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Water Pump Replacement, Thermostat Replacement How-To

76K views 29 replies 23 participants last post by  AWD98 
#1 ·
Your water pump may eventually fail. I hope it never does, but my friend's did on his 96 Astro van. We changed it last weekend along with some other stuff. It was my first time for this on an Astro, but perhaps someone else can benefit from that experience. I won't mislead you, I consider this job kind of a pain. If you're going to do it, replace your hoses and thermostat so you hopefully don't have to mess with the cooling system for a while. It is certainly do-able by many of us, and who doesn't want to have this job done for under $100 when it is needed.

I can't show you a picture of your water pump yet, because we'll need to expose it first.

You'll need your basic metric wrenches, metric sockets and socket extensions. You'll also need a GM fan clutch removal tool. The exact GM tool is J46406, I think, but don't run out and spend $150 on that. Such things are available at places like Advance Auto Parts-they would have rented us a tool kit for this, but they were out so we had to use a Ford Fan Clutch removal wrench set, exactly like this one at the top of the following web site-we found it for $22 so don't pay that price.... http://www.mytoolstore.com/kd/kdengi06.html You may be able to get by with a really large strap wrench and a huge cresent wrench, but we couldn't get that to work.

Before you start this, disconnect the battery!

Water Pump

1. Make sure the engine and coolant are cool. Place a large basin under the van and open the radiator stopcock found at the bottom of the radiator, facing the interior of the van on the passenger side-make sure that the coolant goes into the basin. You may wish to use pliers on the spring for the lower radiator hose and remove it at this point too at this point.

2. Now remove your air intake as per this procedure: http://www.astrosafari.com/viewtopic.php?f=9&t=1142

3. Next remove the upper fan housing as per this procedure: http://www.astrosafari.com/viewtopic.php?f=9&t=1143
3a: Remove the serpentene belt as shown here: http://www.astrosafari.com/viewtopic.php?f=9&t=1144

4. The fan clutch removal tool that I used consisted of a large really thin wrench and an even bigger, but just as thin, crows foot wrench. Because of the tight space we simply could not get good photos of the tool in use. To use the tool, first put something with a half inch drive on the crows foot wrench and slip the crows foot wrench over the four small bolts on the fan/water pump pulley. You may need to align the bolts so that they are all flat side facing the sides of the crows foot wrench-sorry for not writing down bolt sizes, I think they're either 10 or 13 mm bolts. Use the box end of a wrench for that task if you need to do it. Now slip the open end wrench on the large nut between the fan and the pulley, hold the crows foot wrench in place and turn the nut between the fan and pulley counterclockwise (from the drivers side to the passenger side). This may be require considerable effort... Here's a photo of the nut I was talking about and the four bolts on the pulley:


5. Now remove the pulley from the water pump. Because the pulley spins, I found it easiest to zip them off with a 3/8" drive impact wrench. If that's not an option for you, try to hold it in place with a large strap wrench and remove the bolts (10mm socket if I remember correctly, could have been 12):


Okay, there's your water pump.


6. If you are changing hoses-and you should be-you'll want to pull out the lower fan housing at this point. It has plastic tabs holding it at the bottom, so try not to break them as you unclip them. You'll also need to remove the lower radiator hose at the bottom of the pump-his wouldn't separate from the water pump so we just cut it with a pair of pruning sheers-the kind you cut branches with. The hose has a spring in it so have wire cutters handy if you do that... Remember to get a basin under the hose before you remove it.


7. Next pull the line off the top of the water pump as shown.


8. It's probably best if you remove the center top pulley, shown below. To remove it, simply remove the bolt in the center.


9. This will reveal another hose on the top of the water pump. Remove that hose from the water pump.


10. Now you're ready to pull of the old water pump. It's held in by four bolts on the front (15mm bolt heads if I remember right). Remove those bolts, but have a hand on the water pump to catch it for the last one.


11. Sorry, no photos of this, but you'll find old gasket left behind where the water pump bolted on. Scrape those off as best you can. Sorry, no photos here. Apply rtv to the new water pump, place the new gaskets on the water pump and apply rtv to other sides of the gaskets as well.

