Stone Cold after cooling flush and Tstats

[Lt. DMAX]

So I had the dealership do a coolant flush and change as recommended when it hits 100k. I also had them change the Tstats while they were at it.

After, It takes FOREVER to warm up and this is confirmed not only by the cold air but the gauge. I was even running cold with the cover over the grill in above freezing temps. She used to jump right up to the 210 marker and then stay there, but now it rarely reaches the 210 mark, even after driving for some time.

Thoughts on possible issues?

 

[2004LB7]

Didn't bleed the system properly, wrong T-stats, bad T-stats, put in backwards

I would start with trying to properly bleed it. If it looks good and still no heat. Bring it back to the dealership

 

[Lt. DMAX]

2004LBZ, I had purchased the T stats from GM Parts Direct as I had intended to do the work myself. Decided against it when I thought the mess in the drive was not worth it and that they could POWER FLUSH the entire system.

Ill give the bleed a shot.

I was wondering if they put the stats in the wrong spots, but I would expect a SLOW warm up, not a RARELY GETTING TO TEMP.

 

[Lt. DMAX]

It has been over two months since the work was done. Wouldn't any air pockets be pushed out by now?

 

[Lt. DMAX]

Chilly saga continues.
1 Degree morning.
Grill Cover is on.
Block heater in for about hour and a half.
Remote Start Truck and run for 10 min.
Drive down my hill which is 1 mile long using gears to control speed as always.
Continue to location which is 3.5 miles including a short stretch on highway.
Engine Temp per my Radio which can read some parameters via OBD II port - 165.

Would not any air bubbles have been worked out by now?
Fuel Economy is in the crapper at 11 even after a fresh OEM Filter and filter head rebuild.

 

[darkness]

So after about 20 minutes of run time and 1* outside the truck got up to 165?

 

[Lt. DMAX]

Darkness - I know, not a problem you see much in Vegas...

Don't forget the limited time on the block heater AND the grill cover is on.

I just remember the truck blowing warm air sooner than it has been since dealership did a flush and T stat change. Even GF comments on how cold truck is and you know they are all temp sensitive.

 

[DAVe3283]

It really sounds like the new thermostats aren't closing fully. I've had thermostats be bad out of the box. I would personally change them again. It isn't hard, you don't need to drain all the coolant, just a bit. They are right on top, very easy to get to. Make sure you put in the 180°F rear / 185°F front temperatures. That's the stock temperatures, but there are some low-temp models out there. I don't recommend lower temps than stock, these engines are happy at 180-210°F all day long.

When you change them, there is a bleeder bolt on the top of the housing, just take that out and fill until coolant is coming out without bubbles, then close it and fill the surge tank. I find the next 2-3 heat cycles it will burp a small amount of air, so plan to add a little after a couple drives.

It looks like the thermostats run $20-30 each, so if you put the ACDelco OE-grade ones in, it will cost you about $100 including coolant, unless you capture and re-use what you drain out in the process. You can probably do it all super cheap if you use no-name thermostats, but those have a high infant mortality rate IMO.

 

[BlkMax]

X2 What Dave said....



I deal with stats in low temps all the time. If you are not seeing 180*+/- on a real temp gauge, those stats are open. In colder climates the cooling system is just too good without a big load on the truck (even with the winter fronts bumper and grill covers).



What I have found is near 0*F ambient, the heater core can nearly cool the engine by itself. Extended idling without a high idle just burns fuel and does not bring the engine to temp (other than a few minutes to warm the oil).

 

[NC-smokinlmm]

Check your fan clutch, if it goes bad and dosent disengage properly then it will over cool the truck and it will go into speed density tuning and get terrible fuel conomy. I've fought this recently on a buddies truck...

 

[Lt. DMAX]

Thanks for all of the input.

I had researched the process to replace the stats and am up to speed on the process, purchased the stats from GM Parts Direct and intended to do it all myself but changed my mind when I heard the dealership could use a machine to get a good flush and I could keep my driveway clean.

New info - One point of info I had neglected to provide to date was the fact that the reservoir was full and I mean to the point where you did not see the fluid level. I only was able to pull a small amount of coolant out to the point where you could now see the fluid level. Went for a short drive with the usual hill decent, errand to the pharmacy so city driving and so far she was running cold as she has been. Hit a section of highway and no sooner I started getting to speed the temps began to rise and I was now getting the face melting heat off the HVAC and the temps on the dash held at 210 and 181 on the OBD reader.

Could this have been the issue or did the cracking of the bleeder screw revealing only coolant do it? Combination?

Additionally, the dealership cracked the T Stat housing with one of the bolts holding the upper hose on. That's gonna need replacing.

 

[Chevy1925]

Check your fan clutch, if it goes bad and dosent disengage properly then it will over cool the truck and it will go into speed density tuning and get terrible fuel conomy. I've fought this recently on a buddies truck...

Not on a Dmax. Fan does nothing till there is coolant flow and you won’t get any flow through the rad until the t-stats open. He would be seeing spikes and drops from the fast t-stat cycles and stuck fan clutch.



OP, take the truck back. They should be warrantying their work. I bet you got a sticky t-stat or the wrong temp ones in there.

 

[Ron Nielson]

It has been over two months since the work was done. Wouldn't any air pockets be pushed out by now?

YES, for sure. I replaced my leaking EGR cooler and it took several days (not more than a week) for the air to work out completely.

 

[TheBac]

Everything so far sounds normal to me for a cold-blooded Dmax. In low temps, they dont get to operating temp within a short 5-10 mile drive, even allowing for 10min warmup and grill cover on. As o/p said, once he got on freeway and drove a bit, temp came up...