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    Results 1 to 18 of 18
    1. #1
      Join Date
      Jun 2013
      Location
      San Diego
      Posts
      271
      Country Flag: United States

      Hydroboost issues....too sensitive

      Hello,

      Looking for some advise on my hydroboost setup. I have a 1970 Nova with a 5.3 swap and a T56.

      I have two issues with my brakes. 1) The brakes are SUPER sensitive/touchy. Like if you sneeze on the pedal, the wheels lock up. There is no pedal travel....the brakes are off, then BOOM you have full skidding on the wheels. 2) When you press hard on the brake pedal, I can feel "kickback" in the pedal. Its like the pedal rebounds off of something.

      Here is my setup:
      1996 Astro booster (junkyard)
      C3 Master 1 1/8"
      Wilwood prop valve
      C5 front discs
      Factory drums
      10lbs residual valve on rear line
      Booster/Master is mounted with the firewall angle brackets and rod is attached to the lower pedal hole
      HB does use a "Tee" in the return line.

      Overall condition of the brakes is good. All parts are new from Rockauto. No visible leaks. Master was bench bleed a lot. Brakes last bled as a traditional 2 person job.
      Brian

      1972 C10 - 454/TH400 - Short bed conversion - https://www.pro-touring.com/threads/...1972-C10-SoCal
      1970 Nova - LS Swap - https://www.pro-touring.com/threads/...Cal?highlight=



    2. #2
      Join Date
      Apr 2001
      Location
      The City of Fountains
      Posts
      15,484
      Country Flag: United States
      My first inclination is to go with a smaller MC, something like a 1" bore.

      Andrew
      1970 GTO Version 2.0
      1967 Cougar build
      GM High-Tech Performance feature
      My YouTube Channel Please Subscribe!
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      Remote Holley EFI tuning.
      Please get in touch if I can be of service.

      "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

    3. #3
      Join Date
      Jun 2013
      Location
      San Diego
      Posts
      271
      Country Flag: United States
      Andrew,

      I just put on the Corvette 1.125" Master hoping to fix the issue. I replaced the .944 MC that was on the car before. No improvement to lockup or pedal feel
      Brian

      1972 C10 - 454/TH400 - Short bed conversion - https://www.pro-touring.com/threads/...1972-C10-SoCal
      1970 Nova - LS Swap - https://www.pro-touring.com/threads/...Cal?highlight=



    4. #4
      Join Date
      Jan 2016
      Location
      AL.
      Posts
      4
      Country Flag: United States
      I have hydro-boost on my 1969 Camaro. I had to install a valve on the rack that reduced the flow to the brake system. Maybe that is your issue, too much pressure/flow.

      Stephen

    5. #5
      Join Date
      Jun 2013
      Location
      San Diego
      Posts
      271
      Country Flag: United States
      Well after reading some other posts I decided to swap the push rod from the lower pedal hole to the upper......total game changer. I'm thinking the rod might have been binding on something in the lower hole.

      Still have some kickback or bucking feeling in the pedal. I'm wonder if that is air? Bad booster?

      Hopefully I can get a few miles on the car and see what happens.
      Brian

      1972 C10 - 454/TH400 - Short bed conversion - https://www.pro-touring.com/threads/...1972-C10-SoCal
      1970 Nova - LS Swap - https://www.pro-touring.com/threads/...Cal?highlight=



    6. #6
      Join Date
      Jul 2007
      Location
      nw phx
      Posts
      134
      every hydro ive owned or installed does the bucking youre describing when forcefully jammin on the brakes.
      even my stock unmolested truck and tahoe.

      i was going to suggest your pushrod is not adjusted correctly, but seems you have figure that out already.

      also as stated, try a PS reducer inline to change the feed pressures.
      ...life is too short, live for today, tomorrow isn't guaranteed

    7. #7
      Join Date
      Dec 2018
      Posts
      19
      X2 on the kick back being normal. I've felt it also on every hydroboost brake system I've driven, stock or not.

    8. #8
      Join Date
      Oct 2004
      Posts
      2,408
      Country Flag: United States
      Gosh, you guys are making me rethink my plant to upgrade to hydroboost.
      Red Forman: "The Mustang's front end is problematic; get yourself a Firebird."

