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Thread: K2500 brake woes
08-11-2011, 11:31 AM #1
- Join Date
- Aug 2011
K2500 brake woes
Where to start? Well, I have a 2000 K2500: a/t, w/454 cid. This has had brake problems since I got it. It has now 159k miles. The problem is the rear wheels lock up on it. Sometimes it is the right side, but lately it is the left. Let me give some history. Soon after I bought this used from a dealer, the rh wheel would lock up.I thought it was a wheel cylinder or axle seal bad. Not having the tools or time to pull the axle and fix it, I took it to a brake/muffler shop that was recommended. Sure enough it was a wheel cylinder. They ended up replacing both wheel cylinders, brake shoes, axle seals and turning drums at my request. The next day both wheels locked up. Took it back and they informed me it should of had the e/m brake cables replaced. If they would have told me I would have had it done then, but anyway I had them replaced. 6 months later the rear wheels start locking up again. This time I took it to a GM tech and he said the rear drums were too thin. So I had him install new drums and a hardware/spring kit. 11 months later, the rear wheels start to lock up again. This time I bought the tools and removed the drums myself. I found both axle seals leaking. Also I saw where the last tech beat the lip on the rh drum where the oil seal goes. I don't know what he used to install the bearings and seals, but I was surprised the seal held this long. I had the machine shop replace the seals after repairing the seal area, repack wheel bearings and turn the drums for me. The brakes just don't seem to be working right. It has always felt like the front weren't braking more than the rear. (side note: The Lh front wheel speed sensor is bad. I didn't replace it because I did not like the ABS when towing). Anyway 10 months later, yup, the rear wheel start locking up again. It was the rh side. I took it all apart and found nothing unusual. Cleaned the dust out and put it back together. When I removed the Lh side, the seal was leaking. (The one that was damaged). I put a little rtv on the outside of a new seal and installed it. I also took the front brakes apart to check the calipers. It needed pads so I replaced them. The calipers were sticking a little. Instead of cleaning them up, I replaced them with rebuilt ones. The brakes still dont feel quite right to me though. Now the rh rear wheel is locking up again. I was wondering if it is posible that I am having so much problems with the rear brakes because they are working more than they should? Could there be a problem with a master cylinder or something that is using the rear brakes more than the front? I am at my last wit on this. Nobody seems to have any ideas. Can anybody here help me out? Andy
08-12-2011, 07:12 PM #2
Check the proportioning valve. One thing I tell people with this problem, is to adjust up their rear brakes. When they are adjusted up you should feel a tiny, tiny bit of drag on the drum. Once adjusted whenever you back up tap the brakes. When in reverse and hitting the brakes is when they adjust themselves. Also
check the star wheel adjuster in between the bottom of the shoes. If they are froze up they will not adjust either. I believe that is why you can go 7 to 11 months without problems, the rear drum brakes are just getting out of adjustment. So when you use the brakes the rear shoe gets wegded in the drum due to the out of adjustment. If this does not work check the prop valve.
08-13-2011, 08:33 AM #3
Tell us more about how, when and what conditions the brakes lock up.2000 GMC YUKON SLT, 5.3L tow pkg, G80 rear/w 3.73 gear
08-13-2011, 12:57 PM #4
- Join Date
- Aug 2011
Yesterday I pulled the rh rear drum. I could barely get it off the shoes were so tight against the drum. I had to back the shoes off quite a bit. Anyway, I took the drum to Napa to have it turned. The shop tech asked why I was turning it, so I told him the story. After I told him, he asked me which way were the brake shoes on? There is a long one and a short one. This I know and I told him I installed the new ones the same way the old ones came off with the long one in the rear. I asked him if the long shoe is usually thicker than the short one, because this is the first time I ever came acrossed two shoes of different thickness. He could not believe me so we went to the parts counter and pulled a set on shoes. Sure enough there are two shoes that have thicker material on them. These were the long ones also. After a 30 minute discussion, we weren't sure if the shoes were on right. So, does the longer, thicker shoe go on the front or rear?
08-13-2011, 09:04 PM #5
the longer shoe goes in the rear. the reason it is thicker is because the rear shoe does the majority of the braking. the way the rear drums work is when the rear brakes are applied the front shoe pushes and wedges the rear shoe into the drum. So that is why there is more friction material in the rear.
Was the reason your drums were hard to get off, due to the rust ring around the outside of the shoe to drum surface? If that was the case you can take a 6 in orbital air sander with about 60-80 grit paper around the outside. Just enough to get the rust ring off.
Another thing are your brake shoes contaminated with axle gear oil or brake fluid? Or were they ever? If they are that could be causing your problem as well. If they are contaminated the friction surface will grab the drum instead of slipping. Thats about the best I can describe it. Hope this helps further!
---------- Post added at 10:04 PM ---------- Previous post was at 09:55 PM ----------
Just re read your initial complaint. When you changed the front calipers, did you absoulutly get all the air out? The front brakes do 60% of the braking and if all the air is not out when you hit the brakes the rear end is so light it would lock up as well due to air in the front system. I would re bleed the whole system just to be safe, starting with the right rear, then left rear, then right front, then finally front left.
08-13-2011, 10:13 PM #6
- Join Date
- Aug 2011
No there was no rust ring. I have had this drum off about 3 times in two weeks. I think it was the grease from the repack made it hard.
If the rear shoe is the longer and thicker one, than they are on correctly. I believe the grinding noise I am hearing is the new shoes dragging. For some reason they tighten up after I drive it. Or they keep adjusting too tight whenever I back up. What would cause this? I back up alot.
On another note, I drive to work about 20 miles. I have noticed the brake pedal seems to get harder the longer I drive. Does that make sense?
I did bleed all the air out of the front. I checked it twice. Does this have a proportioning valve?
Thanks for your input.
08-14-2011, 09:25 AM #7
Well yes it makes sense cause you say you back up alot. Your pedal will get higher and harder by adjusting your rear brakes (i.e. backing up). Or do you mean in the 20 miles you drive to work. If that is the case then no it doesn't make sense.
If you use your e brake. When the chevy tech replaced your e brake cables did he replace them all? If not pull on your cable under your drivers door and if it hangs up find out where it is hanging up and replace. But if you don't use them and, or they don't hang up, then that shouldn't be the problem.
After thinking about it I do not believe you have a prop valve on that.
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