k5 hydroboost unit

[plugugly86]

the booster on my kids 87 k5 is leaking from somewhere I cant find. I figure its only time before it fails completely. The only replacements I can find are reman'd units from Cardone, which Im not crazy about. Rather run something "new"

Im guessing a chevy HB unit crosses over from rig to rig, with just the brackets being different and possibly pushrods (confirmed by the gal at Vanco. BTW Van is no longer there). However, the 06 silverado units I got my hands on is totally different where the master attaches, with a star washer thing and pushrod already installed, and a smaller body over all. Its been years since I installed the HB unit on my car (purchased from vanco like 15 years ago.) fitting threads seem are the same.

Am I missing something? Are the washer and pushrod pulled from the stock booster when I replace it, and just happens to be in the newer version? both seem to have standard 2 bolt master cyl mounting. Id run a stock master cylinder till I swap discs in the back with the one ton swap and then likely run that late 70s corvette MC which I seem to remember as the right master.

 

[WWRD99]

Just gotta ask what do you mean by leaking. Power steering fluid drives the booster, can leak inside the cab at your feet or in between the master and booster. There's the hoses and power steering pump. Does it get low on power steering fluid you have to fill up every day? If you can't find a leak and the power steering fluid doesn't need filled the pump is going bad.

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[plugugly86]

the HB unit is wet all over, and dripping fluid along the firewall. All hoses are wet as well. yes the PS reservoir was low. I think its seeping from the round metal dohickey (i forget what that cylinder is called) on inboard side of booster. Braking performance is normal for now, and pedal feels god. All fittings appear to be dry at HB.

 

[WWRD99]

the HB unit is wet all over, and dripping fluid along the firewall. All hoses are wet as well. yes the PS reservoir was low. I think its seeping from the round metal dohickey (i forget what that cylinder is called) on inboard side of booster. Braking performance is normal for now, and pedal feels god. All fittings appear to be dry at HB.

Ok so it's leaking so bad you can't tell where it's from. Fluid under the hood. The booster shouldn't leak unless the brake pedal is being pressed. Fluid flows through the booster freely with no pedal applied. If it doesn't leak in park with no pedal it points to the output piston seal in the front of the booster. If it were a hose it would leak all the time. Should be able to brake clean the booster and hit the brakes and see it drip. Changing that front seal isn't that hard. Don't have to cut the pedal piston off just split the case and be done.

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[Jeepadict]

There are CUCV brake booster parts kits on eBay, along with the TM will allow you to rebuild it.

GM had evolutions of the HB booster that seemed to follow with the new body styles...mid-late 70s, 80s, 90s, 2000-2010, 2011-current...you get the point. Some versions were interchangeable, some weren't. If your kid's K5 is a 1009, just go to NAPA or Carquest and tell them you need a new or reman brake booster for an 84 Chevy K5 Blazer...that is not a military unique part at all, and they made the civy HB in a gazillion trucks over the years so parts are plentiful.

The booster is not difficult to change at all, the TM will guide you step-by-step should you want the guidance.

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[plugugly86]

cleaned it up really well yesterday. It appears it is leaking from between the two halves of the HB unit, and best I can tell from where the master mounts to it (just had hip surgery, so there is only so much I can do right now).

At this point, Id rather replace the whole unit than the repair a leaky gasket. Im guessing its going to need a total overhaul.

still not super excited about a reman unit, dont really want to do this more than once. The kids blazer is a civilian unit with 6.2. Id like to find a crossover year that might work that would allow for a new unit.

 

[Jeepadict]

If you're only looking to fix something once, I'm confident that an 87 K5 is the wrong vehicle for your kid to own let alone any imperfect machine built by an imperfect human. I'd advise against attempting an interchange as that complicates things later on unless you're an enthusiast which it sounds like neither of you are. With recent hip surgery I reccomend giving it to a competent repair shop so you can have a warranty should the replacement part fail.

