405 auto tension idler

Hi Folks,

I have recently aquired a 1994 405 TD, and have a couple of minor problems
(cf thread on 405 clunk
One of the problems is that the automatic tension-adjusting idler for the
alternator belt vibrates quite badly at just above idle RPM. Adjusting the
static tension with the manual adjuster alters the RPM that the vibration
occurs.

The vibration gets worse when, for example, the a/c is switched on - i.e.
with increased mechanical load. My 205TD didn't have any of these fancy
self-adjusting things on, so I'm a bit in the dark. Are they supposed to
have some sort of damping, which might have failed?

Any suggestions as to causes/cures gratefully received!

Thanks in advance,
Albert

 

One of the problems is that the automatic tension-adjusting idler for the

Just a thought,- maybe it's the alternator bearings
DaveK

 

My 96 405 td estate (XUD engine) used to vibrate and rattle in exactly the
same way,
I removed the wheel arch cover and found an adjustable pulley at the bottom
of the engine,
after adjusting the pulley , the vibration and noise stopped,

HTH
Fitzy

 

I had this, and was told by the dealer that is was quite normal. Indeed the
engine is still running fine 50,000 miles later. The manual tensioner on the
underside can make a difference. Just tighten the belt slightly.

Brian.

 

in "brian"

Thanks guys.

I don't know about the alternator bearings (davek), although the
alternator isn't making any unusual noises, but I have tried altering the
belt tension using the manual adjuster, as Fitzy and Brian suggested.
Slackening the tensioner reduced the rpm at which the vibration occurs,
whilst tightening it increased the rpm.

I've set the tension so that it only occurs at rpm just above tickover,
i.e. a speed that I never drive around at. I'm sure it shouldn't happen,
but at least it's not an uncommon problem!

Thanks again,
Albert

 

Usually the only cure is a new tensioner assembly, and it is a sod of
a job to change. Am I right in assuming you have air conditioning?
The correct way to tension the belt is, at the rear of the tensioner
you have to line up two holes and pin (special shaped long pin), fit
the belt, adjust the bottom manual tensioner up till the pin can be
removed (no longer held in the two holes under tension).
The trouble is if you leave it, the tensioner will get worse and the
wheel will rub against the cam cover, which is very noisy!!
The way you have set it now gives too much slack in the belt, and
there is a danger of slipping with load on the alternator and the air
con on.

 

Good information there Nigel,,
I wondered why it had a manual adjuster and a spring loaded tensioned on the
same belt,,,,,,,,,
Cheers
Fitzy