08BF_5MightyGAB

7/21/05

10:14 AM

Page 1

by Bill Williams for Mighty Auto Parts
ver since I dissected my first ABS modulator some 15 years ago, I have been of the opinion that these units could be responsible for base brake problems as a result of plugged filters. Over the years I have been inside some 17 different modulators and every one of them are equipped with multiple filters. The low end of the totem pole is the RWAL/RABS modulator at two and so far, the record is the Bendix 10 at 21. Filter placement varies with the type of modulator but in most cases at least some of the filters are in the direct fluid path between the master and the wheel brakesleading to the possibility of them restricting fluid flow to and from the wheels. If we factor in that the average vehicle on the road has never had a brake fluid flush, and the current average age of a vehicle is in excess of 10 years, the possibility of plugged filters exists. The 1995 to 1999 Mercury Villager & Nissan Quest are equipped with the Bosch ABS system
1995 to 1999 MERCURY VILLAGER & NISSAN QUEST: ABS MODULATOR INTERNAL RESTRICTIONS
as shown in Figure 1. This is a 4-channel system due to the diagonal split hydraulic system. The plumbing of the system has the secondary por-

Figure 1

tion of the master cylinder supplying the LF/RR, while the primary supplies the RF/LR. The master cylinder is equipped with a damper in the secondary outlet of the master cylinder. While this valve looks like a proportioning valve, it is not. Its purpose is to reduce the pedal vibration during an ABS stop. I was personally involved in diagnosing one of these vans some time ago and since then have
2005 Mighty Distributing System of America Norcross, GA 30092
noticed enough of a trend I thought it was time to publish some information. The vehicle in question was on its way back to Canada from a vacation in Florida. The brakes started selfapplying in upstate New York while driving down the highway. The van ended up in one of my customers shops and I ended up getting involved in its diagnosis. On first glance the van seemed to be experiencing a one-wheel drag condition involving the LF wheel. The shop had attempted to fix the problem without success. They called me and I was intrigued enough to travel the 3 1/2 hours to Watertown to look at the vehicle. Upon arrival I confirmed the LF wheel drag and approached the problem as a one-wheel drag condition. The list of possible causes included a mechanical problem with the caliper, brake hose, ABS modulator and master cylinder vent port restriction. Since the damper was in the LF/RR circuit it had to be added to the list as well. The problem appeared to be able to be duplicated in the shop by simply applying the brake a few times. Loosening the brake line fitting at the brake hose resulted in releasing the drag, which indicated the problem was upstream. With the problem present we could loosen the brake line at the master and release the drag, which would indicate a problem in either the damper valve or master cylinder. After talking to the dealer we found out the damper was not available anymore. We acquired a used master and valve from a salvage yard and installed only the valve. This appeared to correct the problem so we took the vehicle for a test drive. Once the brakes were at operating temperature there was a noticeable drag so we returned to the shop and checked for drag at all wheels. The drag check showed that both the LF and RR wheels were dragging, not just the LF as we thought previously. After some pressure tests to confirm the condition, the problem was traced down to the modulator. We purchased a used one and installed it and after a lengthy test drive confirmed the problem was gone. I took the old one with me to dissect at a later date. I finally got around to taking the old unit apart and was shocked to find the level of con-

Figure 2

Figure 3

Figure 4

tamination that was present. Figures 2 through 4 show examples of this. It is clear that fluid restriction could be possible based upon the amount and location of the contamination. I am aware of other such occurrences in these vans since my original experience, which is why I am waving the red flag. The symptoms will vary according to which filter becomes restricted. They will vary from wheel drag to a lack of braking at one or more wheels. The key to accurate diagnosis of these vehicles is to make sure the brakes are at operating temperature before checking for wheel drag.
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December 2005

INSTALLATION INSTRUCTIONS
MODEL NO. APPLICATION: 81920
1999-02 Mercury Villager 1999-02 Nissan Quest
WEIGHT CARRYING HITCH CAPACITY 3500 LBS. MAXIMUM TRAILER WEIGHT 350 LBS. MAXIMUM TONGUE WEIGHT WEIGHT DISTRIBUTING HITCH CAPACITY 5000 LBS. MAXIMUM TRAILER WEIGHT 500 LBS. MAXIMUM TONGUE WEIGHT Trailer brakes are recommended for towing loads in excess of 1500 lbs.
WARNING: Although this hitch is designed to safely tow its rated load, we recommend that you consult your vehicle owners manual for possible manufactures recommendations or limitations. Always follow the manufactures installation instructions and always install on the specified vehicle. Before installing hitch, check that the attachment points are in good condition. Failure to follow these guide lines will void warranty. Any modifications to this hitch will void warranty.

PARTS INCLUDE:

1. Receiver Assembly 2. 2215-04 12mm x 1.25 x 35mm Hex Bolt (1) (8) 3. 3730-05 1/2 Conical Washer (8)
1. Temporarily lower the exhaust pipe by unhooking the two rubber mounts. This will allow hitch assembly to be positioned up against frame easier. Tailpipe will be re-installed after hitch is installed. 2. Remove the spare tire from its under vehicle storage location. It will be reinstalled after the hitch is in place. 3. Position the right end of hitch assembly up over the exhaust pipe so that it will align with the two weldnuts in the end of the vehicle cross member and two weldnuts in the inner side of the frame as illustrated. 4. Loosely install the outer bolt in vehicle cross frame first. Be sure the conical washer #3 is placed on each bolt as illustrated. Do not tighten bolt. 5. Install the inner bolt, with conical washer #3, in cross frame second. Be careful not to cross thread bolt into the existing nut in vehicle cross member. 6. Repeat cross member installation procedure on other side of vehicle. 7. Install the two bolts with conical washers #3, in the side of each vehicle frame last. 8. Tighten all the 12mm bolts to 68 ft. lbs. torque. Failure to tighten bolts as described may result in fastener loss or failure. 9. Reposition the spare tire back in its storage location. Re-attach exhaust pipe to its rubber mounts.
For information regarding this product, or our warranty, contact your dealer or write to CUSTOMER SERVICE MANAGER P.O. Box 850, Lodi, CA 95241 NOTE: Some states require a clear view of licenses plate. Remove ball when not in use if it restricts view. NOTE: This product complies with regulation V-5, C.S.A Standard D-264 and safety requirements for connecting devices and towing systems of the State of New York.