Going down a hill, slightly breaking, car shacking

ozana

ozana

New member
Going down a hill, slightly braking, car shaking

the other day I was driving down a hill - pavement street - and I was slightly braking on the way down, just enough to keep the speed under control.Being a long hill I've had time to realize that as soon as I hold the brake down a bit, the car started to shake, especially visible in the steering- wheel. Never noticed it before. If I release the brake completely, the shaking stops, no movement in the steering-wheel. I push the break again just a bit, shaking starts again.Remember, this is going down the hill on a street at a constant speed.
Then I've tried the same thing on the flat street but, obviously on the flat street, braking even a bit will slow down the car and couldn't feel the shake that much. If I push the brake hard to a quick stop, obviously no time for shaking.
I have a 2001 4Runner RS sport ed., with 110,000 miles on it, bought it 2 summers ago, and only changed the oil since then. Not sure if or when the brakes where last changed.
Any suggestions to this will be greatly appreciate it.
Thank you
 
Last edited:
Register to hide this ad
This is likely to be the condition of the front brake rotors. When you're going downhill there is a lot more vehicle weight on the front wheels and less on the rear wheels. The brake systems sees this and will compensate by increasing the proportion of braking force towards the front. This is why you are experiencing it on downhills and not level ground.

Have your rotors inspected for runout (warping).

Also, when writing about the vehicles brakes, they are spelled brake, not break. Otherwise you make it seem like your car is falling apart. Not try to be a smart-ass, just letting you know. :)
 
I agree that it's rotors. But the brake system compensating for down-hill conditions? Eh...it's not like 4x4. When you push the brake pedal, the same force goes to the master cylinder (and proportioning valves) whether you're going up or down or flat. More weight on the front, yes. Increased braking power to the front discs? Don't think so.
 
Qyota said:
But the brake system compensating for down-hill conditions?
Click to expand...
Yes, proportioning valves compensate for rear axle load. They are designed to adjust the pressure between the front and rear brakes depending on how hard you are stopping. The shorter you stop, the more of the vehicle's weight is transferred to the front wheels, in some cases, causing the rear to lift and the front to dive. These valves are designed to direct more pressure to the front and less pressure to the rear the harder you stop. This minimizes the chance of premature lockup at the rear wheels. Going downhill also transfers weight to the front increasing the chance of rear wheel lockup.
I'm pretty sure the 4Runner has this, but I will check.
 
I agree that it's the proportioning valve's job to reduce braking power to the rear brakes. However, are you saying that it is an "active" system that changes as the weight on the rear axle is reduced? That's what I'm having trouble with.
 
techno said:
This is likely to be the condition of the front brake rotors. When you're going downhill there is a lot more vehicle weight on the front wheels and less on the rear wheels. The brake systems sees this and will compensate by increasing the proportion of braking force towards the front. This is why you are experiencing it on downhills and not level ground.

Have your rotors inspected for runout (warping).

. :)
Click to expand...

thank you again. any ideea how much something like that would cost to fix?
 
I'm with Techno

My money is that Techno is dead bang on. He usually is.

I jumped on here cause I thought the car was shacking with another car. We get it "shaking", we knew what you meant ozana.

New rotors are not that pricey... go for a bit of an upgrade while you are at it. But 110K on original rotors is sure not bad either. Personally I would point you at some Brembo rotors-not slotted not drilled just plain Jane Brembo rotors. I think they were around $55 each when I got them a couple years back.

Might as well do the pads too while you are at it. And 2 years with only oil changes?

You likely need several things kept up with...timing belt and water pump done on time around 90K? we'll give you the benefit of the doubt there.

Time for a power steering flush, you must be an auto tranny being an '01 so for heavens sake keep up with tranny maintenance. That could be really pricey to neglect that sucker...you know about the strawberry milkshake condition I hope....
 
Ron Helmuth said:
My money is that Techno is dead bang on. He usually is.

I jumped on here cause I thought the car was shacking with another car. We get it "shaking", we knew what you meant ozana.
Click to expand...

'shacking, breaking', ouch. way too many spelling mistakes. i must be tired or worried about the car. :) or my car is trying to sent me a subliminal message. :))

anyway, thank you guys for all the inputs, i really appreciate them.
i hate to go to a shop / dealer with no idea what's wrong with the car, and then listen to their stories, which most of the times are very expensive stories. :)
anyway, the guy who sold me the car, did a little bit of maintenance, and timing belt was one of the things included. it might have been the pump and the brakes as well, cannot remember for sure now, but i have it somewhere written down. i have to look into changing the rest of the fluids, you are right.

thank you again
 
If you aren't sure if the tranny fluid/filter was ever changed, I'm guessing it's the same for the rear diff, and if it's a 4x4, the front diff and transfer case as well.
 
Qyota said:
... However, are you saying that it is an "active" system that changes as the weight on the rear axle is reduced? That's what I'm having trouble with.
Click to expand...
Yes. Lots of vehicles have this, but I'm not sure if the 4Runner does now. The more I think about it the more I think I remember seeing it on Nissan's. It's raining at the moment so I'm not going to check just yet.

You can tell by looking at the rear axle housing. There will be a valve body that is connected to the axle and the chassis by some sort of linkage. As the axle moves up and down the linkage adjusts the valve proportioning accordingly.
 
theizzardking said:
anything wrong with drilled and slotted? i know the effects are marginally better at best but is there any draw back?
Click to expand...

Off road the slots and holes make nice little places to catch mud or pebbles to destroy your brakes. On the road, they just create a weak point in the steel that will become prone to warping. Blank rotors are the way to go... the other stuff is mostly hype and sugar pills.
 
"I would point you at some Brembo rotors-not slotted not drilled just plain Jane Brembo rotors. I think they were around $55 each when I got them a couple years back."

any idea where I can get those rotors from?
 
ozana I used brakewarehouse.com and I believe they are a division of Auto Parts Warehouse.

I'm simply Google-ing "best prices Brembo rotors" and seeing a variety of vendors.
 
Ok, so I went to a shop and had the rotors resurfaced(machined) - that was a month ago. The other day, going down on a steep hill I've noticed the shake again. Not that bad as before, but still noticeable. What else can it be?
thank you guys.
 
You must log in or register to reply here.

Members online

Total: 347 (members: 1, guests: 346)

Forum statistics

Threads
278,307
Messages
3,554,050
Members
248,016
Latest member
Advally Service

Share this page

Trending content

Back
Top