Changing the water pump on a 98 Chevy Astro: a pictorial.

I figured out where all that water that was missing from my coolant system went the other day when I came out of the laundromat and found a big puddle under the van. Straight out of the water pump. I thought about breaking out the Haynes manual and replacing it myself (if you live in a van you definitely need to have a Haynes or Chiltons for your vehicle – you can click here to find one on Amazon). Then I thought about just paying someone to do it for me. Things are all smooshed together under the hood and I don’t really have all the tools I’d need to do it, tho I could get them. I could hear my mother’s voice in my head tho. My mom was strongly influenced by first wave feminism and totally believes that I can and probably should do things like this myself.

Then the conundrum solved itself – a good friend and customer of a couple years (we’ll call him Bob) pulled into the parking lot. Bob’s a heavy equipment mechanic. I put my mother out of my head, hugged Bob and pointed out the puddle under my van. He confirmed that it was my water pump and something to do with a bearing, and we went on a quest for a new water pump. Apparently the fishing boats use the same water pump as my van, so all the places that were open were sold out. NAPA would be open in the morning. I love NAPA. I can get a discount at NAPA, and so can you – just ask the clerk to put your order under some big company, and pay cash. The clerk at NAPA knows and loves me from last year when the bus was breaking down every two weeks, so he searches through the computer and gives me the best discount available – around thirty percent, usually.

Bob and I had dinner and worked out a deal for an exchange of services. He came into the club that night and Susan and I gave him a couple smoking hot double dances. The next morning I showed up on his doorstep bright and early with a new water pump, some coolant, oil, and a serpentine belt (it needed changing soon anyways).

I got to thinking, while I was watching him work on the van, of all the times I’ve been looking around on the internet for real human step-by-step instructions with pictures. Especially the time we were trying to convert the bus to run on straight veggie oil. So I was inspired to whip out the camera and make for you here a complete step-by-step tutorial for changing the water pump and serpentine belt on a Chevy Astro. I don’t pretend to be a mechanic, or even know much about what I’m talking about, so if you see something wrong please correct me.

Step one: you should probably disconnect the battery. Water and electricity don’t mix well. I didn’t take a picture of this, cause if you can’t figure out how to disconnect the battery you just need to go to a mechanic.

Step two: open the drain at the bottom right hand corner of your radiator to empty it. Again, no picture. It’s pretty straight forward. Make sure you have an adequate container to catch ALL the fluid that comes out and dispose of it properly.

Step three: now you get to start taking apart that crazy maze of stuff. See the air cleaner thing? Disconnect from the hose and you can just lift the whole thing out. It’ll look like this (just click to see bigger):

Step four: see that piece of plastic coming off the back of the radiator? Never would have occurred to me, but that thing comes off. The screws on mine were just at the top corners. Maybe there were supposed to be more, but someone worked on it before and didn’t put them back. Hey, it’s done fine without them all this time.

Step five: it’ll look like this:

See the serpentine belt there? It’s really easy to get off because it has an automatic tensioner thing. Just take it off.

Step six: disconnect water hoses from the water pump. They’re gonna be stuck on there pretty good, and after you loosen the hose clamps you’ll probably need to pry:

Step seven: undo the bolts:

and pull it out:

Step eight: this is the part where it starts to be useful to have some tools. Clamp the water pump down however you can and get the fan and clutch off it.
also disconnect any hoses that are still on it.

Step nine: clean up the spots where the water pump will be connected to the engine block. You want the eventual seal to be water tight, so this part is important.

Step ten: connect the hoses to the new water pump. Make sure everything’s all happy and looks just like it looked before.

Step eleven: put it on the engine. Use the gaskets that came with it and lots of your goop of choice, and then reconnect the hoses.

Step twelve: put the new belt on.

Step thirteen: put the fan and clutch on the front of the water pump, and the funny plastic shield and air filter back together (no picture, but do it just like you did taking it off).

Fourteen: guess what? You’re done! Add antifreeze and check to make sure nothing’s leaking.


  1. What sort of mileage does your astro have on it?

    I can’t remember ever having the water pump go out on any of my vehicles.

  2. Joe, it has 100k miles, 40k in the last 8 months since I bought it. I blame the water pump failure on the radiator flush I had a while ago – there was a bunch of fungus in the radiator and the flush probably dislodged some of it that got caught up in the water pump. In my experience tho, it’s fairly common for the water pumps to go bad on high mileage vehicles.

  3. The reality is; Water pumps often go out because of lack of use and particularly low miles AND not changing the antifreeze every two yrs. High milage vehicles ususlly do not need water pumps within the first 150k miles or so.
    Back in 1977, Mom’s 1965 Olds 98 developed a water pump leak w only 11k miles. Twelve yrs on the same coolant ruined the bearing inside the pump and it was leaking like crazy. Main Point; The coolant has lube in it for the pump bearing.
    Love reading your blog and love your attitude.

  4. I’m sorry, that was rude. I’m a fan and consider your journey and writings quite inspirational.

    (dear everyone: I’m an idiot. please disregard my previous comment. Thank you.)

  5. hey i have a question about when you put the belt on when u turned the tensioner what pulley did you put it over? because i’m having a problem getting the belt on my astro i just can’t get it over any pulleys at all

  6. Put it over all of them except the one opposite the tensioner. Then pry really hard on the tensioner while pulling the belt really hard to get it on. If you can’t get it on *any* of them it might be the wrong belt.

  7. I mean the one on the right bottom. But that’s just the one I used, I’m sure it would work with any of them? If it’s not going on check to make sure it’s in all the grooves – if it’s up on the edges it’s not gonna fit. If it is, and you’re sure you have the right size belt, you probably just need to turn harder on the tensioner?

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  9. This was good…referred to it before changed pump on my 99 Astro at 199000 miles. Few comments: Getting fan clutch nut off pump can be the biggest headache. Mine was standard thread, meaning counterclockwise to loosed…you know, righty tighty…lefty loosey. Anyway, I have heard that some are reverse threaded and this should be noted on decal noting belt wrapping…usually somewhere in front of engine compartment…you can check threads on replacement water pump to verify…if you got the correct pump for your van. I agree with removing pump with fan/clutch attached, then dealing with it off the vehicle. And for replacing the belt…I found it easy to route belt around everything except the “bell” pulley guide that is just above the pump. Why…because it has smooth curved edges, that allow belt to slip over. Great article…it definitely helped me get the work done.

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