    9. #9
      Join Date
      Mar 2015
      Posts
      73
      Country Flag: United States
      Please follow up on this thread. I have power brakes and currently not happy due to lack of pedal feel/response. Not sure how I want to move forward.

    10. #10
      Join Date
      Dec 2018
      Posts
      19
      Quote Originally Posted by 68Formula View Post
      Gosh, you guys are making me rethink my plant to upgrade to hydroboost.
      The kick back isn't bad, it's only really felt if you're stomping it like a kid ran out in front of you, or when you bleed the brakes, normal braking it isn't felt if that's what worries you. I've had 3 vehicles with it over the years personally, and driven thousands more as a mechanic.

    11. #11
      Join Date
      Jun 2013
      Location
      San Diego
      Posts
      271
      Country Flag: United States
      Just wanted to follow up. I have about 200 shake down miles on the car. With the rod moved to the upper hole the car is very nice. Great pedal feel and ability to moderate the brakes.
      Brian

      1972 C10 - 454/TH400 - Short bed conversion - https://www.pro-touring.com/threads/...1972-C10-SoCal
      1970 Nova - LS Swap - https://www.pro-touring.com/threads/...Cal?highlight=



    12. #12
      Join Date
      Oct 2004
      Posts
      2,408
      Country Flag: United States
      Quote Originally Posted by bs46488 View Post
      Just wanted to follow up. I have about 200 shake down miles on the car. With the rod moved to the upper hole the car is very nice. Great pedal feel and ability to moderate the brakes.
      That's great news. Thanks for giving us the feedback. May be helpful for others (like myself ) in the future.
      Red Forman: "The Mustang's front end is problematic; get yourself a Firebird."

    13. #13
      Join Date
      Jul 2008
      Location
      Summerfield, NC
      Posts
      202
      Country Flag: United States
      Just want to add, if you plan on driving your car hard you need to add a cooler to one of the return lines to keep the fluid cool. Mine got hot and started puking fluid when running tail of the dragon in TN then just boiled over this past Sunday running hot laps on a great setup at Caraway Speedway. All the factory GM setups I've seen have coolers on them, I didn't install one due to time and effort, but now it's biting me in the ass. I am running cheap, off the shelf Napa power steering fluid. One guy at the track with a ZR1 came over to console me and said to run Honda CRF ps fluid or something of that nature, said it had a boiling point I'd never see. I can't remember the exact letters he used, SRF?
      *Jeff*
      Project Salty - 1964 4 door Malibu, beaten, neglected, red headed foster child
      Cammed LQ4 / T56 Swap Project Thread <-click to read! 😁

    14. #14
      Join Date
      Dec 2002
      Location
      MusicCity
      Posts
      464

      Hydroboost system tweaks and mods

      Yep - changing your pedal rod connection higher up the pedal was the right move, as these brake units come onto response very quickly. That is why you will see the brake pedal rod connection approximately one inch higher up on most factory pedals if you had a vacuum pedal next to a hydro pedal. Depending upon how you have the unit mounted, you may have also had some pedal rod angularity that was inducing some binding during brake apply if the rod was too far off center. The "bump" feeling in the braking is typically a hydraulic reverberation:

      https://www.pro-touring.com/threads/...droboost-Issue

      The bump feeling under heavier than normal brake apply can also be the over pressure relief regulator inside of the brake unit blowing off over pressure (which prevents excessive internal hydraulic pressure build up inside of the brake unit). You should never feel this during normal to heavy stops - only a very heavy apply of the brakes should kick in the overpressure relief system (which dumps excess pressures out into the brake unit's low pressure return line port).

