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LS400 engine back side noise


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Hi everyone, I am new to this website. Have been guest to learn information about Lexus on this site for a while, great place through 馃憤.

here is my first topic as new member:

my ls400 is 1997, I bought it 1 month ago, recently I found a noise came from back side of the engine, not very loud but noticeable from the cabin, especially when push the gas pedal, it starts developing a metal rattling noise, I check the EGR pipe, there is no crack or leak, also the car doesn鈥檛 lose power and MPG is around 20, I record a video, sounds like has a leak somewhere located in the back side of the engine.聽anybody had similar experience? Thanks

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Usually culprit is the concertina sections on the EGR pipes, there are 2 sections one on top of the rear coolant bridge and the other below so make sure you have checked both parts.

Corroded cat to exhaust flanges are another weak point.


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  • 1 year later...

Hm . I have a simmilar noise on my 1995 LS400 with 120000 Miles on the clock. It is a bit more mechanical and audible mainly when pressing the accelerator briefly when it revs upp a bit.聽
Mostly when cold.聽 Had it as long as I have had the car.聽 7 Years and about 30K miles.
My guess was something mechanical but I really have no clue yet. will try to find source of the noise since it is slowly getting worse.聽

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3 minutes ago, Mikaelse said:

It is a bit more mechanical and audible mainly when pressing the accelerator briefly

don't think I've ever experienced anything like this ...聽 could someone have dropped a small metal summat or other in the under bonnet area at some time and it's still there rattling sometimes ?


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Get yourself an automotive stethoscope, they are similar to medical ones but have a long extendable probe on them for a easier access ( obviously be aware of moving parts when probing).

It should help you localise the cause by having a listen, if the noise gets louder you are getting closer to the cause.


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