How To Adjust Alternator Belt Tension.

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FalcoColumbarius
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How To Adjust Alternator Belt Tension.

Postby FalcoColumbarius » Sun Apr 15, 2012 1:04 am

How To Adjust Alternator Belt Tension.

By Morganizer (Link to original thread: alternator-belt-tension-adjustment-made-easy-5849.html)
_________________________________________________________________________________________________

I gather that adjustment of the alternator to tension the belt is so difficult because they use the same engine whether it's RHD or LHD. I bet on LHD the adjustment is simple; you just lift up the passenger seat and there it is.

Anyway, I adjusted mine today (RHD L300), and it was tricky, but manageable. Here's how I proceded:

1) lift up the passenger seat
2) remove the fan cowling (both halves)
3) jack up the front right corner of the vehicle. It is not necessary to raise the wheel off the ground. Lifting the body just gives you a little more elbow room.
4) remove the brush protection pan underneath the engine (2x 14mm bolts and 4x 12mm bolts)
5) loosen the alternator mounting bolt from underneath the vehicle using a 12mm socket and wrench
6) from the top of the engine, reach in past the fan (keys are in your pocket, right?) and using a 12mm socket and wrench with the long extension between the blades of the fan, loosen the bolt that secures the alternator in position.
7) go to Lordco and pay $17 for a ratcheting 12mm box wrench. Honest to god, I don't see how this job could reasonably be accomplished without it. Or we can have a belt-tensioning meet some time and you can borrow mine. From beneath the vehicle (not through the flap in the wheel well) rotate the bolt clockwise (righty-tighty) to tighten the belt. Conveniently (perhaps an oxymoron in this context) the belts are right there so you can poke them with your left hand as you tighten the bolt with your right. It's tempting to tighten them "once and for all!" but observe the cautions about over-tightening and stretching your belts.
8) go back out the way you came in, tightening everything you loosened, and putting back everything you took off.

The adjustment only took about 15 minutes...if you don't count the trip to Lordco and the time I spent earning that $17. And scouring the Internet for someone who had done this without modifying the vehicle, removing the driver's seat and moving the power steering pump out of the way, or pulling the engine because they happened to need an overhaul anyway. Oh, and the time spent pushing tools half way into various orifices on the vehicle and muttering swear words. But I actually enjoyed that. The thrill of a challenge.
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Growlerbearnz
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Re: How To Adjust Alternator Belt Tension.

Postby Growlerbearnz » Mon Sep 26, 2016 1:57 pm

Pictures shamelessly stolen from Lewis' excellent thread on alternator upgrades for the L400 here: http://www.mdocuk.co.uk/forums/viewtopic.php?p=364765

In the above guide, I'd recommend starting step 7 first. You know, before you pull your engine bay apart and then have to drive to Lordco for a box wrench.

Here's an impossibly good view of what you're trying to adjust:
AdjustBelts.JPG
AdjustBelts.JPG (80.85 KiB) Viewed 1742 times


An alternative (ha!) way to tighten the tension bolt is with a socket and long extension. Remove the driver's side front wheel, lift the rubber flap in the wheel well, and if you're lucky the tension bolt head will be reachable. You may need a universal joint on the socket.

Belts.JPG
Belts.JPG (33.11 KiB) Viewed 1742 times


A correctly tensioned alternator belt will deflect 10mm when pushed with a force of 10kg (or 98N if we're being technical). If they continue to squeak when correctly tensioned you'll need to replace the belts. Don't overtighten them in an effort to stop the squeaking- the water pump bearing will fail. Trust me, I know.

To check tightness, find something that weighs 10kg (about 20lb) and lift it with your thumb- thats how much force you're going to put on one of the belts. From below, push one of the belts with your thumb with a force of 10kg*. The belt should deflect about 10mm/half an inch relative to the other belt.

If you're replacing the belts, make sure you get a pair of belts from the same batch. Some people recommend genuine Mitsubishi belts (part number MD313660) but aftermarket seems fine to me. They're 1090mm long, 10mm wide, so generic part number 10A1090 or Gates 6284MC should be right.
Nothing says "poor workmanship" more than wrinkles in the duct tape.

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Growlerbearnz
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How To Adjust Alternator Belt Tension.

Postby Growlerbearnz » Sun Jul 16, 2017 11:22 pm

Another pro tip:
sub-arctic wrote:From all the searching ive done on here about tensioning alternator belts everyone says drop the lower skid plate and do it from underneath. Well you really do not need to do that. I removed the fan shrouds, took the fan off the clutch (4 10mm bolts) and all you do is kneel in front of the batteries, reach way down with a 1/4" drive ratchet and a 10mm socket on a short extension, loosen off the bottom mount bolt, and the clamp on the adjuster. Then take a ratcheting box end and reach over the lower rad hose and put the ratchet straight up and down with the box end on the adjuster and away you go! then do everything up and you are done, no messing around with the dirty old skid plate, and no getting dripped on by melting ice!

I am an aircraft mechanic and used to working on stuff installed in horrific places, so i knew there had to be an easier way to do it. Oh and I have a +3 ape index so my long arms may help a bit :-D

Other things ive discovered, when doing the EGR removal its not required to remove the black metal intake pipe, you can monkey the EGR out without disturbing it, you do need to take out the flex pipe though
Nothing says "poor workmanship" more than wrinkles in the duct tape.


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