Is there a bypass valve on the power steering pump?

98V70T5 · Post by **98V70T5** » 23 Aug 2011, 14:21

I have a 98 V70 T5, and I just replaced the rack with a high quality reman, but it blew the left side seal after only 4000 miles.

I have been talking to mechanics I know, and they said blowing a reman rack in 4000 miles, is highly unlikely. Out of 2 dozen or so racks one guy did, he never had a customer come back. That is leading me to ask, is there a by pass valve on the pump to release pressure if you hold the steering wheel at full lock? If this wasn't functioning right, and was locked/seized it could be the reason my rack didn't last, and why the first one didn't last either.

Thanks

FCPEURO · Post by **FCPEURO** » 23 Aug 2011, 16:54

I have never heard of a pressure valve like you say. I don't see how that would be allowed being how pollutant the steering fluid would be and also how fast you would run low.

98V70T5 · Post by **98V70T5** » 23 Aug 2011, 19:45

On most Toyotas there is a tiny piston that recircuiates p/s fluid when you hold it at the lock position. Its there to prevent blowing out lines or racks if you are just cranking on the steering wheel. Sort of like a wastegate setup.

Post by **jimmy57** » 23 Aug 2011, 21:43

It is integral to pump in outlet fitting on that Saginaw pump. The not too common failure is the spring breaks and causes too low pressure. I can't think of anything in there that would make it too high as it is a simple plug with a spring behind it and when pressure is too great it pushes plug back and a relief hole is opened.

95SE · Post by **95SE** » 09 Jul 2017, 08:53

98V70T5 wrote: ↑23 Aug 2011, 19:45 On most Toyotas there is a tiny piston that recircuiates p/s fluid when you hold it at the lock position. Its there to prevent blowing out lines or racks if you are just cranking on the steering wheel. Sort of like a wastegate setup.

Does this exist in an 04 XC70 Base system?

I changed my rack and now there is no power steering at idle. Rev to 2k and it returns. It leads me to believe that there is something at play that allows/assists/adjusts power sterring at idle rpm. Like something (a valve) is either stuck open or closed preventing proper function only at idle when the ps pump pressure is weekest.

Post by **oragex** » 09 Jul 2017, 09:27

It's better to post in the 2001-2009 section, but to answer there is no bypass valve inside the pump. Was your car having normal power steering at idle before the rack was replaced? If yes, it may indicate something wrong with the new rack or even just a kinked line to the rack. The rack itself does have a spool valve integrated.

95SE · Post by **95SE** » 09 Jul 2017, 09:59

I will repost over there too.

Yes, all good before rack. Rack was bad for sure though.