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
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
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 : 8
Join date : 2016-06-20
Re: Hydroboost problem
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 : 714
Join date : 2014-11-21
Age : 39
Location : Abbotsford BC
Re: Hydroboost problem
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
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 : 8
Join date : 2016-06-20
Re: Hydroboost problem
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 : 714
Join date : 2014-11-21
Age : 39
Location : Abbotsford BC
Re: Hydroboost problem
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.
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 : 8
Join date : 2016-06-20
Re: Hydroboost problem
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- Posts : 8
Join date : 2016-06-20
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