Hydroboost,

rafterk

Newbie
Original poster
Feb 8, 2022
9
Windsor, CO
I have a 2000 K3500, was purchased as cab/chasssis. The steering box replaced, now when I step hard on brakes, the Left Front brake locks up first. have tried bleeding system but still get bubbles in the power steering fluid, no leaks noted in the hydro system under the hood. Is there a proper bleeding or other procedure to even brakes, or as it is prob original hydro, just get another? Thanks in advance.
 

northcreek

Guru
Jan 15, 2012
2,912
WNY
Not an expert but, I also have a hydroboost and it seems like your problem is on the master cylinder side and not the boost side, could have a bad caliper or hose on the right side.
 
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Reprise

Lifetime VIP Donor
Jul 22, 2015
2,520
I also have one in my Sierra (and, no, I'm not an expert, either).

You mentioned that you know you still have bubbles in the P/S reservoir.
You've got to get the system bled completely -- depending on how much air you have, it'll take a few days to work itself out (and you may have little to no brake and steering assist while it does -- a real butt-puckering feeling!), or you can get the front wheels off the ground and turn the wheel (sloooowly) lock-to-lock a million times.

Because you replaced the steering box, there's air in the system (you know this; just stating the obvious). I did the same repair, along with replacing the pressure / return hoses (I have a 1500HD, which has the old-school, vague-feeling Saginaw gear / idler / pitman / center link, just like yours).

I'll warn you now... if the P/S reservoir ran dry, even if only for a couple of minutes... you'll eventually lose the pump. Yeah, I replaced that later on, too. That wasn't as bad, because I bought a pump with reservoir, and (over)filled it up before swapping it out (so not much air to bleed the second time around). First time around, I filled the reservoir only to the 'max' line and it sucked it all out in about 10 seconds after starting the engine. I put more fluid in while it was running, but she had a lot of miles on her, and I lost the pump not too long afterward.

E.g.; if you're doing a major parts replacement, best to fill the reservoir to the brim for that first start. Once you get all the air out, then use a turkey baster, etc., to get the excess fluid out / back to the proper level (too much will aerate the fluid, and then you're right back to square one).

Once the HB is bled, then you can start looking at the brakes in earnest. Like Northcreek, I think your real problem isn't with the HB (unless they're leaking, they're pretty stout). If they leak, it'll be from underneath -- run your finger around the area where you feel a notched out section underneath. If it's wet... *then* it's time for a replacement HB module (yeah, I replaced that, too -- tried a rebuild kit first, and that was utterly craptastic)
 
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TollKeeper

Platinum Donor
Dec 3, 2011
6,711
Brighton, CO
I agree with Reprise on all he said... Its just a matter of getting that Hydro bled out.
 

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