My heater only gets warm, not hot when driving. Sitting and running it doesn't blow warm at all.
I just bought it so I don't know the history. Coolant leval is good. Heater hoses feel hot in and out.
Heater valve doesn't seem to change position when I move it from cold to hot.
Maybe the cause?

 

do me a favor. do you know where the hoses to the heater core are? if so, disconnect them and flush the heater core out with a garden hose. (one in vegas had LOTS of pressure, out here its no so much) i had same problems you did. means the heater core is going out. if flushing it fixes the problem, you'll know whats goin on. if you dont know let me know ill send you a pic

 

x2 Flush the heater core
That heater valve should move, and allow coolant into the core as well.

 

its weird, the valve on my truck is open (there is no cable to it) and i can still turn on and off the heater. it blows people away.

 

Had the same problem on the g/friend's Altima. They're notorious for it. Had to "burp" the system to get air pockets out. Air collects at the highest point until either relieved or flushed out (such as driving/raising rpms of water pump). Definitely check the heater core as suggested above, too. Could be any combination of things.

 

Thanks guys.
I manage a shop here in Sacramento (Ring & Pinion Svc) and its a little slow, so after lunch I'll pull it in and start checking things.
I am going to start with the valve since its not moving. Then on to the core.

 

top off the coolant also. a bunch of people on these trucks have had heat issues with low coolant levels.

 

yeah, if theres no coolant to flow through the core, then how is it supposed to heat up? lol.

 

See if you can move the valve by hand with the cable disconnected. If it heats up when full open, then you may have a broken or disconnected heater control cable. If there is still no heat, pull the valve off and see if it is clogged internally, I had that happen on my old FJ55 Landcruiser. The back flush the heater core, I use a garden hose and tapered nozzle shoved into the outlet line to force water through the core. Repeat with water into the inlet and repeat until the water coming out runs clear.

And do you hear any gurgling or whooshing sounds from the dash when you rev the engine with the heater on? Might be trapped air or exhaust gas in the cooling system.

 

Well I can't move the valve by hand. I am gathering it should move pretty freely?

 

I think I found a problem. My radiator cap is leaking. I topped it off and disconnected the cable on the valve so I could manually open and shut it. I drove around and when I parked it and watched it running, I could see water leaking past the cap.
No pressure no heat right?

 

ozziesironmanoffroad, thanks I was having the same problem with only getting barely warm air from the heater then I flushed it and burped the radiator and the heat is very hot now! It makes a mess, but my wife will be happy now when it gets cold, thanks!

 

The actuator on the valve should move freely, if it is stuck, pull it off and see why it won't move. Might have some deposits inside or something like that.

Cooling system pressure and heater output are not really related. Up to 212F (or whatever boiling point your coolant mix has) the cooling system should be below atmospheric pressure. Only when it rises above the coolant boiling point would the pressure cap come into play. But yes, replace the cap, it should not be leaking.

 

hey ozzie, could you do me a favor and send me a couple pics or write me a walkthrough???
i dont wanna mess anything up, because my dads silverado backed up and puked the heater core into the passenger seat...
i just wanna make sure i do it right the first time...


thanks!

 

Moves freely with the cable off. The radiator cap was leaking and the filler neck? on the radiator is cracked. I guess I'll be ordering a radiator tomorrow.

 

I just got one on ebay from this place called Radiator Classic for $80 shipped and its actually a nice radiator, it says its a dual row, but its only a single, but it keeps it cool no problems yet.

 

ill get a better pic tomorrow, but for now heres the best i can do. anyone correct me if im lookin at the pic the wrong way.

the red circles are where you need to disconnect the hose, and flush it. get the garden hose right up next to it when your flushing. (make sure the other side is disconnected also). flush until you see the water run clear, then switch sides and flush on the opposite side until you see the water run clear, then go to the other side again, however long it takes for the water to run clear from both sides with NO murky water.

 

Hey Ozzie: a little OT but you don't mean the little red circles holding your grill on your front end do you?
(I am using Zip ties on the Trekker and my Tercel )

Got some good info from this thread, I just might have better heat this winter in my '81..