Weird Vehicle not reaching operating temp after work done

OK, so my wife has a 2012 Yukon XL Denali and we recently had work done to it, new remanufactured transmission, replaced radiator and water pump (ouch at the cost of all that BTW). When it was finally done I went and picked it up I drove into town to get a check to cover the rest of the repairs and then back to the shop. The temp gauge only went up about half way. Which I thought was really strange. It seemed to pump out heat however. I had them take a look at it and everything seemed to check out. Now fast forward to this week with our really cold weather its gotten worse. On Monday my wife let it warm up like 15 minutes and her 15 mile drive to school they froze their butts off. So back to the shop it goes where they had it all day yesterday. They went through everything. Plugged into the computer the temp passed said 212 which is normal. They used a lazer heat gun and the radiator and engine block along with coolant lines all checked out. They checked the temp out of the vents inside and they read 185 when they jacked the temp up to 90. So those things all sound good right?
This morning she warmed it up again for several minutes and off to school again and sure enough froze their butts off again.
What gives here?

Sounds like she should be driving that new re vamped 23 gmc with heated foot massagers and back rubbers.

Did they check to see if the thermostat is stuck open?

Bearcat89 wrote:

Sounds like she should be driving that new re vamped 23 gmc with heated foot massagers and back rubbers.

She actually had to drive it yesterday because she didnt get a loaner and the old Envoy wouldnt start. She is afraid to drive it. When she got home we went out to eat and she said “see I didnt even break anything”. LOL

Youbetcha wrote:

Did they check to see if the thermostat is stuck open?

I’m no mechanic, but this is one of the first things I’d look at as well.

Captain take it for a ride and see if the temp gauge drops back while you are driving it. If it does I’m guessing thermostat. If gauge is steady. Stop and check both heater hoses with your hand. 1(inlet) should be hot. The other should be a little cooler to the touch but not feel cool or cold. If it is the heater core is either plugged or air locked.

CaptainMusky wrote:

<div class=”d4p-bbt-quote-title”>Bearcat89 wrote:</div>
Sounds like she should be driving that new re vamped 23 gmc with heated foot massagers and back rubbers.

She actually had to drive it yesterday because she didnt get a loaner and the old Envoy wouldnt start. She is afraid to drive it. When she got home we went out to eat and she said “see I didnt even break anything”. LOL

Lol , sounds like mine. She won’t drive the new one because it’s to long.
Your issues sound like a t stat stuck, or heater core

Yeah, I will give it a drive tonight and put my hands on the hoses. What is strange is that they checked all those with the lazer heat gun and everything seemed to check out. The timing is just absolutely strange because it literally just started since those repairs were done. I dont understand how their gun could read 189 or whatever at the vent and not feel heat coming out. They will certainly check it over again since these are all warranty type repairs. Wish they would have just replaced the T Stat right away yesterday but they said everything checked out. Ugh.

MX1825 wrote:

The other should be a little cooler to the touch but not feel cool or cold. If it is the heater core is either plugged or air locked.

That is an interesting idea. Since they replaced the radiator and water pump I am sure they had to essentially replace the majority of the coolant. I suspected air in the system too. I will also check the coolant level to make sure its full. That is one thing I am not sure they checked.

Sure sounds like the heater core is plugged, or the regulator for the heater core stopped working. Check to make sure both lines to and from the heater core are hot. If the T-stat was stuck open it wouldn’t heat all the way up to normal temps.

If the temp gauge shows it’s running colder than normal you have two possibilities. Either there is air in the system (unlikely) or your thermostat is stuck open.
The thermostat is what controls operating temp. If your gauge was reading the same as normal I’d suspect a heater core issue.

My guess is that while the cooling system was open, there was debris that got moved around and ended up lodging in the thermostat.
With the amount of money you just sunk into it I would sure hope the shop that did the work would check it out for you. If they wont you need to find a new shop.

Likely a plugged heater core as the check engine light would likely come on if the computer didn’t see normal temps after so much time. It sure did on my 96 Chevy truck when the parts store sold me the wrong coolant temp sensor. It didn’t take 30 minutes for that light to come on and it wouldn’t use forth gear or engage the torque converter clutch

The gauges on the dash aren’t very accurate, my 96 would only show about 165 when my scanner would show well over 200

If the temp gauge goes to half way, that’s about where they should be… I suspect a plugged heater core as well.

It’s not halfway up it’s about a quarter way up. Straight up is 210 but it’s halfway there. When she got home tonight I checked the hoses and they felt warm but I don’t know how warm they should feel. She said it wasn’t cold in the vehicle but like Luke warm. It’s strange.

