Interesting brake issue

[JWatkins]

When working in traffic, occasionally, my brakes seem to release for a fraction of a second and then chatter and perhaps pull a little one way. My first thought was anti-lock, but I haven't been hitting the brakes very hard at all. Seems to do it more when I am applying, releasing and re-applying. Any ideas? I am on my way out to check the fluid levels now.
Jow

[DriVer]

Quote:

Originally Posted by JWatkins When working in traffic, occasionally, my brakes seem to release for a fraction of a second and then chatter and perhaps pull a little one way. My first thought was anti-lock, but I haven't been hitting the brakes very hard at all. Seems to do it more when I am applying, releasing and re-applying. Any ideas? I am on my way out to check the fluid levels now....

JWatkins, If you are asking about a rapidly applied brake pulse when going very slow or coming to a stop say from about 5MPH or so, the problem is with the ABS sensors at the wheel ends. They could either be dirty or out of adjustment. I had 4 new sensors installed and I did not have any further problems.

[Full-Timers]

Wow Jwatkins,
I am experiencing the exact same problem. I didn’t know how to explain it but you hit it right on the head. Mine started doing this right after having the rotors and pads replaced. I was going to take it back to the shop that did the work but being that we live in it, doing so is such a hassle. A while back DriVer suggested to me that it might be the ABS.

Does anyone know if removing the ABS 60amp fuse is the right way to temporary disable the ABS to test if this is causing the problem?

[JWatkins]

I figured it might be the ABS. I think that those are readily replaceable by the DIY type?
Joe

[DriVer]

Quote:

Originally Posted by JWatkins I figured it might be the ABS. I think that those are readily replaceable by the DIY type?

Joe, Oemy has a DIY explanation of how to do sensors on his website. Check it out.

Perhaps Oemy can you point us in the right direction, if you can't find the article.

Essentially, the sensors are pulled out, cleaned (including the sensor socket), lubed and restored to the bottom of the holder. Check the connection between the sensor and the modular connector that goes to the coach.

If you have a bad sensor the condition will persist.

[JWatkins]

Thanks Driver. I was just perusing his site and it looks pretty easy. I will have a go at that and let you all know.
Joe

[Full-Timers]

My test was a success. I pulled the 60 amp ABS fuse and drove it 180 miles today. Every stop was normal and smooth. The funny thing is that after pulling the fuse, the ABS light never came on. I would expect it to. It doesn’t even come on when I just turn the key on like the rest of the lights. I don’t know if it comes on when the key is turned on with the fuse in. Anyway, I am convinced now that the problem is in the ABS system. My next step is to pull all sensors, ohm the out, and clean everything. Hopefully that will fix it.


DriVer, you were right on when you suspected the ABS. I didn’t believe you until Jwatkins described the same problem (http://www.irv2.com/forums/f22/intersting-brake-issue-65756.html), “my brakes seem to release for a fraction of a second and then chatter and perhaps pull a little one way”. I totally spaced on the fact that my left front brake seemed to release causing the motorhome to pulled to the right. I was just focusing on the pulling and chattering part. The only thing that could cause it to release is the ABS.

[wa8yxm]

I have seen this on my car.. (not my motor home)

Though you have done a fair job of describing ABS in operation the idea of ABS is it should NOT under any conditions pull to one or the other side

However a de-lamanated rotor, or a pock-marked rotor... That WILL do it

inspect your rotors

There are other things that might too so do not rush out and spend money till you have had a good look at 'em yourself.

[DriVer]

Quote:

Originally Posted by Full-Timers DriVer, you were right on when you suspected the ABS. I didn’t believe you until Jwatkins described the same problem (http://www.irv2.com/forums/f22/intersting-brake-issue-65756.html), “my brakes seem to release for a fraction of a second and then chatter and perhaps pull a little one way.

FT, Although I have not done it all, I have dealt with several of these types of these issues. I don't like being right as much as being helpful.

[JWatkins]

I am going to attempt the pull, clean, grease and seat that Oemy suggests. Hope that does it. Is the part the $70.00 item?
Joe

[John350]

GM had a problem similar to what you are describing. It was on thier light duty trucks. A different desgn. Symptoms were ABS activation with light brake application at speeds 5mph or less. root cause was corrosion build up under the sensor increasing the gap by a few thousanths of an inch. Reseating and cleaning your sensors might just cure your problem.

Happy Motoring

John