Surging while Stopping?
 

i've got something really weird going on with my h3. when i come to a stop the vehicle bucks like my brakes are pulsating but there's no feedback in the pedal or at the wheel. it doesn't seem to happen right away, it's as if something's heating up after driving for a bit. it gets so bad that just rolling up to a stop in traffic will cause the nose to buck up and down. it's speed, not rpm, related. as if it happens per revolution of the wheel.

a buddy said to check my diff fluid, which i was planning on changing anyway. he's also got an acquaintance who "claims" to have hummer mechanical experience and he said there's a known issue with the transfer case that causes this same symptom. he said it was something about the tc randomly locking and unlocking at low speeds but in my case this happens at highway speeds too if i have to honk on the brakes in the fast lane for any reason.

any thoughts? if so let me know what you're thinking.

Hi,
Just to clarify...
*engine smooth accelaration (NO loping)?
*After the brakes seem to heat up this begins?
*All oem stats or aftermarket addons?
Chris

hey chris:

-engine runs smooth as silk
-it doesn't happen when i first start up and drive. my assumption is something is heating up. whether or not it's the brakes is where i'm coming up short. this would be only too logical except i don't feel any thumping in the pedal or shimmy in the steering wheel.
-bone stock 2006 h3

please keep in mind that it seems to be every rotation of the wheels. also because of the way the nose is diving i believe the problem is up front - seems logical but i may be wrong. it so seems like the brakes heating up but the pedal and wheel stay so smooth.

thanks for anything you've got for me.

That sounds like a transmission problem, bucking and surging or a throttle problem. Hard to diagnose something like that over a forum really. Transfer case locking generally makes it really hard to turn.

What you are feeling doesn't feel like warped rotors?

Im going to lean toward brakes. Ive seen the sleevs on the front brakes corrode and rust so as to bind. The rotos themselves could have hot spots. As was stated the 4wd engaging and dis would make for hard steering. This would also wear on the t-case. Id be cautious.
Chris

One side thought.... the pulsing may be abs related.
Chris

from the passenger seat it feels like brake pulsation, but from the driver's seat there's no feedback at the pedal or wheel (this is what i'm really stuck on). no other issues with idle or steering. i thought about a sticky caliper heating up and causing the a rotor to distort but not feeling it in the pedal is the only reason i question whether or not it is a brake heat issue. i would think if it were any type of electrical or abs issue it would do it from the get go rather than driving normally for the first 5 or so minutes before acting up.

hot spots: i wouldn't feel hot spots on the rotors at the brake pedal, right? but wouldn't i feel it at the wheel? wouldn't it want to pull to that side? this is along the lines of what i was thinking. but again, the way the nose bobs up and down i find it hard to believe i wouldn't get SOME kind of feedback at the wheel. hmmmm .... i think i'm gonna pull it apart and check the way bolt sleeve. if these are binding up causing excessive heat build-up. do you think freeing them up and greasing them would cure this? i'd make sure there were no burs or pits to bind up before re-assembling, of course.

thanks for the suggestions guys and i'll be sure to put these things on my list of things to check.

I FRIGGIN HATE INTERMITTENT PROBLEMS!

using the grease may work

i'll lube them up with some anti-seize. if that doesn't do it i'm afraid we're off to the gm dealership.

So, any further insight as to what is going on?

Chris

funny you should ask. i'm off today and just waiting for it to warm up a bit before i go out there and have a look into the possibility of a sticky caliper. i'll definitely update the thread later today.

no luck but i'm positive it's a brake issue. pads are good, calipers are working fine and i got rid of the rust on the rotors and they "look" good, no bluing from heat anyway. i don't know anyone in town with a brake lathe either to tell me if one's tweaked (BUT DAMMIT I SHOULD FEEL THAT IN THE FREAKIN' PEDAL!). might just have to bring 'em down to meineke - the guy on the phone said he'd turn them for me as long as there within spec. actually contemplating just buying 4 new rotors and being done with it. PISS!

a simple brake test. stop on a hill,ease off pedal. you should drift immediately,no drag. if you slow the drift you might "feel" something.

i use the grassy knoll on my side yard!

no, you get your own.