If the thermostat is working the radiator hoses should be hot enough you cant touch them for very long, like a second long before you get burned.
I have had vehicles in the shop that when the thermostat is sticking open it will pump out decent heat,,,until you take it outside and drive it then it cannot keep up.

I would bet when they changed the radiator they broke something loose and its now stuck in thermostat keeping it open, as efficient as todays radiators are it doesnt have to be stuck open very much.

It likely needs a new thermostat. The thermostat is located inside the water pump on that engine and is generally replaced when the water pump is replaced. Do you know if it was replaced along with the water pump? It’s possible that a new part failed, or that the wrong temp thermostat was installed. Take it back to the shop that did the work.

With the more info. Bad thermostat or debris holding it part way open. Another option it was somehow not put in when water pump was replaced.

My guess was air locked. Maybe just needs bled off.

Bearcat89 wrote:

Sounds like she should be driving that new re vamped 23 gmc with heated foot massagers and back rubbers.

Don’t get me wrong, I love those items but I couldn’t live without a heated steering wheel.

Eelpoutguy wrote:

Don’t get me wrong, I love those items but I couldn’t live without a heated steering wheel.

The heated steering wheel sure is nice! My wife’s has it too and its an absolute must on hers because its got a woodgrain steering wheel. Wow is that cold otherwise.
When I grabbed the hoses last night she had just turned it off so it wasnt running but I could hold my hands on there without any issue. They did replace the thermostat when they did all the other work so its possible that its defective or something got stuck in it. I thought the thermostats were easier to get at than they are on this vehicle so I can see why they didnt just replace it the other day. Either way they said they will make it right. My initial concern was too that they had it in their shop all night (heated) and then were doing all their testing within there. I am not sure if they did a road test at all. I will have to ask them today. Its certainly not helping her gas mileage!!!!!

Eelpoutguy wrote:

Don’t get me wrong, I love those items but I couldn’t live without a heated steering wheel.

I used to think that was ridiculous till I had a loaner Tahoe with the heated wheel. OMG, so nice!

I also used to think a heater in a boat was ridiculous, but lemme tell you, it’s nice!

If the temp gauge is only going up a 1/4 of the way.. you have a partially stuck T stat or like said, air in the system… the heater core could be partially restricted as well, contributing to the poor heat, but not the main cause.

Sure wish my heated steering wheel worked. Ive had my truck almost a year and still no parts to make it work. But hey GM gave me 25 bucks of the truck for the inconvenience. That makes it ok.

JEREMY wrote:

But hey GM gave me 25 bucks of the truck for the inconvenience. That makes it ok.

Maybe invest that $25 in hand warmers and zip ties–DIY heated wheel.

JEREMY wrote:

Sure wish my heated steering wheel worked. Ive had my truck almost a year and still no parts to make it work. But hey GM gave me 25 bucks of the truck for the inconvenience. That makes it ok.

Ha! I was surprised my truck came with it because of the chip issue. I did get a discount for no ventilated seat working (later retrofit) and no steering wheel lock (later retrofit) at $50 a piece. My buddy got his truck around a year ago and it was middle of summer before he got an email that his missing chips were coming. He was out the heated seats and a bunch more things.

big_g wrote:

If the temp gauge is only going up a 1/4 of the way.. you have a partially stuck T stat or like said, air in the system… the heater core could be partially restricted as well, contributing to the poor heat, but not the main cause.

Thankfully the shop is about a block from my house so I will run it over there again probably tonight. They need to do these tests outside. My wife said their teeth were chattering on the drive in yesterday and they had the temp set to 90. She is getting like 6MPG right now too ugh. I have a spare vehicle she could drive but its been sitting for a few weeks and the battery is completely dead and I cant even jump it with my booster pack. Need to get the charger on it today. Hopefully its not toast.

6 mpg is something totally unrelated to the heat issue.. IMHO

big_g wrote:

6 mpg is something totally unrelated to the heat issue.. IMHO

Perhaps, but Im thinking that if its not getting to proper operating temp would pull down the mileage. Oh well at least gas is cheap! LOL

big_g wrote:

6 mpg is something totally unrelated to the heat issue.. IMHO

If it’s running colder than it should fuel economy would definitely suffer.

Sounds like the shop will take care of it for you. We unfortunately see new bad parts all too frequently these days.

If the ECU is seeing half of normal temps and the air temp is cold it will most certainly affect mileage, especially if you are running oxygenated fuels.
The ECU will add more fuel because it is looking at what it thinks is a cold engine.