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View Full Version : dunno what is wrong, mechanic can't even figure it out


mcwlandscaping
09-11-2006, 04:00 PM
Ive been having this one problem since i first got my truck. What happens is as you are comming to a stop from any speed at all using the brake, as you get close to finally stopping, all of a sudden the brake pedal will suddenly looks pressure, drop down a couple inches, and usually make some funny vibrating noise, sometimes pretty loud.... i have braking power, but, its just not right and when im towing a big trailer with a mini skid on it or a full size skid steer or whatever on there, it just doesn't feel right, or safe for that matter...anyone have any idea on what could be going on?? Mechanic first thought it was the speed sensors, but, it apparently wasn't

thanks guys

dcondon
09-11-2006, 04:21 PM
did they check the master cylinder???:confused:

Ron's Lawncare
09-11-2006, 04:58 PM
my guess is the abs system has a problem

sheshovel
09-11-2006, 05:01 PM
Could be sucking air somewhere. The lines or the bleed screws possibly.

mcwlandscaping
09-11-2006, 05:04 PM
i tend to agree as it happens at the same pedal position everytime, dad suggested going to midas or mineke (whichever one of those two is the brake specialist!!) and taking them up on their free brake checkup and see what they say, and I should be able to tell from their findings what is really causing this...hopefully it gets fixed SOON!!

sheshovel
09-11-2006, 05:06 PM
Right, stopping power is nothing to take lightly. Yours or someone elses lives are at stake every time you hit your brakes.


Hey I am a poet and don't know it.

mojob
09-11-2006, 05:14 PM
Sometimes it pays to take it to the dealer when you have a weird problem like this. They probably have already seen the problem before and know just what to do to fix it.

sheshovel
09-11-2006, 05:22 PM
Is this the same truck with the steering problem? How long have you owned this truck?
Has it had other problems besides these?
Is this truck brand new or used?
Have you been doing high speed dougnuts in bumpy dirt areas or off roading it when it is not made for that?

mcwlandscaping
09-11-2006, 05:24 PM
lol, no, these are the only two funky problems with the truck, have had the truck for about 3 weeks now and its awsome, except for those two things!

sheshovel
09-11-2006, 05:28 PM
Answer me..is it new or used?

sheshovel
09-11-2006, 05:29 PM
Ok got it in the other thread

bbailey
09-11-2006, 09:31 PM
It is an ABS problem, definitely! Could be a sensor at the wheel, could be the ABS pump, could be the control unit. Need to know more info on the truck.

Lumberjack
09-11-2006, 10:11 PM
Could also be the brake fluid is contaminated with water....

Tim Wright
09-11-2006, 10:46 PM
I had the same problem with my 84 dump.

As it turns out, the power steering unit is tied in with the brake master cylinder which makes up the system called hydro-boost. Along with this system there is a "load sensor" under the back end of the dump which as it is depressed transferrs or distributes the braking from the front brakes to the back brakes of the truck as it passes through the sensor.

This sensor leaks brake fluid and it had all leaked out of the rear brake reservor. Since the dump body is heavy, and I usually have some sort of load, I am always using the rear brakes more than most vehicles, so as the rear brake reservor was empty "bone dry" I was loosing brakes, even though the front reservor was full.

Notice, on the master cylinder, the front brake reservor is really the back or large reservor, and the back brake is the small reservor in the front.

Perhaps you have some sort of problem similar to this.

Tim

mcwlandscaping
09-11-2006, 11:15 PM
It is an ABS problem, definitely! Could be a sensor at the wheel, could be the ABS pump, could be the control unit. Need to know more info on the truck.
truck is a 1997 chevy silverado 2500, 4*4, regular cab, long bed, 5.7 350 motor

J&R Landscaping
09-12-2006, 04:32 PM
Had a similar problem in my f150. Did your mechanic check the wheel cylinders. Sounds like either a line is loose there or you have a leaky wheel cylinder. Do you notice your brake fluid levels changing at all? It might also help to get the brake system flushed as someone said before, you could have some water mixed in.

stumper1620
09-12-2006, 05:33 PM
It is an ABS problem, definitely! Could be a sensor at the wheel, could be the ABS pump, could be the control unit. Need to know more info on the truck.
I agree,
pull the fuses to the abs sytem and see what happens.

d.m.d.
09-12-2006, 06:30 PM
i think they are correct its a abs problem.is the brake light on?is it a funny growling noise?these are symptoms of a faulty abs.

lawnmaniac883
09-12-2006, 08:00 PM
I had the same problem with my 84 dump.

