Bad Thermostat?

[terryjai]

Hey Guys, i have been looking/searching around the form and can't seem to find an answer so need you help

96 runner limited 3.4 auto

Heater not blowing hot air when driving issue

so car is warming up and normal temp, i turn the heat on, blows ok warm/hot for 10 secs and then cold/warm.... checked rad hoses....top is super hot (can touch for like 3-4 sec)...bottom is warm (can hold on for a while)

so im thinking the thermo is stuck open and messing the system up.....any ideas guys??

please and thanks!

 

[nissanh]

When the engine is cold, open the radiator cap. Start the engine. If you can see water flowing = Stuck open thermostat.

You can hold the top hose for about 3-4 seconds. Bottom you an hold for some time.
If you have an IR thermometer, top should be about 82 C and bottom 73 C.

 

[TheDurk]

You might have air trapped in there. When did this start? Any cooling system work done that required draining? It might be worth trying to bleed it with the front uphill or up on a curb.