Hydraboost backfeeding master

[aray327]

I have been running my hydraboost for a while with no issue. I recently went through a PS pump and replaced it. I was advised to install a cooler to keep the PS fluid temp down and preserve the new PS pump. After installing the cooler the brakes will immediately look up upon firing the car up!

It appears that the added line between the T connection on the return side from the steering box and hydraboost going to the cooler and back to the PS reservoir causes the pressure to back feed to the hydraboost. It looks like the pressure is taking the shortest route and backfeeding the hdraboost. The return lines are T'd together near the steering box.

I am thinking of using longer return lines from both the steering box and the hydraboost and making the T or Y connection much closer to the cooler. My cooler is mounted in front of the core support on the passenger side (only place available). The T is near the steering box, originally connected to the reservoir with approx. 6" line. The new cooler lines are approx 3 ft each; adding an extra 6ft of return line.



Does anyone think i will experience the same issue?

[Hydratech®]

There must be quite a bit of restriction in that PS cooler you just installed to cause that much backpressure in the low pressure return circuits. Your replacement PS pump may also be flowing WAY too much, which will aggravate the scenario even further. That much resistance to flow in the cooler will actually build more heat in the PS system than it will be able to remove, doing more harm than good (due to high pressures in the low pressure return line circuits - ideally should be a MAX of 1-2 PSI). 5-6 PSI or more will cause the brakes to start self applying due to back pressure on the hydraulic brake assist unit's low pressure return port.

https://www.pro-touring.com/showthre...boost-on-track

https://www.pro-touring.com/showthre...ht=#post875181

http://www.lateral-g.net/forums/showthread.php4?t=36999

The links above hold the key to your success - read them through thoroughly.

[aray327]

Thanks Paul for the information. As suggested I did some 'homework' last night, starting with reading your post and the references. After reading I ran out to the garage for some measuring and additional checking of my configuration. I found the T runs straight through from the steering box return straight through to the PS pump return. The HB return connects to the branched end. That makes sense since it worked fine before adding the cooler.

I then checked the output on the pressure side of the pump and the orifice measures 9/64. Based on your reading material, that should be approximately 2.4 GPM flow. I think you suggested that is within the acceptable range? If not let me know.

I measured my 6 AN hoses. I found my hose (which came premade with ends) to be nylon with an interior hose dimension of 0.30. I found the rubber 6AN hose to have a slightly larger interior dimension of 0.34.

I measured my 6AN fittings and found the premade fitting has an interior dimension of ¼, while the non-premade fitting had an interior dimension of 13/64.

I wasn’t able to measure the interior dimension of the cooler fitting, but it’s a 6AN cooler approximately 5x11 in overall dimension. Don’t recall how many passes.

Also, my AN fittings are 90 degree ends. If I have to change out the premade end I will go with a 120 degree end for better fit.

I like the idea of plumbing the HB return straight to the PS reservoir and will look into it. But that alone won’t resolve the restriction issue.

Do you think the 90 degree ends impact the flow? Do you think the interior hose dimension, especially the 0.30 one, is too restrictive? Do you think the 9/64 high pressure orifice flows too much? Any other suggestions?

[Hydratech®]

It is not the ID of the lines or hose end angles causing the issues. If you want to prove this out, simply place the T fitting AFTER the cooler you have installed (as you currently have it installed before the cooler). If I had the choice or various different pump output fittings sitting on the bench (which I do), I would run the .125 orifice first, then road test and evaluate to verify that it provided enough flow for everything I asked of the braking and steering. If so, then I would leave it be. Do you still have your original pump? If it is of the same design, you may want to check it for orifice size and possibly swap it out with the one that is currently installed in your replacement pump (if the orifice is indeed smaller).

Excessive flow builds excessive heat...

[aray327]

I do still have the original pump. I replaced the pump with the same OE pump. I actually took the measurement of the output fitting from the original pump, and assumed they would be the same.

I will try the T after the cooler and run the steering box retun to the cooler first, then from the cooler to a T, then back to the reservoir.

This would mean the HB return doesn't get cooled. I assume since there isn't much coming through that return (as I understand from the reference reading) that it shouldn't matter if its cooled or not. I'm good with that theory.

So if i understand you, you are suggesting the pump is running too much volume causing the backbressure? But it works fine without the cooler. Or you are suggesting the cooler is restrictive. Or a combination. I will try to also gage the flow/restrictivness of the cooler.

