Chevy and GMC Duramax Diesel Forum banner
  • Hey Everyone! Enter your ride HERE to be a part of this months Ride of the Month Challenge!
1 - 20 of 36 Posts

·
Registered
Joined
·
37 Posts
I have an 04 LB7 4x4 and the service brake system light came on. I noticed that my pedal was really spongy and saw that the driver side brake caliper had been leaking for a while. I changed the caliper and bled the brakes. Light stayed on then went back off. The next day light came back on and I noticed a hose from the hydroboost to the power steering pump was leaking. I replaced the hose and made sure the fluids were topped off after running. I got a little firmer brake pedal and it seemed to drive good. Today start the truck and the light has come on again:cookoo[1]::help can anyone help me figure out what's going on with this thing. I've only had it about a week and already tempted to get my dodge back lol. Thanks guys!!
 

·
Registered
Joined
·
7,912 Posts
Did you flush out all the old power steering fluid? That will help the hydroboost and the pedal should be firmer after some new clean fluid.

The service brake light I'm not sure...I'd start with making sure the brake resivour is full. Also I've seen that service brake light come on with low battery voltage, it prolly wouldn't hurt to get your batteries tested. If one is bad replace BOTH.
 

·
Registered
Joined
·
7,912 Posts
These trucks can do weird things with low batteries.
 

·
Registered
Joined
·
37 Posts
Discussion Starter · #4 ·
No I didn't flush the system I just added some fresh power steering fluid to top it off and the brake resourvoir is completely full. How would i change both brake and power steering fluid so I can make sure it has good clean fluid in them? Also I'll get the batteries tested. They do seem fairly old and I didn't know that low battery voltage could throw that code. Thanks for all your help. This is my first dmax after years of having cummins and I'm really wanting to like it lol
 

·
Registered
Joined
·
945 Posts
If the batteries test good check the wheel bearings.
 

·
Registered
Joined
·
37 Posts
Discussion Starter · #8 ·
Ok thanks. I'm really keeping my fingers crossed it's the batteries. I'm tired of staying covered in grease and busting my knuckles on this thing lol
 

·
Registered
Joined
·
7,912 Posts
No I didn't flush the system I just added some fresh power steering fluid to top it off and the brake resourvoir is completely full. How would i change both brake and power steering fluid so I can make sure it has good clean fluid in them? Also I'll get the batteries tested. They do seem fairly old and I didn't know that low battery voltage could throw that code. Thanks for all your help. This is my first dmax after years of having cummins and I'm really wanting to like it lol
There is a thread called something like "how to flush the hydroboost system" on this site....you'll have to use the search function because I don't know how to set up a link...lol

As for new brake fluid I just suck the fluid out the resivour and top off with fresh brake fluid. Then I just bleed the brakes at each corner until fresh clean fluid comes out. Make sure to keep adding to the resivour...if you let it get empty you will suck in air and have to start over.
Maybe you might want to check out stainless steel braided brake lines, they replace they rubber hoses to the calipers....they seemed to firm up my brake pedal nicely. A company called Russell makes a nice set, they run a little over $100...many vendors on here sell them. It's a easy job to change out....and a good time to do the brake fluid change.
 

·
Registered
Joined
·
4,954 Posts
No I didn't flush the system I just added some fresh power steering fluid to top it off and the brake resourvoir is completely full. How would i change both brake and power steering fluid so I can make sure it has good clean fluid in them? Also I'll get the batteries tested. They do seem fairly old and I didn't know that low battery voltage could throw that code. Thanks for all your help. This is my first dmax after years of having cummins and I'm really wanting to like it lol

you can bleed the fluid out from the brake bleeder, but you should not let the reservoir go dry or you will suck air into the ABS module and have a bad day. you can also just get a 2$ turkey baster and suck the fluid out of the reservoir, fill it up drive it a few days and repeat 2 or 3 times and you will get most of the old fluid out. as for the power steering, search the forums for the hydroboost flush thread, it has all the info on that, it makes a huge difference. to drain the power steering you can take off the return hose from the gear box and turn the wheel back and forth till its empty, but you dont want to run the pump without oil in it or you will damage it. another good investment is stainless steel braided brake lines, there 100 ish bucks but really firm up the brakes. If you have access to a techII or other scanner that can bleed the GM anti lock brake cylinder you can fully gravity drain the brakes if you are so inclined, fill, bleed each caliper and bleed the module, you will get 99.9% of the old fluid out. but this is really overkill. the method stated on the previous page would get nearly as much out and save you some hassle, but its easier with a buddy to watch the reservoir and top it off for you.

GM's major source of gremlins on these truck is due to voltage drops, either from poor or corroded grounds or from bad batteries, but a LOT of the problems on this forum you read about are due to low voltage.


also, im sure you already know this but im gonna say it anyway, the brakes are driven off power steering pressure, but the reservoir for the brakes is still brake fluid, and the power steering is power steering fluid and they at no point mix or interchange. also, you may notice on the duramax that steering and or braking get a little meh in parking lots, when the engine RPM drops you lose pressure on the pump and some people experience harder turning and softer brakes at idle. this problem can be made worse by a old pump. you can get a new pump with a higher pressure regulator if you have this issue, some people never have a problem with it (like me, ive never noticed a loss of steering power) but others complain of HUGE loss of power steering at idle, especially while brakes are applied.
 

·
Registered
Joined
·
37 Posts
Discussion Starter · #12 ·
Well I guess I'll try flushing the power steering and brake fluid. Anyone know an easy way of checking the front wheel bearings
 

·
Registered
Joined
·
945 Posts
jack the front up so the tire are off the ground. grab the tire at 12 and 6 o'clock and wiggle it.
 

·
Registered
Joined
·
37 Posts
Discussion Starter · #14 ·
thanks padmax. will I feel anything or should it be tight? also if it will move, how much is acceptable? I've never dealt with wheel bearings before.
 

·
Premium Member
Joined
·
11,309 Posts
I wouldn't want any play in my bearings.
 

·
Registered
Joined
·
1,687 Posts
Scan the ABS module for codes instead of throwing parts at it. That should tell you exactly what the problem is.
 

·
Registered
Joined
·
945 Posts
No play in the bearings.
 

·
Registered
Joined
·
37 Posts
Discussion Starter · #18 ·
Ok guys so one of the batteries was bad. I also noticed the same smell coming from the driver side rear tire. Checked it and looks like the caliper is leaking again. Any ideas. I'm on the verge of getting rid of the truck all together
 

·
Premium Member
Joined
·
26,482 Posts
DRW....sure it's the caliper and not the axle seal?
 

·
Registered
Joined
·
37 Posts
Discussion Starter · #20 ·
Haha no I'm not sure that's what it is I was just assuming it was the caliper since it is wet around the rotor. Yeah it's a drw. How hard or how expensive are axle seals to replace
 
1 - 20 of 36 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top