Hey y'all bout to do a water pump on my 98 extended cab short bed 5.9 1500 4x4. Not overheating yet thank goodness but it's pissing out of the weep hole it started as a drip and now it pisses, I got some sealant the blue and aluminum mix stuff but I haven't wanted to put it in because I'm always scared of that **** plugging up other essentials. Should I run that thru to get some more time out of it. It's the bars leaks stuff seperate blue and aluminum like flake liquid. My problem is I've been looking on rock auto and I can't figure out which pump to order idk if I need a threaded front attachment peice for the heater or non threaded if I need one with the heater tube or not. It's pretty confusing and don't explain much if someone could let me know what I need for this 5.9 and what I should get at the same time I'm doing it that would be great trucks sitting at 250k so I was gonna do the timing chain at the same time. And I'm replacing the radiator because it's chalk full of rust and my water pump didn't leak till I flushed the rust thru the radiator so I think that ruined the seal.

 

I would get the ACDelco pump from Rockauto, as it seems to be the only one that comes with the bypass tube.
Ones that have a threaded port, include the nipple that threads to the port.

And don't use any sealant in the system. Leak from the weep hole says that the pump is on its last leg. I had to use sealer in the coolant system, it did stop the leak, but also reduced heat in cab.

 

Since you're replacing the radiator, I'd suggest going with an all-aluminum unit. Here's an example - https://www.ebay.com/itm/394043140503

As for the timing chain and gear set, I'd suggest picking up a good double roller set. I also use a timing chain tensioner with it - https://www.summitracing.com/parts/clo-9-5387

 

The sealant won't seal moving parts. It seals little pinholes that are static. The turning shaft will keep it from building up. The weep hole is just to keep internal pressure from blowing the seal completely and all at once. It's a slow failure, not catastrophic.

On the pump, what do you have now? The pump in my '96 5.9 uses the tube that pushes into the water pump housing with a rubber O ring in the ump and a bracket held in place with a bolt.

 

I kinda think they're all threaded, some just come with the nipple already installed and others make you install it. Not sure why.

Based upon OP's mention of rust in the system, you definitely want either a pump that comes with the new bypass tube or purchase the tube separately before even beginning the job.

The Fel-pro timing cover gasket kit is nice and comprehensive and priced right.

I think a timing chain tensioner is a good idea but have never bothered as "they survived this long" without

 

Not long ago someone here mentioned that when pulling the bypass tube out from the pump, it just broke off due to rust.

 

I know when I pulled mine, everything below where the o-ring sat, was just gone.....

 

My tube was pretty rusty as well. I replaced it along with a new O ring.

 

If your system is rusty replace it all, My original pump i couldn't get the heater hose tube out and had to cut the pump to release it. You may want to get the water neck also because they do rust out. And drill a small hole in the t stat to let the air from getting trapped in the system. And put some never seize on the threads for the fan, It will help if you have to change it out in the future. Getting a pump from RA do they sell ones with a lifetime warranty? I had more pumps in mine that all my other vehicles combined. So far a Bosch has lasted the longest. First one lasted 5 years and the second lasted about 7. Couldn't get another one(under warranty) from PepBoys because "they don't sell with autoparts anymore" (that's what they told be on the phone). I have one from Auto zone now so see how long this one lasts.

 

Yes, Pep Boys no longer sells auto parts, at least in central VA. Once Carl Ichan bought them out, his goal was to change them all into auto service centers and to get out of the auto parts business.