Weird Hydroboost Issue

So I installed a hydroboost setup about two years ago and everything had been working great. Out of the blue however, when applying the brakes I can feel a slight "bump" or call it a feedback in the steering wheel when turning either direction. Its much more noticeable at slower speeds.

Setup is with the proper pressured Saginaw pump/res and boost return is going directly into the res. System started life with a filter on the gearbox return line, fluid is royal purple, and everything looks clean with no air in the system.

I've flushed twice and performed the boost and steering system bleeding procedure multiple times with no change.

It all works fine except for that slight bump/feedback in the wheel when steering and braking at the same time and wonder if anyone has experienced this.

Thanks.

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Originally Posted by Kraftwork69

So I installed a hydroboost setup about two years ago and everything had been working great. Out of the blue however, when applying the brakes I can feel a slight "bump" or call it a feedback in the steering wheel when turning either direction. Its much more noticeable at slower speeds.

Setup is with the proper pressured Saginaw pump/res and boost return is going directly into the res. System started life with a filter on the gearbox return line, fluid is royal purple, and everything looks clean with no air in the system.

I've flushed twice and performed the boost and steering system bleeding procedure multiple times with no change.

It all works fine except for that slight bump/feedback in the wheel when steering and braking at the same time and wonder if anyone has experienced this.

Thanks.

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Might be worth bypassing the hydroboost and driving it on manual brakes to isolate the issue with the hydroboost unit itself?

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Originally Posted by rlovell383

Might be worth bypassing the hydroboost and driving it on manual brakes to isolate the issue with the hydroboost unit itself?

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Makes sense and since those lines would be removed and ports capped, gives me the chance to blow out those lines. Been wondering about blockage. I did find some other info online. Looks like a worn spool and/or piston could be letting pump pressure bleed by into the steering gear. But, it would have other issues as well which I'm not seeing.

At any rate, does sound internal to the booster. After that isolation check, probably time to take that thing apart and have a look.

Thanks.

This "bump" you are feeling can be a hydraulic reverberation simply caused by some remaining air still trapped in the system. With the engine off, step on the brake firmly a few times to discharge any pressurized fluid stored up in the accumulator cylinder - there may be air trapped in there. After that, fire the engine and let it idle for a few minutes, then run the steering from lock to lock a few times which will repressurize the accumulator (controlled by a one way pressure check valve design). Then road test the vehicle while keeping your RPM's down. Any air still trapped in the PS system will be pulverized into suspension in the fluid just as if you put it into a blender and hit puree if you rev the engine up, so give it time to burp all possible air out under low RPM cruising. Some cases require up to 500 miles of road use to clear all of the air out. Note that it is best if you ran some short trips to get everything hot, then let everything cool. Do that a few times to thermally cycle the PS system and it should help. If it is still misbehaving, pour this snake oil in:

https://www.lubegard.com/products/psf-protectant/

One last thing this "bump" can be is that the PS pump is not putting out proper volumes at low idle speeds. Let's not "go there" until you have done the easy stuff above first.

:drive1:

Quote:

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Originally Posted by Hydratech®

This "bump" you are feeling can be a hydraulic reverberation simply caused by some remaining air still trapped in the system. With the engine off, step on the brake firmly a few times to discharge any pressurized fluid stored up in the accumulator cylinder - there may be air trapped in there. After that, fire the engine and let it idle for a few minutes, then run the steering from lock to lock a few times which will repressurize the accumulator (controlled by a one way pressure check valve design). Then road test the vehicle while keeping your RPM's down. Any air still trapped in the PS system will be pulverized into suspension in the fluid just as if you put it into a blender and hit puree if you rev the engine up, so give it time to burp all possible air out under low RPM cruising. Some cases require up to 500 miles of road use to clear all of the air out. Note that it is best if you ran some short trips to get everything hot, then let everything cool. Do that a few times to thermally cycle the PS system and it should help. If it is still misbehaving, pour this snake oil in:

https://www.lubegard.com/products/psf-protectant/

One last thing this "bump" can be is that the PS pump is not putting out proper volumes at low idle speeds. Let's not "go there" until you have done the easy stuff above first.

:drive1:

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Finally getting around to addressing this still present issue. Was working on a fuel delivery problem but now ready to sort this out.

Thanks for the help and will try this shortly and report back.

Cheers!

Quote:

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Originally Posted by Hydratech®

This "bump" you are feeling can be a hydraulic reverberation simply caused by some remaining air still trapped in the system. With the engine off, step on the brake firmly a few times to discharge any pressurized fluid stored up in the accumulator cylinder - there may be air trapped in there. After that, fire the engine and let it idle for a few minutes, then run the steering from lock to lock a few times which will repressurize the accumulator (controlled by a one way pressure check valve design). Then road test the vehicle while keeping your RPM's down. Any air still trapped in the PS system will be pulverized into suspension in the fluid just as if you put it into a blender and hit puree if you rev the engine up, so give it time to burp all possible air out under low RPM cruising. Some cases require up to 500 miles of road use to clear all of the air out. Note that it is best if you ran some short trips to get everything hot, then let everything cool. Do that a few times to thermally cycle the PS system and it should help. If it is still misbehaving, pour this snake oil in:

https://www.lubegard.com/products/psf-protectant/

One last thing this "bump" can be is that the PS pump is not putting out proper volumes at low idle speeds. Let's not "go there" until you have done the easy stuff above first.

:drive1:

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Well, guess we may have to go "there". :0) Repeated your recommended procedure a few times with some slow speed driving. Don't think I've hit 500 miles as yet but no change so far. The steering gear, pump, and hydroboost are all fairly new but that doesn't say much these days I guess (not your gear BTW but wish it was). I haven't tried the snake oil so once I find some I'll give it a try and then it may be a new pump after that(?).

Thanks again for the help and MTF........

Just to close this one up and after reading a bunch on the subject, flow was ultimately the problem. I disassembled the pump, removed the flow valve, and opened the 1/8" orffice to 9/64". The pressure valve already had no shims installed. No more noticeable feedback into the steering. Also, the hydroboost return going back to the resivoir was not completely submerged in fluid. Read that this can cause the system to pull in air so modified the return.

Bottom line: All good now and learned a bunch reading through your old posts. Thanks!

Yay! Fixed it fixed it fixed it - good deal :cheers:

Thank you for following up with what ultimately fixed it, as so many of these threads never get summarized to completion.