This is my first diesel pickup, and I am completely new to this type of braking system. I have about 120K miles on this puppy and I was going to change my brake fluid today. When I opened the hood and looked behind the master cylinder I do not have the pancake vacuum for the fluid. From the research I have done on this forum I believe this piece is called the hydrobooster (I think).

When I looked at the piece behind the master cylinder there seems to be a slow leak on this piece. There is fluid that has leaked out, and dirt and grime have attached itself to this piece. I am wondering what the part number would be to replace behind the master cylinder.

Also I always thought a diesel pickup used power steering fluid to stop b/c a diesel does not produce a vacuum. However, when I looked at the writing on the master cylinder it said to use only DOT 3 fluid. So I guess it is a completely separate system from the power steering, correct? Thanks for the help.

 

In a nutshell, the truck uses hydraulic pressure from the power steering pump to provide power brakes, where normal vehicles use vacuum to provide vacuum brakes.

The power booster (whether a hydrobooster or vacuum) is separate from the brake master cylinder. In other words the master cylinder uses brake fluid, and the hydrobooster runs on the power steering fluid (in this case Mopar ATF is used for power steering).

Are you still under warranty?

 

No I am not still under warranty. I have about 120K now, and it looks like I need to replace the hydrobooster. I have light fluid build up on the hydrobooster. It is not dripping or anything, but you can tell there is moisture coming from somewhere and accumulating on the booster.

I have read on this site that if you are going to replace the hydrobooster, at that time you should go ahead and replace the master cylinder. If I replace both of these units can someone recommend a good one. I do not mind paying more, b/c if I figure if you are going to replace something you might as well replace it with a good part. Thanks.

 

I have the same issue on my 1999. It's a somewhat slow leak and I have just been adding steering fluid. I'm wondering if it is just an o-ring I can replace. Anyone know? Rebuild kit? I think I came across mention of a kit online before, but it may not be available any more.