Mechanical question

[Where~the~wind~blows]

The other day I drove down a very long (over 2 miles) steep grade, and as you enter this area is has a fairly big warning for large trucks. I was in PA and the road was 487, the area was called "red rock", anywho... as I descended, my steering wheel started to shake heavily, I panicked and thought oh damn what the heck is about to break? Nothing did ut my van never did this before, I do have some play in the wheel... was that a factor of was something else going on? Thanks in advance....Autumn

here is the road I was on: http://en.wikipedia.org/wiki/Pennsylvania_Route_487

 

[Lucky mike]

Tie rod end ?.......brake caliper sticking......Shitty road , not necessarily in that order!

 

[Iggy]

I had the same thing happen in my old pickup. It was a warped rotor from having no brake pads left.

 

[sparky1]

does sound like "Hot spot "n the rotor from Hot "Possibly" dragging caliper..Brake fluid will boil causing more force---and Brake Fade too.
normally when it cools off back to "normal?

 

[Patrick46]

could be the wheel bearings are shot too. or ball joints

but You need to get this checked out ASAP!!!

This could be seriously dangerous...your vehicle is trying to tell you something....you'd best listen!!

 

[WheelEstate USA]

Please, do get it checked. We want you and everyone else safe out there.
A further occurrence might not turn out as well :s

 

[westriver]

There are no big issue here, just a need for a bit higher level of experience, and a new skill to practice, for use while descending long, steep grades. You have slightly warped rotors on the front brakes of the van. Typically they are not an issue. When they overheat, they not only warp, (causing the shake you experienced) but the next step is that they start to fade, then fail. Not only can this be fatal to you, but on that road it HAS been fatal to others. I recall at least one driver who left the state park campground at the top of the mountain, pulling a camper, and didn't survive the ride down, due to brake failure.

The solution is real simple. You need to use the transmission to limit the speed of the van, and learn to intermittently apply the brakes to scrub off speed. This means that you pick a target speed, say 40MPH. As you decent the grade, before the vehicle reaches that speed, you downshift the lever to 3, 2, or 1. until you determine which gear will keep the vehicle from exceeding your safe limit. Next you intermittently apply braking to keep the vehicle below your safe limit, then intermittently keep your foot OFF the pedal between braking events. This will allow the system to cool, and the rotors will not warp, nor will you lose braking ability during the several minute ride to the bottom. If you are now experiencing a wheel shake during normal, or semi-aggressive stopping, you probably warped the rotors. This can be a harmless nuisance if they are just slightly warped, if it is intolerable, they need to be resurfaced, or replaced. Good luck, glad they you got to experience a truly beautiful part of northern PA.

 

[WheelEstate USA]

When you deal with 4-5 down hill grades of 7-8%, running 9-10 miles each a few miles apart, such as across southern Oregon's Hwy 140, you better have all your wits about you and your beat skills at hand (and foot)

2000-3000' right over the edge, with no guard rail to slow you down. They'll bring up anything that's left of body parts, if any, but the twisted wrecks remain as a reminder how deadly it can be.

 

[GotSmart]

If not fixed, that can cause other parts to go out, and more and more expensive repairs.

 

[SternWake]

There is one Paper out there that says that few "warped" rotors are actually warped, they say it is more like uneven brake pad deposits on the rotor, which are grabbier on certain parts of the rotor and slippier on other sides, causing that pulsating pedal feel.

There are strong opinions on either side of this argument. Here is a link, form your own opinion.

http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths

Since reading the above paper I have taken care, after a hard stop or anytime I know i have heated both rotor and brake pad up in the super hot zone, not to leave the front brakes clamped hard on my rotors( use Emergency brake instead to stay stopped, and I have not had the pulsating pedal since.

There also seems to be some correlation in pulsing pedal to driver habits. Some brake late and hard and keep a lot of pressure on the pedal waiting for a red light, more than which is needed to hold the vehicle stopped. These people seem to find their pedal pulsating more so than those who brake earlier, less hard, and only exert enough pressure on the pedal at a red light to hold the vehicle immobile.

Fewer shops carry disc brake lathes these days, because new chinese rotors take less time to install. Yet quality can be all over the board on these. I had a horrid set of Duralast rotors which lasted 10k miles before the bearing races started spinning in the bores, which were also machined too deeply. Those cheap Chinese rotors really cost me a bunch more in the long run when I had to replace both bearings(SKF) and rotors( Brembo) at the 10K mark,

One mechanic I trust will not put new rotors on vehicles without turning them first on the lathe, and he claims that this has reduced come backs by 90%.

Certainly other suspension issues could be attributing factors to the OP's condition, such as worn suspension components, but it is likely the rotors are warped, or have uneven pad deposits on them, and turning them on a lathe is the remedy, and perhaps driver awareness of the cause can help to keep them at bay in the future.

