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Discussion Starter #1
This thread has been a long time coming so anyway the brakes in my LMM seem really weak the brake pedal ends up even with the gas pedal to get the thing stopped at corners when it empty and no trailer behind if it is a very easy stop. When I am towing a trailer the trailer brakes and turbo brake then I push the brake pedal just about to the floor (less then 1" from floor) for the last 20 mph. The brakes in this truck were the way they are when I bought it also so I replaced the rotors and pads as they were worn then I flushed the PS fluid and also put on SS lines to replace the rubber lines. There is not air in the system.

My question is do these DRW trucks have no pedal or is there something wrong with this thing and if so what is it. The power steering works good.:help
 

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There was no contamination in the PS fluid? I know if the hydro-boost is going bad it can contaminate the PS fluid, but I am not aware of how to test for this. Sure would be a thought, though never had that issue :Knocking on wood till knuckles bleed: so I am not sure if this would be your symptom, or if petal would be real hard to press, like on a vacuum system (my guess). Have you flushed the Brake fluid? As it absorbs moisture (it does) it can cause similar issues as it'll boil much sooner. Just a thought, as most people don't think of this when doing periodic fluid drain/refills.
 

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There isnt any cross contamination but good thought. I replaced all of the brake fluid when I put the SS lines on and never let the master cylinder run out and the brakes are the same as before I replaced the lines and fluid. The pedal goes down about 2 inches before you feel anything. Might have to stop by a dealer and see if they have a simular truck on the lot. The lml could stop 10k without the trailer brakes on easier then the lmm can stop itself.
 

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I would hazard a guess that your hydro-boost unit has hemorrhoids. My brakes are awesome. I tow around 12-14 thousand pretty regularly and have never had the factory brake controller over 4.

The only reason I put stainless steel brake lines in was to smooth up the stops with the horse trailer and it was a good mod to do for that reason.

Because, like you, I have a CCLB, my rink-a-dink brake flush unit would not get it done because of the length of the system to the rears. I had to resort to the “wife in cab” method, working the pedal with the engine running, to really get the system bled properly.

Hope this might help.
 

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well it doesnt really matter if you didnt let the fluid out of the cylinder. it really just sounds like u need to re bleed all fours. shouldnt be down that far on any vehicle especially that has that kind of gvwr
 

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well it doesnt really matter if you didnt let the fluid out of the cylinder. it really just sounds like u need to re bleed all fours. shouldnt be down that far on any vehicle especially that has that kind of gvwr
It was the same before I even touched the truck though. I am going out to measure pedal height....
 

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Back from my truck. Truck running for test. From pedal to floor on parallel to travel is 5 1/4" goes to around 3 before you feel anything. Could call 3 1/4 to 2 3/4 its hard to tell. Can push pedal to floor with about 50-75 lbs of force I would say truck whines when you do it a bit.

GMC for me if you get a chance sometime if you could measure the throw on the pedal or someone else with a drw long pickup like this I would really appreciate it. I would love to bring this thing to the dealer and have them fix it but they are unable to locate there rear-end with both hands without assistance.
 

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Discussion Starter #8
Any other ideas?? A way to test the booster??
 

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50-75LBS and you're ACTUALLY on the floor? I don't have an Lmm or DRW but that aint right. No way. If fluid was flushed, I'd have to say air is still trapped somewhere, somehow. Since you've got a lot of real estate between the Master and your rears it may take a bit to get any air in the lines to the calipers and out.
If not, I'm trying to think what pad/caliper issue could cause this but nothing's jumping out at me, you've checked for a slow leak, right? If you hold the pedal firm but not stomping, (30-40lbs maybe) for a bit, does it start to get easier to get it to the floor? Maybe after 20-40 seconds or so (Steady, no pumping) Could possibly be a damaged seal or scratch in the bore of the master cylinder?
 