      As far as fluid boiling over? It may not always actually be a thermal issue, instead being that it is foaming over. PS fluids have a very high boiling temp, just like engine oil, so it would take extreme temps to really have it boil. We have always had excellent success with the Redline, Royal Purple, and the Lubegard synthetic fluids. Take a quart of PS fluid and put it in a blender and hit puree. This is what extended high RPM blasts can do to PS fluid, causing it to foam up and puke out. Cheap fluids will foam faster, run noisier, as they do not have the extreme pressure anti foaming additives. GM race teams had a problem with the C4 Corvettes doing this under racing conditions. What was the GM million dollar engineering fix? Reducing the PS pump flow to reduce high RPM fluid turbulence. How can you do that in your car?

      https://www.purechoicemotorsports.co...rod/prd412.htm

      KRC pumps have it good - real good, in that they have almost infinitely adjustable flow rates:

      https://www.krcpower.com/ecommerce/p...c-25312000.asp

      This is also a good read on the topic:

      https://www.pro-touring.com/threads/...droboost-setup

      If you have a thermal temp gun and do actually find your PS system temperatures are getting higher than ambient engine compartment temperatures, then pick out a small transmission cooler that has the size and shape you could fit best and mount it in front of the radiator where it can get a good amount of steady airflow across it. It is imperative that you plumb the low pressure return out of the steering gear directly into the cooler FIRST, then head back to the PS pump with the return line IF you are running a T fitting low pressure return line arrangement from the hydroboost. If you have the T fitting installed into the line going into the cooler, some slight restriction in the cooler may be possible to cause back pressure issues on the brake assist unit's low pressure return line (which you do not want). You see how I emphasized the use of a trans cooler? This is because we have found most all listed power steering coolers to be restrictive, causing more harm than good due to the back pressure. A tranny cooler flows like Niagara Falls reducing chances of back pressure and also has a higher BTU rejection rate (higher fin counts). Interestingly, if you were to look at an '80's IROC Z28, you would find that GM did a "loop cooler" on these - simply a 5/16" steel line that looped from one end of the bottom of the core support to the other, just enough to make a cheap PS cooler effect...

      There IS a difference - Thank you for choosing Hydratech!

      Paul M. Clark
      Founder / Master Engineer

      Hydratech Braking Systems ®
      www.hydratechbraking.com

    15. #15
      Join Date
      Jul 2008
      Location
      Summerfield, NC
      Posts
      202
      Country Flag: United States
      Quote Originally Posted by Hydratech View Post
      Yep - changing your pedal rod connection higher up the pedal was the right move, as these brake units come onto response very quickly. That is why you will see the brake pedal rod connection approximately one inch higher up on most factory pedals if you had a vacuum pedal next to a hydro pedal. Depending upon how you have the unit mounted, you may have also had some pedal rod angularity that was inducing some binding during brake apply if the rod was too far off center. The "bump" feeling in the braking is typically a hydraulic reverberation:

      https://www.pro-touring.com/threads/...droboost-Issue

      The bump feeling under heavier than normal brake apply can also be the over pressure relief regulator inside of the brake unit blowing off over pressure (which prevents excessive internal hydraulic pressure build up inside of the brake unit). You should never feel this during normal to heavy stops - only a very heavy apply of the brakes should kick in the overpressure relief system (which dumps excess pressures out into the brake unit's low pressure return line port).

      As far as fluid boiling over? It may not always actually be a thermal issue, instead being that it is foaming over. PS fluids have a very high boiling temp, just like engine oil, so it would take extreme temps to really have it boil. We have always had excellent success with the Redline, Royal Purple, and the Lubegard synthetic fluids. Take a quart of PS fluid and put it in a blender and hit puree. This is what extended high RPM blasts can do to PS fluid, causing it to foam up and puke out. Cheap fluids will foam faster, run noisier, as they do not have the extreme pressure anti foaming additives. GM race teams had a problem with the C4 Corvettes doing this under racing conditions. What was the GM million dollar engineering fix? Reducing the PS pump flow to reduce high RPM fluid turbulence. How can you do that in your car?