Thanks again for your input.

[Hydratech®]

The replacement pumps we have seen over the years can have totally different orifice sizes - you may find it to be the same as the old pump. IF you find the replacement pump does have a larger orifice than the original, I suggest you swap out the pump output fitting to run the smaller orifice. The pump may be flowing more than needed AND / OR the cooler is too restrictive. It befuddles me how many coolers we have run across that do not flow freely despite their outward appearance.

[67 455 Bird ragtop]

I'm switching to a hydro system on my 67 Bird and switched to a 76 Eldo pump. Designed to run hydro and has two returns. May help someone else down the road.

[aray327]

I've got to get this cooler sorted!

Update, I plumbed the return after the cooler and it seemed like it was going to work. Got everything together and took the car for a drive. The brakes would hold for a second after releasing the peddle. I tried various situations to confirm i wasn't going crazy, on a hill, holding the brake firmly, lightly, etc. Each time and especially if i held firmly, there was a delay in the final release of the brakes while running the cooler.

I disconnected the cooler and ran it without. They worked as they have except the fluid got super hot in 80+ weather that i could hear the unit make noise and steering effort increased at low RPM. Fortunately i allowed things to cool and they were fine again.

So I am not rulling out that the cooler doesn't flow sufficiently. But I checked the flow runing through the cooler and it seemed to flow adequately. Do you think that the extra length of hose introduced with adding the cooler adds additional pressure (similar to line loss for excessive length runs)? The extra line is about 3+ft in each direction. All 6 AN. I may connect the cooler lines together at the cooler to see how that reacts?

If i change the cooler (which i am considering) do you have a suggested brand? Or ones to avoid?

[Hydratech®]

Hi Aaron - it sounds like you are 'tickling' it in the right spot. Did you ever get a chance to check your original pump's orifice sizing? Is it 9/64th's or smaller? Excessive flow leads to excessive temperatures and induces back pressure issues where there normally wouldn't be any, so I'd like to focus on your flow rates before all else. For instance, if you are currently running a pump output fitting with a .170" or larger sizing, and were to swap in a different fitting with a .125 to .140" orifice sizing = can make all the difference in the world with operating temps and back pressure issues.

OR?

Order in this AN-6 bulkhead adapter, graft it in just about anywhere you like in the PS pump housing, and this will then allow for a dedicated low pressure return nipple into your PS pump housing to completely eliminate any type of back pressure issues in the brake assist unit's low pressure return line (which induces the delayed brake release issues you are experiencing):

http://www.summitracing.com/parts/RUS-670850/



http://www.lateral-g.net/forums/showthread.php4?t=15052

Most typical transmission coolers vastly outflow power steering coolers, therefore most typical 3/8" inlet / outlet transcoolers flow well enough to not induce backpressures. We have run the PSC Motorsports coolers with great success:

http://www.pscmotorsports.com/catalo...teering+cooler

If you can blow through it without a considerable restriction being observed, you should be fine. The line lengths do not induce any particular restrictions - we have thousands of street rod customers with underfloor mounted brake assist systems with over 6' line lengths to and from the brake assist units without issue.

The RedLine and Royal Purple upscale synthetic PS fluids also do much better at temp then many other fluids do. RedLine lists "50% greater high temperature viscosity" on there version, and it really does make a difference.

[aray327]

I want to thank you Paul for your advice and expertise.

I checked the orifice of both the old and new pump and they are both 9/64.

I will add the bulkhead fitting and eliminate the T. That will even look nicer!

I didn't see much resistance in the cooler line so I will start with re-routing the return direct to the reservoir and plumb the cooler from the steering box back to the reservoir. I am also going to change fluid to the Royal Purple.

With the orifice at 9/64 (0.140) now, and since you mentioned flow rate OR direct return line, do you think changing the output to 0.125 is worth the effort? If so it’s going on my parts list as well.

[Hydratech®]

We try to run the lowest pump flow rates needed to cover the demands of use as a tuning step - too little is not enough, and too much creates heat. I suggest you mod for the independent low pressure return line connection to your PS pump housing as the primary step. If all is well, leave it be as the 9/64 (.140 thou) orifice is generally on target. The installation of the .125 orifice in place of the .140 would be a fine tuning mod that you could eventually pursue, but not enough of a concern to trouble with right now.

[aray327]

Thanks, again Paul!