Tensioning Belts

[MN Driver]

My 95 Geo Prizm with a 1.8 liter 7AFE engine is in need of a new alternator/water pump belt. I am going to be doing this myself and was wondering what you guys usually do for tensioning belts. Do you generally just go with belt deflection as a means of determining best tension or do use a belt tension gauge. If it's pretty accurate to use deflection then that is what I will use but I was wondering if it would be worth buying either a Denso, Borroughs, or Kent-Moore type gauge to gather a tension pressure reading?

The reason for only changing one belt is the other two belts look brand new, have no cracks, are still dark black and have that nice rough feeling that you get with a new belt but the water pump/alternator belt has a smooth surface, looks a little gray, and has a 6 inch split(separating two of the ribs from the other three) down it that hasn't grown in the past 10,000 miles but it is obvious that it is far beyond it's useful life.

I'm surprised that I haven't seen question this come up and I didn't find much searching. So should I buy a belt tension gauge or use deflection? ...And where do you buy one of these, I've never come across one before.

 

[Vilan]

Just replaced the belt on my 94 Metro a couple weeks ago. The old one squealed a fair bit and eventually flew right off

hence the replacement. So my first measure is by not squealing.

Secondly by deflection... should be under half an inch, at least on this one. No problems since I installed it.

 

[George7941]

All the multirib belts I have come across have an automatic tensioner. Does your Geo have a multirib belt that is manually tensioned?

 

[porcupine73]

On a new belt I usually snug her up per the manual which has different reading for 'new' vs. 'used' belts. I try to err on the 'loose' side because too tight can eat up the accessory's bearings. If I notice any squealing, I just snug it up a little more. If you do notice squealing, don't let it squeal too long, as I've noticed this generates a surprising amount of heat.

 

[MN Driver]

Quote:

---

All the multirib belts I have come across have an automatic tensioner. Does your Geo have a multirib belt that is manually tensioned?

---

You can see the setup just goto the Autozone web page, click on repair info, repair guides, choose a 1995 Toyota Corolla and go into general maint., routine maintenence, then belts. I have the type that is shown in the picture that uses the adjusting bolt and not the 'sling-type'.

Yes, it has 5 ribs and is tensioned by a screw-type mechanism. The belt itself is about 4 feet long. To loosen the belt for removal I just screw the tensioner so the alternator curves in toward the engine, pull the old belt off, slip the new one on and tighten it back up again.

 

[MN Driver]

Thanks porcupine, I'll use your advice and use the looser side of the recommended adjustment which I think the tightest they recommend is 1/4" deflection at largest gap between pulleys. I will probably drive around for about 30 mins tomorrow and I will see if the belt still feels cool that way I can have the feel for whether or not the new belt is too loose and slipping after All. I still have the old belt on, I was going to change it today but ended up doing an oil change for somebody instead. The belt will be for tomorrow.

It also looks like a new belt is supposed to be a bit tighter for its first run, 150 lbs. according to the cardboard sleeve it came in, and then 100 lbs. once its broken in.

 

[porcupine73]

When I had the slipping belt problem the belt felt cool but the accessory pulling upon which it was slipping was cooking hot. A new belt will stretch a little bit in it's first bit of life hence the tigher specs for a new belt. A new belt might not squeel at first but might start squeeling after a day or two after it stretches especially under high load conditions like turning steeing wheel when stopped, lots of accessories loading alternator, A/C turning on, etc.

 

[Drew99GT]

Also, adjust the tension when the belts and engine are at operating temp. If you crank them up nice and tight when the engines cold, they will be severely over tensioned once the engine and belts get hot.

MN Driver, I just go by feel on my Corolla. I looked high and dry for a belt tension gauge and never found one. I also took a flat wooden stick and measured out a 1/4 inch and marked it; that should be how far the belt deflects. Once it starts feeling tight, grasp it in the middle and wiggle it up and down; there should be a snug feeling to it but not super duper tight and not really loose/sloppy.

 

[MN Driver]

Just an update, I replaced the belt, it was difficult to loosen the lock bolt that was at the bottom of the alternator because of the small space between the frame and the alternator itself and it took a little bit of time to find the correct angle to get at the adjusting bolt but now that I've done it once I could probably do it again in 10 minutes. I'll keep the old one in the trunk as a spare in case I need it to limp home someday.
I checked the factory service manual and it said to have .25-.35 inches of deflection which I am around the .35 inch amount right now, no squeaks yet, I suppose I will find out if its too loose when a wet day comes.

 

[Drew99GT]

You'll squeek with 3/10s of an inch, especially with a new belt that will stretch. I usually have to re tigthen new belts on my car about 3 times until they stay snug.

I honestly think it's easier to go by feel. Way too loose and way too tight can be had between 1/4 and 3 tenths of deflection.

 

[porcupine73]

Sounds good! I just installed my first new accessory belt ever a few weeks back. I have had to tighten it a little bit about three times now because it squealed for a second on startup. I am paranoid about going too tight though because I just had to replace the power steering pump because I tightened the heck out of the last belt.

 

[Drew99GT]

Me too porcupine! If I get the alternator belt too tight, the bearings in the alternator get noisy. I used to be crazy anal about keeping them a hair on the loose side but as soon as temps start dropping a bit in the fall, I'll get some squeal in the mornings.

Now, I just cinch them up snug via grasping the belt in the middle and wiggling for and aft; you can really feel when it's just right. A couple turns of the adjuster too much and it feels like it's cranked on there; a couple turns not enough and it feels sloppy loose.

Most people's vehicles that have manual adjusting belts where they have installed them and I've checked them, they are cranked on so freakin tight it's insane! When I used to work for a courier, the owner would tighten the belts so tight it was unbelievable. Every morning when I'd start my truck (Toyota 2.7L), all the bearings in accessory items would howl and whine. On one of the Corollas we had, whenever the A/C turned on, it sounded like a hound dog howling or something!

 

[MN Driver]

I've checked it again, it's been about 200 miles and seems just as tight as before but I'll tighten it up as it loosens, no squeaks or squeals yet, no hot belt or pulleys.

 

[Dave H]

MN Driver,

Like Drew, I do mine by feel. I have my '97 Maxima's FSM for the specs, but I can't seem to find a way to get that accurate. For mine, with 22 lbs of pressure applied to the middle of the belt, it should deflect 3.8-4.1 mm (0.150-0.161 inches). I don't know about you, but when I'm laying on my back under a car, I just can't seem to "see" the difference between .15 and .16 inches. So I just snug it up by feel to the point where it doesn't squeal. If it squeals the next morning, I tighten just a hair more until it never squeals. I'm really paranoid about over-tightening and ruining an expensive accessory.

Good that you put the old one in the trunk for a spare. I do the same. People have asked me why I'd save it, but it is still in good enough shape to get me home.

Dave