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There have been a few power steering pump questions lately.

I've heard responders mention a power steering pump vacuum leak test to identify where air is getting into the power steering fluid system.

I've turned that over in my head quite a few times and am wondering how such a test would be performed.

What is the procedure to perform a power steering vacuum leak test?

Is there more than one way to skin this cat?

Edit: Add on questions

What is the tool used to create the vacuum?

Is it like a might-vac or something?

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  • Yes, just a hand held vacuum pump with a catch can. MVA660 for a universal cone adapter. Added a picture of the procedure. – Ben Jan 22 '16 at 22:51
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I'm unsure if it would actually pinpoint a leaking fitting/seal.

Using a hand vacuum pump with a reservoir you fill the system and apply ~20inHg. Repeat until you stop seeing fluid entering the reservoir. Leave the vacuum on the system and walk away for 5 or so minutes. If pressure doesn't drop you're good.

Generally if you don't see a fluid leak, look at the return side fittings and rack seals. When fluid is flowing it can create a low pressure vacuum leak and draw in air without any actual fluid leak.

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That will not pinpoint a vacuum leak. It will however let you know if you do have one. As long as you have ruled out a leak on the high side of your power steering system, (i.e. no loss of fluid and visible leaks) then it is probably a leak somewhere on the suction (low pressure) side of the pump. Vacuum leaks are very difficult to locate, your best bet, unfortunately, is to check all of the gaskets, flare fittings, and other connections on the low pressure side if the system.

  • This doesn't quite address the OP's question about performing a vacuum leak test. Could you please expand on how to perform that test and use the results in conjunction with your answer? – Hari Ganti Mar 31 '17 at 20:48

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