Which water-pump part number do I need?

[Victorkilo31]

Little back story. I've got a coolant leak on my truck that I suspect is coming from around the water pump. Its not much, mostly few drops noticed at a time, doesn't steam out or get all over the place. Don't see any signs of it anywhere else (in the oil, on the exhaust, things like that) but its not something I want to let get worse. I've got a dye kit I'm going to use to check once the weather breaks up here a bit more and try to find out for sure where its coming from. Currently I'm suspecting the water pump as the problem, since thats the only place on the engine that has been wet at all. In my research I've come across some problems on what replacement one I should get. Its an older M998 (1993ish), and unfortunatly the orginal data plates were removed so I can'd do much with that. I'm fairly confident that I've got a 6.5 in the truck, and not a 6.2. My question is what part number water pump would I need order? Here is what is confusing me. The TM (9-2320-280-2 pg 3-130.4) has a caution that states:

Ensure water pump P/N 251-591 is used on 6.2L engines, or damage to equipment will result. Ensure water pump P/N 12534772 is used on 6.5L and 6.5L detuned engines, or damage to equipment will result.

The TM 9-2320-280-24P has nsn: 2930013535794 listed for the truck that I'm pretty sure would work on mine, however, that caution makes me wondering which would be correct for my truck. My truck has the vblets, so I'm pretty sure it falls under the detuned 6.5L engine but I'm not sure on this one. I've looked up the part numbers listed in the caution and they are similar in appearance, but this isn't something I'd want to make a mistake on in ordering or attempting to install. I know that appearance isn't everything as some of the water pumps (the newer 6.5 if memory serves) spin counter clockwise, and the older spin clockwise (or vise vesa). I'm sure there's a few other differences as well, but hitting the high points. Anyway just trying to get the right part.

My second question is that in a few of the pics I've seen for the NSN out of the 280-24P there is a timing plate gasket included with the kit. The TM (9-2320-280-2 pg 3-130.4) for installing doesn't mention this gasket, only putting some sealant on the plate and the reinstalling on the engine. Is this a publication discrepancy or did it change and the gasket replaces the sealant? Or does it require both, or one or the other?

I get the feeling I might be over thinking this, but any help or suggestions would be greatly appreciated. I don't want to make this an expensive learning experience. Want to get this done right the first time, should it turn out to be the water pump and not a hose or something small.
Thanks for the assistance

 

[Action]

Do you have sets of V-belts on the front?

 

[Victorkilo31]

Do you have sets of V-belts on the front?

Yeah. I have 3 on the alternator and 1 on the ps pump

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[DSO_351]

H20 pump has a weep hole (drips) when bearings have or are close to failure. V Belts = H20 Pump for 6.2 engine only. A civilian one will work. Use rock auto or local auto parts cross reference for 1985 6.2 diesel with J engine code.

Some use gasket, some may not. look while disassembling yours.

 

[DSO_351]

Consider changing hoses, flushing block, heater core, etc. Hose sets are on popular auction site or distributors. Take time to do it right. Most costly repair if let go.

 

[doghead]

I think (assuming) the difference in water-pumps is, rotation. Guessing the 6.5 water-pump is for serpentine belt setups(reverse rotation).

 

[Victorkilo31]

Part of my plan is once I determine where the leak is, repair or replace the part, along with some other parts. Planing on flushing the coolant system since I'm gonna drain it for a block heater, new hoses, new belts, glow plugs, and a few other things while I'm in there. First I want to determine what's leaking, and given what I'm seeing so far it's leading to the water pump so I wanted to get an idea of what pump I needed but the TM threw me off today

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[86humv]

6.2, and 6.5 de-tuned use same pump and backing plate...6.5NA's and turbo's use reverse rotation HO pumps .
They won't interchange due to shape and backing plate.

 

[Victorkilo31]

Thanks for all the help with this. Hopefully soon I can get started figuring out where the drips coming from and get it taken care of.
Is there enough room to get it out with out totally disassembling the whole from end? My garage is a bit small for pulling hood and all that off so if I don't have to pull everything out i can take more time to do it at the house. If not I'll need to find an alternate location

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[Victorkilo31]

Another quick question while I'm thinking of it, is the thermostat different between motors? I haven't checked part numbers yet, but if I need the 6.2 water pump I figured I would ask if I need a 6.2 or 6.5 thermostat if it matters. Thanks

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[86humv]

Same thing

 

[Milcommoguy]

Check the short stubby 3/4 sized hose from the top of the pump to the cross over manifold. Easy to check. I have seen them cracked or loose clamps. GI Joe doesn't seem to replace them when needed. CAM

 

[NormB]

Check the short stubby 3/4 sized hose from the top of the pump to the cross over manifold. Easy to check. I have seen them cracked or loose clamps. GI Joe doesn't seem to replace them when needed. CAM

I posted on that months ago. PFC Snuffy used a 5/8 hose outlet on the crossover, but there was a 3/4 outlet on the water pump (what‘s supposed to be in both places). I replaced the hose and still had leaking. took the hose off again to fix it and couldn‘t help noticing the top/crossover end was choked down. Replaced the fitting and it works fine now.

One other thing, when you knock out the freeze plug, be prepared to get soaked. Or have towels, buckets, short kid’s wading pool to catch it. LOT of residual water in the block.