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Hydroboost brakes - list of part numbers?

Discussion in 'The Garage' started by jms, Jul 13, 2005.

  1. jms

    jms 1/2 ton status Author

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    Does anyone have a list of part numbers for everything needed to convert a K5 ('85 in my case) from vac assist to hydro?

    As far as I understand it, the following parts would be necessary:

    PS pump (a pump for an '89 K3500 w/ 350 and DRW looks to have the required four ports) - what about bracket and pulley?
    Pressure and return hose assemblies between pump and hydroboost unit
    Booster assembly
    Master cylinder for hydroboost
    Brake pedal assembly

    BTW, I'm getting a bit disenchanted w/ the Caddy rear disks - no problems for two years, but lately I'm not so convinced anymore. I'm having a hard time locking up the brakes if I want to (on pavement; neither front nor rear); nothing obvious, no leaks, just had the whole system flushed, pads are o.k., it brakes straight without puling to the side, pedal is reasonably firm and high, but methinks this could be better... and since I'm not getting to do any fun mods this summer, brakes might be a good thing to upgrade...

    One more consideration, though, before I jump into this: my engine (Q-Jet) likes to die on really steep descents (by that I mean the occasional nose-into-ground steep, not just any hill, my Q-Jet is dialed in fairly well), and I've considered getting one of these little electric vacuum pumps to run in just such a situation and thereby get the vacuum assist back. Going to hydro would remove this option - and upgrade to TBI or Diesel swap (to keep the engine running in such a situation) is not in the immediate future. Anyways, opinions and part number are greatly appreciated, thanks, michael.
     
  2. Eric M.

    Eric M. 1/2 ton status

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    I have no part numbers for you, but I do have a parts list from when I converted my 91 3/4 ton Burb.

    Hydroboost List

    -Brake pedal is the same. Should not need as part of swap.
    -Need rod in back of Hyrdroboost unit which connects to brake pedal.
    -Need master cylinder (could buy new ).
    -Need rod and retainer clip between master cylinder and hydroboost unit.
    -Need Hydroboost unit (could buy rebuilt w/ core charge).
    -Need mounting plate for Hydroboost unit to firewall.
    -Need bracket which holds hoses and fastens to master cylinder mounting bolts.
    -Need 2 high pressure lines to Hydroboost unit (could buy new).
    -Need 1 metal and rubber return line from Hydroboost unit (rubber is store item, metal part isn’t).
    -Need power steering pump with 2 return line inlets. Some have cap on unit, others have remote reservoir which bolts to the alternator bracket.
    -Need power steering pump brackets, 1 on front of pump, 1 at back.
    -If remote reservoir, will need reservoir, hose to reservoir from pump and bracket (alt. bracket) which reservoir bolts too.


    If I were you, I'd find someone selling a complete hydroboost set up (or find a doner truck) using the list above to make sure you get what you need. Buy a new master cylinder and hoses and a rebuilt hydroboost unit, no sense in upgrading the system with old parts . Most of the other items are dealer only parts and will cost you a fortune.

    As with the vac. assist brakes, you will get a few more brakings from the hydroboost if the engine dies, but after that, you'd better have your foot over the parking brake pedal.

    The medium duty trucks have hydroboost units with built in motors to keep the unit working when the engine dies. I saw a light duty truck that was retrofit with that style hydroboost. All I can say is it can be done, I didn't ask details.

    I noticed a slight improvement in braking when upgrading my axles and brakes from 3/4 ton to 1 ton (with the 3.5" wide rear drums).

    I noticed a big improvement when upgrading to EGR front brake pads.

    Last I installed the hydroboost ... there wasn't that much of an improvement, but no more poor braking when engine vac. dropped.

    Good luck,

    Eric M.
     
  3. frankin5

    frankin5 Super Mall Crawler Premium Member

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    you need the parking brake cables atached to the caddy unit. this is what adjusts the piston to take up the slack as the pads wear.
     
  4. mouse

    mouse 1/2 ton status

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    The brake pedal was different when I did the swap. The stud for the rod end was higher and slightly bigger. I used 1981 diesel 1/2 ton hydro boost and installed it on my '77 Blazer.
     
  5. Eric M.

    Eric M. 1/2 ton status

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    Hmmmm, I installed a hydroboost set up from a 91 V3500 crewcab on my 91 V2500 Suburban and the pedal bolted to the rod just fine. I had to adjust the brake sensor switch a bit as the height of the pedal was off a bit from the vac. booster set up, but that was about it. I guess things changed a bit over the years.

    Eric M.
     
  6. jms

    jms 1/2 ton status Author

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    Eric, thanks for the detailed list of parts, great info!

    ...or so they say. E-brake cables are tight and actuate the levers on both sides evenly. E-brake does work at the mall and in the garage, but does nothing to slow down the truck when in motion...
     
  7. mouse

    mouse 1/2 ton status

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    As a side note, I also had to use the brake light switch actuating bracket from the '81, as the stud hieght was different. I'm glad that I anticipated some of these problems and got all of those parts at the junkyard at one time, without having to go back many times!
     
  8. jarheadk5

    jarheadk5 1/2 ton status

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    For that reason alone, it's best to try and find a donor truck to rob the parts from. I got lucky - my '87 K5 will be receiving the 6.2 and Hydroboost from the '87 C10 I acquired (legally!) for $100....
     

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