 

[offroad]

This discussion is very relevant. My vehicle has pulsating brakes. But is currently a car, and i live in the flat lands. From listening to CARTALK discussions about similar issues this can be a sticky caliper, or it can be the simple warped rotors, or bad bearings. Unfortunately you do need to fix each one of these issues.

Your vehicle will be an experiment for a while. Even if you fix the easy issue by getting new brake pads and new rotors, you might mask the real problem for a short while. A sticky caliper, might still be happening. Do you have antilock brakes? That can also cause issues.

---

So in summery.

1). Bad bearings or bad tie rod ends. Should be easy to tell via inspection. Ask for that inspection. Do you have factory bearings? Ever have a wheel bearing replaced? If so are the wheels over heating because of bad brakes and warping, and causing lubrication loss in bearings too from excessive heat? Ask these questions.

---

2). Cheap rotors from a previous brake job? If they are not factory part from dealership you could have poor quality rotors that warp too easy. Or were not machined properly at factory. Kind of like the idea about machining the new rotors a little. Always use new pads as they are cheap to replace. You want perfection in brakes at 80 mph downhill in mountains with 100 foot drop off cliffs at every bend.

---

3). Sticky caliper is the grabbing mechanism that pushes the pads onto the rotors. When you apply brakes, there should be a constant pressure. Constant pressure means constant heat and brakes should handle this in all normal situations. If you manually pump brakes they are heating-cooling for a little, and still should handle this. --- but if you have a sticky caliper. Now that wheel is hot all the time while driving. Going down the highway at 80 mph that wheel is constantly hot, boiling that brake fluid in the caliper. Making it mushed soft when you apply the brakes. All because of a sticky caliper. Ask yourself and your mechanic about a sticky caliper. Usually one wheel is hotter than the other in temperature. Does your mechanic drive the car around and check the wheel temperatures for consistency? How do they check wheel temperatures?

---

4) last the rare antilock brakes could have a problem. Is the sensor bad? Causing brakes to pulse? Can you bypass the sensor and that computer? Can you turn off the antilock brakes for testing? Hope so as you need to eliminate this as an issue. Antilock is nice to have but not needed and will cause false issues if not working right.

---

If you are lucky and have a great mechanic and get really well designed parts then you might spend less than $500 getting this fixed.

 

[Optimistic Paranoid]

As for turning off the anti-lock brakes for testing, this system is USUALLY on it's own fuse, and it's as simple as pulling that fuse. The owners manual will tell you which fuse, and also if there is anything else on that circuit.

Regards
John

 

[offroad]

Good note john!!

 

[Zil]

There are many things that cause shimmy and looseness in the front end. A long list to guess your problem. I ride on the same roadways as you. I don't want your accident to be mine. Get it fixed. Jack up the front so the tire is off the ground. Grasp the tire and try to shake it off the vehicle. Top to bottom and side by side. The amount of loose is related to how dangerous you are to the rest of us. Find the old local shop that does front end alignment and get the estimate.

 

[SoulRaven]

I know this road and it’s a killer to those that do not put your transmission into a lower gear.

If you are in PA and see a sign that says trucks stop here and proceed in lower gear you need to downshift ASAP.

Must likely your brake rotors and pads are toast. In 1980 I bought a new dodge short wb van with rear glass, slant six w 4-speed manual overdrive on the floor only for $3800. It did just as you described not only downhill at first but then while breaking on the level. The problem was that the brake calipers had plastic pistons from the factory, which was a recall, and the dealer did replace the calipers with ones that had steel pistons.

 

[offroad]

Zil - good note. Except that having a jack holding a car up while you shake the tire is damn dangerous. Please put it on a lift and do that wheel wrestling.

 

[Where~the~wind~blows]

thank you everybody, I will have my rotors (and other parts) looked at, I'll be honest it scared the crap out of me! so I will not take any chances, thank you to a few that gave great detailed info on how to handle this until I get this fixed!

 

[highdesertranger]

the old death shakes. in your original post you didn't say if you were applying the brakes when this happened. where you applying the brakes? if you weren't I doubt it's warped rotors. any worn part in your front end system could cause this. misaligned front ends could also cause this. back in the day certain vehicles were more prone to the death shakes. sorry if I missed it but what type and year vehicle are we talking? everybody here has given good advice but without some more info we are only taking stabs at it. highdesertranger

 

[akrvbob]

Westriver is right, the fact it is only happening on a long downhill says its the rotors.

I'm afraid we skipped over his advice. This is life and death so I'm going to repeat it:

1) Gear down at the top of the hill in either an automatic or manual transmission.

2) Don't ride the brakes!!! They'll get hot and burn up.

Instead, allow the van to accelerate to as fast a speed as you are comfortable with then get on the bakes hard!! Slow down too much then get off the brakes and let the van speed up again. While you are off them, they'll cool down, if you ride them, they just keep getting hotter and will burn and fail.

I learned this the hard way in the mountains of Colorado. It's a lesson I'll never forget!
Bob

 

[offroad]

Good to know. A stuck caliper will overheat and cause brake failure. Your front wheels should be the same temperature at all times.