3.0 water pump known issues??
 

93 4runner will not stay cool. 14000 on motor and all parts. Have changed every cooling system components except water pump and still overheating. Looking for signs of water pump failure, any known issues with them? I noticed there is no relief valve in these pumps. Is it possible for it to go out without loosing fluid. This morning it backfired through intake until warmed up. Could the water pump bearing be out and effecting the timing when cold being it runs off the timing belt? Looking for ideas here. Thanks for any responses.

only issues i know of are the usual; bearing or seal failure...evident by coolant leaking through the seep hole, usually. wouldn't throw the timing off unless it was a catastrophic failure...like the pump simply falling totally apart....but, it would stop circulating coolant. while it's running you should see coolant flowing through the radiator tank with the cap off once the thermostat opens. if not, it has failed

sounds to me, though, like your coolant temp sensor is malfunctioning.. that would greatly affect timing and cause backfiring

water pump.
 

I can see water flow, but only if I remove the water in the tank to a level of about 1/2 in of water. Then you can see water moving, but not very fast. I am used to Chevy's where the water flows fast even with the tank full. This one really doesn't flow much. I did find yesterday that the new radiator cap was bad and I also read that generic T-stats do not work well in the 3.0, so I am changing to a Stant unit, or Toyota T-stat. As far as the temp sensor, it is new and the gage seems to respond to even minor changes. When the cap was leaking the gage would jump around every time it lost pressure. Seems to be responding as it should. I have gained so much HP now from tuning that I have now gone back to the clutch fan and that helps with keeping it cool, but still overheats if stuck in traffic or in a drive through line where it is idling for more than 10 minutes. It is more drivable with the clutch fan when outside temps are at 111 to 120 degrees.
Thanks for the responce

i mean coolant temp sensor for the efi/ecu ...not the sending unit for your temp gauge. the coolant temp sensor is on the back of motor opposite side of the sending unit on the sensor cluster

Turned out to be high trans cooler temps and high ac condenser temps. added an aluminum radiator and move one of the trans coolers out of ac air intake and put it on one of the ac output vents. All running well now.