I would lean toward just replacing the four roto if you can sing it. It is cheaper then takin it to the shop these days. Lol!

that's the plan

Why would you replace something if you don't even know what is wrong? Any shop can pull the wheel and mic the rotors to see if they can be turned. If you have pulsing rotors you are most definitely going to feel it in the pedal.

ok, so what do you suggest?

it's not the transfer case locking up randomly because it does it whether it's locked or not, it does it when i cruise to a stop light in neutral which rules out the transmission (right?) and nothing seems to be binding in the diffs. this IS a brake problem and the way the nose bobs up and down is telling me that it's a problem with my front brakes. agree? it's as if they heat up and then grab in one spot on the rotor just like when your brakes pulsate - just without the pedal or steering wheel feedback.

i'm at a point where a replacement rotor is going to be cheaper than sending it in for diagnostics, only to get soaked by a dealer for 4 new rotors, pads, and whatever else they have laying around and want to unload. so, i get 1 new rotor and put it on the side i suspect is the problem. if that doesn't cure it i turn the old rotor i just pulled off and swap it onto the other side.

Have you detached the front DS and tried driving it? Second have you defeated the ABS (if possible)?

Also, I totally agree about the price for pads, rotors being a heck of allot cheaper to replace then taking it in to have it checked. Lol! the rotors go for $50 a piece and the pads about $50 for the pair. That's aprrox. one hour labor here in SE. WI.

Chris

i've determined that it's definitely not a drive-line issue.

replaced passenger's side rotor and got rid of 90% of the problem. that was the side that seemed to dip the most. i'll get after the driver's side tomorrow.

Ordinarily Talusfan may have a point. In this case, since you're likely to need rotors at some point, you are not wasting money. As you said, put new rotors on and if it's not the problem big deal you have an extra set of rotors for when the time comes.

Good job Talusfan

because through process of elimination i do know what's wrong - i just defies all logic. it WAS a bad rotor that didn't thump the pedal or jerk the wheel and it didn't do it until the brakes generated heat. the true test will be stop and go rush hour traffic and that won't be until monday. in the meantime i think i'm just gonna leave well enough alone.

now it's time to put a clutch in the dirtbike so i can get out there on sunday. it's supposed to be almost 60 degrees here!

bingo!

And did you by chance also replace the pads then so they will bed with these new rotors?

Rotors have a long life span, generally you can have them turned 2-3 times and it is not uncommon to get 150-200k out of a set. I worked for dealers for over ten years so method of diagnosing a problem is to find the problem and not shotgun the vehicle with parts hoping to get lucky since that would pretty much have got me fired in short order.

Yes maam, well it looks like your gonna need some new rotors, a driveline, couple wheel bearings, engine mounts, new crossmember, an alignment and some washer fluid and 16.5 hours of labor. That SHOULD get rid of that vibration, if you'd just sign here real quick.........

i did not replace the pads but as mentioned, the issue was resolved with just this change. i only started this thread to see if anyone else had this same problem with their h3 because every symptom, along with every bit of my basic diagnosis pointed to a bad rotor - all except the fact that there was no feedback to the driver.

i've worked with cars off and on for the past 25 years, 15 of those years in an automotive machine shop that supported over 20 ford dealers in the greater boston area so i'm quite familiar with the way "my local dealers" operate :rolleyes:.

for the record i hate these forums because things are often taken out of context. i mean no disrespect and i don't mean to sound argumentative. because i took every suggestion given to me and factored in what i'm experiencing first hand, i was able to properly diagnose and resolve the issue in 15 minutes by replacing a single part that cost me only $65. not bad, thanks everyone.

Excellent, glad to hear it.

Yea, Ive learned to take it in stride. Lol!
Just do what seems right for the moment. I was glad to hear the pos outcome.
Chris

Glad to hear it got resolved. Just want to add that I continue to have issues with my 06 braking system. The rear brakes do not seem to be operating as they should and having a grinding sound during hard braking. there is a TSB about the back rotors/pads. Might want to check to be sure the "rear brake assist system" is working properly as it might be causing premature wear on your front brakes. Just a thought.

i didn't know that, i'll definitely look into that. mahalo.

