Let me first say that I know the obvious diagnosis which is brake rotors, and if it was that easy I wouldn't be posting :-)

Vehicle is a 2010 Grand Caravan with about 38,000 miles

Symptoms

• When van accelerates over 60 mph, then apply brakes firmly but not hard, steering wheel will shake severely as speed drops below 60 mph, down to 50 mph. But as soon as reach 50 mph, shake stops.
• Will not do this the first time, but will fairly consistently do it the second and subsequent times this is repeated.
• Also, when applying brakes as coming to a stop (<10 mph) will often hear a grinding noise.
• All of this is distinctly coming from the front wheel, passenger side.

When this started, I was convinced it must be a bad brake rotor. I had a pad that was wearing quite a bit. I decided that I would just replace the pads and rotors. I always use the premium pads. I bought the pads and rotors at a well known national parts supplier. For years have changed pads and rotors myself but found that the rotors were rusted on an could not get them free. (Live in Central NY).

I took it to my mechanic and they put on the rotors and pads for me - reputable mechanic with proven history. The day after I picked up the van, was on the highway in conditions mentioned above, and the shake still is there and still as severe as ever. I have checked his work and they are clearly the brand new pads and rotors ... and he thoroughly lubricated all pivot points.

Next thought was a caliper hanging, so I experimented with driving for 30-45 minutes where I used the brakes but somewhat sparingly. I found that the brakes were totally cool and this was on a hot day.

So then was thinking that it may be a wheel out of balance, so switched my front and back wheels on the passenger side. Absolutely no, not even the slightest change.

So then I am on to thinking wheel bearing, but checked and there is not any chuck in that wheel at all. Not to mention the fact that there isn't the typical noise you would hear around curves and there isn't evidence of a problem outside of the conditions above.

Any ideas?

 

mine does this too. not saying rotors he put on where not warped.they could be, I get a clunk sound on bumps but at low speeds and bumps that are friquient, I going to machine my rotors when I have a chance to see. someone here machined there new rotors and fixed issue.

 

CV Axle?

 

You have done a lot in trying to pin down the problem. Very logical way to go. :thumb:

- passengers side for sure? Sometime problems can transfer around, it seems.

- steering wheel shaking indicates front end for sure.

- only when applying brakes.

- only at certain speeds.

- grinding noise when coming to a stop.

Any looseness in the front end?

Tires can cause sporadic vibration at times depending on road surface and ambient temperature. Is the wear even on them? Are there any scalloped areas on the tread?

Grinding noise indicates brakes/brake area for sure, possibly unrelated.

Just thinking out load. If your tires aren't directional, try switching front tires. Amazing what that can do for vibrations, something to do with changing the direction of rotation, I guess. Otherwise I would look for something loose in the front end. Could consider getting your tires "road force balanced" (versus the regular balancing). Do you have winter wheels you can swap?

Then there's the ABS. Wonder if that can act up in a way to cause your problem, a faulty sensor maybe? Take a look at the condition of your sensor connections at the hubs. Check for looseness of a connection.

Good luck with this one, it's a dowser of a problem.

 

Rear rotors cause more pulsation issues than the front rotors. Might want to start there.

 

I was going to suggest ABS as it's normal to feel a little vibration in the brakes when braking under the conditions you describe but the other symptoms you describe lead me to believe it's not the normal ABS action. Still wouldn't rule out an ABS sensor problem as TJeepman suggested, though I would think you would get a CEL or BRAKE light if that was the case.

Have you checked the tie rod ends, CV boots, and suspension bushings? Look for any cracks or tears in rubber parts down there.

Just wanted to chime in on this specific point especially since Tizzy1 suggested rear rotors...I thought the same thing the first time I tried taking the rotors off a 5th gen GC. I sprayed PB Blaster and WD-40 in there, and I hit the rotor from both sides with a hammer, and still failed to get the rotor off. Turns out that the factory rotors are installed using a really strong adhesive so that they stay on there as the van travels down the assembly line (other cars I've worked on use small screws to accomplish this). I had to jury rig something using a couple of lug nuts, the caliper bracket mounting bolt, a short large head bolt from a hardware store, and a breaker bar in order to get the factory rotors off. If you want details let me know.

 

So tire wear looks good, no evidence of scallops. Took your suggestion and swapped front tires (they are not directional). Did not seem to make a difference.

I would really be settled on the rotors being the problem if it wasn't for the fact that I changed rotors and it made no difference, and while it is possible for a new rotor to be warped, that just seems unlikely.

From what I see from your post and the others also, this will get into things I do not want to get into myself. I feel better knowing that the posts are at least validating that the problem is not obvious.

Thanks for the suggestions ... I'm going to pass them on to the mechanic ... we'll see what he comes up with.

 

Ask the shop to slap a dial indicator on the wheel hubs and check for lateral runout. That's the #1 cause of brake pedal pulsation. Especially since you said the old set was rusted on. Rust between the rotor and hub can also cause enough run-out to damage a rotor. 3M makes special pads just for that purpose--to remove hub rust.

 

Or maybe the rear rotors are the problem