Alternator Belt Tension Loss on Sharp Turns

rybateman · Post by **rybateman** » 21 Apr 2012, 20:08

Hey guys,

Been struggling with a rather frustrating issue keeping tension on the alternator belt on an 89 740. Couldn't pinpoint what the hell was going on until recent. It would drive fine for 24 to 48 hours and then suddenly would lose electric and eventually die when it didn't have enough juice left.

Just retensioned the belt after waiting a couple weeks and let it run for a bit. Just out of curiosity I tried out a few things to see if it resulted in a loss of tension. When I cranked the wheel hard to the right or left I got a really loud squeal and noticed immediately after that the belt was much looser.

Any tips on what might be causing this?

lummert · Post by **lummert** » 21 Apr 2012, 20:46

Crank Pulley (harmonic balancer) outer ring slipping? Or, the alternator's rubber mounting bushings are worn out?

rybateman · Post by **rybateman** » 11 Jul 2012, 18:39

Believe it or not I'm still dealing with this issue. I have a daily driver and the GL was bought cheap as a car for my girlfriend, so I've worked on this every now and again when I have time. I also don't have a garage and live in Fairbanks, AK (avg. winter temperatures are maybe around 0F?). Needless to say, this thing has been sitting in the driveway since winter and I'm coming up on having some time to work with it. I have done the following things:

1. Tightened the alternator belt a dozen times (normally drives for 24 hours or so, although I had it running for nearly a week after I replaced all of the belts in the system)
2. Replaced the v belts on power steering, a/c, and alternator
3. Replaced power steering pump

I've avoided the harmonic balancer because I don't really have the tools (I have read you need an impact wrench?) and it sounds like it would give me a lot of trouble. I did check the rubber mounts for the alternator and everything seems fine. I'm not opposed to eventually doing it, but I want to rule other things out first.

So here's the irony of it all:

Now that I'm reading up on the net about the problem again in preparation for working on the car this weekend, I've noticed something. The whole time that I've dealt with this, the alternator has been rather difficult to adjust - and I always wondered why people said it was easy, and all of the instructions include reference to an adjustment screw and a "set screw" or something similar. But I've always just only had a bolt that runs through the rail that the alternator hinges on, not the adjustment screw. What they're talking about is this screw here, correct? I was then reading some additional posts from folks asking about having broken their adjustment screw, and the consensus seems to be that the adjustment screw is necessary to retain tension on the belt. Also, where does the adjustment screw go if I do in fact need to get one?

Confirm/deny? I'm starting to lose my head over this one. Other times when I've gotten the car running it isn't so much that the alternator throws the belt violently - the car slowly loses electric power, headlights dim, radio turns off, and when I stop and check the belt it has about 3/4" or so deflection, just enough to not really spin the alternator.

TL;DR: Do you need the alternator adjustment screw to maintain alternator belt tension? If not, what should I do next?

lummert · Post by **lummert** » 11 Jul 2012, 19:33

The adjuster bolt is needed to tension the belt properly. One of the 2 nuts you loosened on the alternator to adjust the belt is supposed to have the place on the bolt head to accept the long adjuster bolt. One suggestion: after tensioning the belt and tightening the bolts loosen the long bolt just enough to take off the tension.

rybateman · Post by **rybateman** » 11 Jul 2012, 19:40

So the adjustment bolt is necessary to maintain tension, or just to get up to tension? I've gotten the belt nice and tight quite a few times but it still loses tension. And as far as the 'receiver bolt' goes - I'm not sure I have that. I just have a bolt with a nut on the other end that compresses on the rail (the roundish slotted thing below the alternator). Is that not the right setup? I have a lingering feeling a past owner may have replaced these incorrectly. Is it possible to buy both parts anywhere?

Edit: Also, is the receiver part you're mentioning something like the banjo bolt you'd find on the fuel filter?

lummert · Post by **lummert** » 11 Jul 2012, 20:26

This site says to suspect the mounting bushings.

http://swedishbricks.net/700900FAQ/Engi ... tml#Engine: Seals, Belts, Crankcase Ventilation

Volvo1man · Post by **Volvo1man** » 15 Jul 2012, 04:32

Here is my $0.02; see if it fits your situation. A few years ago I changed the alternator belt on my 1994 940 Turbo Wagon (B230FT engine). For weeks afterward, the belt kept slipping and not charging properly. I tightened it so many times I lost count. I checked the rubber mount bushings, and those were fine.

I finally sucked it up and took it to my local Volvo shop and the service tech told me to look under the alternator. There was a THIRD mount point with a bolt and nut to hold the alternator securely. I don't remember whether mine were missing or just loose, but I bought a new bolt/nut pair for the THIRD mount point and snugged every thing up. The alternator tracked perfectly in line and has not given me any problems since.

Maybe your third mount is loose or the bolt and nut are missing? Just a thought.