So I've got a '94 S-10 Blazer SUV that has an annoying water leak somewhere near the water pump from where the water drops appear to be coming from, I dont have the tools to fix it here at my house, so I'm stuck living with it for a while. (Next time I can get to my parents' to fix it is 2-4 weeks away; we're pretty much tearing the whole thing apart to check for a head gasket leak and various other problems due to a recent drop in gas mileage from ~19-20 to 15.)

Now one of my coworkers has said that water in the radiator resevoir is not supposed to refill the radiator and is basically a one-way path for water out of an overheating radiator.  Is that correct, or can I just keep the resevoir filled to the line and not worry about it except on long drives? (my commute to work is less than five miles, so my daily mileage is like 15-20 miles depending on where I go for lunch)

Kharn

How fast is the leak? The water is supposed to flow back into the radiator out of the resovoir, but it would still be best to periodically check the actual water level in the radiator.

Less than 4-8oz a day, I think, but I still get a 6-10" diameter damp spot under the car whenever I leave it for more than an hour, water is warm so its not the AC condensation.

I first noticed it the other day when I got a "check gauges" light and pegged temperature gauge, the radiator took 3/4gal and the resevoir was bone dry, so that took another 1/2 gal to fill.

Kharn

The radiator will suck coolant out of the reservoir as it cools. If the motor heats up and boils over a little, the reservoir will catch it and will be returned when the coolant cools back down.

You might want to check around the water pump shaft. Bearings go out all the time and that's where they would leak.

Hope this helps a little.

WIZZO

Wizzo:
Ok, good to hear.

I dont think its leaking from the shaft, the water's running down the 2" diameter hose going from the water pump into the radiator, a good 2-3" from the water pump shaft's seals, when it finally drips onto the frame crossmember and onto the ground.  It may be coming from the gasket between the water pump and the engine or the 2" hose itself, I havent had a chance to dig into the engine when it's cold yet.

Kharn

Quoted: I'm not sure about the water pump on the Blazers but any small block Chevy water pump I've changed has a small hole in the casting where the shaft is in the pump. If the seals go..it will drip out of that hole. That's the curse of chasing a water leak. The wind from the fan blows the water all over the place.

Oh, I thought it'd drip out the front of the thing if the seals went.

My truck has the 4.3L V6, which is the 305 with two cylinders chopped off, they might even use the same pump.

Kharn

Quoted: Quoted: I'm not sure about the water pump on the Blazers but any small block Chevy water pump I've changed has a small hole in the casting where the shaft is in the pump. If the seals go..it will drip out of that hole. That's the curse of chasing a water leak. The wind from the fan blows the water all over the place. Oh, I thought it'd drip out the front of the thing if the seals went. My truck has the 4.3L V6, which is the 305 with two cylinders chopped off, they might even use the same pump. Kharn

Actually, it's the 350 with 2 cylinders chopped off

They probably do use the same pump, I just can't remember off-hand.

Should be relatively cheap to replace, though.

WIZZO

I knew it was one or the other, didnt want to over-state the size.
And yeah, the manual says its easy (just have to remove the fan and its cowling), and shouldnt be too expensive, just need to find the time to do it.

Kharn

Quoted: I'm not sure about the water pump on the Blazers but any small block Chevy water pump I've changed has a small hole in the casting where the shaft is in the pump. If the seals go..it will drip out of that hole. That's the curse of chasing a water leak. The wind from the fan blows the water all over the place.

Hi Striker, that's great advice about the casting hole, we call them 'weep holes' over here.

The water pump in the 4.3L V6 is esentially the same as the standard small block Chevy V-8 pump, part numbers be damned. So there will be a weep hole on the bottom of pump casting, on shaft tube area, many also have one on top as well.



Kharn, you can look for the trail of fresh and/or dried up coolant coming from the weep hole on the pump, it should be bone dry if good.

Based on what you describe though, it sounds like the weep hole is leaking. Verify by checking from below with a light, it may be difficult without a lift but find the weep hole and see if that's where the cooant is coming from.

Don't forget to change the Thermostat and gasket. Hoses should be changed if too soft(spongy) or too hard (small cracks, dry rot etc.), but T-Stat is a definite must on any water pump job.

Good luck Kharn, my wife has the same exact truck, it keeps me busy all the time, good thing I work at a shop

you should be able to spot the leak if it is comiing from the weep hole. Just use a flashlight and look aroud while its hot and running. Also some leaks only occur when the engine is in the heat up/cool down stage.  Water pumps are fairly easy to replace too.

It's designed to leak when the front bushing goes out.  The thing only has water to lubricate it, so it can wear out kind of quick.  look for caked on dirt to.  Just make sure you have the special tool to get the fan clutch off. IIRC it has 2 prongs that fit into holes, so you can hold the pully in place while you unscrew the fan.