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Dtimekw 12-07-2010 07:57 PM

Heat problem and door blend
I have the same heat problem many of you have or do (no/low heat at idle and gets hotter as the engine RPMs go up) I've searched and read threads until I passed out....wait, that may not have been the reason:beerchug: Regardless, heres a question and hopefully a tidbit to help others. I located the blend door actuator (I hope I called it the right thing). I can see the shaft turn (and step with the temp switch). My question is this....It turns 90* from cold to hot. Is this correct? If so, then I can rule out the blend door not operating. I know it needs to be aligned or zeroed but I would find it hard to believe it would since it just happened. Can anyone confirm the rotation being 90* from hot to cold? Thanks!


Dtimekw 12-07-2010 08:22 PM

I probably should have mentioned what I have found and am working on. It started after replacing all of the hoses. I didn't check heat for about 3 weeks after. Before doing the hoses, cab temp at the vent and at idle was ~140*. Now, it is 110* and gets to 120* with the engine revving up. I flushed/backflushed the heater core when I did the hoses and replaced the t-stat as well. As of right now, I have the truck on a pretty good incline. I ran it like this for almost an hour the help "burp" it. About every 10 minutes, I would blip the throttle to see if I can hear the air bubbles which I can. At 8 MPG, I decided to leave it overnight on the hill with the rad topped off and the cap off. I'll see what it looks like in the morning. Any other ideas?

latitud 12-07-2010 08:56 PM

if you have a locking radiator cap, then burping is just a matter of lifting the lever. I usually run it for a while and then burp it...once or twice is all it takes. Are both heater hoses hot in and out of the firewall?

Dtimekw 12-08-2010 04:49 PM

Yes, both are hot. I am not sure what you mean by locking? Do you mean the type that releases pressure by lifting up on the tab? I have the kind that goes on with a 1/4 turn. I am going to try the CLR thing I've read about. Perhaps I have crud caked up in the core.

RamTech 12-08-2010 04:54 PM

90 degrees movement on the blend door is right.

GTyankee 12-08-2010 05:04 PM

to check out your heater functioning correctly, you might look at this site & videos

Dtimekw 12-08-2010 05:43 PM


Originally Posted by RamTech (Post 377154)
90 degrees movement on the blend door is right.

Whew! Thanks. saved me some time

Dtimekw 12-08-2010 08:22 PM

**Update** Flushed and backflushed again, this time with CLR sitting in the heater core for 5 mins. By the way, CLR does not recommend using this on copper amongst other things. Just a little heads up. I parked on a hill, burped big blue and managed to achieve 130* with fan on high and engine at idle. This was 20* better than before the flush. I did notice ambient temp has A BIG EFFECT on the temp at the vent. With the hood up I lost ~8* at the vent and noticed my temp guage go down a bit. Good to know. Luckily I am in Fl so it's not as bad as some of you. Hopefully this info helped out!

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