 (permalink)
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Quote:
I have been experiencing similar problems with 88 7.3.
Styles, what exactly is your particular problem? If it's a slowly sinking pedal while at a stop, just like the symptom of failing master cylinder cups, Raybestos, BW or whoever produced the original RABS came out with a TSB regarding reoccuring failures. It's a mechanical failure due to brake fluid crud buildup, unplugging it has no effect and they can't be rebuilt. Counting the original, I'm on my 3rd one in 20 years.
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Old 12-10-2011, 09:46 AM   #14 (permalink)
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The RABS system is made by Kelsey-Hayes and referred to as RWAL, rear-wheel antilock brake. Here is my first google hit (but I've been there before so...) which is relevant:

Kelsey-Hayes RWAL Antilock Brakes
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