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[plugugly86]

lol. Im pretty competent at building off road cars. built my current off road car from the frame up. Replacing a hydroboost unit should not be a common thing, unless you use a reman unit like cardone or one of the other shit rebuilders that are out there. My current HB unit in my car was originally in a different car and has years of hard offroad miles on it without issue. The stock one lasted nearly 40 years. MOST of the time, the difference is in the mounting plate and pushrod, not so much the booster itself. Mounting plate and pushrod are pretty easy to replace. MC to pushroad clearance can also be an issue. Trying to find a suitable newer unit versus rebuilding my own with questionable quality "gaskets" or questionable reman seems to make a lot of sense to me. The hip will be fine in a few months, just need to get my kids car back on the road.

here is the car I built for proof since I guess its needed. you could say Im a bit of an enthusiast

 

[Jeepadict]

It's your kid's whip. Get him a reman from Napa and let him do the work while you look on so if the o-rings leak again (there are no gaskets) then he will know how to fix it, and the parts are warrantied...then he can teach his kid, or he can take it to a shop. IMPO you're asking pretty high standards of parts for a 40 year old ride...it's a naturally aspirated late 80s Squarebody oil burner, not exactly a collectors item. If you're dead set on new parts for a 40 year old burner, call up the hotrod shops like POL that specialize in HB conversions...those guys know what Vette thingy works in a truck gizmo and on and on...but prepare your wallet for a price that's 6-10 times higher than that reman from Vatozone you don't like for reasons I don't comprehend.

Have you tried any of the companies that cater specifically to the Squarebody community? Summit Racing? Tuckers? LMC Truck? Classic Specialties? (Or any of the other dozens of catalog companies) Have you tried to use Google?

Let's be honest with ourselves, the grumpy old guys on here are mostly the type to buy the CUCV NSN kit off eBay or from Eastern and would use the CUCV TM to rebuild it in less time that it's taken us to type all this stuff out because most of them did it during WWNam while getting shot at in 127° in the shade with 200% humidity. Perhaps you may have better luck with a more specific enthusiast forum like k5.com where talking about this sort of thing is likely old hat and they know where to buy the fancy new part stuff. You stand better odds there especially since you have proven experience in the offroad realm.

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[WWRD99]

cleaned it up really well yesterday. It appears it is leaking from between the two halves of the HB unit, and best I can tell from where the master mounts to it (just had hip surgery, so there is only so much I can do right now).

At this point, Id rather replace the whole unit than the repair a leaky gasket. Im guessing its going to need a total overhaul.

still not super excited about a reman unit, dont really want to do this more than once. The kids blazer is a civilian unit with 6.2. Id like to find a crossover year that might work that would allow for a new unit.

Glad you found where it's coming from. Sounds like a mess. I have kits for those but being a civi and a 87 I'm not sure about sizes. I have one good booster that I'd have to dig out to see what the output piston size is though. I've seen several diameters of those. The input shaft length is important too. Buying one new or rebuilt from a company shouldn't be to tough to find but I have no input on who. If you have access to a mig welder I'd recommend rebuilding it yourself. It's only 4 gaskets and nothing weird inside not much different than a starter rebuild...kinda has the same bendix pivot inside. My first one took me 2 hours...can do them now in about 30. Rebuild kits are 30$ or so. Hit up a YouTube video quick and see if you'd want to tackle it. Oh and changing the mounting plates is not easy. They are held on with a 4 point nut that is recessed...you need a 8 inch deep socket to get it off. They sell them online though but it's not something you probably have laying in the toolbox.

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[plugugly86]

when you say input shaft, are you talking the length of the pushrod between MC and HB?

Ive got a welder, just cant imagine what its needed for. Now ive got to go look up the rebuild vids......

 

[WWRD99]

when you say input shaft, are you talking the length of the pushrod between MC and HB?

Ive got a welder, just cant imagine what its needed for. Now ive got to go look up the rebuild vids......

Input shaft hooks to the brake pedal. They can be all over the place on length. The eyelit on that end needs cut off to get that shaft out of the rear of the booster...there's 2 lip style seal that seal that side of the booster. They are on that shaft. Then the eyelit gets welded back on...add a touch for the part that got cut. If yours isn't leaking you don't need to do that. They aren't that tough to do though. They do push in the cylinder so the lip seal is easy. Just make sure you get the correct size. I cut off the eyelit right at it so when I weld it back on it doesn't heat up the seals. The output shaft I always use the one that's in the original booster...they can be all over in length too. When you split the case there's one big spring on the valve...not a ton of tension...just gotta know it's there. That's where the starter bendix looking pivot is. A small check valve in the front body too...it may fall out but know it's there. The front piston has a lip seal in the case...it does need pushed in to allow the piston to go back in...I use a lip seal tool for transmissions...basically a very thin feeler gauge that feeds the lip seal around piston. Really not hard..I've had luck using a very sharp pick as well going around it. That is the hardest part of the rebuild...but it's not that tough. If you've ever rebuilt a brake wheel cylinder it's the same thing with the lip seals. Catch a few videos for fun. There's a guy that builds one on his pickup tailgate. He did the center gasket only.

