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?

 

TLDR the whole thing but probably a leak from the weep hole is a bad pump even if it occurred 3 times in row in my opinion. Make 100% sure that's where the leak is coming from.

But if you're fishing for ideas I'd make sure the coolant is not over pressurized and your belt isn't too tight. But even over-pressurized I'd expect someting else to give out before the weep hole leak...? There's some give-and-take from the cooling system to the overflow as it gets hot and cold, I guess I could see a bad radiator cap holding pressure in when it gets hot blowing out the water pump seals, but that's really not very likely.

Also there's a way to check the flex in the belt to see if it's overtightened (wrong belt for example) but again that's not likely. I think 97 vettes had LT1 and no belt on water pump (camshaft driven) but 98 vette is belt driven...? Not sure but I'm only mentioning these oddball ideas because I understand 3 water pumps in a row being bad does hint something else weird is going on but my gut just says you probably had 3 bad water pumps. And if you're sure it's the weep hole I can't imagine any install error causing that.

 

I was thinking about an issue with the belt alignment or tension which makes sense given the issue but the belt would probably be coming off at high revs or making noise. The LS1 water pump has a service plate on the back sealed with an o-ring and some little bolts, i've had these come loose on replacement pumps causing a leak from the back of the pump and dripping down over the weep hole, simply take the pump off and remove each bolt one at a time and put blue locktight on them before tightening back down. Use the soft aluminum fel-pro water pump gaskets with the blue seals and also check and replace the coolant cross over seals underneath the front of the intake manifold as I've had these seep coolant on older engines on hotter days, again this could drip coolant down the front of the block around the water pump

 

Added a little TLDR now, just wanted to include as many details and as accurate a timeline as possible. Thanks for still replying though. I've had a few people tell me that it probably is a defective water pump and that I've just been unlucky, it's just hard to believe that I've gotten 4 bad pumps across 2 different brands. My pump is indeed belt driven. Do you think going to an electric pump would be one way to avoid any further issues? I'm willing to do it at this point.

 

Thanks for the reply. Thankfully I haven't had any issues with belts flying off, just had to keep replacing the stupid things because all the coolant ruins them. I'll be sure to mention the service plate and lock-tighting the bolts + the intake manifold cross over seals to the mechanic if I end up doing another pump. I am almost 100% certain that the first two pumps received the Fel-Pro gasket with the blue seals but they may have tried another brand with the current one. I've always used Fel-Pro's so I'll make sure they use them again if necessary.

 

What sort of clamp was on this hose? The OEM constant tension style should never be able to "blow off" under any normal operating conditions, for any reason (unless the clamp has catastrophically failed). Or was the clamp replaced with some sort of worm gear type that had simply come loose?

 

The tension clamps were replaced with regular clamps unfortunately. I'm convinced that it was just loose and had nothing to do with my pump issues now that I've replaced the reservoir cap and the issues have persisted. Just thought I'd mention it.

 

Years ago I suspected a leak only at high pressure and I took a prestone flush T connector and put it inline with the heater hose and attached my air compressor to it on an LS1 FBODY. I was able to demonstrate that my radiator cap was indeed allowing pressure out to the overflow at exactly the rated pressure written on the cap, proving the cap wasn't "stuck closed" creating an overpressure situation (like slight head gasket leak or something). Kinda hacky and I don't even know if the C5's have this design but might want to try to see. But if you blew off a rad hose and also keep having water pump seals possibly blowing out I'd consider trying something like that to see if maybe you have a combination of broken/stuck rad cap and head gasket leak.

Honestly, this shouldn't be YOUR problem, this should be the SHOP's problem, they're the pros and they should be fully capable of figuring out why THEIR water pump install(s) are failing.

 

I wouldn't go to that extreme if it were me.

If this was an electrical part I'd totally condemn all the pumps, something in the supply chain is causing aftermarket electrical parts to have like 50/50 failure rates right out of the box. I didn't think straight mechanical parts were also having quality issues, but I could be wrong, maybe that's the whole problem here. Also note that sometimes different brand pumps have the same supplier just different name stamped on it. If you eyeball the two brands, do they look exactly identical?

I'd put even money that any given Dorman electrical part is bad out of the brand new box. (not true with Dorman mechanical stuff AFAIK). Maybe water pumps are following that trend now

 

I just received some interesting information over on the Corvette forum. Apparently, the 1998 Corvette corresponds to two different Water Pump Part Numbers. For ACDelco's, they are ADO-252-846 and ADO-251-744. To make matters worse, apparently the 252 pump is intended to spin counter-clockwise and the 251 pump is intended to spin Clockwise. The guy who told me this said that my car requires the counter-clockwise pump. When I look at the engine, I see that the smooth outer side of the belt spins the pump, not the grooved inner side so I agree with him on my car requiring the counter clockwise pump. Do you think it's possible that they have been ordering clockwise pumps for the car and that this is what is causing the issue?