12. Now, bolt the new water pump back on.


13. Reinstall everything you removed. Sorry, no more photos there.

Thermostat

1. To replace the thermostat, you'll need to first pull the upper radiator hose from the thermostat housing. Here is the upper radiator hose, follow it back toward the motor.

It connects to the thermostat housing. Here is the housing with the thermostat shown inside (hose pulled)


Now pull the wiring harnesses off of the sensors that are in your way.


Next unbolt the thermostat housing cover and pull it off. Note: On the back side of it (facing the engine, you'll actually find two nuts. One attaches a ground lead to the back of the stud on the back of the thermostat. I mention it so you don't break the thing trying to pull it off.


Pull out the old thermostat.


Pop the new thermostat and bolt the cover back on. Remember to reattach the sensor wiring harnesses you just pulled and the pulley. Sorry, no more pics.

Torque Settings
Thermostat cover nuts: 18 ft/lb
Water Pump Bolts: 33 ft/lb
Water Pump/Fan Pulley Bolts: 18 ft/lb
Fan clutch nut: 41 ft/lb - I have no idea how you'd set that... :banghead:

Notes:
* You may wish to double check my torque specifications before using them for your vehicle
* Engine coolant is poisonous, generally sweet tasting, and harmful to the environment. Be careful to collect all of it and properly dispose of or recycle it. This goes doubly if you have pets
* I am only providing this procedure to tell you how I did this. In no way am I telling anyone to do this, especially if they're not comfortable with this repair. Also note, I'm a chemist not a lisenced mechanic, so as with all things, consider the source.
 
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#2 ·
That's a great write up chemist, I'm sure others will really benefit from it, Thanks.:)
 
#7 ·
Good write up!
Some guys will loosen the fan clutch using an air hammer with a flattened chisel or round head bit. They hit on the edge of a flat to loosen or tighten the nut. I didn't have either tool to do my van, so I took the back off the old pump (off the van) and jammed a screw driver into the impeller while turning the clutch nut with a big adjustable wrench. I put it back together with the adjustable wrench and a strap wrench.
 
#8 ·
This is a great post. (I wish I would have found/read it before I changed the water pump on my 1998 Astro AWD).

As far as the fan clutch tool, I visited AutoZone, which only had the Ford tool kit to rent out. I did not come home with the tool as there was nothing in the kit that could be used to hold the water pump sheave from turning when trying to loosen the big nut on the water pump shaft.

I had success (holding the pulley) by using a short length of swing-set chain through one of the four pulley mounting bolts. As a precaution (and not to mess up the threads of the original bolt), I did buy a slightly longer Metric bolt to secure the chain. I took the other end of the chain and secured it over steering links directly below with a "quick-link".

The steering linkage was of heavy diameter to take the load as I worked the big nut loose with a large Crescent wrench. The (right-hand thread) nut was on tight, but not Godzilla tight. I recall the GM manual saying the tightening torque for the big nut to be about 48-Ft-Lbs.
 
#9 ·
I found this and made a similar tool for fan removal. It worked perfect and was free!!! I actually did it a bit different. I took one of the 4 bolts out and drilled the hole in the bar the same size and threaded it back on so it held the tool against the black bit and made sure it wouldn't slip off and smack my hands on something.
no need to buy proper tool
 
#11 ·
Two ways to get that big nut loose, a strap wrench and a 36mm wrench, or the other cheaper way if you need to buy a tool ( that wrench was 40 bucks! ) ...went and bought me the biggest crescent wrench I could find within reason and a 2 1/2lb mini sledge. Put the crescent wrench on the bolt and smack it with the hammer to loosen. Might take a few blows ( keep the belt on for now ) but it'll come off.

As far as the water pump itself, you can leave the pulley on it until you get it off as it's not really in the way being that the 4 bolts that hold it on ( the water pump ) are on the left and right of the pump.

