yamadude

I will be as short as possible. 97 F-150 with 4.6 engine. Got the truck 3 years ago during the summer. Winter rolled around and for the first part of it the heat worked great. Then the thermostat went bad before winter was done. Changed the t-stat and can not get the heat to work again unless I am on the gas hard as in going up hills. 2 years, 4 gallons of 50/50 mix and 3 more t-stats later I still can not get it to work right. I have bled and burped so many times that I have went through at least a full tank of gas. I have tried it at all idle. Tried it at holding a fast idle. Tried it level, with it on ramps and just the driver side on a ramp. Flushed the system. Made sure the heater core was good and not stopped up. Even back flushed the heater core. What the hell is it gonna take to get it working right again? It is not the little door that controls air temp. It has to be air in the system because it gets good and warm when on the gas. But at idle like at a stop light is barley gets a tiny bit warm. I added a true temp gauge and the temps fluctuate from 0 at cold to 230 before t-stat opens the goes back and forth between 190 and 160 while driving. Tired of freezing my *** off. As much as I like this truck I am seriously about to part this thing out. Any suggestions is much appreciated.

jkenprice1

I'd check the water pump. I had a 97 that the vanes on the water pump completely corroded away.

yamadude

Forgot to mention that i put a new water pump on when i installed the 2nd t-stat.

RLXXI

Experiencing a gurgling noise (water moving) from the dash?
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yamadude

I have heard it from time to time.

77Ranger460

You have air trapped in the coolant system. It needs burped.

yamadude

I know and i have tried and tried to get it out. i have followed the manual. I have tried tricks from forums. I don't know what else to do to get it out. This is the stupidest setup i have ever dealt with. I am seriously about to go back to a chevy and i hate those trucks. But i gotta have heat lol. I have even put a bleeder in one of the heater hoses and still can't get it all out.

jhelrey

If you can't get all of the air out, it could be a head gasket. Happened in my Honda... Bleed it a few times, worked great, then it got bad again.

Eric Kleven

Check your pressure cap, they're notorious for failing. no pressure = boiled coolant = air in the lines.

yamadude

ok i will try a new coolant cap. it is not building any pressure at all. it doesn't boil over or lose any coolant but no pressure. thanks.