TLDR AT END

Hello everyone, I've been a lurker on these forums for a long time but I'm at a total loss on this issue and have finally decided to make a post. Two summers ago, my 1998 A4 began to smell like coolant and sprung a coolant leak shortly after. After a quick trip to a reputable garage that my family has dealt with in the past it was determined that the car needed a new water pump. The original factory water pump was still on the car at the time so it was not surprising that it would need to be replaced. The garage replaced it with a NAPA unit along with new upper and lower rad hoses and a new thermostat. Unfortunately, this is where the problems began. Although the car seemed to have stopped dripping, the scent of coolant never totally disappeared. This happened near the end of that season and I ended up storing the car for that winter before any leaks occurred.
Unfortunately, when I pulled it back out the next spring, within a month it was leaking just like before. At this point I was able to identify that the leak was coming from the weep hole on the bottom of the water pump. I quickly brought the car back to the garage and had a new NAPA pump installed under warranty, as the mechanic was convinced that the first replacement pump was defective. Fast forward another month or so and surely enough this second replacement pump also began to leak. I once again returned to the garage and they installed yet another new NAPA pump. There were some minor intermittent leaks that occurred with that pump for the rest of that summer but at that point I was quite frustrated with the car and hoping that perhaps it was a leaking hose or something else causing these leaks that we hadn't noticed. I was able to store the car for that winter without any major leaks occurring but was skeptical about the issue being solved.

Almost immediately upon pulling the car out of storage this summer the leaks from the weep hole once again began, this time occurring nearly every time I drove the car. I brought the car back to the garage once more in late April but this time demanded that they install a different brand of water pump. They installed an ACDelco water pump and it seemed as though the issue was finally solved. About a month ago, I began to smell coolant again and surely enough the car began to leak from the weep hole, just like before. Since then, I began to notice that whenever I left the car slightly below the full coolant level it would leak much less than if I filled it to the full line. Eventually, the coolant got low enough to trip the low coolant message and I finally refilled the reservoir.

The next night while out for a drive the car blew off the upper rad hose as I was returning home. I was able to limp it home without overheating, reattach the hose and back the car in for the night. That night I read that faulty reservoir caps could cause pressure issues in the coolant system and ordered a new OEM cap. The next day I installed the new cap and refilled my reservoir while the car ran, letting the car hit operating temps so that the thermostat would open and I would not get air pockets in the system. Since then, my coolant leak has gotten significantly worse. Up until this point the leaks had always been a few drops after heavy acceleration or when shutting off the car. I would smell them, hear the belts squealing and could see evidence of leakage from the weep hole on the rail directly underneath the pump when they would happen but it was never a substantial amount of fluid being lost. Now, the car is leaking a significant amount. I constantly smell coolant while driving, there is a visible amount of coolant underneath the pump on the rail and there are puddles of coolant on the ground whenever I shut the car off. As well, I think I can see multiple drips now. I still see the drip from the weep hole (which is much faster and longer lasting now) as well as a drip from somewhere around the middle of the pump. To make matters worse, coolant is getting into my belts and getting flung around the front of the engine bay, making it harder to track leaks. What's really bizarre is that I have not had a single cooling issue throughout this entire debacle, the car has never ran hotter than normal operating temperatures despite all the leaks and issues.

At this point I am at a total loss for what to do next. In all fairness to the garage, they are very well respected in the community and their mechanic has been working on sports cars and muscle cars for decades. Is it really possible that this is yet another bad pump? Is there a chance that the pumps are being installed incorrectly or is there another underlying issue causing these leaks that I'm missing? I'm extremely frustrated with this issue and desperate to find a fix before winter rolls around again. If any of you guys have any ideas or have dealt with anything like this before, PLEASE let me know, I greatly appreciate any help that I can get to reach the bottom of this.

TLDR: Car is on it's 4th replacement water pump in 2 years. All four have leaked from the weep hole. Are the pumps really all defective or do I have an underlying issue?

 

Try some paragraphs and editing. Brevity is our friend.

 

Editing is done. What do you think I should do regarding my issue?

 

Are you filling the reservoir all the way to the top?

Is your harmonic balancer wobbling? Is your belt tensioner operating correctly? If the water pump’s drive pulley is vibrating, the pulley bearings will wear and eventually fail. This reduces pump efficiency before eventually causing failure.

These are questions you can respond to. Also take some pictures and a movie of the balancer with the engine running.

If indeed it’s just a bad pump read on…

This water pump is easy to change. If you have basic hand tools you can do it yourself in an hour or two. Make sure to use new hose clamps.

