danman79

recently i have been having some problems with my heat. it takes awhile for the truck to heat up enought for heat then the heat will only come out if the truck is being driven hard. on thursday morning i drove through PA and NJ in a snow storm and had no heat the entire time i was driving 60mph or slower at 70mph or higher i had sufficent heat. i have a 97 150

iowaredneck

Sounds to me like you have a plugged heater core.

danman79

wouldnt a plugged heater core stop the heat all together. i do get heat but only when im driving. i have gotten heat when my truck was parked idling. i dont know if that miht make a diffrence. ohh and correction i have a 98 150

Good old Bill

Is engine temp registering normal? Do both heater hoses feel the same temperature, (this represents flow thru heater core)? Verify blend door is functioning correctly. Check other posts about the blend door, several right ups.

danman79

well i was about 1 gallon low on anti freeze so now i have someheat upper hose gets warm but not hot. im gonna assume its probably because of a plugged heater core. thanks for all the input everyone

re54drider

Before you assume the core is plugged, check your fan clutch. My 98 was slow to heat and had poor heat because the fan was at engine RPM all the time. Hard driving would overcome the fan cooling effects but at idle the fan would overcool the radiator, decreasing the heat temperature. Hope this helps.

Good old Bill

Just make sure you have all the air out of the system, could be a bubble in the core causing the no flow. Also just a reminder, find out where your leak is. A gallon low is not normal.
Prior post about the fan clutch is an interesting senario, and deffinately possible. Have to confess, new to me.

torkum

Sounds like a headgasket going south quick

danman79

yea i know the gallon low isnt good. you can smell the sweet smell of anitfreeze when you open the hood. i will deffinatly check the headgasket. im also gonna check the fan clutch. if you guys have anymore spots i can check for anitfreeze leaks please any bit information would help and thank you

Good old Bill

torkum is the guy, believe the open valley system collects oil before leaking to ground, would tend to believe this same valley will collect coolant as well and not be noticed.