      https://www.purechoicemotorsports.co...rod/prd412.htm

      KRC pumps have it good - real good, in that they have almost infinitely adjustable flow rates:

      https://www.krcpower.com/ecommerce/p...c-25312000.asp

      This is also a good read on the topic:

      https://www.pro-touring.com/threads/...droboost-setup

      If you have a thermal temp gun and do actually find your PS system temperatures are getting higher than ambient engine compartment temperatures, then pick out a small transmission cooler that has the size and shape you could fit best and mount it in front of the radiator where it can get a good amount of steady airflow across it. It is imperative that you plumb the low pressure return out of the steering gear directly into the cooler FIRST, then head back to the PS pump with the return line IF you are running a T fitting low pressure return line arrangement from the hydroboost. If you have the T fitting installed into the line going into the cooler, some slight restriction in the cooler may be possible to cause back pressure issues on the brake assist unit's low pressure return line (which you do not want). You see how I emphasized the use of a trans cooler? This is because we have found most all listed power steering coolers to be restrictive, causing more harm than good due to the back pressure. A tranny cooler flows like Niagara Falls reducing chances of back pressure and also has a higher BTU rejection rate (higher fin counts). Interestingly, if you were to look at an '80's IROC Z28, you would find that GM did a "loop cooler" on these - simply a 5/16" steel line that looped from one end of the bottom of the core support to the other, just enough to make a cheap PS cooler effect...

      Thank you very much for the info! Just purchased ps return hose to plumb in a cooler and will switch fluids then. I'm running a stock GM hydroboost ps pump w/ return fitting on reservoir. My pump was making noise during high rpm passes so it must have been the fluid foaming which then led to pump heating up. Mine got so hot during the track day you couldn't touch the pump, once it got to where you could lay your hand on it for a few seconds I added fluid back to the system. I am running to 6400 rpm which I know that system wasn't designed for.
      *Jeff*
      Project Salty - 1964 4 door Malibu, beaten, neglected, red headed foster child
      Cammed LQ4 / T56 Swap Project Thread <-click to read! 😁

    16. #16
      Join Date
      Dec 2002
      Location
      MusicCity
      Posts
      464

      Factory hydroboost pumps

      Note that most factory hydroboost spec pumps "out there" are truck model pumps, unless you specifically ordered in a passenger car spec pump from say an early '80's GM diesel car (though usually only can find low end remans, as the days of new old stock on these are gone). The truck spec pumps flow a LOT - typically around 3.5 to 3.7 GPM, while the passenger car spec pumps flowed in the area of 2.5 - 2.7 GPM - MUCH less. That high flow is great for short slalom racing where you want the fastest possible steering response, but highly destructive for extended high RPM blasts on a road course. Swapping out the PS pump output fitting to one with a smaller central jet / orifice size will bring the flow rates down, cooling the system down considerably. Adding a cooler is always a good idea, as short of freezing temperatures, PS systems prefer to run on the cooler side. Too cold, and you won't burn off any moisture in the PS fluid, and it can take MUCH longer to degass the fluid (air in suspension in the fluid). Short of using an A/C condenser (!) as a PS cooler, you will always count on everything under hood to run at a similar ambient temp, so the PS system will always come up to basic temp. Steering gears solidly bolted to the frame actually reject some heat throughout that area of the frame, providing a measure of some inherent cooling - not much, but measurable. Rack conversions can actually lower PS system temps a bit more, as the racks are typically in a good air stream, made of aluminum which conducts heat well, and have a pretty good sized overall surface area to radiate heat (providing some cooling effect). The auxiliary cooler is a way of also adding fluid capacity to a PS system, which is always a bonus. What a lot don't realize is that the cooler is pretty much along for the ride when just rolling down the road. BUT, as soon as system temps start climbing in a road race scenario for instance, system temps start rising quickly. This starts "passively activating the cooler", as the higher the temps climb, the more heat the cooler starts transferring. If the ambient air temps are 90 degrees or so, and the PS system is at a general under hood temp of say 180, the cooler will be actively radiating heat off in the airflow. The hotter the system gets, the more heat the cooler will radiate as the temperature differential increases. 90 degree day, 180 system temps, basic heat radiates. The same 90 degree day with a PS system temp approaching 200 degrees, the temp differential increases where the cooler then starts radiating a larger amount of heat. It's an interesting fact that these cooling dynamics exist. Again, reduce your pump flow and go for a trans cooler - not a PS cooler...

