Been having a problem with overheating.

Verified that the fans come on at 3/4. Coolant reservoir got really hot.
There are no leaks we see, from hoses or intake gasket..
Not sure if the water pump is bad. It's not making any weird noises..

The only noise we heard yesterday (while heating the car up) was something trying to kick in. It made a woosh/pulsing sound with two clicks. That didn't come from the engine area. Not sure where that came from. That happened at about half way on the temp gauge.

The fans however did not come on when the AC was turned on.

Any other ideas on what it could be, if it's not a leak? Thermo? sensor? Fuses?

 

Is this the same 2000 Malibu 3.1L as in your other thread https://chevroletforum.com/forum/mal...er-pump-49362/ You had "a load of fluid leaking from under the car" there but "no leaks" here? Anyway, with engine off, open the air bleed valve (located on top of the thermostat bypass pipe near the thermostat housing) to let the air out. Close it once you see a continuous stream of coolant. Then, fill and pressurize the cooling system and look for leaks (buy or rent a cooling system tester kit).

 

yup, sounds like you can rule out thermostat,,, water is just fine for testing for leaks, however the green coolant/or orange dexicool, is often easier at spotting leaks than plain water. If your fans are not engaging at all, i would be very suspicious of that. Pinhole leaks, are often very difficult at locating,but this still would not explain the large amount of fluid you seen. I recommend draining entire radiator and flushing, refill system with a 50/50 water to coolant, bleed system as EinST has said, and try again. cooling system tester kit works good. With car off i would grab each fan and try to spin by hand, look for restriction/excessive noise/play/ from bearings. just re-read your comment,,,what do you mean by Verified that the fans come on at 3/4.