Antharro

LS400 smoke from PAS fluid vaccum fault - also LS430?

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The fault on the LS400 which sucks power steering fluid into the engine via vacuum lines - does this affect the LS430 as well or is it strictly an LS400 problem?

Thanks!

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I have never heard of this fault in 25 years of owning the ls400 could you refer me to your source.

If it is a fault on the 400 its likely to be a fault on the 430 as its the same engine but for higher cc.

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I've never heard of this fault either on the ls400 

 

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I've read about this on the LS400, its the Idle Control Valve on the power steering hose/pump that goes bad and when it leaks it sucks fluid through the vacuum hoses and causes white smoke out the exhaust. If it gets really bad the leak will drop onto the alternator and cause issues.

It's number 2 issue mentioned here: https://www.clublexus.com/forums/ls-1st-and-2nd-gen-1990-2000/261358-the-first-gen-power-steering-bible.html

Dont know if its on the 430 though...would hope Lexus would have fixed it by then. 

 

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This valve is fitted to all LS400 and LS430 models and is a known failure problem, it is a vacuum controlled valve that provides extra power steering assistance at low engine RPM i.e. when manoeuvring out of a parking space at idle speed. The valve internals fail which allows power steering fluid to enter the vacuum pipes which in turn is then sucked into the engine. This is then burnt in the fuel mix and produces a cloud of white smoke at a cold start up.

Once the initial leakage has been sucked out and burnt the smoke will disappear but small amounts will be constantly sucked into the engine which over time could cause damage to the catalytic converters.

The fix either involves the replacement of the valve or removal of the valve replacing it with a suitable sized bolt and blanking off the two vacuum pipes, reports suggest the latter has no noticeable effect on power steering feel.

Due to the position of the valve under the pump body it’s not an easy job access wise, the alternator needs to be removed to get to it.

The fluid leaking onto the alternator below is another issue in that the O ring seal on the reservoir fails, this allows fluid to escape which eventually soaks the alternator directly below  leading to its demise.

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The fix either involves the replacement of the valve or removal of the valve replacing it with a suitable sized bolt and blanking off the two vacuum pipes, reports suggest the latter has no noticeable effect on power steering feel.

I would only add that the replacement pump on my own car having a bolt in situ, it is noticeable that you cannot move the steering easily unless there is some throttle.  Its OK on cold start up revs level,  but not at 650 revs idle.  I have considered replacing the old part on this replacement Pump, but as it only happens very infrequently I've learned to use my left foot to brake and use slight pressure on the Throttle to be able to move the steering, say when stuck behind a Car and needing to pull out on a very narrow road.

 

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Cheers Stuart for pointing out it does affect low idle steering, given that mine has now started smoking due to this fault it’s going to get the replacement valve and not the bolt. 

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hope it never happens to me .................. 😲

Malc

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4 hours ago, Malc said:

hope it never happens to me .................. 😲

Malc

If it’s any consolation Malc mine did 26 years service 😀

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Thank you all for the feedback, especially you, @steve2006. Definitely something I will look at for my ailing 430.

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