07 duramax classic 2500 not heating up the cab like it use to

[Nytroxpress]

So I have the above truck. Had it from day 1 of its relatively easy life. I have noticed over the last 2 years the cab will not cook ya out as it did before. I did a coolant flush approx 2 months ago, plugged the holes in the bumper, and placed cardboard in between the rad and trans cooler. The engine runs between 140c - 180c with ambient temperature of -20c +/-. I have tried the stock winter front and no noticeable change. (I like the hidden look better than the black tarp look) the heater blower moves good air but even so I need to keep it maxed out on temp (both sides climate control) and fan on high. Guess it's comfortable (way better than the alternative of no heat) but wish I was able to turn the fan down and the temp.setting ( peace of mind that if I need more heat I can turn it up) guess what I'm looking for is has anyone else experienced what's describe and what was the culprit? Anyone ever change to stock thermostats to higher temp ones and get far superior in cab heat results?

 

[team dirt]

Check the air side of the heater core. Could be dusted off. Also you can try to take hoses off heater core and flush with a garden hose. Could be full of corrosion. If it worked and has gotten worse it's got to be plugged up on one side or the other.

 

[rsaint]

I have same year as you will check mine and see, was there not a cab filter on them ore was it earlier years.

 

[Nytroxpress]

As far as I know there is no cabin filter buy good point that maybe was over looked

 

[prelude48]

You can check your heater hoses going to the heater core under the hood, with engine at operation temp one should be hot and other should be only warm as it takes the heat out of the core (with interior fan on), if there both hot means heat is not being removed from the core, if there not hot at all then no coolant is circulating to the core, could be a blocked core or lack of coolant flow or air flow over the core. I believe duramax has 2 thermostats, if they where stuck open your gauge wouldn't come up to operation temp. Is the engine fan stuck on? makes a crazy loud roaring noise when there on as they move a massive amount of air, I'm sure you have hear this in summer if towing. Air pockets in cooling system also cause lack of heat as coolant won't flow correctly but if no leaks and coolant is up to correct level then i would doubt this and heat in cab would fluctuate. Hope this helps

 

[tex78]

Just fixed a truck yesterday with same issue

Cabin filters where plugged up

Blower motor goes to beat hell, but can't draw the air it needs to blow the core

Take pass side lower cover off, there is a low spot with flap that has one screw and flip tab on other end

Take filters out, blow crap out of hole with cover off and put cap back on without filters and try it

sent while drinking tea's

 

[tex78]

Also the d max has 2 t stats that are different temp to open in stages

sent while drinking tea's

 

[Nytroxpress]

I was completely unaware the 2007 LBZ (classic) has filters I'll look into it. Just to check it's the old body style you are speaking of ?

 

[tex78]

Yes classic 07 has them, 07.5 new ones and up till the 14 body's don't


And seeing as you didn't know, they will be plugged lol

sent while drinking tea's

 

[tex78]

Has 2 in there, pull first one down, then slide the other one over and down

sent while drinking tea's

 

[Nytroxpress]

Excellent. I will give it a try. Thanks very much for the info.
So I don't waste your time the cover u suggest I remove where is it? Under the hood or just above the foot well passenger side in the cab

 

[Nytroxpress]

Update.

I did a Google search for 2007 GMC classic cabin filters and now to my surprise it tells me GM quit with the filters in their trucks in 2003. Can anyone confirm this as I don't want to take it apart to look for something that is apparently non existing

 

[ippielb]

Both of my 06's never had cabin filters there is a kit you can put on to install them

 

[tex78]

Mabe the 07 I did yesterday had one installed after the fact


Come to think of it did a blower motor a few days ago on a 05 and don't recall seeing the cover now


Possible yours had one installed??


If not there then definitely possible plugged air flow in a.c evaporator or heater core

sent while drinking tea's

 

[Merc63]

If your engine isn't coming up to 180f and staying there your thermostats are leaking. How many km on the truck and have you even changed them? There is two and when they start to leak the engine will have a hard time coming to temp. You should hit 180f and stay very close to that. Coming down to 140f is a sign the thermostats are leaking. It might come up to temp on the highway or pulling but will be low around town.

 

[ippielb]

Mabe the 07 I did yesterday had one installed after the fact


Come to think of it did a blower motor a few days ago on a 05 and don't recall seeing the cover now


Possible yours had one installed??


If not there then definitely possible plugged air flow in a.c evaporator or heater core

sent while drinking tea's

Pretty much what I'm thinking too, I just bought the kit for my truck, just the piece of plastic cover with the screw. Gotta cut the hole and slide the filters in and then install the cover. I'm tired of cleaning the inside of my windows from 430,000 of dust.

If your engine isn't coming up to 180f and staying there your thermostats are leaking. How many km on the truck and have you even changed them? There is two and when they start to leak the engine will have a hard time coming to temp. You should hit 180f and stay very close to that. Coming down to 140f is a sign the thermostats are leaking. It might come up to temp on the highway or pulling but will be low around town.

In the winter even on the highway with a solid winter front my duramax never made it up to temp before I changed thermostats. Dead give away if you can't get up to temp the air isn't going to be hot enough to cook. Another thing is the resistor for the blower motor, is the fan spinning up as fast as it use to? I lost my fan speed control it slowly went downhill until it stopped all together, had to be -40 when it did. And had to drive into the city without heat and then install it in the dark outside.

 

[Merc63]

I just did my thermostats with 205k km on the weekend. Easy to change and it comes up to temp (with winter front) within 5 to 10 mins of driving. Before changing, it wouldn't come up to temp unless working it. Fuel milage was taking a beating too.

 

[Summitric]

2007 chev classic 2500hd with diesel does not have cabin air filters... Check bumper to bumper and napa


AND ALLDATA CONFIRMED, NO CABIN AIR FILTER:


2007 Chevy Truck Silverado Classic 2500 4WD V8-6.6L DSL Turbo
Vehicle » Maintenance » Filters » Cabin Air Filter / Purifier » Service and Repair
Service and Repair
This vehicle is not equipped with a factory installed passenger compartment air filter.

 

[tex78]

Unless installed after at a dealer with filter kit

sent while drinking tea's

 

[X-Treme]

You can check your heater hoses going to the heater core under the hood, with engine at operation temp one should be hot and other should be only warm as it takes the heat out of the core (with interior fan on), if there both hot means heat is not being removed from the core, if there not hot at all then no coolant is circulating to the core, could be a blocked core or lack of coolant flow or air flow over the core. I believe duramax has 2 thermostats, if they where stuck open your gauge wouldn't come up to operation temp. Is the engine fan stuck on? makes a crazy loud roaring noise when there on as they move a massive amount of air, I'm sure you have hear this in summer if towing. Air pockets in cooling system also cause lack of heat as coolant won't flow correctly but if no leaks and coolant is up to correct level then i would doubt this and heat in cab would fluctuate. Hope this helps

This is false. If one hose is hot, and the other is not, then the coolant is NOT circulating properly. The heater box doesn't remove enough heat for you to feel a difference in the hose temps. Both hoses should be too hot to touch. If one is untouchable, and the other, you can hold your hand on, the core is plugged. Flush them separately from a full system flush. They need to be flushed by themselves. Garden hose works great. Back and forth multiple times.