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Don Bagnall
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New Zealand
I have LESS Soarers than Hayden :-(

Posts: 4252
Reg: 05-2005

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Saturday, July 22, 2006 - 11:41 am, by:  Don Bagnall (Baggs)

Blair,
This was posted by Roger Costello, and may be very relevant.

This is a common problem on Lexus LS400's, it probably is on Soarer's and Celsior's as well. The basic system is the same on both the V8's and Six's. Does anyone else have PS fluid disappearing without a trace?

A few years back our 1991 LS400 started using a little and eventually a lot of PS fluid even after new hoses plus a full pump reseal. The cause was a leaky diaphragm inside the vacuum pressure switch that lifts idle speed when the PS load increases. This lets PS fluid from the high pressure side of the pump seep/dribble/piss into the inlet manifold via the vacuum hose. Symptoms were a puff of smoke at startup and PS fluid disappearing somewhere. Lexus said it was a very common problem along with the PS Pump needing rebuilding and owing to the cost of the part, not cheap to fix. From memory I think it was about $450.

My 1991 UZZ31 Soarer recently started using PS fluid with no apparent leaks and when I pull the relevant vacuum hose off the inlet manifold there is PS fluid dribbling out of it. For a 1991 UZZ31 p/n for the valve is 17630-70020, description is "valve assy, air control". The same part number valve is used on everything from Celica's to Crown's. It lives on the union connecting the outlet of the PS pump to the high pressure hose. There are different p/n's for later/other Soarers so check first if you are ordering a replacement.

Given the ridiculous price of the switch at almost $400 and its small size it could be worth sourcing them from Japan. I will probably have to go and get one from Toyota because it is a bit too urgent. The problem does start at just a few cc's per month and get's progressively worse over time. I can only find one unresolved reference to this in the ALSC archive and a few on US sites. Lexus of Perth tell me they have had this happen on many of the older LS400's in WA so this could be a problem we should all watch out for.
Some good news. The local Toyota substitutions guru has come up with an option!

17630-16040 Valve Assy, Air Control @ $170 inc GST

New version of the part which is a direct replacement with an improved diaphragm and more realistic price, in stock!

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