I bought this truck last week, it is a 97, 360 with 160,000 miles. At first I noticed that after the truck has warmed up and at idle I get just a little heat out of the vents. At higher RPMs the heat is OK/good. I was thinking clogged/restricted heater core at first or an air bubble in the system. I tried to jack up the front of the truck and let any air out that way, nothing seemed to happen. Then after I did that this happens, the last two days on my first drive of the day the temp needle rises rapidly to just over 200, at this point I am at a stop light(same route to work every day, and I am just comming off the freeway, short 5 mile drive). When I take off from the light the temp needle drops fast back to about 1/4 of the gauge (cooler). What do you think?

 

im not sure about u but my truck also has heater problems... i cant figure it out, it drove about 15 miles and let it warmup for 5 minuts before that and it still wouldent through hott heat, the temp didnt get up very high either but im thinking it has a 180 thermostat in it, would that couse it to not warm up on a cold day? i hope its nothing to do with the heater core because iv read that thats a long proccess of changing it

 

jnk111: Sounds like you either have a LOT of air in the system (low on coolant) or your water pump is going south (or has an underdrive pulley on it). Park on a pretty good incline (nose up) and run it a while with the radiator cap off ... see how far down the coolant wants to sit.

red98ram: A 180 degree thermostat shouldn't cause THAT much difference in perceived heat ... and a heater core swap shouldn't be necessary unless it's leaking ... and you would know if it was leaking.

 

I checked the coolant level when I had the front end jacked up seemed ok. I tried to rev the engine to maybe "push/force" the air out. The truck has a new water pump in it, I think that was done within the last month.

 

JNK111, My thought is a thermostat. It seems to me that it is sticking open and closed, not allowing gradual vavle movement, but after the temp changes more, it will move and get stuck again. Just change it anyway, they are cheap and usually the cause of not enough heat!Think about it,the enginealways makes heat, your radiator isn't sometimes cooling better, you checked for an air pocket, and you have a new water pump. My money is on the thermostat! Good luck!

 

yah im with this guy, iv got a 99 half ton with 328000KM and iv got crap for heat my windows will defrost on a good day and i will freeze the temp guage says its just below 100 and my coolant is topped up...Help im a popsicle

 

i had a same problem
replace thermostat
if not that, then alot of air is in system.
try loosening up the coupler on the passenger side to the heater core and let some coolant
flow out (when cold, or ouch) and see if any air hisses out easily.
IF NOT THAT
then let me know and i will research for you.

 

Sure sounds like the pump, but, you have a new one. I'd try the T-stat first. I remember reading in the forums somewhere that you can drill a small hole through the T-stat flange to prevent air pockets, do a search for the info to be sure, or if someone here can verify this info..

Justincredible5, try switching your heater hoses around. Maybe someone had them off and didn't put them back on properly. My dad's '87 Ford P/U had the same problem as you and that fixed it.

My Ram's toasty warm, even in the -30C weather we've been having

 

Spend 10 bucks and get a Prestone flush kit for it. Simple to install on one heater hose use the left side as it already has a connection put the flush tee in there and flush the system, make sure the engine is running, heat turned on high and the radiator cap and drain plug are out or the radiator. you may have blockage in the heater core. My money is on the thermostat for the rapid rise and fall of the temp however. GL

 

The problem with the gauge seems to be just on the first drive of the day. I have heat when the rpms are up and it is good heat, the problem is at idle, the heat is just OK.
I did buy a thermostat, I have yet to install it though. I am still thinking air or restricted heater core. I am not sure when I am going to do this but when I do the thermostat I am going to back flush the heater core with a garden hose. I had a problem like this on a 98 bravada with dex cool and the back flush worked great. I then replaced the dex cool with the regular green antifreeze. No problems after that.

Looks like I will probably wait until next thursday to do this, it will be close to 40 degrees (I'm in Minnesota). I won't have to worry about icing up the drive way then.