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I have a 2003 3500 with the lb7. My brakes were weak last week, so I started searching for a bad brakeline. The puddle of fluid after a few days led me to look up front. I removed the drivers side inner fender to make it easier, and the bottom side of the booster and master cylinder are wet. My power steering fluid is low. It looks as though it is leaking where the two meet. How do I tell if its the booster or master cylinder leaking?

Thank you for any help
 

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The Hydroboost uses Power Steering Fluid and helps with Steering and Braking functions

The Hydroboost is well known to lose a seal or two and go bad..

You can have someone sit in the cab and turn the steering wheel and push the brake pedal with the engine running to try and hunt the leak down but it may be too small to notice..
 

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There is a rebuild kit available (basically new seals) for the hydroboost part if that turns out to be the problem.
 

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Second on the Hydroboost... common issue with our trucks....top off PS fluid and watch to see if Master or Hydroboost levels go down.....amount of time and loss of fluid is the giveaway....New Hydroboost W/O core is a couple of hundred dollars from RockAuto or amazon...or if you are near a reputable rebuilder pull the hydroboost and have them rebuild it with a kit:clap: There are you tube video's on this subject matter:bounce:
 
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My symptoms same as yours - bottom side of the booster and master cylinder are wet. My power steering fluid is low.

Replaced the hydroboost this week. You don't have to crack the brake lines. Two hours to replace it. Easy to bleed the power steering system, just rock the steering wheel lock to lock several times.
 

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it must be that time if the year cause just today my 03 LB7 hydroboost is leaking too. lol i am just going to rebuild the hydro, buy a new master, and a new power steering pump with new lines. its cheap enough and then you wont be chasing any problems. my $.02
 
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it must be that time if the year cause just today my 03 LB7 hydroboost is leaking too. lol i am just going to rebuild the hydro, buy a new master, and a new power steering pump with new lines. its cheap enough and then you wont be chasing any problems. my $.02
Good idea. The power steering lines are pretty cheap.
 

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I know this thread is a little dated, but after putting on new fuel lines and brake lines this month, I discovered some "wetness" and a small drip at the hydroboost. See photo. For those that have tackled this job, would the "3 seal" rebuild be enough, or should I do a "full seal" rebuild. And of course, just get a remanf one and swap it out. Just curious as it looks like a "main" seal is only leaking in the photo.

For those that have swapped it out with a new one, any thoughts on brand?
Pondering my options......
 

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I should also add, that on occasion when I push the brake pedal, sometimes I get a "fading" pedal as it gets to the bottom. Would that go beyond a "3 seal" change?
 

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I know this thread is a little dated, but after putting on new fuel lines and brake lines this month, I discovered some "wetness" and a small drip at the hydroboost. See photo. For those that have tackled this job, would the "3 seal" rebuild be enough, or should I do a "full seal" rebuild. And of course, just get a remanf one and swap it out. Just curious as it looks like a "main" seal is only leaking in the photo.

For those that have swapped it out with a new one, any thoughts on brand?
Pondering my options......
If I was going to rebuild it I would do a full rebuild and be done with it.
When I replaced my Hydroboost about 4 years ago I just used a Cardone Reman unit from OReillys and it has been fine.
 

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I should also add, that on occasion when I push the brake pedal, sometimes I get a "fading" pedal as it gets to the bottom. Would that go beyond a "3 seal" change?
Looks like my hydroboost was leaking where yours is - the "weep" hole.

I just got an entire new unit instead of rebuilding it. A replacement unit was a lot quicker to install and came with a warranty. $216 from O'Reilly. Core was $33. Took me two hours.

Afterwards, it felt like it had a brand new truck - braking feel was excellent.

A few months later, I flushed out the power steering and hydroboost unit. It's real easy.
 
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We just put a GM hydraboost in my Father in laws 2011 2500hd about a month ago. I think it was just a little more our cost than an oriellys or autozone (we have a bodyshop). It was we quicker than getting one from any aftermarket. I think I have a good used one from an earlier model. We tried it in his truck, but the shaft to the petal was a different length.

Sent from my SM-N960U using Tapatalk
 

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If you replace the Hydroboost unit, make sure you keep the push rod from the old unit. Replacement units come (at least mine did) without that much needed part!
 

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If you replace the Hydroboost unit, make sure you keep the push rod from the old unit. Replacement units come (at least mine did) without that much needed part!
FYI, my rebuilt unit came *with* the pushrod.
 

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On mine I have just done the single (main) seal. Never had another problem.
 
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