Correct bolts and washers for Renix MJ water pump?

[kentsu66]

Greetings. I am working with my brother @jamespwsullivan on his '87 Comanche 4.0L. I am trying to do something I thought would be simple -- verify whether the water pump mounting bolts he current has are the correct original style. I'm finding it's not so simple in reality...

 

I first consulted the '87 - '90 parts book and, much to my surprise, found that Diagram 7-2300 (page 172 of PDF) isn't correct! It shows a pulley flange from what I associate with a much later engine (e. g., TJ era) and says there are 5 mounting bolts, which is wrong--there are 4 mounting bolts. (There are 2 additional bolts for mounting the power steering pump, so 6 through holes in the water pump housing total; 4 not threaded and 2 threaded.) I then checked the '91 - '93 parts book and it shows the same incorrect pulley flange! The part numbers for the pumps themselves are correct though.

 

I happen to have access to the 3 relevant types of water pumps so I took a picture of them (attached). The '87 - '90 is on the far left. The pumps are rotated so that the mounting holes are in equivalent positions. (The intake for the 3rd pump is at 3 o'clock, which is quite different from the earlier designs.) By the way, the 3rd pump *does* use 5 mounting bolts--and no additional through holes.

 

In any case, the '87 - '90 water pump mounts with 4 bolts - 3 of one length and 1 of another (longer). The bolts on my brother's truck are standard hex bolts with a captive flat washer. Is this what was originally used for '87 - '90? The parts book pages (which I don't trust) seem to show hex head flange bolts with split lock washers.

 

I have also looked in the 4.0L sections in the '87 FSM supplement, the '88 rebuild supplement, a Chilton manual, and a Haynes manual. I didn't find anything helpful about bolt style there (and at least one of the AMC books has the same wrong pump diagram!).

 

I am also attaching the two parts book pages I mentioned.

 

Thanks for any info and insights.

Diagram 7-2300 from 1987-90 Parts Catalog.pdf Diagram 7-2100 from 1991-93 Parts Catalog.pdf

Edited August 17, 2023 by kentsu66
Fixed title and added detail about the number of bolts and holes.

[Pete M]

I can check what my 88 has tomorrow if no one chimes in before (I'm not at the house today)

[Pete M]

the 88 in the driveway has flange head bolts with no washers at all. 

[jamespwsullivan]

Pete-later reply but we appreciate your checking.  We replaced the mismatched bolts with 4 of the type you described.  Thanks!