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On the left is the Series 1 water pump, on the right the Series 2. Both are AC Delco.

I just happened to have a new AC Delco Series 1 laying around when we did Matt's cam swap a couple years ago at my place. We did the comparison at that time, found them to be identical EXCEPT the Series 2 pulley doesn't have a hole in the middle, and won't mount to the Series 1 pump. Solution? Dig out a spare S1 pulley from my buckets 'o parts, and the problem is solved.

The Series 1 AC Delco water pump impellers are a far more efficient design (cast, curved blades) than the Series 2 stamped impeller, and is less prone to cavitation. It will move more water smoothly at higher rpm's than the S2. This is especially important on cars with raised shift points, although the few seconds of cavitation may not have much of an effect. Even the curved profile of the casting helps with flow. It's a gradual lift towards the shaft when compared to the S2 pump.

It's a direct bolt-on, and uses the same gasket, as long as you use the S1 pulley (wrecker, new, cheap).

Other than that, I prefer not to use plastic gaskets for these, if the new one comes that way. I prefer the black paper with red stripes. It's worth getting the right gasket before starting.

willwren wrote:The pump we installed on myfirstbonnie's 2k was an AC Delco pump. I got it from either Rock Auto or NAPA (I usually keep a spare on hand for the two cars due to the low cost). 30 something bucks. You MUST use the S1 pulley to make this work, gaskets are interchangeable between them. The S2 water pump pulley is the same diameter, but has a full crown face that will not bolt up to the S1 pump. Rock Auto used to have the pulley too, but I don't see it any more. Wrecker or any local dealer should. It should have a HOLE in the middle for the spindle of the pump to come through, not a full face-crown like the S2.

The AC Delco pump SHOULD be the right one on Rock Auto, but I see two. I doubt I still have the old box to check. Keep in mind that even if the pic on Rock Auto has cast impellers, if it's a rebuild, the core may not have. NAPA is your best bet. If they don't have one (not likely) have them order it, and check it before you leave the store.

myfirstbonnie wrote:As John said, you need a series 1 water pump with the cast impeller and a series 1 waterpump pulley. I am seeing about a 10 degree difference with this pump, compared to the series 2 pump with the following set up:180 degree t-stat and the fans are programed to run all the time.

Ok, let me get this straight then...I am going to be getting a Series 1 AC Delco pump, an S1 pully and a black paper gasket with red stripes?? NAPA have all this or is there some other place that would be better?? Thanks Bill...

edit...also going to need the part numbers for both water pump and gasket to make sure I am getting the right thing!!

Just go in and ask for an AC Delco pump for a 93 SSEi. Open the package (they'll order it in a day or two if not in stock) and verify the impeller is cast. If it comes with a blue plastic gasket, ask for a paper gasket, it'll be in stock (same part number as yours).

You MIGHT have to go to a wrecker for the pulley. Any GM FWD 3800 from 1987 to 1994/5 (Series 1) will be correct, NOT 1995 L36 cars though.

NAPA is the best choice, and specify AC Delco. IIRC, it's about 36 bucks. They might be able to get the pulley too, also specify the same year.

Ok, I am having a hard time finding this thing locally...it amazes me but yes no one seems to cafrry AC Delco parts here in beautiful Fresno?? If anyone has a part number or somewhere online that has this particular part please let me know. Just when you are feeling like things are going somewhat smoothly...here comes the curve ball!! Thanks

Rock Auto has all you need. If you order from them, make sure you use the discount code.

water pump, ACDelco, cast impeller.......part # 252694........cost $25.79

gasket, ACDelco...........part # 251664............cost $6.96

Pulley, Dorman............part # 300934............cost $18.14

You could save a little if you get a pulley from the wrecker or even see if a local store carries it.

If you inquire locally, use these part numbers because there is actually a listing for a stamped impeller with a different part number.

EDIT, important info, ACDelco does make a cast impeller series II pump, it is part number 252693 with cost of 27.79 and uses the same gasket as I listed above. If you get this, you would not need a new pulley.

Click the more info button by each item on the RA page to get the descriptions.

Thanks for the numbers...the discount number doesn't work though! It said something about being used up or out of date?? Anyway I will get them ordered today. Thanks again!

edit: Also do I need the stud kit for this pump? part #902803

edit,edit: Also, has anyone done a detailed write up with pics on this install/replacement? I cold really use one but if not then maybe I will have to try and do one from a novice standpoint! Thanks!!

Your bolts should be fine to re-use. You will want some sealant for the threads on some of them (all of them for safety), use the blue stuff rated for water pumps. You don't need to order anything else.

FYI, that water pump says cast, but the info tab on it says 'cast or stamped', so beware. It may just be a generic description. If you order that one, some confirmation here will save people money in not having to order the S1 pulley.

other then possible small leaks as discribed earlier what other signs would a water pump going bad be?
Mine is making noises off and on.
If I need to replace it pictures like Mac077 said would be nice. It looks pretty straight forward but references would be nice.
If I change to the S1 style pump and pulley the belt from my S2 will work fine?

Yes, the belt will work fine, the diameter of the pulley is the same, it's the mounting that's slightly different.

It is pretty straight forward, but here is my list of tips.

1. Drain coolant, you will still have some come out when pump is removed so you may want a catch pan or rags underneath
2. Loosen(do not remove) the 4 bolts holding the pulley on the pump
3. Remove the belt and then the water pump pulley
4. Remove the PS pump mounting bolts. Accessed through holes in pulley, 2 bolts
5. Remove 4 large and 4 small bolts holding water pump on.
6. If it hasn't been done yet, do a coolant flush and change the thermostat no matter how old it is.
7. Make sure you use sealant on the threads of the 4 larger bolts when re-installing. These go through the front cover and into the block, two of them are tapped into the water jacket.

Ed slightly different how on the mounting? Because the styles slightly different?
The hoses will all reach ok?
I had planned on new coolant and thermo anyway so this will be a good time to do it.

Hoses do not get involved at all. He is referring to the mounting of the pulleys. The Pulley on a Series I has a hole in the middle and the hub of the pump comes through it. On the series II pulley, it is solid. Go back to Willwren's picture and you will see the only differences are the pully mating to the pump and the impellers.

Ok. Just wanted to be sure before I tried.
Thanks for the help. If I need more I'll ask.

Is there a certain ft lb the bolts should be tightened too?

Techinfo is your friend.

Get intimate with it.

viewtopic.php?f=39&t=215

The force is strong with you willwren

Parts ordered. If I need any help I will be asking.

Well pulley came in but the pump and gasket hasn't even been shipped.
Hope it comes soon. Weathers been to nice to let the car sit.

Well, mine are all here and I am ready to rock and roll...hopefully someone will be standing by in case I get muself in trouble???? 1st step, take off lower radiator hose and drain coolant into a pan...

Wow...ok, anybody got any tips on draining the coolant? This looks it might be the hardest part...I can't see the bottom drain plug at all...help already???

Done with 1/4 in hose in radiator fill hole and siphoned enough to make it happen...

Does anybody know what the pully is that is in my way in order to take the water pump off? It is the lower big bolt towards the front of the car. I took a pic and am waiting for it to hit my email so that i can get it on here for you to see but if anybody knows what I am talking about please chime in asap!!! Need to get this done asap as the ass end is hanging outside and I can't close the garage door. Thanks!!