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Hello!

I don't know if this is the right subforum for this problem, but I'll try here

So, as it has been raining quite heavily recently I got quite a few occasions of driving through water in larger puddles. And this is what I noticed:

Every time I pass through this deep water - deep enough to make a good splash (it is no big deal to find some rivers running right on the road surface now) - right after or in a little while I would hear this 'yelping' noise very similar to one that you'd hear from a car with manual transmission with worn out clutch disk (or whatever part it is ). It would go away once all water 'dries' out. And it is only heard after heavily splashing under the car with water - on dry days be it cold or hot it never appears, even on wet days if it is just rainy with no big puddles. I mean, you have to splash it quite a bit to hear.

Any suggestions what can that be? Is it normal or not really to have that?

Hi. Have you checked the tightness of all the drive belts? A slipping belt will make a screeching noise and will happen if the tension is borderline and everything gets wet. It could be the alternator, power steering pump or air conditioning drive belt becoming slippery when wet.

i agree


BB

Typical symptom of a slack belt made even worse by water induced lubrication causing slippage.

I have to do one of these belts tomorrow when Tony Reddaway and I rebuild his 300 R6 after a water pump to block hose burst the other day. First job is to clean the adjuster bar of corrosion and ensure nuts run up and down the threads without sticking. Plenty of copper slip to be used.

Correct tension adjustment is when you can turn the belt at its longest run point 90degrees from its normal flat run. Less than 90 is over tensioned, more it is too slack. Before tensioning the belt, take it off and bend it back on itself. If the belt is worn lateral cracks will be clear to see. Replace if in such a condition.

Here is the old one off my S-type with that defect at 75k miles.
Mike

Thanks very much to everyone who replied!

It sounds that there is one more thing added on the "To Do" list soon to be submitted with the car for annual servicing!

Here is the adjustment rod detail on an X300.

Note cleaned up threads and copper slip. To adjust belt tension, the nut at the bottom of the rod must be slacked to allow the alternator to travel through an arc as tension is applied to the lower of the two nuts on the threaded portion of the adjuster. (Strangely 9/16" AF) Also slacken the long lower 17mm hex bolt pivot and nut passing through the lower alternator mounting bracket underneath the alternator

The pivot bolt on the adjuster at 90 degrees to the rod lock nuts, fitted to the alternator must also be slackened. Tension the belt with the lower rod nut then lock off with the top nut having checked that the belt can be twisted through 90 degrees at the longest part of the belt run. Then re-tighten the pivot bolts and the lower rod nut and the job is done.
Mike

Thank you very much, Mike! Very useful advice!

Update:

It appeared that tension belt was not tensioned properly. It seems to be fine after that adjustment for now...