When I change my engine oil, I always check and change the brake fluid. Remove it with a syringe, clean the reservoir as best as possible and refill with fresh new fluid. The fluid does get dark and dirty. Wife thinking about upgrading to a H3 so doing research on problems with it. Wondering what caused the rotor to warp. Maybe a hung brake pad.

Great idea with the syringe!!!! I tried to bleed my brakes the old fassion way and found that you couldnt do the rear without having the key on. Since then I have had pulsating in my pedal on the initial press and the head light dims. I think I messed something up, but it doesn't affect braking effectiveness.

So i am thinking i have the same problem. I was wondering if you felt any brake drag in the gas pedal? it feels like my pads are rubbing on the rotor and when i turn the wheel slightly it grinds even more. i also started to feel that surging here and there when I've been driving in stop and go traffic. I just changed my brake pads but didn't change the rotors.

key on for power brakes
 

the power unit is a small motor that pumps fluid up into an air chamber. you can hear it with key on,ign off. each 2-4 brake hits,it pumps. thats why you need key on to bleed the "old way".
it might cause a slight dimming of lights,,??

if you stop on a hill,up/down,ease off brake,you should drift immediatly. keep on pedal slightly you would feel any uneven drag or bump on rotor.
i see no reason why it would change while turning.

Double check that wear indicator bar to make sure you didn't inadvertently bend it in. They don't always squeal, sometimes they scrape.

i felt no drag and when i popped the calipers off they compressed without any drama.

I've had the same problem for the last year or so.. thinking it was the rotors, i turned all 4 and changed the pads..
Problem continued even with all this work done.
It's like a catch and release after brakes getting hot.
Now what I heard from my mechanic is the following :
The caliper's pistons are plastic and not metal and when they heat up, they expand thus causing this catch and release syndrome.
Anyone has heard anything to this effect ? and could the pistons be changed to metal ones or did GM change them on later models ?

Problem is not major, but can become irritating sometimes..

sounds like the made up bs is flying again!. the enginneers know about heat caused expansion and non metal pistons could be more stable than metal.
ive driven 2/h3 and i routinly check drag by drifting on hills. so for with total of 40000miles on 2/h3,ZERO DRAG. i can drag the brakes on purpose and never get drag whin i let it drift on a grade.

i have noticed THIS, on veh when i did brake jobs;AFTER compressing calipers,they never seem as free to move in/out like the unmolested new calipers do.
you know they move in on pedal press and move back slightly on release,(when operating new/normal) the piston sticks to the rubber o ring and is pulled back. when the pads wear enuf the piston slides a little to self adjust and sticks again till auto adjust it needed
on old cars the rubber hoses close in/constrict and prevent the juice to escape back where it belongs. thats tricky to find.

I too own an '06 H3, and have had a surging braking problem, in particular at slow speeds. I finally broke down and purchased 2 front rotors and a set of pads, problem appears to be solved after a quick trip around town. Actually what I was getting on here today for, I was doing a bit of research earlier between this forum and Google to figure out why my passenger front rotor was so damn hard to remove. No good responses except the "tap gently with a hammer and hardwood" and "not too hard, don't want to damage wheel bearings". After some head scratching, I took one of the new rotors to Ace, found that the extra two threaded holes in the bolt pattern were 10mm X 1.25, purchased 2 about an inch and a half long, and bolted them into the stubborn rotor at home and no beating required. I don't think I even got to 10 ft-lbs of torque before it slid off. And yeah, I'd removed the retainers already.. Just passing my experience along. Later folks.

My does same thing. replaced all rotors and pads and it went away but now its back and I am think ABS and thinking to check ECM for ABS fault codes.

I have a surging problem while stopping too. But mine is the engine is surging when I'm rolling to a stop gently on the brakes, can't hear any vac leaks, no CEL, it's friggin weird. Anybody got any idea's?