I know there are lots of posts on this and have read a ton, but I am still confused on issue. I have 98 Ram 1500 and it blows luke warm air at best. I have had the coolant flush done, new radiator cap and new thermostat. Adjusted the cable setting and can hear it "slap" the stop when I turn quickly to hot. No coolant smell in cab and no wet spots in carpet. i notice that if fan is on low it feels warmer, but as turn fan up it gets cooler. Definitely feels much warmer with warmer temps out...but gauge reads the same when colder out or warmer out. No overheating.

My next thought was heater core, but no build up on windshield, no smell and doesn't appear to be leaking inside cab. Also, top radiator hose and both heater hoses are very hot to touch after driving (lower radiator hose is barely warm) so this makes me think it is not the heater core. Is there another way to tell for sure? Is there something else I should check.

I know local parts store sells a cleaner, better than the flush cleaner from prestone that was used on flush. Should I try this (believe still from prestone, but you run just water in it for 50 miles, flush out, run for 10 minutes and flush again and fill with coolant) Could there be air trapped in system...with cap off and let warm can see coolant is moving. Is there a different way to "burp" the system? Resevoir is full.

Any information would be appreciated. Thanks!

 

I had a no heat issues yesterday. I attempted to burp the system "normally". Didn't work.

I ended up disconnecting the lines going into the heater core, at the connection by the valve cover, and blowing it out with an air compressor.

Worked like a charm

 

I may not have this correct but I am willing to bet the truck is the same as my wife's old Grand Cherokee. She had the same issue with it and it was her blend doors. On older vehicles they used a valve on the heater hose to control the amount of hot coolant going thru the heater core.
On newer rigs they now control the heat by the use of blend doors. So what happens is that the motors are running all the time and the doors close against a stop but they are made out of plastic so they strip out sometimes. So now the shaft is just turning inside the door.

Check out this site for some help and maybe this will fix your issue.
http://www.heatertreater.net/

 

I saw this post and it listed part for year of my truck...but in looking at the truck it does not appear there is an actuator motor. My truck has a cable, so do not think I can use this fix unless I am just not seeing where it is located.

 

Nope. no little motor until 2000 model year. Yours is cable operated. (just like mine.)

If you don't have A/C, you can drop the blower motor, and actually look inside to see what the temp door is doing. If you have a/c.... can't see it at all. (evap core is in the way.)

Probably still have an air bubble in the heater core. They can be a real pain to get out.

 

Heater core is bad, does not need to be leaking to be clogged.

 

flush your heater core by removing the heater hoses and see what comes out of there. the heater core sits higher then the reat of the cooling system. any crap will settle in the heater core. give it a gOOd flush...

 

Flushed core 4 times (gallon or so each time) both ways. No real sediment and flow out about same same as flow in on flush. Cleaned water with 15-20 psi air and filled with radiator flush cleaner and let sit for half hour or so. Flushed both ways 4 times again, with no sediment and equal flow. Blew hose water out of heater core with low psi to get rid of well water. Feel pretty good no blockage or sediment build up in core.

Went to "burp" and after 20 minutes, looked like new thermostat opened but gauge barely raised above 130 (min). Slight increase. "Burped" several times but no hot air. Drove 15 miles highway speed and never left 130. Guessing bad tstat. Hope to put new one in tomorrow otherwise next weekend and see. Thinking air in system coupled with bad tstat was issue...guess will find out.

New thermostat was put in with hughes plenum kit. In looking on net, some say can just remove support bracket and can replace, others say will need to remove alternator and ac compressor. Will I have to remove them to swap out?

Thanks!

 

You might be able to get it out without removing anything.... but, it can be fun. have a look, see what ya got, take it from there.

 

New thermostat in, refilled and feels hot. Wondering if was air, before the "new, old" thermostat quit as temp gauge was at same level. Broke down and bought the Lisle filler setup...well worth the money I think as watched the bubbles come out.

Guess we will see for sure once sledding season comes back around. Onto the next fix when comes up as seems like always one on this truck.

Thanks for input.