Mechanic help, Heater/Coolant system

[deerlick]

I usually jear about how shops have that fancy gadget you just plug in and tells you whats wrong, maybe try one of those.

[Buckmark]

I usually jear about how shops have that fancy gadget you just plug in and tells you whats wrong, maybe try one of those.

Please tell me your kidding

[Sandberm]

The mix door is what moves to adjust from the different options, dash vent, floor heat, etc. And it appears to be operating correctly.
My best leads so far is that there may be a partial blockage in the heater core area. I also was just told that it is possible that intake gaskets could be bad and could be sucking in air from that. The guy said that Dexcool is more acidic and can cause that to happen to the gaskets besides the fact of the age and miles of them as they are probably original. The mechanic seemed fairly certain that there is not a clogged heater core, but if it is only partially clogged.... 
I hope I can nail down one of those. The hoses seem all good at this point but wont be overlooked.
If with all that I can figure that part out it will be great.
Then gotta see why the fan only kicks on when the ac compressor is running.
Thanks everyone for the help, I appreciate it very much!

You need a new mechanic 
I could write paragraphs about what you've been told and all about the calamities of a 3.4 with this many miles and cooling system issues. But i wont, good luck.

Go ahead Buck, spill the beans. Are you a mechanic by trade or did you own one of these vehicles?

[Woodchuck]

Please pass the popcorn.

[Buckmark]

Both +, 38 yrs in the repair business, Wanna be Tech, Tech, Service writer, Shop owner,  Punching bag etc and owned a GM with the 3.1 which predated the 3.4 and has the same issues. Like jacklope i have made a few house payments due to the problems related to these and many other manufactures. Im on my phone if i get to my laptop at some point i will try to send more.
There are a few members in the repair business that i suspect agree with what ive responded with before?
Jackelope, Woodchuck, Coach and others i wont name as im not sure they want it known that they are/were techs etc.
From an engine stand point the 3.4 is not bad BUT i suffers from cooling system issues as you get to the upper mileage range that can be costly to repair when you are paying someone to do the repairs, my 3.1 had head gasket issues around 180k which if i had to pay someone to fix i would not of, but since my cost was parts only at wholesale i did it and as far as i know its still running (traded in at 235k).

[Woodchuck]

Absolutely and fully agree with what you stated here. I will add that as jackelope stated, a blend door motor will not cause air to get in to an engine's cooling system. Gurgling noise in the cooling system is caused by air in that system. There are two ways that happens, it has a leak or something is pushing air in to the system. The cooling system in the OP's vehicle operates at about 16 psi so it can not suck air into it. If it isn't leaking it is getting air pushed into it by something like a head gasket pushing exhaust in to it at a higher pressure than the cooling system. The fact that the cooling fans are not working makes me highly suspicious of the head gasket. I also agree with Buckmark that this engine with this mileage is probably not worth the dollars it would take to fix it if this is the case.

[jackelope]

I usually jear about how shops have that fancy gadget you just plug in and tells you whats wrong, maybe try one of those.

That will work about as well as @Timberstalker 's mix door actuator motor in this scenario.

Really, that will work as well as his mix door motor actuator in any scenario you expect the thing to just tell you what's wrong when you plug it in. 

[h20hunter]

Service guys are so overrated imo. Just go the the parts store, they plug the thingy in, diagnoses done,  buy the parts,  put em in. Pretty simple.

 

[Woodchuck]

Service guys are so overrated imo. Just go the the parts store, they plug the thingy in, diagnoses done,  buy the parts,  put em in. Pretty simple.

 

And don't get me started on parts guys, sheesh 

[h20hunter]

Please....

[Woodchuck]

 

[Timberstalker]

Damn it.

Just determined it cannot be the mix door or the mix door actuator.

FYI to all interested parties.

@jackelope
@Woodchuck

[jackelope]

Damn it.

Just determined it cannot be the mix door or the mix door actuator.

FYI to all interested parties.

@jackelope
@Woodchuck

[deerlick]

so did you get it plugged in

[Buckmark]

Oh god, not the google/youtube tech.....
Parts guys are like catchers, all catchers want to be pitchers 
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I will add that as far as “air” getting in the system that a breech in the system (leak/lack of proper pressurization) can cause non obvious coolant loss (visual coolant on the ground ), vapor venting or evaporation can cause the system to become low which then leaves a void in the system which is an air space that can air-rate the system causing things like cavitation, gurgling, low heat output, interupted fan operation etc.
You state the fans don’t work under non override situations but no overheating at idle? You state you sometimes get a coolant smell (that indicates a leak or loss of pressure, like a bad coolant system cap not holding pressure) we know the fan circuit is good as they work in override (A/C on), heater core blockage can be an issue etc, there is more than one singular issue with your situation i feel but thats all i can guess given the info at hand. I also dont feel like an hour diag would get to the root of the issue, but that is my opinion.
I also will add that head gasket issues, intake gasket issues can also be culprits to cooling system issues, both of which are known problems with the 3.4
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Like i said before, based on what you posted you need a new mechanic. Pressure test? HC test with block test fluid? Very thorough visual inspection after a hard run test, Scan data of CTS for fan control (sorry im not in a place that i can look up fan circut operation for your vehicle at the moment). I have lots of questions that run down a check list as i do this.