      I don't want to open a can of worms with this statement (I can hear it already), but I have "modulated" the viscosities of PS fluids in some road race cases over the years by spiking them with a bit of synthetic gear oil. Why? If you have an inherently hot running road race car that doesn't have adequate PS system cooling, the PS fluid starts getting thinner and thinner and thinner as the temps climb - almost water thin when super hot, next step leading to a system foam out. Spiking the system with 4 to 8 ounces +/- of the synthetic gear oil provides extreme pressure additives, more viscosity, and a large dose of anti-foaming agents. I do not recommend this for basic street / strip use, reserving this trick only for cases that are acting up at the track. After the road race is completed, we advise the system be drained, an appropriately sized cooler (typically 8" X 4" thereabouts) be installed, with a good clean fill of a quality aftermarket synthetic PS fluid. This is just a quick emergency band aid for a temperamental road race PS system to get it through to the finish line.

      6400 RPM isn't that high. Factory SVT Cobra 32 valve Mustangs had hydroboost, winding WAY higher than that out on the road courses. What you may have to look at besides everything I mentioned above is your pulley ratio. A general street / strip car would for instance have an average of a 8" crank pulley to a 6" PS pump pulley - an overdriven PS pump speed to provide proper parking lot performance. Dedicated road race cars will run a smaller under drive crank pulley to keep alternators from exploding, water pumps out of cavitation, and PS pump over speed. The NASCAR teams are now running power steering to reduce driver fatigue, but their pulley ratios are specifically set up for the sustained extremely high RPM's - small crank pulley compared to a large PS pump pulley (also much smaller cam ring profiles inside of the PS pumps producing much less CC's per revolution) - not much assist while in the pits. You may want to look into what may be available to downsize your crank pulley. Do please keep in mind that this could cause some negative side effects at idle speeds less than a 1000 - 1200 RPM though - it's a trade off of low speed operations for high speed stability, so don't make a huge change in crank pulley size - 1" smaller can make all the difference (or optionally go the other way with a larger PS pump pulley if possible). I recall when I grenaded an external alternator fan blade at 7800 RPM - it shot shrapnel right through the hood, wheel well, and right out the fender! All of the other pulley speeds were ok, so the installation of a larger alternator pulley solved that, but at the expense of idle speed charging output...

      There IS a difference - Thank you for choosing Hydratech!

      Paul M. Clark
      Founder / Master Engineer

      Hydratech Braking Systems ®
      www.hydratechbraking.com

    17. #17
      Join Date
      Dec 2002
      Location
      MusicCity
      Posts
      464

      One more thing...

      We have been running into quite a few people that have had their twin low pressure return line nipple pumps plumbed incorrectly, which can definitely lead to foaming. Make sure that the lowest nipple / entry point into the reservoir is where you have the return from the steering gear connected to. Getting this backwards can cause headaches. Sometimes we even have a hard time getting the point across, asking the customer to send over some pictures of how the system is plumbed. If you post up a pic or three, I can tell you if you have it right or wrong. Basically, the placement of the second return line nipple is irrelevant to overall pump operations, as you are only exhausting the pressure built up in the brake unit casting every time you let off of the brakes - just a tablespoon or two of fluid, depending upon how hard you apply the brakes. Now the other low pressure return from the steering gear? That's always flowing at a rather high rate, so it is important to get that one right. If you aren't sure, look at some pump images online, seeing where standard non hydroboost low pressure return lines enter the reservoir. This will give you a visual as to which point on your housing is the return nipple for the steering gear. Again, the second auxiliary low pressure nipple placement varies from housing to housing - could be in a lot of different places, but since it is an add on, you should be able to see where the primary return line nipple is. Sometimes if a customer doesn't want to get into all of the discussions, we will simply suggest to test swap the low pressure return lines if a problem seems to exist. If the problem clears up, then it's fixed! If it gets angrier instead, then swap it back...

      There IS a difference - Thank you for choosing Hydratech!

      Paul M. Clark
      Founder / Master Engineer

      Hydratech Braking Systems ®
      www.hydratechbraking.com

    18. #18
      Join Date
      Sep 2010
      Location
      Beach Park IL
      Posts
      2,514
      Country Flag: United States
      Make sure that the lowest nipple / entry point into the reservoir is where you have the return from the steering gear connected to.
      That's a solid piece of information. Thanks! Fighting with an install right now that was done at another shop with a Concept One reservoir and this may be the fix.

      Donny

      Support your local hot rod shop!