bad smell

Hi, my 2000 Grand Prix Gt has a sour smell coming out of the vents when the heat is on, not so much with regular vent but its still there. I figured there may be a slight leak in the heater core so i put BARS peletized stop leak in the car (wasn't sure if it may be leaking elsewhere too so i figured id try the stop leak). The smell was pretty bad before and more like coolant, now its more of a sour type smell but still coolant. Is it OK for me to put some BARS liquid aluminum stop leak in with whats already in the system? I can't tear into the heater core now, its too cold out and i need to get by till warmer weather.

Also, what would be a sign my water pump is going out, i think maybe its leaking and that could be causing the smell because my carpets are clean/dry and don't smell like coolant is leaking from the heater core. Let me know, thanks!

A sour smell is indicating a leak in the a/c system. The R134 refrigerant and it's oil have a sour smell, where coolant has more of a sweet, maple syrup type smell.

Do not add another form of stop leak to your car. If the first didn't seal a leak, the second will only end up clogging up the passages in the radiator and heater core. Are you actually losing coolant, or is it just the smell youi described?

The water pump has two weep holes in the case by the bearing. When the seal fails, coolant will leak out one or both of these holes to indicate a problem. The holes are in the housing just behind the pulley, where the casting starts to form the neck of the pump.

Thanks for the info, that makes sense actually. The lower and upper intake manifold gaskets were replaced last December at a reputable GM dealer so I doubt thats whats leaking. I checked and the AC is very weak (only gets cool on the passenger side) which i recall is caused by low refrigerant. I checked with my gauge and it reads less than 25lbs with AC on high. Granted it was only 50 degrees so i thought maybe the low temp was causing the low pressure reading. I'll have to put some more charge in the system and see if it drops again. Then maybe i'll try the R134a with the dye in it to detect leaks. Thanks again!

You're welcome. Let us know what you find to help others reading this thread with a similar issue.