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Any other ideas?? A way to test the booster??
climb under check for possible calipar failure. lines leaking and so on and so on.
if nothing bleed your brakes. put a clear rubber hose on the bleeder screw and blead the brakes. if you have air you will see it. and do it several times to get all possible air pockets out. just cause you get a steady stream of fluid once doesnt mean there isent a air pocket in the lines or calipar. after you do this check your brakes. you shoudl feel a difference. you shouldnt have to test drive to be able to tell if there is an air pocket. the pedal will feel spongy and not stiff like it should. if it feels stiff your good. test drive if it still hasent fixed the problem you might have bad calipers. calipers can get stuck and not work properly after pads have been changed cause when you push the piston back in the dirt on the piston gets in the sleeve and causes it to stick. or you just need brakes. check the rotors for glazing and check the brake pads also for glazing. if it has a mirror like reflection they are bad and this could also be a problem. once brakes get a glaze there is no real way to get it off its easier just to replace the brakes.

but id go with bleed the brakes then pull all wheels and check for a sticking calipers. i did a brake job on my old dodge and a month later the caliper stuck and cause the wheel on fire. thats was alot of fun. i still kick my self in the a$$ for putting the fire out.:rolleyes:


i hope this helps:thumb
 

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have the hydroboost or master cylinder ever been replaced? if there is absolutely no air in the system at all(doesnt hurt to bleed just in case) then might even be a pushrod length issue if either the master or hydro have been replaced.
 

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I'm also interested to hear about this issue. Although mine don't appear to be nearly what the OP is describing.

The brakes on mine seem a little "soft" compared to my SRW F250, but no problem stopping. I wonder, is it a DRW thing?

Sent from my HTC EVO 3D X515a using AutoGuide App
 

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Don't you have to bleed the ABS module also?
 

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Sorry about my delay on getting back on here. I dont think there is air in the lines. As I said they were the same when I bought the truck used a year ago. The brakes dont feel like they have air. I have bled brakes on other vehicles before and I know how they feel and these just seem like low pedal just not sure why. I guess I will bring it in to the dealer to see what they think. The only confident dealer dealer around is about 40 miles away so I will start with the local dealer maybe they will surprise me.... I was hoping there was a way to test the pressure of the booster or something.....
 

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Sorry about my delay on getting back on here. I dont think there is air in the lines. As I said they were the same when I bought the truck used a year ago. The brakes dont feel like they have air. I have bled brakes on other vehicles before and I know how they feel and these just seem like low pedal just not sure why. I guess I will bring it in to the dealer to see what they think. The only confident dealer dealer around is about 40 miles away so I will start with the local dealer maybe they will surprise me.... I was hoping there was a way to test the pressure of the booster or something.....
did u find anything out yet? my 06 does the same thing, my 03 will stop on a dime
 

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my brakes feel soft too,ive got 57,000 and just bought it 6 months ago and GM just replaced the rear rotors and pads because rears were metal-to-metal,my 02' and 06' were way better
 

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I would hazard a guess that your hydro-boost unit has hemorrhoids. My brakes are awesome. I tow around 12-14 thousand pretty regularly and have never had the factory brake controller over 4.

The only reason I put stainless steel brake lines in was to smooth up the stops with the horse trailer and it was a good mod to do for that reason.

Because, like you, I have a CCLB, my rink-a-dink brake flush unit would not get it done because of the length of the system to the rears. I had to resort to the “wife in cab” method, working the pedal with the engine running, to really get the system bled properly.

Hope this might help.
Where did you buy your stainless steel lines at? I want a set
 

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I bet I know what it is. As I was leaving for work one morning I head this noise like something had lost its prime or air. When I stepped on my brakes, the brakes on my 2007.5 LMM had no air or boost. The brakes felt like driving a car back in the 60's with no power brakes. Took it in to the dealer. At first the dealer couldn't figure out what was wrong. Then later on they called me and told me they replaced the power steering unit. I asked why the power steering unit. They said the brakes gets it air from the power steering unit. The noise I heard was the power steering unit loosing its prime or air. It did not affect the power steering part just the brakes. Solved the problem. Covered under warranty.

Hope this helps.
 
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