Okay, I found an escalade being parted out locally and got all the hydroboost parts to convert my denali. Booster, master cylinder, pedal, and all 3 lines. Kept my original PS pump, tee'd the low pressure hydroboost return hose into the return hose from the PS cooling loop (that feeds cooled fluid back into the side of the PS reservoir).

I've owned and driven this truck for 4 years and 53k miles, so I know every sound and senstation it normally makes. PS worked perfectly prior to the conversion, no noise from the pump even with the steering wheel near full-lock. IT would whine slightly when at full lock as is normal.

After the setup was installed, I topped off the system with new PS fluid, turned the wheel lock to lock about 20 times to bleed it with the engine idling, then bled the brakes thoroughly. The PS reservoir is full to the line on the dipstick.

I've driven about 3 days on the hydroboost setup now. Brakes are about 4 times as firm as before...it is like the brake pedal is a brick, you just barely touch it to get response. And when you put some effort into them, they will put you into the steering wheel. Brakes are great, no complaints there.

However the first thing I noticed is that my power steering is heavier...less assist. I guess I expected that, and I can live with it, normal driving is still acceptable.

However, the problem is, the pump is groaning and whining a lot. It happens a little bit even when just idling or accelerating around town, not even using the brakes or steering. IT's much worse when you're in a parking lot using both the brakes and steering at the same time...it whines loudly enough that passengers could hear it and ask what it is.

I can't imagine that stock hydroboost equipped trucks do this. However from what I've read most people who do the conversion use their original PS pump, and that there is not supposed to be any difference in hydroboost and standard PS pumps other than the additional outlet on the reservoir for the low pressure return hose.

So has anyone else who did this conversion experienced this? Anything I can do to improve this? I guess the obvious suggestion is to try and get a PS pump from a hydroboost truck and swap it to see if it makes any difference...but I dont want to waste time if it isn't going to make any difference.

I love the response of the hydroboost brakes so far, but I find myself questioning if it is worthwhile if this whining and groaning PS pump is going to continue.

Also, does anyone know for sure if these trucks use power steering fluid, or auto trans fluid in the PS system? Some vehicles use ATF from the factory, and what came out of the system looked more like ATF than PS fluid.

 

You probably have a connection that is sucking air. Check and make sure all the lines and clamps are tight. Even an old o-ring can let air in.

 

If one of the o-rings on the high pressure lines were leaking, it would let fluid OUT too, would it not? As the high pressure lines are, well, under pressure, it stands to reason that fluid would come out before air got in. That is not happening.

 

My pump whines slightly more now since hydroboost since the pump is having to supply additional pressure than just the steering system. If there arent any leaks, and its bleed properly, and works correctly, then I wouldnt worry about it.

 

It shouldn't whine. I used my original pump and it doesn't whine at all. You either had a pump that was already on its way out and the hydroboost is exaggerating the noise because of the increased load or you have a restriction in the system.

 

I wanted to update this post for others who may search for info later.

I think I've resolved this issue.

First, note that my truck is an 02 Denali, and the truck I pulled my hydroboost lines/booster/mastercyl from was an 02 Escalade. I did not get the PS pump from the escalade. The line that goes to the PS pump went to the same spot on the escalade, as the stock non-HB line on my denali.

My denali's stock PS pump has an electrical connector on the bottom/back, and the pressure line screws into that. This would seem to be some sort of metering valve for pressurized fluid...in other words something to control how much assist/flow comes out of the PS pump.

Note that the pressure hose that attatches to this points forward.



I did not notice if the escalade had this electrical connection/valve or not...but the fitting was in the same place and pointed forward.

Well, I got a deal on a low mileage hydroboost PS pump assembly from a later model truck. Not sure what year, but it was newer than 02. It happened to come with a hydroboost pressure hose, which was unexpectedly beneficial (since I already had one).

When I went to install this one I noticed the connection for the hydroboost pressure line at the PS pump was different. There was no fitting and no electrical connection at the back...there was only a bung/hole there that the line screwed directly into. Nothing to restrict flow/assist.



Also the hydroboost pressure line that came with the new pump, was made differently than the 02 hose that I was using...to suit the different pump, it pointed backwards and not forwards. This was lucky for me, I could not have used the hydroboost hose that I already had with this new pump.

Now that it's installed and working, I have ZERO whine at any brake load or steering load. Also the steering is more solid than it was with my original 02 pump on the hydroboost conversion. My best guess is that the stock pump with electric valve was restricting assist flow, and it was not enough to feed the hydroboost brakes AND the steering anymore. This new pump is unregulated and full flow going to both parts at all times.

I'm quite pleased now.

 

My factory HD hydroboost system whines, Not very loud but I can tell. It doesnt bother me what so ever, turns fine, stops 10k OK lol, but I'm not worried about it. At times it sounds like its a super charger.