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1998 SVT ABS Brake problem (Happened to mine)


BuckeyeSVT

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About last summer I noticed that when I started my car the lights would dim real low when the ABS pump would self-test. Being that I never really used the ABS I never thought much about it. Most of us don't depend on our ABS brakes to stop us too often and I'm not one who drives depending on them ;)

 

Anyhow - Since winter is here I started having some strange problems. First off the ABS brakes would work for about 2-3 seconds and then make a loud sawing noise and the brake pedal would go to the floor (consequently causing all 4 wheels to lockup and an interesting 180 degree spin). The first time it happened I thought for sure the brake system itself was boned up. So I inspected everything (lines, calipers, pads..... even the power and grounds into the ABS unit) all checked ok. So I performed a brake fluid flush and found some rust in the rear caliper fluid and also the fluid had a dark green tint to it. So I changed the fluid and bled all 4 wheels according to the manual. This didn't seem to help at all. I then drove the car to a local Ford dealership and explained my problem ( and also had them do a NGS Bleed on the ABS system just in case I missed some trapped air in the ABS Hydraulic pump ). They said they found alot of air inside the ABS pump assy and the ABS was functioning fine. Well, not even a day later I was faced with an opportunity that I had to depend on my ABS to help out with and it did the same thing (ABS worked for a couple of seconds, lights dimmed and the pedal made a sawing noise and went to the floor - locking all 4 wheels and causing the car to slide sideways). This severely pissed me off, and after calling the Ford dealership they told me that they hadn't had any problems with the ABS units and that possibly there was something in the brake system that was preventing the ABS unit from properly doing it's job.

 

Hearing that they hadn't encountered any problems made me curious - So I headed over to the NHTSA.Com website and browsed all the customer defect complaints on 1998 Contour models. 28 complaints total for brake failures, over half are ABS concerns where the wheels locked up and loss of control was reported. For grins and giggles I searched 1999 models for the same problem and guess what? Not a single report of an ABS problem. Hmm... what changed?

 

ABS5.jpg

 

As you can already guess starting in 1998.5 Ford switched to a new ABS pump/hydraulic unit. The Mecatronic 3 unit was phased out for the lighter (and more reliable) Bosch 5.3 unit. Shown in the pic above is what the unit entails including the brake lines. Feeling the Bosch unit over the Mecatronic was night and day. The Bosch unit was approximately half the weight of the old unit and has a smaller footprint underhood. Now, most of you have never seen your ABS unit or where it's located, the location is on the drivers side firewall under the Brake Booster unit. Now to gain access to the pump you will need to remove the master cylinder and brake booster. The booster isn't that much fun to remove ( I've had plenty of experience in getting the booster out before on other cars so I had a slight edge in getting mine out..) Here's a pic of the old ABS unit removed, and a pic of it on the ground.

 

ABS1.jpg

 

It's a fat and wide unit - Weighs around 12 lbs. It has 6 lines going in, 2 from the Master Cylinder(feed) and 4 output lines. The connector on the old unit cannot be used on the new unit. It has a two row connector vs. the three row used on the Bosch unit. Here's the difference:

 

ABS7.jpg

Mecatronic 3 connector (Factory equipment)

 

ABS6.jpg

New Bosch 5.3 connector (Factory harness)

 

This meant that I had to splice the harness to make this work. Luckily the ABS speed sensor wires are all the same colors so that is easy. The only real hurdle is the power/ground and ABS light. The ABS light does not work the same in the 98.5 cars then they do in the 1998 cars. I still have to re-wire mine, but I don't care to see the ABS light as long as I know it works :)

 

Installation is pretty straightforward as long as you have all the brake lines coming off of the unit. I lucked out and found a unit (Thanks Matt) that has everything intact. Suprisingly it did bolt right in without too much drama. The wiring wasn't that bad as I had a copy of the diagrams for both units sitting in front of me. Before and after installation pics here:

 

ABS4.jpg

 

ABS8.jpg

 

Yes, it can be pretty un-nerving and also extremely difficult for the normal joe. I'm not the normal joe and I've never had it easy :) so I'm used to it. Trust me, replacing the ABS unit is far more simple than replacing the alternator on a 2.5 ...

 

After all the installation was complete, the booster and master cylinder re-installed and lines secured - I bled the system to purge all the air in the lines and took it out for a test to see how effective it was. It was a night and day difference in ABS performance over the old unit it replaced. The ABS on my car never worked that great from the beginning and this unit is incredible for how it modulates the pressure to keep the car straight. Anyone who is in the same situation with their 1998 SVT ABS system malfunctioning I would HIGHLY suggest instead of replacing it with a new/used Mecatronic unit to convert to the newer Bosch system and feel the difference in the performance.

 

At least now I can drive without worrying about sliding/losing control in a panic stop. That in itself is worth the conversion.

 

-Doc

 

P.S. If anyone is interested I can help with wiring diagrams and also tips on installation - Just email for details.

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So, were one to have this same problem, I wonder if the dealer would

opt to replace the original unit with the Bosch unit if they did determine the problem to be the ABS or would they just replace it with

another "old style" unit?

 

Karl

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I would say they would probably change it out with the same unit (Be aware though the unit costs around $700.00). Luckily I found mine used (Off of a totalled 98.5 SVT) and saved a ton.

 

-Doc

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Memory test...!!!!!! The older ABS units had problems re electricical/electronic internals as I recall.....bad plugs/connections etc......the only info other than that is that bleeding the abs,if a new unit is fitted..involves 'cracking' a few unions to get the air out before you go to bleed at the wheels..the only other no-no is 'dot 5' brake fluid...DON'T use it in ABS cars....the unit hates it.....