What gave me fits was getting the pump back on without crushing one of the gaskets. I took 3" bolts of the same thread pitch, cut the heads off, ground a slot in the end for a screwdriver and put them in to guide the water pump up to the block. For me, it's a necessity since I have a hard time handling a cast iron water pump with one hand while trying to thread the nuts ( carpal tunnel sucks ), so the guides did the trick for me ( after 2 sets of gaskets blowing out shortly after warming the motor up to temp ) There's room to do it, I wish GM had just studded bolts in at least 2 of the 4 bolt holes in the first place.

Oh, and make sure you have perfectly clean gasket mating surfaces or you are asking for a leak. If you use water pump gasket sealant, don't slather it on, just a nice thin film is all you are going to need.
 
#13 ·
thanks for the write up, all i'm attempting is the thermostat, but i'm glad you pointed out the double nuts for the ground wire. i did have the water pump replaced at the dealer (yes, was a bit pricey, but it wasn't something i was willing to attempt.) now the thermostat is shot... i figured i could give that a try since is is sorta visible just looking at the engine. took off the air cleaner, and top radiator hose, disconnected some sensors and started wrenching. got the first nut off from the grounding wire OK, when i tried the bolt on the back of the thermostat housing i rounded off the nut... used a craftsman 6 point deep socket and it just spun around... i tried a 'gator grip' socket with the pins inside that is supposed to grab onto anything, well the stud is too tall for it to get a grip. now i'm worried about the other bolt in the front. my deep socket is too tall to fit under the cruise control bracket and yanking on it with an open end wrench isn't working yet either... i have them both soaking in liquid wrench, but i don't think rust is an issue.

anybody have any suggestions?

thanks for listening
ed
 
#14 ·
Tapping on it can help sometimes, also heat or heating while tapping. Once you get it cracked loose, if it's still stiff to get out, work it back and forth progressing a little farther each time.
 
#15 ·
thanks for the tip, i did manage to get them both out. it turns out that the nut for the electrical ground was 14mm but the housing nuts are 13mm. managed to move the cruise control bracket just enough to get a socket on. both studs came out with the nuts still on them. i'm thinking i'll replace those too. these forums have helped a bunch over the years.
my wife thanks you all as well since it's her van :)
 
#20 ·
Wow, i'm stuck at step 1, lol!

Is the drain petcock supposed to be a 1/4 turn unit like the petcock on a gas tank or garden hose? Or do you have to unscrew it a lot? I'm afraid that thing might be broken because i had to get pliers on it to turn it, and nothing happened at 1/4 turn, or a full turn. After several turns (counter-clockwise, unscrewing) i started to get coolant but i'm pretty sure it was coming out around the petcock itself, not from the drain tube.

That petcock is hard to reach! I guess i'd have to pull the whole radiator to replace it. I'm not excited about this whole thing. I just want to sell the van and somebody test drove it and it started leaking coolant at the pump! Now it's leaking pretty badly so i'm going to have to fix it before anyone will buy it. *grumble*
 
#21 ·
To the guy whose cruise control bracket is in the way of getting a socket on the forward thermostat housing bolt...remove the 10 mm bracket bolt going into the firewall and then the bracket can be pushed an inch over to get your deep well in there.
The stud will unscrew with the nut so don't keep ratcheting thinking the nut will come out in the socket, (in other words don't let the stud drop down where you can't find it, (I lost the t-Stat housing hose clamp like that).
 
#22 ·
Good article.

I recently replaced the water pump in a 2001 Safari and I could have used your article.

I removed the fan nut by striking it straight down with a heavy, tapered marlin pin with a fairly blunt end. At least, I placed the tip of the marlin pin on the nut and tapped it's large end firmly with a claw hammer. I was aware of the force used but reasoned that it was attached to the old water pump and would likely cause no damage.

Tapered steel has the property of transmitting taps on the large end to compressed impact on the small end. Anyway, a couple of hits loosened the nut enough for it to turn with a small pipe wrench.

Be sure to turn the nut the right way!!