Heres a couple videos, and there’s plenty more on YouTube




Lots of folks buy knock off pumps and are happy. A water pump is not where I cut corners. This is the genuine article, GM’s OEM replacement. Not from China…. Mine came direct from Detroit.

https://www.summitracing.com/parts/ADO-251-744

 

First, it is easily possible that the second and third pumps were bad.

My car's second pump was bad, the first an original began leaking at 76,000 miles the second made bearing noise from the minute it was installed and I changed it eight months later at 78,000 miles. That third is still going strong 13 years later at 120,000 miles.

It is taking the Chinese a while to figure out car parts.

 

I've always filled up the reservoir to the full line, never any higher than that. I've had my suspicions about the balancer and was planning on changing it next spring when I pull the car out but have been told that it shouldn't have an impact on the water pump. I didn't think that sounded quite right but at the same time I have a hard time believing that a bad balancer would destroy a perfectly good pump in just a few weeks. The ACDelco pump you linked in your reply is the one currently on the car which makes this situation all the more disappointing. Going by what you're saying + what I've been told by some of the guys over on LS1Tech I might try to get through the rest of the season with the car as is and install either another ACDelco pump or an electric water pump and a new harmonic balancer with the ARP bolt in the spring.

 

When the car was going through the NAPA pumps I really wasn't very surprised. I told the garage I wanted ACDelco originally but they were adamant the NAPA unit would be fine. Then they said they had to keep using these crappy Chinese NAPA pumps or it wouldn't be covered under warranty by their supplier. After 3 of them I refused to put any more of them on the car and finally got the ACDelco I originally wanted. What's worrisome is that the pump on the car now is the ACDelco pump I originally wanted and yet the issue still persists.

 

Its why I suggested an external source. Have checked the pulley for good bearing and that tension is working properly? Just trying to cover bases that might be working on the seal. Have you watched the balancer for any wiggle, and is the ring still lined up. Something would need to be out of alignment or creating drag, like a bad pulley.

 

Interesting info on coolant flushing on new after pumps…

 

I agree with @vette4fl regarding using a premium WP like ACDelco. I have a '99 and just replaced mine last week due to some leaking issues and like you I had no leaks prior to parking her and letting her sit for 2 months due to other repairs I am working on which are unrelated to the WP. The pump that I pulled off was an aftermarket and I have no idea what brand it was because the PO replaced it. I am the second owner and unfortunately the PO kept no records (as he said) of any repairs. The one thing I did notice on the 2 pumps was the back plate. The one which came off the vehicle had a screwed on back plate (area of the leaks) and the ACDelco 252-846 was pressed on. So far no leaks and she is a DD. The PN mentioned above ADO 251-744 with the OEM 12681185 I am familiar with because it is one of the types that is cross referenced with my 252-846. GM also had a practice of installing whatever pump was on the shelf so that could be the answer why the OEM number is different from yours to mine. My OEM is 89018034 and it has a cross reference of with the following

Car 2006 Pontiac GTO V8 6.0L 5967CC 364CID Base, United States
Car 2005 Pontiac GTO V8 6.0L 5967CC 364CID Base, United States
Car 2004 Pontiac GTO V8 5.7L 350CID Base, United States
Car 2004 Chevrolet Corvette V8 5.7L 350CID Base, Z06, Canada, United States
Car 2003 Chevrolet Corvette V8 5.7L 350CID 50th Anniversary Edition, 50th Anniversary Edition Pace Car, Base, Z06, Canada, United States
Car 2002 Chevrolet Corvette V8 5.7L 350CID Base, Z06, Canada, United States
Car 2002 Pontiac Firebird V8 5.7L 350CID Formula, Trans Am, Canada, United States
Car 2002 Chevrolet Camaro V8 5.7L 350CID Z28, Z28 SS, Canada, United States
Car 2001 Chevrolet Corvette V8 5.7L 350CID Base, Z06, Canada, United States
Car 2001 Pontiac Firebird V8 5.7L 350CID Formula, Trans Am, Canada, United States
Car 2001 Chevrolet Camaro V8 5.7L 350CID Z28, Z28 SS, Canada, United States
Car 2000 Chevrolet Corvette V8 5.7L 350CID Base, Canada, United States
Car 2000 Chevrolet Camaro V8 5.7L 350CID Z28, Z28 SS, Canada, United States
Car 2000 Pontiac Firebird V8 5.7L 350CID Formula, Trans Am, Canada, United States
Car 1999 Chevrolet Corvette V8 5.7L 350CID Base, Canada, United States
Car 1999 Pontiac Firebird V8 5.7L 350CID Formula, Trans Am, Canada, United States
Car 1999 Chevrolet Camaro V8 5.7L 350CID Z28, Z28 SS, Canada, United States
Car 1998 Chevrolet Camaro V8 5.7L 350CID Z28, Z28 SS, Canada, United States
Car 1998 Chevrolet Corvette V8 5.7L 350CID Base, Indianapolis 500 Pace Car, Canada, United States
Car 1998 Pontiac Firebird V8 5.7L 350CID Formula, Trans Am, Canada, United States
Car 1997 Chevrolet Corvette V8 5.7L 350CID Base, Canada, United States

