Hydroboost Problem
 

Been reading on here for a while and have gotten alot of great info, but now I have a problem. I did the Hydroboost conversion on my 06 1500 ext cab, front disc - rear drum. At the same time, had the rotors turned and put on new pads. A few weeks later, the rotors were warped. Figured that the rotors were too thin after turning and I would just have to wait until I could get the cash to replace them.

The used hydroboost unit was from an 05 2500HD. New M/C (reman), used reservoir. New high pressure hoses and return line hose from Advance Auto. Using original P/S pump.

Fast forward to this past Thursday, replaced the rotors and put new ceramic pads on the truck. Drove ~60 miles round trip, didnt notice a problem. Today on my way up north (about 45 mile trip) I noticed that the truck was shaking going about 45-50 mph. When I got to my stop and check the brakes, the front rims were so hot that I couldnt touch them. They were dragging, but I didnt know it or feel it.

I've attached some pictures of the results on the rotors. I have read the search results on HB from here, but other than a guess at replacing the HB unit itself - I didnt get a clear answer as to what the problem might be. If I cant find out what's wrong, I'm going to have to go back to the original vacuum booster setup until I can. Any help would be greatly appreciated!

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could be a caliper hanging up was it both sides? kind of doubt that though , since your truck is so new. id say either master cylinder isnt completely letting pressure out or your hb unit is keeping pressure on the master.

Is there suppose to be a gap between the M/C and the HB unit? Because there isnt one. If I remember correctly, I think that there may have been one when I put it together, but I tightened up the bolts to eliminate that issue. So that might be my problem if the HB is pushing on the M/C. I'll look into that when I get back home, thanks!

no gap is supposed to be there it should together nice and tight.

I know I may be over-simplifying this, but it would seem as if you could jack up the front of your truck to get the wheels off the ground. See if you can spin the wheels with no brake drag, which there shouldn't be. Crank the truck and try and spin them again to see it the HB is affecting the system. If nothing was found in the pervious two checks, I'd hit the brakes and check it again to see if the system is not releasing the pressure once it's applied.

Ok, got home this afternoon. Brakes are definitely dragging but the brakes, rotors and wheels are still quite warm. I will check it later once everything has cooled down completely. I loosened the M/C to see if there was any pressure being applied by the HB unit and found that with the engine off, there was no pressure. I left the M/C loose about 3/16" and started the truck...there is pressure being applied to the M/C while the engine is running. This would explain why the brakes are dragging as the M/C has a constant pressure applied. Am I correct in thinking that there is a problem with the HB unit? Could it be a problem of the brake pedal connecting rod adjustment?

did you swap brake pedals? did your hydroboost come with the longer rod? there are two different rods they come with one is longer and if so it would put presure on the brakes.

Yup, got the new (correct HB) pedal. The HB did come with it's own rod.

No drag once everything is cool. I removed the M/C from the HB unit and started the truck. The internal pushrod slowly extends all the way (at the same time, the brake pedal inside the cab drops all the way to the floor). Looks like a bad seal or some other internal problem with the HB unit. Is it worth trying to fix or just replace with a reman unit? Thanks.

Found the problem. I had originally attached the return line from the HB unit between the gear box and the cooler, this was the problem. There was a significant amount of pressure after the gear box and this was pressurizing the return line - causing the HB unit to apply pressure on the M/C.

So I would recommend to anyone doing this conversion that you either get the correct P/S pump with the 3rd connection OR you connect your return line AFTER the cooler.

Thanks to all that helped.

Had the same problem and just spoke with Van from Vanco Power Brake Supply (an expert on hydroboost systems).

He said if your brakes are dragging and you have separated the master cylinder from the brake booster to identify that it is indeed the hydroboost causing the problem (not kinked brake line, old calipers or something else), there are two likely causes:

1. The pedal rod is too long. To diagnose, disconnect the rod from the pedal, then start the truck, if it has stopped dragging, then you need to put spacers in between the brake booster and firewall to space the rod out appropriately.

2. There is resistance in the low pressure return line. It is either blocked, kinked or just isn't flowing well. To diagnose, disconnect the return line and let it drain into a bottle while the truck is running (shouldn't be a gusher, just a trickle of fluid). Plug the connector to avoid fluid spilling. If this fixes it, then that is your problem. If it is T'ed in, then the straight part of the 3/8" T fitting should go from hydroboost to reservoir and the steering box line should be at a 90* angle as it is less sensitive to flow resistance (this is likely my problem, haven't fixed it yet b/c I just found this out today). Another problem is that the T is overclamped and flow is being blocked with the hose clamps. Or, the hose could be old, too small or kinked. He said that the power steering pump should not cause your brakes to drag, so don't haul off and replace that first without testing these things out.

In the picture above, it looks as though the problem was that the T fitting was set up wrong with the 90* fitting going to the hydroboost instead of to the steering box. Hydroboost to the reservoir should be in a straight line through the T fitting.

Hope this helps someone else. I couldn't turn anything up about it. (yes I know this thread is 3 years old)