I'm having problems with the heater on my my dad's 1999 Toyota Corolla (1ZZ-FE motor, automatic) with 135k and I suspect it may be a weak water pump, but I would like some other opinions.

I put in new radiator hoses and a thermostat at around 105k as a preventative thing, but it still has the original water pump (1ZZ has a timing chain so you don't do a timing belt/waterpump service to it). Here are the symptoms: when you start the car in the morning the heater will not blow cold at stop light/idle. As you get moving (or if you tach it up from a stop) it will blow hot air like usual, but then it cools off if you get to a light and stop. The temperature gauge never climbs above the middle where it should be, although I acknowledge that stock temp gauges are usually dummy gauges and this one seems no different. It also doesn't seem to be an obvious electrical problem or I would expect the heat to not blow at all. The A/C system works fine btw.

I've done a couple things. I opened the radiator cap when the car was cold and topped off the coolant and bled the air out with the heater running at full, just to see if that would help. The same symptoms emerged-- cool air coming out even after the thermostat opened, but once I tached it up a little it immediately blew out hot air. I checked the factory service manual (which my dad happens to own) and the Haynes manual and their troubleshooting sections had nothing on this.

I suspect the waterpump is weak because it's old, but here's the thing--there is no sign of leakage from the weep hole. Also when I squeeze the upper radiator hose I know there is supposed to be a "surge" if the waterpump is working correctly but I'm not sure what that's supposed to look or sound like. And the temperature has never climbed up, nor can I hear a sound of squeaking bearings (although it's possible I could have missed it).

So should I go and change the waterpump? It's only $50 for a new one at Advace but I don't want to put more time and money into the car than necessary because my dad is planning on getting a new vehicle this coming summer. What else could it be?

12/9/2007 7:33:58 PM

gg

[Edited on December 9, 2007 at 8:01 PM. Reason : .]

12/9/2007 7:53:47 PM

why dont you have to do a pump and chain on it?

12/9/2007 10:04:17 PM

sounds like to me you either have air in the system or a stuck thermostat

12/9/2007 10:11:06 PM

need to be 100% you bled it properly

12/9/2007 10:14:22 PM

Quote :

"why dont you have to do a pump and chain on it?"

what i meant was, because a chain lasts longer than a belt my dad didn't get a 60k timing belt + waterpump service like you would on a civic.

zxappeal also suggested stuck thermostat. I'm positive there's no air in the system. I replaced the thermostat at 100k with an aftermarket one. I may go back to OEM.

[Edited on December 10, 2007 at 11:04 AM. Reason : .]

12/10/2007 11:02:43 AM