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Valvoline Synthetic DOT 4 for me. I didn't however crack the unions to bleed the system but I did get all the air out (No bubbles in the bleeder tube). The system is working better than it did when new - And my lights no longer go dim while the ABS pump is running.

 

-Doc

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  • 7 years later...

I did this almost 8 years ago, I don't have the wiring diagrams handy anymore. I used a factory paper manual for the scematics which I lent out and lost a long time ago. I would suggest a Ford CD for the 1998 model year which will cover both systems as the break point was in the half year (1998.5). Besides, the diagrams I can print now don't make any sense at first glance because you have to follow 2 pages for each system to get the gist of where the wires connect.

 

-Dom

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  • 3 weeks later...

I know it been awhile, but do you remember anything about the power wiring... I wired my bosch unit up and it works great, except for the fact that its constantly powered on and its draining my battery... From the schematics, it looks like there is an external relay on the bosch unit, where the merc unit had it built in. Did you have to wire anything up externally to make this work right?

Thanks

Gordon

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I've installed 4 of these so far with zero issues. Are you sure you have your power and grounds hooked up correctly?

 

Aside from the ABS unit and the matching harness no other relays or parts are needed.

 

Lol... on second thought. Did you try to bypass the brake light switch input by switching it to positive feed? You must run a seperate wire inside to the brake pedal switch for activation otherwise it will stay on all the time..!! Perhaps that's the malfunction???

 

-Dom

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...more memory test here Dom..I know you and I talked of this YEARS ago...and apart from the unit etc,I ,on one I did...waaaaaaaaaaaaay back that started off with corroded pins/connection and when I went to swap connectors etc and to re wire ,found the dreaded wire harness issue...the harness was also 'falling apart' inside etc...I think on that I go another harness and carried out the plug/rewire mod on that for he new unit. Yes, the stop lamp switch issue also 'rings a bell'..damm, this was years ago!!!

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Thats what i was curious about, i did not run a wire anywhere but in the harness... SO i need to connect a line to the brake pedal for the activation, this make sense...

I have documented the wiring that i did on the other forum...

ABS swap - mecatronic to bosch - CEG Forums

 

So looks like the orange/green wire from port 6 on the bosch connector needs to connect to the brake pedal.

Is it pretty self explanatory as to how to connect the wire to the brake pedal switch?

 

is this the wire? From the schematic it looks like its a ground wire that is completed with the brake switch.

 

gallery_8785_268_3901.jpg

 

 

Thanks

Gordon

Edited by matthewsgordone
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Dotted lines on the diagram don't necessarily mean ground wiring.

 

The orange/green wire must to be connected to the output of the brake lamp switch (hot when the pedal is depressed).

 

-Dom

 

P.S. I copied your diagram off of CEG - I'll look it over with what I have and post later when I get off of work.

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...the written word on dotted wires/ground according 'the book from Ford..says...

 

 

'Other circuits are also grounded at GXXX but are not shown can also be referenced in Ground Distribution...'

...and also ' 'A thick dashed line represents 2 or more wires...'

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After reviewing the diagram I have come up with the proper wire sequence.

 

New connector wiring

Pin #1 : Empty

Pin #2 : RR+ Speed Input - Old Pin #9

Pin #3 : RR- Speed Input - Old Pin #10

Pin #4 : RF+ Speed Input - Old Pin #7

Pin #5 : RF- Speed Input - Old Pin #8

Pin #6 : Stoplamp circuit (Must run wire to stoplight switch (Orange/Yellow) wire).

Pin #7 : Not Used

Pin #8 : F7 BJB 10A Power Input - Old Pin #5

Pin #9 : Not Used

Pin #10 : Not Used

Pin #11 : Not Used

Pin #12 : Ground - Old Pin #1

Pin #13 : Power 12V (Shared with Pin 14) - Old Pin #3

Pin #14 : Power 12V (Shared with Pin 13) from 60A F3 BJB - Old Pin #3

Pin #15 : Ground - Old Pin #2

Pin #16 : BK/BU Park Brake/Low Fluid Level ground input (Optional)

Pin #17 : Not Used unless equipped with Traction Assist

Pin #18 : Not Used unless equipped with Traction Assist

Pin #19 : Not Used

Pin #20 : LF+ Speed Input - Old Pin #21

Pin #21 : LF- Speed Input - Old Pin #22

Pin #22 : LR+ Speed Input - Old Pin #23

Pin #23 : LR- Speed Input - Old Pin #24

Pin #24 : DLC ( Direct to DLC - No PCM) - Old Pin #11

Pin #25 : ABS Indicator (With older cluster will cause ABS light to stay on permanently) - Old Pin #20 if you want an idiot light on all the time.

Pin #26 : Not Used

Pin #27 : Not Used

Pin #28 : Not Used

Pin #29 : DLC - Through PCM - Can't be used with 1998 RJL1 PCM

Pin #30 : DLC - Through PCM - Can't be used with 1998 RJL1 PCM

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  • 1 year later...

Ok so I am in the process of doing this and have some issues. I saw the above write up on the ABS swap and had some questions for you. Hopefully someone can remember some things. My questions are towards the wiring. I am looking at the pin diagram and you stated that Pin #16 : BK/BU Park Brake/Low Fluid Level ground input (Optional). My question is do you hook this up and if so where do you connect it. Also I was looking at the factory schematic and was wondering if it could be hooked to the small BK/Ye wire that is pin # 19 on the old connector/abs unit. Also has anyone hook up Pin #25 that is the one if connected it would cause the ABS light to stay on. Also how easy was it to bleed the system after everything was connected. Also on the new connector, the wires that aren't used, do you just tape them up and secure them?

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  • 2 months later...

ABS has no effect on cruise. Check your wiring to the brake switches under the dash.

 

 

 

-Dom

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