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[plugugly86]

Input shaft hooks to the brake pedal. They can be all over the place on length. The eyelit on that end needs cut off to get that shaft out of the rear of the booster...there's 2 lip style seal that seal that side of the booster. They are on that shaft. Then the eyelit gets welded back on...add a touch for the part that got cut. If yours isn't leaking you don't need to do that. They aren't that tough to do though. They do push in the cylinder so the lip seal is easy. J

gotcha. I have done something similar except I tapped the pushrod and used a heim. It all depends on what kinda brake pedal setup you are trying to attach to I guess. When moving from 94 bronco (which needed the formed "flat" style mount that fit into the brake pedal switch) to the scout that never had provisions for power brake, i need a "cut and swap" similar to what I understand you to be saying


thanks for the help all. Im still going to chase down a crossover, newer unit for now. The concern with throwing new seals or buying a reman, is pitting/scoring on these older units. Ive got a few options Im looking at still, was just hoping to save time if someone had the answer. With the kid starting college locally, Im trying to just get his rig on the road while watching from the sidelines.

 

[WWRD99]

gotcha. I have done something similar except I tapped the pushrod and used a heim. It all depends on what kinda brake pedal setup you are trying to attach to I guess. When moving from 94 bronco (which needed the formed "flat" style mount that fit into the brake pedal switch) to the scout that never had provisions for power brake, i need a "cut and swap" similar to what I understand you to be saying


thanks for the help all. Im still going to chase down a crossover, newer unit for now. The concern with throwing new seals or buying a reman, is pitting/scoring on these older units. Ive got a few options Im looking at still, was just hoping to save time if someone had the answer. With the kid starting college locally, Im trying to just get his rig on the road while watching from the sidelines.

Could absolutely to a heim joint...just cut it down a smidge more to make threads. I haven't had one pitted before since there's only power steering fluid in there...the output seal you could run stones in to hone it...the input are to small. Really shouldn't need to hone the output though since it has an aluminum piston in there that seals on that. Easy to clean that. Just makin the point these are not hard to build. Wish I had a direct replacement to get you!

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[plugugly86]

if anyone is interested, ive been doing some research. Someone had mentioned a GM 178-1036. it led me down the rabbit hole of searching. was able to find a 178-1037, which durmax folks say is the "new' version of the 1036, and about 30 bucks cheaper. I have a few pics compared to the stock K5 unit. It seems to be pretty much spot on except for two points. The pedal pushrod hole is .2" smaller (6.34 for k5 and 6.21 for this 2011 unit), and more importantly, the booster to MC pushrod is about 1/4" too long. Not sure if the 1036 i was told about would be any different, but I didnt want to buy one from amazon as you cant return it. I imagine I can just swap the pushrod from the K5 to this new booster, but I can not verify that as I dont have mine pulled from.

 

[Jeepadict]

One p/n (1037) is for the LMM trucks, the other (1036) is the very popular upgrade that only came on the '11 LML trucks which is highly adapted to the GMT800 trucks for a substantial braking upgrade...hence why they're cheaper and widely available. As noted, both of the p/n you referenced are from the 900 bodystyle trucks and AFAIK will require notable modification to the mounting plate and pushrod to get them to fit and function as design intended.

There are companies that sell just the mounting plate for the C-10 trucks which is likely what you will need if you commit to Frankenstein a booster. POL makes a brand new turn-key solution (likely using parts from a late 70s Vette) for your kid's truck for just under $1k and will save all the hassle you're fighting with. I still say you're spending a dollar to save a dime, the truck could have been driving down the road by now.

Note: GM has different part numbers than ACDelco. The numbers you listed are Delco numbers.

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[plugugly86]

best I can tell by measuring bolt spread is the brackets are exactly the same. The 87 on the left and 1037 on the right. I found a 1036 finally, locally, and it too seems to be the same with slightly shorter pushrod but still too long for the 87 booster by about 1/8 inch.