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Modified serpentine belt routing

D

Dr. Dyno

NAXJA Forum User
Location
Al Ain, UAE
If your idler pulley decides to bite the dust or the mounting bracket bolt hole threads get accidentally stripped when you replace the pulley, there's an easy solution. Get rid of the pulley altogether and reroute the belt. Of course this means you'll need a shorter belt. The stock '92 XJ belt is 2475mm long and the replacement belt needs to be 2315mm long. Lo and behold, the '97-'98 TB belt and the '91-'01 2.5 XJ belt is exactly the right size and carries part no. 53011035, so that's the one that I used when it was time for the idler pulley to RIP. Here are the belt routing diagrams:




It works very well and there are no clearance issues. The resulting modified belt routing is almost identical to that of the '97-'98 4.0 XJ except that the latter has an idler pulley between the PS pump and crank pulley. With the original idler pulley gone, there's one thing less to go wrong. You'd also be able to remove the t'stat housing more easily 'cause the belt will no longer be in the way.
 
Last edited by a moderator:
that looks good. now if i took out the fan pulley too and went straight from the crank pulley across to the alternator and up to the A/C, would there still be enough surface contact/tension for everything to work properly???
 
scorpio_vette said:
that looks good. now if i took out the fan pulley too and went straight from the crank pulley across to the alternator and up to the A/C, would there still be enough surface contact/tension for everything to work properly???
Click to expand...

I doubt it, I think losing the idler pulley alone doesn't have enough wrap for the AC compressor but I guess it works. But losing the fan would allow for hardly any contact on the crank pulley and alternator.
 
yeah that's what i was worried about.

what is rule or guideline about how much contact there has to be on a pulley. i know there is always talk about having enough contact, but sometimes i wonder........the hardest part is getting the the alternator or other devices spinning. once it's spinning, it really shouldn't require that much force to keep it going right???

so basically what i'm wondering is. everything would be week at startup, but once the pulleys are up to speed, it shouldn't matter to much how much contact there is, cuz it just has to maintain the rotation. right??? just wondering.
 
Pictures still not working....
 
BlueCuda said:
I doubt it, I think losing the idler pulley alone doesn't have enough wrap for the AC compressor but I guess it works. But losing the fan would allow for hardly any contact on the crank pulley and alternator.
Click to expand...

pretty much. i tried a way i found online by using some mercedes belt and going from the crank to the alternator. the crank gets enough belt but the alternator doesnt.
 
scorpio_vette said:
that looks good. now if i took out the fan pulley too and went straight from the crank pulley across to the alternator and up to the A/C, would there still be enough surface contact/tension for everything to work properly???
Click to expand...

There would probably be just enough belt contact with the alternator pulley 'cause it doesn't need very much but it would be marginal with the crank pulley. It'll work OK as long as the belt is tight enough but if the belt even becomes slightly loose, you might have a problem with the belt slipping and not turning the pulleys properly so it's slightly risky. If you do decide to run my set up but without the fan pulley, leaving only 5 pulleys to drive, you'll need a belt that's about 1890mm (74.4") long.
Hell you could even remove the A/C compressor, mount the alternator in its place, and drive only 4 pulleys.
 
Dr. Dyno said:
There would probably be just enough belt contact with the alternator pulley 'cause it doesn't need very much but it would be marginal with the crank pulley. It'll work OK as long as the belt is tight enough but if the belt even becomes slightly loose, you might have a problem with the belt slipping and not turning the pulleys properly so it's slightly risky. If you do decide to run my set up but without the fan pulley, leaving only 5 pulleys to drive, you'll need a belt that's about 1890mm (74.4") long.
Hell you could even remove the A/C compressor, mount the alternator in its place, and drive only 4 pulleys.
Click to expand...

i tried it that way and no matter how much i tightened the belt it still would slip on the alternator at low RPM's
 
what about when you get rid of the A/C? 5-90?
 
GreenbeltXJ said:
what about when you get rid of the A/C? 5-90?
Click to expand...

Then you can end up with something like this if you mount the alternator up high where the AC used to be:

BELT6_mod2.JPG
 
Dr. Dyno said:
Then you can end up with something like this if you mount the alternator up high where the AC used to be:

BELT6_mod2.JPG
Click to expand...


I'm doing that as we speak, my ac packed it in, the alt has already been killed by mud once so I made a custom bracket that puts the alt so hi that the hood will barely close. SHOULD work, the only prob I see is theres only half a wrap on the fan pulley. Guess we'll see if it's enough......
 
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