LS - 1st and 2nd Gen (1990-2000) Discussion topics related to the 1990 - 2000 Lexus LS400

ls400 has a knock!!!!?!!

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Old 09-22-13, 04:09 PM
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cocainels4
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Default ls400 has a knock!!!!?!!

Hey guys I bought this car a week ago. Did an oil change when I got it and today I was in a drive thru and heaard a knocking sound. Checked under the hood and it seems to be coming from the power steering resevoir/pulley area but its pretty loud. If it idles for a bit it goes away then comes back. Any suggestions on what it could be? Oil level is good. Nosmoke or anything.
Old 09-22-13, 04:54 PM
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LScowboyLS
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Originally Posted by cocainels4
Hey guys I bought this car a week ago. Did an oil change when I got it and today I was in a drive thru and heaard a knocking sound. Checked under the hood and it seems to be coming from the power steering resevoir/pulley area but its pretty loud. If it idles for a bit it goes away then comes back. Any suggestions on what it could be? Oil level is good. Nosmoke or anything.
have you checked the power steering fluid level, as well as the engine oil?

in fact, while you are at it, check ALL fluid levels, as well as the serpentine belt and cooling system hoses

what kind of oil and filter did you use?


Fluid levels that need to be checked:

● Oil (use 5W-30, full synthetic preferably)
● Power Steering fluid (use Dexron III)
● Transmission fluid (use Toyota T-IV)
● Brake fluid
● Coolant (use Toyota red long-life coolant 50/50 with distilled water)
● Differential
Old 09-22-13, 06:30 PM
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cocainels4
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Yes checked all fluids. Everything looked good.
Old 09-22-13, 07:04 PM
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LScowboyLS
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take off the serpentine belt and see if the noise remains - this will quickly narrow it down on what is causing the noise! - you do not need to unbolt anything to remove the serpentine drive belt

if the noise disappears with the belt off, then the noise is either the belt tensioner, PS pump, A/C compressor, idler pulley, fan pulley, alternator, or the belt itself
Old 09-22-13, 07:15 PM
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cocainels4
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Originally Posted by LScowboyLS
take off the serpentine belt and see if the noise remains - this will quickly narrow it down on what is causing the noise! - you do not need to unbolt anything to remove the serpentine drive belt

if the noise disappears with the belt off, then the noise is either the belt tensioner, PS pump, A/C compressor, idler pulley, fan pulley, alternator, or the belt itself
Good call. Il have to do that tomorrow and see for sure. Thank u
Old 09-22-13, 07:26 PM
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LScowboyLS
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it is fine to run the LS400 for brief testing/diagnostic sessions of a couple of minutes without the serpentine belt installed!
Old 09-22-13, 11:35 PM
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sounds like one of the pulleys may be loose/seizing.

Grumbly bearings.
Old 09-23-13, 06:03 AM
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make sure u don't run it for too long..maybe 1 minute at most
Old 09-23-13, 06:46 AM
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^ It can be run longer than that without the serpentine belt. The water pump is powered by the tiiming belt. Just keep close eye on the temperature. A couple minutes is fine as long as the temp is under control. Only minor concern would be running the battery down with no charge from the alternator but the motor would probably overheat long before the battery dies.
Old 09-23-13, 10:51 AM
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cocainels4
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i don't plan on running it for that long. usually u hear the knocking after 10-15 seconds upon start up. if u rev the engine alittle it goes away. then it randomly comes back.
Old 09-23-13, 11:05 AM
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Hope you get it sorted. Keep us updated
Old 09-23-13, 12:56 PM
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Originally Posted by cocainels4
i don't plan on running it for that long. usually u hear the knocking after 10-15 seconds upon start up. if u rev the engine alittle it goes away. then it randomly comes back.
in the rare case of a startup knock from the engine itself, such as valve train, you can use the Motorcraft FL-400S oil filter to get oil to critical areas faster on startup.
Old 09-27-13, 04:08 AM
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cocainels4
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ok so i had some time yesterday come to find out its my alternator. That thing is makign a racket. So gonna replace that soon.
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