overheating

[wolfus]

I have a 1999 4runner 4wd 6 cyl that overheats sometimes. Could it be the thermostat getting stuck sometimes that would cause this? I bought a new thermostat but I am not sure of the CORRECT way to drain the radiator . I dont want to take off the nuts from the studs and have anti-freeze leak all over the place.

[kball]

Is your coolant level okay? How does it look? There's a drain at the bottom of the radiator. Thermostat can stick.

[wolfus]

the level is good thanks and the color is grn like af

[jetwhine]

wolfus,
Since you have the standard anti freeze in it I would drain it and put some Toyota fluid in it. . It has better properties for the Aluminum engine components. The Toyota coolant is Red in color. It is much more expensive but worth it in the long run. And yes also agree on the sticking. You might also put the new T-stat in a pan of water and heat it up to make sure it opens when hot. Just a precaution so you don't have to trouble shoot a bad from new T-stat. I have seen them bad new and it causes problems when trying to figure out why a rig is still overheating after T-stat change. Hope this helps.

[MattInLA]

That can cause overheating
CLOGGED RADIATOR - LEAKING CAP - BAD THERMAL SENSOR - BAD FAN SWITCH - BAD FAN - BAD FAN CLUTCH - LOOSE FANBELT - BAD THERMOSTATIC VALVE - HEAD GASKET FAILURE - CLOGGED ENGINE PASSAGES... I'm sure there's more.....

[jetwhine]

The only problem I have with the Clogged Radiator, Leaky Radiator cap, Bad Fan, Bad Fan Clutch, Loose Belt, Head Gasket failure, Clogged Engine Passages is that it would overheat all the time. It is an intermittent problem which I would suspect the T-stat first. Now the only thing I did not mention is that if the rig does not act/sound like it is overheating then I would suspect an indication problem.