Serpentine Belt Tensioner Bouncing

sweedish_taboo · Post by **sweedish_taboo** » 28 Feb 2012, 13:57

I have searched and read a couple threads, but can't find an answer to my problem. On my 1993 850 n/a saloon with egr and auto trans, I replaced the serpentine belt, tensioner, and idler pulley. All of the parts were volvo oem parts. The belt is quiet, seems tracks straight, no squeals or chirps, but the tensioner bounces forward and back at idle. When I come off idle, it smooths out. I don't think this is normal. I popped off the belt and the alt, p/s and a/c pulleys all seem to spin smoothly and the pulleys appear round. Anyone else having this issue? I noticed that there are two tensioners, one for egr, and I'm starting to wonder if I bought the wrong one, but can't find any info on it. I just don't want the tensioner or other parts to fail prematurely from the dancing tensioner. Anyone else delt with this issue?

claymore850 · Post by **claymore850** » 28 Feb 2012, 18:37

Did you check your belt alignment? sometimes just one small diference between the air conditioner compressor, makes the belt jump, and it varies the tension over the belt. Also check you idle, and with the air conditioner off check again.. Does you belt tensioner bearing is making some noise?

Post by **precopster** » 28 Feb 2012, 23:41

What part number is the tensioner you bought?

sweedish_taboo · Post by **sweedish_taboo** » 02 Mar 2012, 01:21

Thanks for the replies. The serpentine tensioner that I bought is oem #6842019. I have the early serial motor with egr. I'm not sure how exactly to check the pulley alignment. But there is no noise or squeal. I spun the pulleys by hand and they all feel smooth. I put in a new idler pulley. No bearing noise that I can detect. At idle the tensioner is bouncing, but when I give it gas and the rpm's increase, the tensioner settles down. Maybe the idle speed is too low?

Post by **precopster** » 02 Mar 2012, 05:36

From FCPs listing:

"Note: Volvo 850 Automatic Belt Tensioner. This tensioner fits all 1993 models with a manual transmission and some 93 850 models with an automatic transmission. You will have to locate the engine serial number on your timing cover to get the correct unit. This fits models with EGR before engine serial number 122376 and models without EGR before engine serial number 121674. "

Does yours fit the criteria?

sweedish_taboo · Post by **sweedish_taboo** » 02 Mar 2012, 12:38

Yes, my 1993 auto with egr has engine serial 112040 so it appears that I have the correct tensioner.

Billc1015 · Post by **Billc1015** » 02 Mar 2012, 12:50

There was an update to the belt routing for a better contact on the alternator. With this update I believe there was a different part #. You may want to check the belt that you got and see if it is the new or old style.

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sweedish_taboo · Post by **sweedish_taboo** » 02 Mar 2012, 13:33

The new belt that I got is the longer belt (#9186352) with the new routing that wraps more around the alternator. Are you saying that there is a different part number for the tensioner?