I saw an ad for a magnetic filter that fits in series with the power steering fluid lines. I know that air gets into the power steering fluid lines, and that power steering fluid in my volvo is ATF. Is a power steering filter necessary or just a waste of money?

I put a strong magnet in the plastic PS reservoir of the 940. After 15k mi I fished it out and found it spotless. So I conclude that there's no benefit. A particulate filter inserted into the return line might be a different matter, and as long as it has enough throughput capacity so it doesn't restrict flow, can't hurt.

I do have a magnetic oil pan drain plug in all cars, and they have a slight coating of metal sludge at every oil change.
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Bob (son's 81-244GL B21F, dtr's 83-244DL B23F, 'my' 94-944 B230FD; plus grocery-getter Dodge minivan, hobbycar MGB, and numerous old motorcycles)

I had a mysterious problem on my '78 245; the P/S was jerky and uncertain. After replacing everything but the rack, as a last try before doing just that, I installed one of those filters, and within 5 miles, the problem was gone.
Later, on another car I did replace the rack, and the new one had a lifetime warranty IF a filter was installed. That's enough for me to always use 'em.
IIRC, I pay ~US$15 each at the local CarQuest.
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Jim McDonald

Well, for what it's worth, I have never used one in any of my 240s, and I haven't had any real major problems... One of the racks is leaking a bit, but I think it has more to do with the fact that it has a good 300K miles on it...

On the other hand, I don't think adding a filter would hurt anything.

Good question. I'll be watching the replies on this one.
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If you listen to the radio in Portland, OR, you may know me as "Portland's Favorite Soul Brother!"