heat trouble

[john 2500]

i have a 1996 blazer and the heat does not work inside until the truck revs at 2,ooo rpm's. The radiater and water bottle are full. Also thr truck does not over-heat. Could it be a stuck thermostat?

[wirenut699]

Yes, stat may be stuck in open position.

What temperature is the guage going to? Any gurgling noises from heater core?

[john 2500]

the temp never gets above 195

[john 2500]

the heater core did make gurgling noises before the heat went out

[wirenut699]

Gurggling means air is getting in. That could be a leak or a bad radiator cap. Hoses and or core could be full of sludge and dirt (and some air) All of which impede heating.
If the antifreeze at the radiator seems clean, it may be that any flushing you may have done in the past did not include flushing the heater core and it built up with crap. The extra RPMs get some fluid through.

195 degrees is pretty normal. How long does it take to get to 195? a long, long time would indicate stat stuck open.

I would flush the heater core by itself in both directions through the two heater hoses (consider changing the hoses if brittle) If a lot of crap comes out, that's probably all it is. If relatively clean, change the stat and cap. They are cheap so you may want to do them anyway. A lot of people on this site say don't use a DELCO cap> use a STANT or other brand.

Remember: don't mix orange and green antifreeze in the same vehicle.

Don't forget to check for leaks. Small leaks are hard to find. You may need a pressure tester.