I should also add, I found that all of my rad hose clamps were a bit loose so I'm leaning towards the rad hose blowing off being unrelated to my pump issues.

 

Man that seems so odd. Two different rotations for the same C5 LS water pump?
It's easy to route the belt wrong.
I only have run 2002 Camaro FEA on my LS swaps. Smooth side of the belt spins the water pump and the idler. Grooved side of the belt runs the the crank pulley, alt, ps pump and the tensioner.
Car Craft mag ran what they called a "one shot" mag that showed the belt routing for Camaro, C5 and truck.
This is pic of my 79 with stock LS1 Camaro FEA. The difference to the C5 is the alt is high and the PS pump is low.

 

My belt runs almost exactly like yours with the outer side of the belt spinning the water pump. I understand now that there was a revision at some point in the C5 run that changed the water pump and that I have likely had a later C5 pump and thermostat housing installed unknowingly. A while back I changed the thermostat thinking that my leak may have been coming from there and the housing gasket I ordered was completely incorrect. It was a little rubber O-Ring rather than a proper paper gasket. At the time I assumed they sent me the wrong part but I looked at the package again just now and it says 350CI 5.7L V8 LS1 (VIN G) 1997-2001. 2002 was a revision year for the C5 and another guy on the Vette forum with a 2004 told us that he runs the clockwise pump without issue so I'm guessing that 2002 is when the pump design changed. Additionally, my car has a G in the VIN so I'm inclined to believe that this gasket should have worked for my car. I had a new pump and housing installed originally so I'm pretty certain now that I have had 2002-onwards pumps and housings on the car this entire time, hence the gasket not fitting and all the issues. I'm having a hard time verifying if these pumps meant for the later C5s actually spin clockwise but regardless they are not the pumps that are meant to be on my car so I want this current one taken off and replaced with a correct early model pump ASAP. It actually started making noise today so it's definitely nearing it's end. Going to talk to the garage again tomorrow, tell them about all of this and hopefully arrange a date to finally fix this once and for all.

That's a sweet project by the way. Those Camaros are cool looking cars and a nice LS1 is just what the doctor ordered to liven them up haha.

 

I seem to recall the updated pump (with revised t-stat housing) being the service replacement used for all LS1s after a certain point, meaning they were backward compatible. Does anyone even make the early pump design at present?

FWIW, all LS1s had a "G" in the VIN, including the 2004 cars, so VIN designation never changed even when the pump design was updated with a revised t-stat housing (and yes, the earlier ones used an O-ring gasket and the t-stat was integrated into the housing).

 

I was just going to suggest replacing the tension clamps. I had a tension heater hose clamp fail, but nothing catastrophically. It lost just enough tension that when the engine was up to 185°-190°, it allowed a very slow drip. Nothing under the car. I was ready to pull the heads for a gasket replacement, when I saw it drip on a still warm area, and almost immediately evaporate!!! Tension clamps can be damaged by removing them improperly, as in squeezing them with channellock pliers, past their elastic limit. Wish I could help more.....

 

Your not alone, I have also had terrible luck with water pumps on both of my current LS1 cars. One is my DD, 100% stock car. Its on its 3rd pump since Ive owned it for 5 years now. Other is a H/C fun car, Ive had that car for a little over ten years, gone through 3 pumps on that one too. They all eventually leak from the weep hole as well. Starts with a slow drip, eventually to where I can smell it while driving and belts start squealing. If I get 18 months out of one I call it a success lol.
Its hard to get quality parts anymore, even most of the big name manufacturers that we used to know for quality have outsourced their manufacturing to China or Mexico. Not saying all China parts are junk, but most are. The last Napa China alternator I installed was bad out of the box.

 

That orange 79 Camaro was my first LS swap. Did it 18 years ago?
My LS6 swapped 98 Wrangler has been going great for 15 years with the same 02 Camaro water pump. Granted I only put about 2-3K on it every year.
I remember years ago when I was having an engine built by a very good local builder. He said every GM car/truck had some type of radiator/cooling system sealer added to every cooling system. Would that be worth a try?

 

Can you pressure test it and see it leaking?

Could it be leaking from the front cross over tube or the o rings were it bolts to the heads?

 

Every GM internal combustion engine on the assembly line gets a “sealant tablet wafer” dropped in the radiator or in one of the radiator hoses. I do the same with my sleeved block builds, to help seal the sleeves internally. Steve at RED recommends the same.

 

In an odd way, this is almost comforting to hear haha. I'm starting to worry that there's something else ruining these pumps but at the same time I guess it still is entirely possible that these pumps are just all crap. I might look into buying a more performance oriented pump that is higher quality before doing anything more drastic.

 

Never heard of this before, I'll look into it. Thanks for the info!