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Old 01-16-2012, 09:30 AM
ianacole ianacole is offline
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Default Power Steering Issue Diagnosis Help

So, I could use some guidance here. I pulled in to the gas station to fill up on Thursday, and fluid was leaking from every vent and seam on the hood of my '73 40 (Chevy powered). Quick review indicated that the power steering pump had hemoraged on the fan, spraying fluid everywhere. With the amount of build up and gunk around the PS pump I figured it had just given up and needed replacing.

Odd, though, it never got difficult to steer.

So, picked up a new pump for $45, and a new cap as well, replaced this weekend. Went driving, and the same issue. I took a close look, and near as I can tell is that the fluid came from the cap area. This to me would indicate a pressure build up in the pump, causing the springed cap to open up to release the pressure. And this is where I get confused. In order for pressure to build up in the pump, wouldn't there need to be a blockage in the system somewhere? And if there were a blockage somewhere, wouldn't it become difficult to steer? Are my next steps to replace the lines and then rebuild/replace the steering box?

Thanks for any suggestions!

Ian
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Old 01-16-2012, 10:10 AM
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There should be a high pressure bypass valve in the steering gear. That way when you are turning the wheel hard against the stops you don't blow anything up. Its supposed to let the excess pressure bypass and return to the pump. Sounds like that valve may be stuck closed or only partially open. Thats why you are still getting pressure to the steering assist but excess pressure is building in the pump. Does your rig have the Saginaw PS conversion since it's a chevy V8 now? Those steering boxes are very inexpensive and fairly easy to replace. If you have a Toyota FJ40 power steering gear they are difficult to find. You might have to do a mini truck steering gear conversion. If you already have the mini truck gear they are easy to find.
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Old 01-16-2012, 10:55 AM
ianacole ianacole is offline
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Thanks Randy. I believe it is the Saginaw conversion, but I haven't determine via part number that that is indeed the case. Would a replacement of the whole box, or would a rebuild be better?
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Old 01-16-2012, 11:34 AM
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Quote:
Originally Posted by Air Randy View Post
There should be a high pressure bypass valve in the steering gear. That way when you are turning the wheel hard against the stops you don't blow anything up. Its supposed to let the excess pressure bypass and return to the pump. Sounds like that valve may be stuck closed or only partially open. Thats why you are still getting pressure to the steering assist but excess pressure is building in the pump. Does your rig have the Saginaw PS conversion since it's a chevy V8 now? Those steering boxes are very inexpensive and fairly easy to replace. If you have a Toyota FJ40 power steering gear they are difficult to find. You might have to do a mini truck steering gear conversion. If you already have the mini truck gear they are easy to find.
Hmmmm....Never seen a bypass valve in the gear before. Bypass valves are usually (for sure on a Saginaw pump) on the pump at the head of the high pressure hose. What you are describing does not sound like bypass valve failure but rather air in the fluid. Common characteristic of a sticking or malfunctioning bypass valve is steering assist in one way and not the other. (IE able to turn easily to the left but difficulty or intermittent difficulty to the right) Are you using power steering fluid or ATF? PS fluid is designed to not support air bubbles to stay trapped in suspension. ATF can and will allow foam to stay in suspension because Auto trannys have flat filters in the pan designed to strip the foam from the fluid while PS systems do not. If you have any water or other contaminants in the system it will also foam. (this includes a mix of synthetic and dino based fluids) I suggest a system flush with fresh PS fluid.

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Old 01-16-2012, 11:57 AM
ianacole ianacole is offline
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Thanks Kevin. Now that you mention it, I think the original fluid was ATF, as it was pink in color, and the PS fluid I put in was clear. I thought the PO used Royal Purple PS fluid, giving it the color, so I didn't think much of it. I didn't think about doing a full flush, but saw that mentioned in a search here for similar issues. I will run through that tonight.

Is using ATF in power steering a common practice? Are there benefits?
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Old 01-16-2012, 12:16 PM
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Quote:
Originally Posted by ianacole View Post
Thanks Kevin. Now that you mention it, I think the original fluid was ATF, as it was pink in color, and the PS fluid I put in was clear. I thought the PO used Royal Purple PS fluid, giving it the color, so I didn't think much of it. I didn't think about doing a full flush, but saw that mentioned in a search here for similar issues. I will run through that tonight.

Is using ATF in power steering a common practice? Are there benefits?
Dextron ATF used to be the norm for PS. Now that Dextron is in it's third revision (Dextron III) it is no longer suggested for power steering fluid. Use specific power steering fluid! Never mix synthetics with petroleum based fluids. Royal Purple is a very good but purely synthetic lubricant. Synthetic PS fluid is highly desirable because of it's ability to withstand very high temperatures but also very expensive. Running normal PS fluid has it's advantage by being available on any shelf in any store whereas synthetics are not.
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Old 01-16-2012, 12:27 PM
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Now that Dextron is in it's third revision (Dextron III) .
try 6th revision...yup, we are up to dexron vi
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Old 01-16-2012, 12:35 PM
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Originally Posted by Uncle Ben View Post
Hmmmm....Never seen a bypass valve in the gear before. Bypass valves are usually (for sure on a Saginaw pump) on the pump at the head of the high pressure hose. What you are describing does not sound like bypass valve failure but rather air in the fluid. Common characteristic of a sticking or malfunctioning bypass valve is steering assist in one way and not the other. (IE able to turn easily to the left but difficulty or intermittent difficulty to the right) Are you using power steering fluid or ATF? PS fluid is designed to not support air bubbles to stay trapped in suspension. ATF can and will allow foam to stay in suspension because Auto trannys have flat filters in the pan designed to strip the foam from the fluid while PS systems do not. If you have any water or other contaminants in the system it will also foam. (this includes a mix of synthetic and dino based fluids) I suggest a system flush with fresh PS fluid.

Right, but he said he installed a new pump and the problem did not go away. So he either has a blockage in the steering gear or in one of the hoses.

It doesn't seem likely that it is a wrong type of fluid issue. I assume it was working OK for an extended period of time with that same fluid in it, then all of a sudden he started spewing fluid all over?

If it is air in the fluid then something must be causing the pump to cavitate and foam it up.
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Old 01-16-2012, 12:59 PM
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I can't help with the issue but on the fluid, after a lot of searching this is what I put into my '97 LX450:

http://www.grainger.com/Grainger/wwg...N=0&sst=subset

Before the change out the pump was a whiny SOB and after, quiet as a mouse - I don't know what weight oil is suggested for your system so this may not be applicable. But if it is, the local Grainger store should have it. I just ordered it online and it arrived the very next day - shipping cost was about what it would have cost me in gas to drive over and get it.
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Old 01-16-2012, 01:02 PM
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Originally Posted by nuclearlemon View Post
try 6th revision...yup, we are up to dexron vi
Yup....I meant after the third revision. I'm old ....give me a break!
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