HOW TO DO AN ADVANCED SEARCH.

Mon Jul 08, 2013 3:56 pm by Admin


For the benefit of 944Hybrids users there are two search functions available for you to use.
The purpose of this sticky is to explain the "Advanced Search" function because it is much more powerful and is the best choice when researching information.

When you log on to the site a list of options is shown in a line at the top of the page. One option is labelled "Search", use this option (NOT the search box lower down on the right).

After you click on the upper search option, a drop down box appears. At the bottom of this box is a radio button marked "Advanced …

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Hydroboost problem

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Hydroboost problem

Post  JohnG on Sat Mar 18, 2017 3:31 pm

Just completed the install. Turn One PS pump "sized" for HB and Porsche PS rack, Porsche MC with TPC adapter. Return from HB tee'd in just below the PS pump reservoir. All pretty much the "standard" installation. Drove the car some with the Turn One pump before doing the HB install, and steering seemed normal.

After completing the install and filling and bleeding the hydraulic and brake systems, upon starting the car, the brake pedal is pulled to the floor by the HB; brakes on hard. Turning the steering wheel with the car parked in the shop seems to show that the power steering is working normally.

Some online searches found that this seems to be a fairly common problem, and one of the searches turned up a thread that chased it down, with the conclusion that it was due to flow and pressure from the PS rack return to the pump putting enough pressure into the return line from the HB to move the spool valve and apply the brakes.

I pulled the return line off of the reservoir to check for obstructions, but found that it was clear. I have seen some posts that said they solved this problem by moving the tee from a more remote place to just below the reservoir to minimize the pressure buildup in the HB return line, but I already have this configuration. I also learned that some factory HB systems have two return fittings on the pump reservoir, but they use a different pump/reservoir combo than that used by Turn One.

I am wondering if the Turn One pump is actually developing too much volume and/or pressure, and this is why there is too much pressure in the HB return line. If I don't come up with something else this weekend, I will call Turn One on Monday.

So, have any of you had a similar experience? If so, what was your solution? Any ideas or suggestions?

Thanks, John

JohnG

Posts : 7
Join date : 2016-06-20

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Re: Hydroboost problem

Post  sharkey on Sat Mar 18, 2017 4:06 pm

i cant offer much help, but a test you could do would be to remove the tee and just stick one of the return lines into the top of the resevoir. this would tell you if the T in the return line is causing your issue. if that fixes the issue you could always add a second return fitting using a bulkhead barb fitting

sharkey

Posts : 343
Join date : 2014-11-21

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Re: Hydroboost problem

Post  JohnG on Sun Mar 19, 2017 6:41 pm

Good suggestion from Sharkey. Unfortunately, the result was the same with the HB return routed in the top of the pump reservoir, so my theory didn't pan out.

Next step is to remove the brake MC and see if the HB still acts the same. Assuming that it does, the next thing that I can think of is to replace the HB.

Any other ideas?

Thanks, John

JohnG

Posts : 7
Join date : 2016-06-20

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Re: Hydroboost problem

Post  sharkey on Sun Mar 19, 2017 8:56 pm

are you 100% sure your lines are hooked up correctly? having the high pressure in and out lines in the wrong place could cause issues.

sharkey

Posts : 343
Join date : 2014-11-21

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Re: Hydroboost problem

Post  JohnG on Mon Mar 20, 2017 12:01 pm

I wish that it was just plumbing, but what I did matches the diagrams on this and other sites.

I removed the MC to see if behavior was the same. It was, to an extreme. The hydraulic pressure shoved the power piston out the front of the HB and left a pool of fluid on the floor under the car. Next step is a new HB.

JohnG

Posts : 7
Join date : 2016-06-20

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Re: Hydroboost problem

Post  JohnG on Fri Mar 24, 2017 1:58 pm

Just to finish off this thread, I installed a Cardone rebuilt HB from Rock Auto, and that fixed the problem. The problem was the salvage yard HB that I started out with.

JohnG

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