Let's talk water pumps

[tugboat95]

So what's the difference in factory OEM direct fit pumps. One gives me 2 5/8" diameter hub and 3.72" hub height. Other one is 3.313" diameter hub with a hub height of 2.31" both say they are direct fits for my 4.0L and are OEM. What does the difference do to the belt placement? And why?

 

89 Comanche

Eliminator

2wd

4.0L

5 speed PukeGoat

Factory Original

 

 

 

[Big Dan]

This won't directly answer your question at all. However, to be safe, just get a Mopar pump for a 2000 or 2001 XJ. They're still available and you know you're getting a correct fit part.

If you don't want to do that, hopefully someone can provide additional info on the question.

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[eaglescout526]

I think he’s correct in terms of the OEM water pump still available and the original one supersedes I think well into 2001 XJs. 

[75sv1]

I am taking it as the same year MJ or XJ. The WJ has an extra bolt hole and a slightly different bolt pattern.  I don't want to get into that story, but I does relate to what I think you are looking at. There are to my knowledge two different heights of water pump for each year. I do not know why. Then there are the matching height pulleys. I have not run into this personally. 

[eaglescout526]

68382488AA is the latest number. Used from 1987-01. If ordered through me it would only be a $60 pump. 

[schardein]

I haven't researched the numbers, but I know that a water pump for a YJ 4.0 application has a different drive flange for the center mounted cooling fan.  As opposed to the XJ/MJ 4.0 with an offset cooling fan that uses a pulley only on the water pump.  

 

I've dealt with this swapping an XJ engine into a CJ requiring a center mounted fan.  Had to switch water pumps.  Other than the drive flange (that the fan/pulley bolts to), the pumps are the same.  If memory serves, the larger diameter flange is for the XJ/MJ.

[tugboat95]

I haven't researched the numbers, but I know that a water pump for a YJ 4.0 application has a different drive flange for the center mounted cooling fan.  As opposed to the XJ/MJ 4.0 with an offset cooling fan that uses a pulley only on the water pump.  
 
I've dealt with this swapping an XJ engine into a CJ requiring a center mounted fan.  Had to switch water pumps.  Other than the drive flange (that the fan/pulley bolts to), the pumps are the same.  If memory serves, the larger diameter flange is for the XJ/MJ.

That seems to it. The "other" size had something to do with actually mounting and running a fan. My application doesn't do that. So I bought the shorter height and larger diameter hub.. Fit perfectly.

89 Comanche
Eliminator
2wd
4.0L
5 speed PukeGoat
Factory Original

[AZJeff]

Guys,  I would think what hub size will work is really dependent on whether it will fit the PULLEY on an XJ/MJ with the 4.0

 

The pulley (and it's bolt pattern) is the determining factor, is it not?

 

[schardein]

2 hours ago, tugboat95 said:

That seems to it. The "other" size had something to do with actually mounting and running a fan. My application doesn't do that. So I bought the shorter height and larger diameter hub.. Fit perfectly.

41 minutes ago, AZJeff said:

Guys,  I would think what hub size will work is really dependent on whether it will fit the PULLEY on an XJ/MJ with the 4.0

The pulley (and it's bolt pattern) is the determining factor, is it not?

That's basically what I was getting at.  The pulley on an XJ/MJ application has a different bolt pattern than the center mounted fan (and pulley) of a YJ application.  I never noticed, but apparently the height is different as well-- although I'm sure the difference is made up in the pulley offset, since there is no difference in the other accessories.