Alternator belt flipping

[roosmith]

I had the crank pulley changed this week, after 5 miles or so I heard an unusual belt noise. Taken a look today and the inner alternator belt had flipped over!

Couple of questions, I loosened off the alternator however there is a coolant pipe behind it meaning it won't loosen off enough to get the belts on very easily. After lots of bruised knuckles and trapped fingers got the belt turned round. Put everything back together and tried the engine, all good for a couple of minutes until it flipped again.

The belt isn't in great condition now so I will put a new set on. Is there another reason for the belt flipping or will changing it for a new one sort it out?

[g8dhe]

There was a previous case on the forum of this but searching for the relevant terms isn't finding it, think the solution was a different brand of "V" belt.

Ah found it http://www.igmaynard.co.uk/bongo/forum/ ... 51#p556451

[Northern Bongolow]

if one alternator belt is older than the other the tension on one belt will be different to the other, have you had fitted a pair of new alternator belts, always better to fit a pair, or are they the old ones. a worn slack belt can whip when slack.
or something is out of line !!.

[roosmith]

Thanks both for the replies. I didn't replace either belt, just changed the crank pulley (well someone else did!).

I've ordered a new set of 3 belts, do the whole lot and hopefully it won't happen again. Otherwise the pulley must be on wrong, I suppose, seeing as that is the only other bit to change.

[Northern Bongolow]

there is one thing that can be put on out of line, if you look carefully at the alternator mount, it has a spacer in it, if the spacer is lost or put on wrong it moves the position of the alternator forward or backwards, i cannot remember which, its only a couple of mm, but enough maybe to derail the belts, especially if one of the pulleys has a chip out of it, this chip can catch the belt.

im not saying this is a good one or owt but this link shows the spacer/insert in the mounting hole mentioned above, the gen mazda one is very similar.

http://www.ebay.co.uk/itm/MAZDA-BONGO-2 ... 234cdfcf20

[roosmith]

I've changed the belts, that has sorted it however as always seems to be the way, one step forward, one step back, I now have a slight whistle. Could it be the belts are too tight? I made rookie mistake of testing, putting engine tray back on before taking for a run. Only found the whistle on run and of course with the tray in place can't get to lower tensioner. The alternator belts are definitely loose enough not to be whistling (will need tightening back up a tad)

I've tightened them to flex as deep as their width, as I've been taught but is that too tight?

[Northern Bongolow]

sounds like they are too tight. spray them briefly with a squirty bottle of water, if they shut up its the belts rather than the tensioners.
the whistle may quieten as the belts wear in, a new belt is thicker so sits taller in the V of the pulley, so old belts sit lower in the pulleys, this lets rust and belt dust etc build up on the un used bit of the pulleys, its good maintenance to clean off the pulleys with a wire brush or similar.
tight belts tend to strain the water pump, tensioners and alternator bearings, so i must admit i always go for running them slacker than normal, if they dont slip then that will do.

you can get at the tensioners from above, just stick the socket on a longish extension bar between the two belts after loosening the lock nut, another reason for leaving the belts on the looser side.

[roosmith]

Thanks for your help once again Northern. I did manage to get at the lower tensioner from above, taken everything back a notch and while they aren't tight they don't appear to be slipping, so a happy medium. They still whistle though but perhaps not as loud (or maybe hum is the right word). I tried the sprayer trick however it made no difference.

I'm happy that nothing is about to explode, so I'm going to see if it quietens down any, as they all bed in. Failing that I suppose i need to start looking at bearings. Which should be fun! I'm going on holiday next week, so a 1500 week should tell me whether they are going to bed in or not! Fingers crossed.

[BigPanzer]

Hi,

I've only ever had a belt flip once, many years ago. It was a very slight misalignment on the pulleys and the giveaway was the wearmark on one of the pulleys - the part that goes shiny was wider on one side of the vee than the other.

Peter

[mikexgough]

A quick add on to this one....... some Bongo "suppliers" are flogging belts that are the wrong size.... and less than well known brands too....

Please watch out for what you buy..... some are poor quality materials with a poor V profile and some are selling a set of 3 belts where the Air Con Belt is short by 25mm or more where the belt wont even run over the crank and aircon pully yet alone the idler/tensioner.....

I use http://www.gatesautocat.com/drive/MAZDA ... 95_10-98/0 which are available from most trade counters....

Just some info from what I have experienced on recent Bongos...