articfriends

iTrader: (1)

Today was towing a empty trailer that weighs about 5000 lbs, everything was fine for 30 miles, stopped for lunch and when I left the truck was shaking like it had a flat tire or loose lug nuts on a wheel, stopped and looked and everything was fine, being only 3 miles from my shop I drove it the rest of the way home. Upon reaching my shop I looked it over and when I jacked up the front end BOTH front brakes were applied and wheels would not turn (even with 2 grown men turn as hard as they could on od of tire), there seems to be a little play in the idler arm (08 with 42,000 miles) so when the front brakes were dragging it made the slop amplify. Did a couple of quick checks, unhooked the front brake line from master cylinder figuring if there was a problem with the hydro boost or master cylinder it would bleed off the pressure and they would free up, they did NOT.. So I know the problem is in the proportioning valve (if it has one) or abs module. Pushed a customers truck off the hoist and pulled my truck on , brought it up in the air and they suddenly turned normal so we could NOT diagnose any further, pumped them up but can't get them to stick.
Now, I am a ase certified mechanic and I do know that both front calipers could not suddenly stick and then both simaultaneous un-stick at the same time, I also know that there is no wasy both front brake hoses have failed internally and now suddenly work perfect again. I pulled one caliper off and ran both twin pistons out until they almost came out and compressed them both all the way in a couple of times to see if there seemed to be a problem with fluid returning towards master thru the abs module,, felt perfectly normal. I do not want to randomly start changing stuff and am wondering IF someone else has had or seen this exact problem, or works at a chevy dealer and seen a tsb or similar problem, there is no way mine is the only truck this has ever happened to. I took a look on the online diesel forums to see if there is a definate problem others have had but all I found was a bunch of idiots blaming the hydroboost, sticking calipers and bad hoses (again, both hoses or calipers will NOT go bad at same exact time and then suddenly work perfect at same exact time). Looking for input and also asking IF there is a proportioning valve or if its built into the abs module. I have to tow 10,000 lbs tonight at midnight (after work) and don't want this to happen again if I can avoid it, truck is still on the hoist and my son who works for me is still there and is meeting me with the truck tonight, Smitty

FIXX

iTrader: (2)

pads are swelling from the heat,when they cool off they shrink...they are known for it around chicago land..remove the shims,wire wheel the half moon part that the shims go over,,order a set of centric 105.07840 brake pads or if you need the hd ones 300.07840. after you wire wheel use high temp grease to keep the rust from duilding up under the shims,,i usually take a round file and file the inside of the brake pad backing plate so they slide real easy on the ss shims..also machinr the rotors and put a fine finish on the rotors,,thease pads are scorched so you dont have to brake them in..
this one of the best brake pads o\i have found,i use them on every car i work on,never had any issues and they have great touchy braking power..

articfriends

iTrader: (1)

Thanks, I will check it out, I haven't had the truck out much since its been hot and they released before I could ever get it on the hoist and crack the bleeders but what your saying makes sense. I guess I could verify what your saying is happening in a few seconds too by cracking the bleeders if it does it again before I can get it back on the hoist and seeing if it realeases or not. The pads and rotors were new this winter and I haven't put 500 miles on it since it was hot out this year so if what your saying nis correct the new pads must have a little bigger plates on them then the original ones? Smitty
We are a transmission shop so we don't do alot of brake work except on our own stuff for the most part!

FIXX

iTrader: (2)

also on the newer chevys the caliper slides have a tendency to get all rusted up so make sure you use some hi heat purple permatex (2400*) caliper pin grease and not antiseize,,antiseize drys out with heat and causes all kinds of problems..if the pads went on tight file the part with a round file so the pads slide easier but they stil need to be sorta snug..

575cat

And make sure the brake fluid is not filled to the brim when your done test driving , gotta have room for expansion .