Before placing the water pump on the engine block, I cleaned and inspected the engine block water port faces to be sure they were free of contaminants, then applied some gasket cement to them. I coated the water pump port openings and gaskets with gasket cement and applied the gaskets, aligning the gasket holes with the water pump bolt holes. Then I inserted the bolts, holding them in place while I aligned the pump bolts with the threaded block holes.

Once I had the 4 bolts started, which is not that easy, I slid the pump forward on the bolts till it made contact with the block. It's important to do this carefully so as not to knock grime off the block and get it between the gasket and the block ports.

It might not be a bad idea to remove the alternator as well, to get better access to the water pump bolts.

Then I tightened the bolts one at a time till just before they were snug. After that it was a matter of tightening them diagonally till they were tight enough.
 
#23 ·
Zombie thread bump! I did this last Wednedsay with the help of this thread. Thanks everyone for the tips.

Autozone has the flat wrench set for $25. They said it's returnable for a full refund.

One tip I'll add for using it, which was demonstrated to me by my brother-in-law. He is an autoshop teacher and former dealership mechanic:
If you can't get the larger spanner to grip across the four bolt heads, put the serpentine belt back on, use only the smaller wrench, and tap the end of the wrench handle with a mallet to get the large clutch nut to start turning. This worked like a charm and saved me hours of struggling with lining up the bolt heads.

Another tip was to thread the four pump bolts through the gasket holes and start each bolt with only a turn or two, then walk the bolts in one at a time with only a half turn to a turn per bolt. Sort of like walking a wheel onto the studs with lug nuts. Then when the four bolts are seated, torque each bolt only partway and go around adding a bit of torque to each. This is to prevent wrinkling or misaligning the gaskets.

He also cautioned me to use the gaskets dry without RTV. I was skeptical about this but FelPro's website confirms that their gaskets are designed to be used without sealant or compound.

The one thing that did go wrong was when I installed the new bypass hose, I somehow started a hairline crack at one of the clamps. What did I most likely do wrong in installing it that caused it? Could this be caused by trying to nudge it into place without spreading it enough?
 
#24 ·
Whiskeyrebel said:
He also cautioned me to use the gaskets dry without RTV. I was skeptical about this but FelPro's website confirms that their gaskets are designed to be used without sealant or compound.
Dry is definitely the recommended way.
 
#25 ·
Whiskeyrebel said:
He also cautioned me to use the gaskets dry without RTV. I was skeptical about this but FelPro's website confirms that their gaskets are designed to be used without sealant or compound.
If you read the fine print on the gasket manufacturer's claims they likely specify absolutely flat surfaces on the water pump and block faces and with corrosion and possible warpage, that is not likely to be the case with an older block.

I used a thin coating of high temperature RTV on both sides of gasket to ensure imperfections in the metal were accounted for. Also, the gasket I received from the supplier had no instructions.

I think it's far more important to ensure all dirt and grime is cleared away from the mounting surfaces and that none gets knocked off to fall between the mounting surfaces. It's been over two years now since I replaced the pump. I added a fluorescent dye to the cooling system water recently and using a UV light, there are no tell tale signs anywhere of water leaks.

I was disappointed in a way because I have been trying to track a tiny leak that is possibly spraying coolant onto my fan belt, causing it to squeal. Nary a sign of the fluorescent die anywhere, not even on the fan belt. There is a tiny amount of fluorescent green at the end of a heater hose, coming from the heater control valve where the hose attaches to the block. It's the hose with the metal pipe in it.
 
#26 ·
Ericglo said:
Here is a pic of the Autozone rental tool. I struggled with this till I finally figured out what was going on. Loosen the four bolts to line up on the tool. Just remember to tighten them when your done or you will get a noise that you won't like. :D
To quote myself, I went to Autozone and they have a new tool. I wish I would have rented that one. It is free, so I don't know why I didn't get it just in case. I ended up going to Advance and their tool was slightly to large, but I was able to get a grip on the bolts. They didn't have a small enough tool for the fan clutch nut either. I was able to find a large enough adjustable wrench to fit. Frustrating when you don't have the correct tools.
 
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