Hydroboost issues....to sensitive

[Hotwire]

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.