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Author Topic: Hydroboost Replacement - 3rd Gen Cummins  (Read 11784 times)

Offline FroneDaddy

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Hydroboost Replacement - 3rd Gen Cummins
« on: December 07, 2011, 09:10:39 pm »
This was done on an ’03 Dodge 5.9 Cummins.

The hydroboost is located in the engine compartment, on the driver’s side firewall above & connected to the brake pedal…



Prior to starting you need to discharge the pressure from the accumulator, to do this press the brake pedal 5-6 times with the engine off.

Next you need to separate the master cylinder from the hydroboost, there are 2 nuts that need removed, you can see the one in the picture, it's  the loose one, the other one is on the other side of the master cylinder…



Those 2 nuts also hold on a bracket that holds the 2 high pressure lines going to the hydroboost in place, unclip the lines from the bracket and set the bracket aside. Let the master cylinder rest on the intercooler tube but don’t force it, you don’t want to kink the metal lines coming off of it…



Next, loosen both high pressure lines, one on top and one on the side and slide the clamp out of the way on the low pressure line. Have a large piece of cardboard under the truck as you will make a bit of a mess. These are the 3 lines I’m referring to, the top high pressure line is at 12 o'clock and is loose, the low pressure line is on the right side of the hydroboost with the clamp on it and the other high pressure line is directly behind the low pressure line…



Now you need to disconnect the rod going from the hydroboost to the brake pedal. There is a clip on the back of the pedal holding the rod in place. Looking at the orientation of the clip in the below pic, you need to push up on the clip with a flat head screwdriver on the left side of the clip and slide it off to the right…



This is a better view of the clip…



Now, there are 4 bolts from the hydroboost coming through the firewall, the nuts need removed from inside the cab, they are the 4 larger bolts pictured. This puts you in a very awkward position and the nuts aren’t easy to access either, I found it very easy to use a 3/8” drive ratchet (shorter handle due to lack of room to ratchet) with about 16” worth of extensions, a u-joint and a deep socket. After the nuts are removed go back and completely disconnect both high pressure lines and the low pressure lines from the booster. You should now be able to pull the booster out of the engine compartment. You may have to push the master cylinder out of the way a bit further, just be careful of the metal lines…



Here is the old hydroboost on the left and the new on the right. At this point you need to make sure the rod going to the brake pedal is the same length on the new booster as it is on the old. I just turned them in opposing directions and put the end of the rod of the new booster to the rod mounting surface of the old booster, in turn the rod of the old booster fell in the same spot on the new booster indicating mine were the same size. I was told the rods come in different lengths which will be a problem and to verify their length. Also, you can see they are a bit different. The new one doesn’t come with a mounting flange and also doesn’t have the master cylinder rod installed. They need swapped over from the old unit. To do this, remove the 2 nuts at the top and bottom and the mounting flange will come off. Inside the old unit yet is a spring, rod and a piece of metal that resembles a star which keeps the rod and spring in place. The teeth of the star are bent which grab themselves on a lip inside the bore. They need slightly bent to slide one at a time past the lip, eventually you will be able to work the star out. Make sure you don’t bend them so far as to crease the metal. Once you get the star out, the rest will come out as well…





Install them into the new unit, the star is a lot easier to put it. It will clip itself onto the lip in the bore of the new booster. Then bolt the mounting flange on the new unit as well. The bolts that hold the mounting flange onto the booster aren’t at exactly 12 & 6 o’clock but they ARE in a position that if you didn’t mark how you took it off, it can be rotated 180* and still work. This is everything swapped over to the new booster…



Installation is the reverse of removal, set the booster against the firewall and bolt it in place. Connect the brake rod and install the clip by sliding the open end of the clip over the tit on the brake pedal until it snaps in place. Remove the plastic caps over the ports on the new booster and install their respective lines. Bolt the master cylinder in place along with the bracket, clip the high pressure lines back into the bracket and you’re done.

I cranked the truck several times without starting it to get some fluid moving around, then I started the truck with the front end off the ground turning the wheels lock to lock several times to removed trapped air. I shut the truck off and topped off the fluid, start it back up, go lock to lock several times, top it off and repeat the process until the reservoir is full.

Even though the brake pedal rod length was the same on both units you may run into a problem like I did. I noticed that my brake lights would not turn off. Reason was because one of the booster units had about 1/8” – 3/16” play in the rod which was giving the brake switch a fit. In turn I had to replace that as well. $9 from Advance, it takes longer to go get the switch than it does to replace it. The switch is on a bracket right above the brake pedal. It was too hard to get a picture, but when you look up there you’ll see the plunger making contact with the pedal. The plungers are not adjustable after installation, so a new one is needed. This is the switch…



To remove it, undo the wire harness first. The harness has a red sliding lock on top of it that you can’t see, feel up there and slide it out of the way, press down on the black release tab and pull the harness out. Here you can see the red lock…



To get the switch out just turn it about 30* counterclockwise and pull it out. The plunger on your new switch will be considerably longer because it is self adjusting. Prior to installing it make sure the black tab on the side of the new brake light switch is in this position. These switches are a one time installation, so if you realized this tab is locked you’re not gonna be able to use it. 1 – You won’t be able to adjust the plunger, 2 – When you clip it into it’s bracket a piece of plastic breaks giving it a tight fit, if you remove it and try to put it back in it will probably fall out…



You can see from the new switch to the old switch that the tab is in different postions. Put the new switch into it’s bracket and turn it clockwise 30* to lock it in place. Install the wire harness and then flip the black tab to the lock position. This will set the plunger to the correct depth.
« Last Edit: December 07, 2011, 11:58:24 pm by FroneDaddy »
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Offline Buford445

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Re: Hydroboost Replacement - 3rd Gen Cummins
« Reply #1 on: December 08, 2011, 01:43:51 am »
Great Write Up  :2cool:


Thanks To HTS Transmission

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WHAT YOU DID, OR WHAT YOU SAID ~BUT~THEY WILL
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