So the seal is leaking in the cab and it looks to be the original so I ordered a new one. While I'm there should I replace the master cylinder also?

Ouch. If your hydrobooster is leaking into the cab you should go to Pirate Jack's and get the seal kit for the hydrobooster. The input seal might require cutting the rod and weld it back together being the pedal eye won't allow it to pass.

yes definetly Pirate Jack's and not some MIC bad copy, well saying that I found a MIUSA "small" seal kit first off of ebay.com but while I was waiting for it to arrive I was pointed to PJ's and saw he does a "full" kit  so I also ordered that too, being in the UK and using my truck for work truck in bits and no parts is not an option so I always make sure I have everything I need then some just in case.  Also be aware there are plenty selling on ebay.com stating MIUSA, I messaged and asked and a lot weren't

I just unbolted the master cylinder and left it hanging  and did not reseal it, the Hydroboost is easy to reseal and on my truck I didn't have to cut the rod as some years you do and some years you don't, now mine is 1998 first of the 24v so If I didn't need to cut the rod and yours is 2002 I'd guess you might have to cut the rod, PJ's instructions tell what needs to be done

 

I did use PJ's full kit but be aware the kit covers more models or Hydro variances then just your truck so you will have parts left and you "could" fit the wrong parts if not careful

 

Just remove it and when disassembling lay it all out on a clean surface in order and match the new parts to old first..... IIRC there are some seal differences but the instructions are good so no bother 

 

I'll rephrase what I said earlier, now I've sat and thought I can't be 100% sure I didn't have to cut my rod, memory not as sharp as it was !

Yeah I've got my Pirate Jack's kit at home on my dinning table. Just gotta get home and finish the truck I've got in the shop. Then shove Beast in and tear it down.

Pretty nice that kit is universal. I own three vehicles with Hydroboost, maybe I should order a kit to have handy, and hope the seals don't dry out by the time I need it 😄

4 hours ago, LorenS said:

Pretty nice that kit is universal. I own three vehicles with Hydroboost, maybe I should order a kit to have handy, and hope the seals don't dry out by the time I need it 😄

Pretty sure the others were chevy stuff