Where's the water going?

Did you have a leak before you changed the water pump? If not, most likely you have a leak because the installation of the new water pump is not just right. You probably have a small leak, and you are only losing steam through the leak after the engine heats up. Look for a white residue around the hose connections and the gasket surface of the water pump. It is also possible the pump is bad and you are leaking out through the pump seal. The weep hole is likely to be hard to see, so you might have to examine it with a mirror.

It is also possible you did not get all the air out of the system after you installed the water pump, and the water level is just going down as you work the air out of the system.

You could always add some Bars Leak to the system. Many manufacturers actually include it in the car from the factory to handle weeps like you have (see

Ed White

IMO, all good advice except for the Bars Leak. I am not a fan of any "stop leak" additives unless you are in dire straits or the vehicle is on its last leg. Any air in the system due to a leak could cause the stop leak stuff to solidify, clogging the internal workings of the cooling system, radiator, or heater core.

A common mistake when refilling the coolant is leaving the heater closed, causing a large air pocket that gradually fills, lowering the apparent coolant level. make sure the heater is set to full hot position when refilling.

The OP mentions water instead of coolant. Water has a lower boiling point than coolant and so hot water engering the overflow bottle could evaporate more quickly.

Also look for white steam coming out the tailpipe, a sign of an internal coolant leak like a head gasket or cracked block.

All good advice but start by replacing the radiator cap.

regards A.G.

I used to stay away from Bars Leak also, until I found out many manufacters ship it in new cars. I don't know if Toyota does, bu Nissan and GM do.

Ed

Are Nissan and GM expecting their new vehicles to leak? ;-)

Thanks for the responses; yes I did have a leak before and we were assuming it was the fault of the pump because of all the residue around it. It was ood we changed it ecause it was in bad shape. I'll keep looking req

I had a cracked head once that had the crack between the water galley and an exhaust port. The coolant leaked directly into the exhaust stream. The leak was very slight, and I never saw steam coming out the back, but one day -- just by chance -- the motor was parked with the valve open, and the cylinder filled with coolant and hydrolocked when I tried to start the car the next morning. I pulled the plugs and a cup or so of coolant came flying out when I turned the motor over by hand.

Not after they fill 'em with Bars Leak ... ;-o

GM expects their new engine to burn oil, leak coolant, throw timing belts, crack blocks and have electrical failures. And you wonder why they have to give $15,000 off a Tahoe and $3,000 off a G6 to get you to buy one.