As it turns out, the power steering unit is tied in with the brake master cylinder which makes up the system called hydro-boost. Along with this system there is a "load sensor" under the back end of the dump which as it is depressed transferrs or distributes the braking from the front brakes to the back brakes of the truck as it passes through the sensor.

This sensor leaks brake fluid and it had all leaked out of the rear brake reservor. Since the dump body is heavy, and I usually have some sort of load, I am always using the rear brakes more than most vehicles, so as the rear brake reservor was empty "bone dry" I was loosing brakes, even though the front reservor was full.

Notice, on the master cylinder, the front brake reservor is really the back or large reservor, and the back brake is the small reservor in the front.

Perhaps you have some sort of problem similar to this.

Tim


Hydroboost systems are used only on diesels because they generate no vacuum to assist in braking.

bbailey
09-12-2006, 08:32 PM
Chevrolet is known for it's abs problems. The newer trucks are under recall to clean the wheel speed sensors. I had a 98 Chevrolet and I had the same problem, I went to the local salvage yard and bought a wheel bearing assembly and put it in and that took care of the problem. You may want to check on a new bearing it might not be to expensive. All you have to do is figure out which one it is. A local tech should be able to plug in and tell you.

Tim Wright
09-12-2006, 09:42 PM
My GMC 84 is a 350 gas. Oh I wish it was deisel.

So I don't know about your info.

Tim

stumper1620
09-12-2006, 10:21 PM
My GMC 84 is a 350 gas. Oh I wish it was deisel.

So I don't know about your info.

Tim
So, Did you try pulling the plug or fuse from the ABS pump?

lawnmaniac883
09-12-2006, 10:23 PM
My GMC 84 is a 350 gas. Oh I wish it was deisel.

So I don't know about your info.

Tim


Well, I guess in that case since it is a dump they added a hydroboost for extra braking power??

mcwlandscaping
09-12-2006, 10:54 PM
i think they are correct its a abs problem.is the brake light on?is it a funny growling noise?these are symptoms of a faulty abs.
yup, a funny growling noise, ill have to tell my guy what you have mentioned on here, on that note, anyone have any idea on what ABS parts ide need and about how much they'd run new since i don't have the time to do this myself and need teh truck back up and running asap.

stumper1620
09-12-2006, 11:08 PM
yup, a funny growling noise, ill have to tell my guy what you have mentioned on here, on that note, anyone have any idea on what ABS parts ide need and about how much they'd run new since i don't have the time to do this myself and need teh truck back up and running asap.
Way too much to bother fixing. pull the plugs and forget it.
Abs is a separate braking system from your normal brakes, your pump probably has an internal leak causing it to overrun, a pump with the accumulator for an older truck like that is going to run around a grand.

LindblomRJ
09-12-2006, 11:29 PM
Would the OBD II tell is something was wrong with the ABS? If that is the case take it to an autoparts store that offers you to plug a reader into it, it might be able to tell what the problem is. Can be done for free with the understanding that you would buy the parts to make the repairs from them...

Does the ABS light come on when you turn to ignition on? (if not might either be a burned out bulb or problem.)

mike lane lawn care
09-13-2006, 12:08 AM
Would the OBD II tell is something was wrong with the ABS? If that is the case take it to an autoparts store that offers you to plug a reader into it, it might be able to tell what the problem is. Can be done for free with the understanding that you would buy the parts to make the repairs from them...

Does the ABS light come on when you turn to ignition on? (if not might either be a burned out bulb or problem.)
from what i know about my code reader, it will report anything wrong with ABS and other issues, and tell exactly what the part is that is malfunctioning. (or at least get you in the right range of systems.

YardPro
09-16-2006, 10:10 AM
we had an identical problem on our 99 s-10

it was something in the abs system.

mcwlandscaping
09-18-2006, 07:40 PM
well, found out today it was just a cut wire near the tranny that had to do with the ABS!! Totally fixed the problem, my mechanic is great, went back there today to see what he was going to charge me for all his time trying to find the problem but, he just told me i was all set, he spent a good day and a half trying to figure this out!! He is a great guy, im glad my parents found him as a mechanic years ago and ill deffinatly be using him from now on for my own truck!