front brakes

[Ron Moss]

I have a 1999 3500 daully 4x4,it has 43000 miles on it. About a week ago I started having problems with my brakes,when you slow to around 10 miles an hour,the pedal starts to pulsate and you can hear the abs. When i had new tires put on awhile ago they told me my brakes were getting bad. So today I went and put on new front brakes,I did'nt replace the rotors because they looked good,pads were wore but not real bad. When I left I still have the same problem,any ideas? The brake light and abs were never on even before I replaced my brakes and they are not on now. When I got home I removed the 40amp abs fuse and the problem went away,but when you do that you have no front brakes,I don't want to run it that way so any help would be great. thanks Ron Moss my e-mail address is -- email address removed -- send me some ideas and i will check back in here in a couple hours

 

[Archive]

Ron, Did you have the front rotors turned?? A lot of times the rotors look OK, but are a little wavey... turning them will take the waves out. . Take them off and have a brake/clutch shop turn them down. (some autoparts stores do this too, but most can not handle the size of these rotors. ) Good luck.

Bryan

 

[rod77zilla]

I can't tell if you are trying to say your abs and brake lights are both on or neither of them are on. It says they were not on, but then you say you pulled the abs fuse. I suppose to make it cut off.

If the lights are not on, simply get the rotors turned to get rid of the vibration and bleed the brakes to get rid of the air. I don't have front abs and I never unhooked anything on mine and I still had to bleed it to get rid of a spongy pedal. I bet your abs is "feeling" the spongy pedal and trying to take up what it thinks is slack. but it's not turning the light on or setting a code.

By the way, I found this out entirely by accident while doing my front brakes last week, but it is possible to put the calipers on 360 degrees out of the right position and this will be evidenced by a twist in the rubber brake hose. this twist can kink and restrict fluid flow. I really don't think this is your problem, it would be worth checking to make sure you got them on there right.

If the ABS light and the red brake light are on, I suggest the following: From what I understand, your truck has 4 wheel abs. After checking the fluid level, and bleeding the brakes, I'd find someone with a scanner and check abs codes. From the 2000 service manual: "the red warning light alerts the driver if a pressure differential exists between front and rear hydraulic systems, the parking brakes are applied or if the brake switch is not functioning properly. "... Which is why I say bleed them. it also says:if the red warning lamp is illuminated with the amber warning lamp, this may indicate an electronic brake distribution fault. " EBD is what they use instead of proportioning valve on 4wheel abs Rams. (I haven't looked but I bet its on the abs circuit)

I would double check everything and make sure you got the brakes on there right, bleed them and make sure fluid level is right, and hopefully the lights will turn off. Without the codes, I don't know what to tell you, but I do have all the books. so If yer not gonna take it to the stealership, post the codes and i'll tell ya what the good book says... . good luck!

 

[THubbard]

Pulling rotors and having them surfaced without knowing if they are warped or not is not a great idea. It appears as though you are not very mechanicaly minded, so I suggest you find a qualified mechanic and have the rotors checked for "run out" with a dial indicator. If either rotor has runout in excess of the manufactures specs, then have that one done. The more you cut the rotors, the thinner they get. The thinner they are the more apt they are to warp again. Thin rotors will not tolerate heat as well as a new or near new rotor. Do yourself a big favor and find a good pro to do the job. Your life has to be worth more than the few bucks you might save playing around.

 

[dan_gilson]

Have rotor checked for runout. If they need turning, turn them on the truck. This will reduce the runout caused buy reinstalling them.



Also, I think you have it wrong: Thinner rotors actually disipate heat faster because of less mass. There is also less steel to go through to get to the venting in the center of the rotor. They heat up faster though because they can absorb less heat because of their decreased mass.



I believe that they tend to warp easier because they heat up faster and there is less structural strength because they are thinner.



Are we saying the same thing? Who out there is a physicist?

 

[THubbard]

I understand that my two years of college do not make me an expert. I do beleive that they do warp more easily after turning. I was a mechanic or owned my own repair shop from the time '59 I graduated until '95 when I retired. The point I wanted to get across is that this is a job for the professionals and just guessing is not the correct way to get it done. Turning rotors on the vehicle is an excellent way to do it. My shop was not so new that it had the latest equipment and so we removed them. Other than 4x4 I think it was great anyway. We got to do a proper bearing pack that more that likely would have been done by the owner. Thank you for correcting my faulted thought. I guess we all know that the bigger the piece of iron the more "Q" it contains at the same given temperatures.



Just poke fun back at you... . The rotors are made of "cast iron" not "steel".....



Tom Hubbard

 

[dan_gilson]

Many apologies... I did not indend to offend.



I am a computer engineer. I had to go through all the physics and chemistry stuff and they are not my stronger areas. In other words I could be completey wrong here. I also know the racers will lathe down rotors to save unsprung weight and then pump more air into the hub to get it to cool quicker.



Yes! a good shop that treats people well is the place to go. They seem to be getting harder to find.



I had my rotors turned on the truck and they turned out great. The shop that did this was older shop that likes to keep up with technology when they can. I will be happy to provide their name and number if interested.



You were right! It should have been cast iron and not steel.

 

[THubbard]

No offense taken. I am happy that this is a light hearted forum where we can exchange ideas and help one another.

I enjoy it when I can lend a hand on a subject the I have more than a little smarts. I sure don't know it all; but 35 + years of wrenching and serving customers has taught me a lot. If nothing else, "It is a sad day when you do not learn something new"!



Tom Hubbard

 

[BillGotthelf]

I'm not a physis-oh whatever-thinner rotors will shed heat and gain heat faster but they are more susceptible to warping. Drag racing brakes are both light and thin and would not work on a street car whereas Winston Cup cars have massive thick rotors crossdrilled to dissipate heat faster.

 

[THubbard]

Ok,



I was in a hurry to get to church service the other day and did not do a good job on the rotor warp ie: thick vs thin and so I did not devulge all the information I have in the back of my 64 year old head... This may be lenghty; but if you are interested read on.



The material used in everyday brake rotors is cast or "grey" iron. It is used because it is inexpensive and easy to cast and machine and has good "wear properties. I am sure there are more but I donated my metalurgy book a long time ago. One thing cast iron does not do well is to be subjected to "differential" heating and retain it's origional shape. This is what happens when rotors warp. They are heated to point of deformation and allowed to cool; but not evenly. The reason they do not defuse heat evenly is because of the great big "mass" called a caliper and brake pad.

There is the senerio. You heat a rotor to the temperature of defomation and then stop. If the vehilce is not driven until there is enough heat released the rotor will dissipate the heat that is not under the brake pad and caliper at a different rate than the rest of the surface. When this happens the rotor takes a "set" that is not in the same shape as it was before the heat. I can tell you that I have seen what we call shadows or ghosts of the brake pads on the rotors where there has been large amounts of heat applied and the rotor sat an cooled. This is why it is more common to have the rotors warp the more they are machined. IYou may have seen race cars with the rotors showing orange from heat during tv races. If you get another picture when they are not on the brakes the orange is gone. That is a good example of even heat distribution and even then some of them suffer from warp.



Please understand I am a graduate of a 2 year college in Automotive Tech and not a PHD. I did take a course in Metalurgy that I did very well in, one I liked, and do remember some of the experiments that we did and to some extent some of the theroy.

I am sure there are "holes" in this post; but I can tell you from 40 years of working on cars of all sorts, airplanes and what ever else I got my hands on I have learned a considerable amount about the subject.



Talk it for what cost... ... .





Thomas Hubbard