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-   -   Heater doesn't blow as HOT as it used to? (

Rusty Nib 01-17-2011 06:40 PM

Heater doesn't blow as HOT as it used to?
Hey Guys -

I've got an 03 with the 5.7. In the last week or so, the temperature of the air coming out of the heater has been cooler and cooler. Granted, it's 0 degrees out right now and this morning on the ride in to work it was -8, but I've never had the truck blow tepid air before on even the coldest days for years now.

It's not cold air, but it's definitely not hot air either. A couple minutes with the heater on in the past was enough to roast a chicken on the dash, so I'm kind of stumped.

Any ideas would be greatly appreciated.

squintay 01-18-2011 12:29 AM

rusty i have a suggestion or 2. i've had the same prob with my 99. i would check ur thermostat and make sure its not stuck open or broken. then id go after the water pump. and check the temp sensor. flush ur cooling system too

Rusty Nib 01-18-2011 10:06 AM

Thanks for the suggestions. What did the problem on your 99 end up being?

RamTech 01-18-2011 10:13 AM

A stuck open stat would set a rationality code in the PCM and the operating temp would stay low, so that's not my first guess but it's still possible. Start by making sure the coolant level is correct and that the strength is correct for the temps in your area. You'd be surprised how many half frozen systems I've encountered. Both heater hoses should be hot (about the same as the radiator hoses) and if you have an infared temp gun, you can check them that way. The difference between inlet and outlet hoses should be about 15-20 degrees. If that's ok, it's time to start thinking heater core obstruction or perhaps a blend door problem. A faulty water pump could also be causing decreased flow to the core.

Rusty Nib 01-18-2011 12:05 PM

Thanks for the tips, Randy. Operating temp seems normal which is why I doubt the thermostat theory, but I will look into all of the above. The coolant level is correct, not sure about the mix though. It certainly couldn't hurt to have a flush.
I have a buddy with one of those newfangled infrared heat guns who would LOVE an opportunity to do more with it than point it at the cat and his wife's butt: An average of 10 degrees cooler than the rest of her body if what he says is true. ;-)

RamTech 01-18-2011 12:42 PM

If you have any residue or obstructions in the core, a back flush may clear it out and improve the heater performance.

GTyankee 01-18-2011 01:03 PM

check out
to help trouble shoot

squintay 01-19-2011 02:10 AM

i had a leak comming out of the top of my water pump and my temp gage was sitting low, it looked like my temp sensor was leaking too so i did them both.

GTyankee 01-19-2011 02:29 AM

IF you have to replace your thermostat, make sure you replace it with the stick open kind, that way if it ever goes bad, the water still is able to flow, the old styles when they went bad, they stuck closed & didn't allow the water to flow & the cooling system got so hot, they blew head gaskets, cracked heads, & all kinds of bad things

squintay 01-19-2011 02:37 AM

1 step ahead of ya GT. when i bought this truck it had a blown trans, and a recipet in the glove box reguarding the heads, which the owner forgot to mention im just lucky i have the know how and the resources to work on my truck or id of lost my shirt in the first year of owning it

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