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Ls400 Mk3 Tensioner Inspection ?

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Hi everyone

Could someone give me a hint on how to inspect the alternator belt tensioner?

I can easily and without effort press the serpentine belt and see the tensioner moving.

Also my Battery seems to go flat and pulley is squeaking but alternator is charging at 14V on idle.

I am definitely going to change the belt but Lexus Coventry just quoted me £170 + vat moor tensioner.

Thanks any advice is most velcome.

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At the rear of the tensioner pulley there should be an indicator scale and a pointer on the tensioner showing the allowable movement of the tensioner which should sit somewhere between the 2 extremes if the belt is within stretch limits.

If you can press the belt and see the tensioner moving it sounds OK and means it can still apply tension.

The squeeling is normally the idler pully not the tensioner and seems more noticable in cold weather but disappears when the car has warmed up, I gave the bearing on mine a dose of WD40 a couple of years ago and it has remained quiet since then.

You can actually buy the correct specification bearing for the idler and replace it for around a tenner.

Picture 4 on the link below shows the tensioner a little better and the marks on the alloy casting (not the timing marks on the crank pulley).

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Thanks for your replies.

The Battery seems normal it goes flat gradually, it was probably a week between the first time I have noticed lazy starts in th morning and the point where the car wouldn't start. Also I am using heating on seats a lot.

Can anyone recommend a place for bearings and maybe what bearing sits under the pulley?

I'm trying to avoid wd40 as I think it may flush away grease in the bearing.

Another thing is that when I operate windows (4 at once) I can definitely say that headlamps are going dimmer. This is going on for a long time now. Would this be a voltage controller on the alternator?



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It seem your belt might be old & needs replacing its about a 30 minute job, Make sure you draw yourself a diagram of where the old belt runs before removing it & then you wont go far wrong. a new belt will be around the £20 mark so its a cheap elimination & a good place to start. You would replace it as a matter of course if it was more involved anyway. Give it a go & see if things improve.

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Squirted my belt and tensioner for twelve months I bet.....bloody ell those 400's were well built.....I bit the bullet in the end and just got on with it.....

Take off the tensioner and knock out the bearings....go to bearing shop and get new ones....drift or press new belt too of course....and off you go I bet....

done mine a few years ago....afternoons work taking your time....great feeling once its done....all quiet again ....also there should be a sticker on the bonnet showing the route of the belt.

Good Luck pal. :innocent:

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