Heat isn't very hot

[lukecp]

The heater in my truck isn't working too well. In fact, it hasn't worked very well since i have owned the truck. It blows fairly steady, but the air coming out is kinda lukewarm. It dosne't get too cold in Missouri, but i like to get roasted when i turn on the heat . Anyway, the truck usually runs around 190-200 degrees when its warmed up. Would the heater core be bad? I have also heard that the heater box could be letting in some cold air if the inside is kinda messed up. So...where should i start looking for the problem?

[mrein3]

The very first thing I would do is check the level of the water. Burp the system then look further.

[Mudder]

I dont know. If its not your probably gonna need to take the heater box off and see whats up. Could and most likely has a lot of trash in there that wont let the little door open or close.

[70c10]

Start by changing the anti-freeze and thermostat if it's been awhile since they were changed.

[bobs409]

With the engine hot, feel both heater hoses close to the firewall. If one is noticably cooler than the other, your core might be blocked. You could back flush it with a garden hose which usually works.

If your engine is reaching 190 like you mentioned, the problem has to be with the heater core.

[JimKshortstep4x4]

As mentioned, check the coolant level, flush the heater top first and then the bottom until clear. I have used spray wands at car washes and this works pretty good. Make sure that your controls are moving the doors that need to be moved, (check out the operation for each lever).

The engine temperature should be good.

Jim

[lukecp]

I have topped off the system, but since the truck dosen't have an overflow tank, it usually leaks out so the level is about 3-4" down in the radiator. I will check the hoses tomorrow and see if they are hot or cold. The antifreeze and thermostat are both about 18 months old, and have 14xxx miles on them. Thank you for the help .

[mudman]

I live in South Dakota and started to notice my heat didn't work real great either. It was Kind of luke warm like you stated. I started by changing the antifreeze and flushing the system and heater core. Changed the thermostat too. Still didn't work.
I finally took off the heater box(non AC truck). Had to take off the inner fender. That wasn't as bad as I thought.I found that between the heater core and the fan was full of a mouse nest. The plastic blower was chewed up too. The rubber gasket on the little door that blends the warm and cold air was also chewed off. I can't believe how much hot airflow I have now.

[allgmcs]

I went through this same thing. Tried all the same things mentioned here. I had coolant flow through the core and good air flow. I decided it must be the flapper that shuts off the air to the core. So I took the air box off and the flapper was fine. I decided to change the core since it was the only thing I hadn't checked/changed/repaired. The old core looked fine until I compared it to the new one. I could hold the new one up to the light and see light through it. Not the old one! But it did not appear to be that dirty. Also, I blew into the new core and there was no resistance. Not the old one. It took a hard blow to get any air through it. Any way, after installing the new core, the difference was dramatic. It will run you out of the cab. Hope this helps. Good Luck.