04 chevy express 2500 . The van has 133 K miles always garaged I m the only driver. Well maintained . Not sure why pumps leak .I check oil and coolant on a regular basis . This will be 3rd pump and replaced with original equipment not rebuilt, any info would help. Thank you jz.
3rd water pump
- Thread starter jackz
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Stick with original equipment.
Which Coolant?
Green stuff will cause WP seal wear, if EVER used.
Green stuff will cause WP seal wear, if EVER used.
AutoMechanic
Site Donor 2026
OE water pump would probably be best. As stated above was the right coolant used?
If mechanical check the fan for balance or worn wobbly fan clutch. If off balance it would be hard on the bearings/seal. Pumps leak cause the shaft seal fails. cheapo knockoffs or seal damage from contamination.
+1 I would check the belt tension, and the belt tensioner [if equipped]. Too tight a belt can cause premature water pump failure as well.
+2 almost definitely a fan blade, fan clutch pulley alignment/ belt tension issue.
My guy is O/O over 35 yrs worked for chevy& GMC very honest knows his job. Thanks for the help keep them comming also great info. Thank you. jz
AutoMechanic
Site Donor 2026
Yes definitely check the belt and tensioner too I haven’t seen water pumps keep leaking like that unless their was a problem somewhere else.
Always use the ACDelco one, I learned the hard way that aftermarket ones for LQ4s are junk out of the box.
Is he using delco OE? Delco professional and delco OE are not the same quality level.
I believe this design of WP was used before Dexcool was put into service.
I changed the pump on my 2001 Chevy at 80,000 miles. It turned out only the gaskets were leaking, but I changed the pump anyway since I had bought a new one. I didn't know the difference between the AC Delco "Professional" and "OE" lines at the time, and got the professional. That one was leaking at the weep hole by 120,000. Belt, idler, and tensioner were changed somewhere in between. The third pump is Delco OE. Fingers crossed. I have always used the Prestone Dex-Cool and distilled water, and Fel-Pro gaskets instead of the ones included with the pumps.
Don't overlook the heater hose connectors at the heater core, assuming vans have them like the pickups. I got Dorman replacements for the first job, but could only get one to go on and reinstalled the other original. That connector started leaking this year, and broke off when I tried to tighten the clamp. Luckily I had a spare, another Dorman that clicked right on.
Don't overlook the heater hose connectors at the heater core, assuming vans have them like the pickups. I got Dorman replacements for the first job, but could only get one to go on and reinstalled the other original. That connector started leaking this year, and broke off when I tried to tighten the clamp. Luckily I had a spare, another Dorman that clicked right on.
I read it that the most recent replacement is OE, but not sure about the other. Perhaps JZ could clarify.
I used the OE pump p/n 12703898, but the OP's van might use a different one. I also used the updated t-stat and changed both tensioners with OE, belts with the ACDelco HD, and both heater hoses. My truck has 281k when I bought it in June and the pump was leaking.
Maybe so , or maybe not. My point was that not everyone realizes that delco or delco professional is not the the same as Delco OE.
Some people think that if it says ACdelco, it's original equipment , not so . ACdelco has like 3 price lines.
That’s great.
Regardless of what price point AC Delco water pump you get, to be on the 3rd pump in just 133K means something is not right. Even the cheapest Duralast water pumps will last longer than that. I'd look into a gasket issue, maybe the wrong gasket came with the pump, maybe the gasket surfaces weren't cleaned enough, etc. Also could be something else like the tensioner is faulty causing the water pump bearing to fail and leak prematurely.
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