ACDelco 19195105
ACDelco 251-722
ACDelco 252-846
ASC WP9189
Autostar 130-7290
BORTEK 20321
Bosch 99175
CARDONE New 55-13136
Chevrolet 89017456
Chevrolet 89018053
Gates 45002
General Motors 89017593
General Motors 89018034
General Motors 89018164
GMB 130-7290
Omnicraft JAMZ 8501 CP
Omnicraft QPW-86

As you can see your '98 is included with my '99 so therefore it should work. Again the problem with mine was the screwed on back plate. Hope you get yours figured out and good luck. Subscribed to keep posted. Cheers!!!

 

I'm fairy confident that the belts are configured correctly because I had them changed a month or so after installing the current pump when I thought the issue was finally solved. They've once again been ruined by coolant but they should be operating correctly. I will check again tonight and take a closer look at the balancer while the car runs. At this point I highly doubt there's any old or crappy coolant left in the system. It got new coolant and a proper flush with the last two pumps.

 

So there are two different ACDelco Water Pumps in circulation that both work on these cars? The ADO-252-846 unit that you are talking about and the ADO-251-744 unit that @vette4fl mentioned? I knew I had an ACDelco pump on the car and assumed that there was only one unit designed for these vehicles. I'm leaning towards believing that the ADO-251-744 is what I have because it is much closer in price to what I paid than the one you brought up is. Is there any real difference between the two? I know that nowadays there's the genuine GM ACDelco stuff and then the Gold and Silver Aftermarket ACDelco stuff but these listings don't mention any of that. Either way, I'll be sure to be pay attention to the design of the back plate on whatever pump goes on next. I'll keep in mind that your unit (ADO-252-846) has the pressed on plate.

 

There are differences in water pumps. Later pumps use a thermostat housing separate from the housing. Diameters are different and early thermostat/ housings do not fit later pumps.

 

That is correct sir, mine had the thermostat embedded with the housing. Cheers!!!

 

Here is another detail for you to consider regarding your pump. The 252-846 is a counter -clockwise rotation whereas the 251-744 has a clockwise rotation. Therefore, if that is true according to the specs for each of them then I would think if the pumps are rotating incorrectly their seals may be getting damaged and causing the leaks. BTW your does turn counter clockwise. Cheers!!!

 

Yeah, that’s weird. And both part numbers correspond with the ‘98. Only other thing is the 252-846 is the “Gold” aftermarket version, whereas the 251-744 is the “OEM”.

Due to a casting number that was different from the current part number on the 744, I spoke directly with the tech team at ACDelco in Detroit. They confirmed the 251-744 is the correct pump for my ‘04. I had no reason to ask about 252-846 reverse impeller China junk.

@Bill Curlee

 

That's okay Bill because it fit and performs perfectly to my benefit. Some day soon all parts will be made in China so be ready. Food for thought, when I was in China back in'86, I bought some parts and some other things and guess what? Some of those things actually had a UAW sticker that said Made in USA!!! Go figure.

Al

 

Wow, talk about making things confusing. If this is indeed the case and they have been ordering parts that are substitutes for 251-744 it could explain all of my issues. Regardless of brand if they're spinning the wrong way they're going to be destroyed eventually. So you're 100% certain that my pump spins counter-clockwise from the factory? I'll make sure that they pay attention to that when ordering if that is the case.

 

I believe mine had a proper gasket rather than the little O-Ring style gasket that I've seen before but I'm not 100% sure about it. Do you know which years had which type of thermostat housing gasket?

 

My experience is that rockauto.com will deliver the correct pump for your year. For '98 they list a number of pumps including ACDelco 252846 and GM GENUINE251744.

https://www.rockauto.com/en/catalog/...ater+pump,2208

The caution is that your car could have a later pump on it- which would require a different thermostat and housing.