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Belt tension on Serpentine belt?

Planetcat

NAXJA Forum User
Location
NorCal
Does anyone know how to determine the serpentine belt tension on my '96 XJ? The FSM says something like 130-150 lbs. The only belt tension guages I can find are the ones where they wrench onto a spring pulley (n/a for XJ's). Pep Boys, Autozone, Kragen, etc. don't sell the type that I need. Seems sort of difficult to put a tensioner on the belt and pull on it until it reaches 150 lbs. Or is eye-balling it good enough?
 
I remember someone on this forum said that NAPA sells one that is cheap and does a good job on an XJ. Not sure of the name though.

Sorry so vague.

Burley
 
The FSM is no help - someone posted here the best way is to tighten it (repeatedly) until it stops squealing - which is not that hard, using the tensioner under the p/s pump.

Without the special guage, it makes sense.
 
I got mine at NAPA it is called the Kricket II and was less thatn $20, think it was $12.

Here the info off the box
Front Label

NAPA KRIKIT II V-BELT TENSION GAUGE
KR2 bar code 0 29769 35216 8

end label

KR2
7401-0102
1 EACH

It has a range of 100-300 lbs.

For my 88 XJ the manual says to check the tension on the section of the belt between the idle pulley next to the AC compressor and the power steering pump; in addition, here are the belt tension values:

New Belt: 180-200 lbs
Used Belt: 140-160 lbs
 
New belt gets between 180lbs and 200lbs and 140lbs to 160lbs used, used belt is defined as one that has been run for 15 min or longer.
Pg 7-38 on the 98FSM.

The krikit gauge works great for this.
Now I don't know about the 96 but my 98 has the idler pulley almost directly behind the electric fan on the drivers side, it takes a 15mm wrench to loosen it 1/2 turn so you can release tension on the adjuster bolt next to the PS pump. I bought a l-o-n-g 15mm open/box ratchet that allows me to loosen and tighten this bolt without having to remove the electric fan which is the only way I could get a wrench on that idler, got it from MAC.
 
Thanks, I'll go to Napa.

Thanks everyone for the info. I'll get the Kriket at Napa. Didn't think about trying them. We're all consistent with the info on the pulley and how to tighten/loosen it, where it's located, etc. Sounds like it didn't change much across years.
 
If you have a Haynes or Chiltons there is usually a generic bolt size/grade/torque value in the front of the book.
 
From what I have been told is when you can barely twist the belt 90 degrees its good. At least for the 87-96 4.0L
 
From what I have been told is when you can barely twist the belt 90 degrees its good. At least for the 87-96 4.0L
You should not be able to twist it 90 degrees. I've told myself I'll get the gauge but I haven't yet. I tighten it to what I think is good and tight without wanking the bolt, then I run it.

If it squeaks I'll give it another turn. I needs to be amazingly tight though, but like said, you don't want to get out the breaker bar to tighten it.
 
You should not be able to twist it 90 degrees. I've told myself I'll get the gauge but I haven't yet. I tighten it to what I think is good and tight without wanking the bolt, then I run it.

If it squeaks I'll give it another turn. I needs to be amazingly tight though, but like said, you don't want to get out the breaker bar to tighten it.
serious? I've been running my 89 4.0 for 4 years, with a/c and the works using this method (90 degree) without troubles at all!
 
Old school rule was the tension was right when the longest run of the belt could be deflected about 1/2".
 
Old school rule was the tension was right when the longest run of the belt could be deflected about 1/2".

That sounds just about right...and I AM old school!!

...and as far as the 90 degree rule...sorry Johnnie Walker...I was wrong...I thought that meant long ways...I get it now, sideways...that works too, I just went out and tried that.
 
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Next old school rule was to guess at tightening it, just past squealing. If it's not slipping, it's working.
 
Short story -

When we were fixing my PS pulley on the Rubicon in 06 after my rollover, a couople of "old school" guys from the next camp came over to watch. Between the two of them, they had like 60 years of mechanic experience.

My buddy was tightening the belt and one of the old guys reaches over to twist the belt. He says, "That's good right there". My buddy whips out his Krikit II and the tension was nowhere near tight enough.

He proceeded to tighten it to 160 ft/lbs. And the "old school" guys never said another word.
 
I use to have problems getting the belt tension just right. It would squeak, I would tighten it some more. The old school methods never worked for me. Got the Krikit and its a lot easier now.
 
Short story -

When we were fixing my PS pulley on the Rubicon in 06 after my rollover, a couople of "old school" guys from the next camp came over to watch. Between the two of them, they had like 60 years of mechanic experience.

My buddy was tightening the belt and one of the old guys reaches over to twist the belt. He says, "That's good right there". My buddy whips out his Krikit II and the tension was nowhere near tight enough.

He proceeded to tighten it to 160 ft/lbs. And the "old school" guys never said another word.

Old school drop out? Sorry, I was the Old school class clown! LMAO!
 
You can also push on the belt just on the itself on the water pump pulley. :wave:


That trick won't work for later XJs as they changed the belt routing and it doesn't pass in front of the tstat housing.
 
190lbs brand new, 170lbs if it's been run more than 15 minutes.
 
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