355 AC Compressor Belt Tension

I got the 1-sec "grrr" sound coming from the LH side of the engine upon starting the cold engine when the AC kicks in. Never happen before. Happening after a week of parking. If I start the engine on a next day, the "gr" sound is shorter or not coming at all. On the hot engine all is good. Suspecting the AC belt getting lose after the years. Seems it's just 2 nuts on the top of the compressor but what is the proper procedure? - Don't want to 'break and learn' on the 355 lol.

The WSM vol. 3 section "I" states it should be on the p. I36 but the last page for the I-section is I27.

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I was trying to say in the above post that the pages for the Compressor belt tension are not present in the publicly available WSM vol.3 I have had downloaded. As you referring the tensions in the manual, are you able to suggest of where to find the WSM that contains those pages?

 

This statement does not make any sense.

 

He talks about the "frequency app" but using a tension measuring device in the video. Plus, this video with the measuring device is taken from a 360 as in 355 there is no window in the firewall.

Seems this "frequency" thing is like: "I've heard somebody had said something.."

Don't see anything meaningful in that video comments.

 

If the app is measuring the RPM of the belt (the ## of how many times the marks on the belt rotate in a minute), it's unrelated to the tension completely. Loosen belt when tensioned up will have less RPM than a new one which will rotate more often on a shorter distance. Hope this helps.

 

Makes sense now. I see. Very good. I already tied up the AC belt on Saturday when it was no any replies I put a mark with a marker on the bracket and on the stud and tied the bolt for 2mm. Started the engine and it still was making the "grrr" sound. Tied another 3mm. No sounds upon engaging the AC pump. Usually the belt cools down for over the week so will try this weekend if it needs some more adjustment. I like alexanderfitu suggestion to twist the belt 90 degrees with a moderate force but I do like your solution with the app too although it's more harder to crawl to under the car and do the guitar thing on the AC belt lol and have the iphone next to pick up the tone.

Very good! Thanks all!

 

[QUOTE="Frequency readings on my belts: Download the FREE 'Gates' app on your smartphone from APP or Play Store Alternator/Waterpump: 120Hz A.C Compressor: 164hz PAS: 263hz[/QUOTE]

Higher frequency means higher tension. WSM vol. 1 on pp.B65/B66 says the tension on alternator belt needs to be 120 (whatever units on STAEGER tension meeter it is) while the AC belt tension needs to be 115 (110-115 for old belt). I.e. tension on the AC belt is lower than on the serpentine alternator belt while your AC belt has higher frequency than alternator belt means higher tension.

The power-steering pump belt need to have a way lower tension of 70 while your PAS tension is twice higher than the main alternator belt.

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I don't know of how the Staeger meter works if that is what he did then measured the frequencies - great! One thing for sure you either need to take off the fuel tank for the Staeger meter to put in or to drop the engine.

I wasn't able to measure the frequency of the AC belt tension. It says on my phone Gates Carbon Drive won't work for my device so I tried Belt Tension Meter and Easy Tension. Both apps were showing the waves when I was plucking on the belt but wasn't able to capture the frequency. I tried a few days later on a 987 Boxster and it caught right away 123Hz for the serpentine belt both times I tried.

 

That is what I ended up doing plus to the point once tighten it slips only next weekend on a cold start. Also I am having the F1 and had a few F1 oil overfills so with the excessive heat I found the belt little bit greasy and tried to de-grease it cleaning it with gasoline a few times each time I was tightening it.