Braking causes "hopping"
#1
Braking causes "hopping"
Hi all!
Have a question and need some help. I have a 1992 w250 that has 227000 miles on it. VERY well maintained.
whenever I put any pressure on the brakes to slow down or come to a stop, the truck hops. HOPS down the road. There is NO pulsing in the brake pedal and there is no pulsing or weird feeling in the steering wheel. The tires are not out of balance as it goes down the road straight and smooth. The shop doesn't know what is causing this, they've had it apart and are inspecting it again.
Any ideas?! Anything is appreciated!!!!
Have a question and need some help. I have a 1992 w250 that has 227000 miles on it. VERY well maintained.
whenever I put any pressure on the brakes to slow down or come to a stop, the truck hops. HOPS down the road. There is NO pulsing in the brake pedal and there is no pulsing or weird feeling in the steering wheel. The tires are not out of balance as it goes down the road straight and smooth. The shop doesn't know what is causing this, they've had it apart and are inspecting it again.
Any ideas?! Anything is appreciated!!!!
#4
Registered User
Rear Wheel Anti Lock valve is in the inside of the frame near the rear wheels on the driver's side. It is supposed to modulate the rear wheel brakes to prevent lock up. Sometimes they goof up.
#5
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Join Date: Jul 2013
Location: Washington State
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As it is garbage. I completely removed and bypassed mine after hours of scanning threads on the REAL system that or trucks have.
#6
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#9
Administrator
That is it, but you should probably do a little testing before you replace it. I would temporarily bypass it to see if that resolves the issue. Grease or oil on the brake shoes can cause the brakes to grab and maybe produce your symptoms. Check all of the axle mounts too. The function of that valve is to release hydraulic pressure during wheel lockup, so it would not likely cause higher pressure that would lock up the wheels, IMHO of course...Mark
#11
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Join Date: Dec 2010
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Keep it simple stupid.
Behind the glove box is the abs controller, unplug it. Drive around
If the hopping stops you're on the right trail. If not , pull the drums, and inspect as Mark suggested. Ive experienced this when my rear brake shoes were oil soaked or the drums became mirror polished.
#12
Registered User
#13
Registered User
Mine did the hop routine on initial stop every day till I junked the RWAL system. When working well, it's performance is marginal, especially compared to more advanced antilock systems.
The sensor is on the differential housing. Here's a delete:
The sensor is on the differential housing. Here's a delete:
#14
Registered User
Mine too resides in the scrap pile. the thing scared the hell out of me too many times.
#15
Thanks all for the help, the shop was going to move to this possibility as soon as they were done finishing looking into their theory. They took my front rotors off again and had them looked at much more closely and it turns out they weren't warped but bent somehow. Brakes are as smooth as glass now!!! The fact that they weren't warped is why we weren't feeling it in the pedal.