2000 Yukon-Long warm up time - partial heater core restriction possibly?

[OR VietVet]

How simple is it to put a clamp on that hose we talked about? Easier than doing a thermostat. Your call.

 

[rockola1971]

I wouldnt care too much about how accurate the thermal gun is. Lets say its 5 degrees low. The reading will be 5 deg low on both readings you took. Taking temp readings WHILE THE HEAT is on you SHOULD see a substantial heat drop on the outlet. The heat went into your cabin. With the HEAT AND BLOWER TURNED OFF you shouldnt see much of a temp drop between inlet and outlet of heater core. If you do then your core is plugging up.

Sure sound like your thermostat isnt regulating very well. Id replace it.

 

[Splorg]

Sorry, I only glanced through the messages, someone may have asked already - thermostats are cheap. Replace it. Stuck open thermostat would act like this.

Is your fan clutch working? I don't have a ton of experience with mechanical fans, but I'm assuming if it was running full tilt it could cause this as well. Most likely it's a combination of a stuck/improper thermostat and your fan clutch spinning the fan at max all the time.

Sent from my SM-S727VL using Tapatalk

 

[UmmScott]

Just following up with you guys.
I bought a GM original stat for a much lower price online. Going to replace it but i wanna share what a local shop said while i had them test my ABS system. (Separate issue).

They think my heater core is restricted. They said i have large temperature drops across the hoses going to the heater core with the fan on high.
My thoughts (and what another guy said on here).. if you have the fan on high and its 0F outside youre gonna have a temp drop no matter what. Blowing cold 0F air across a 170 to 180F heater core im gonna bet there will be at least a 30F drop in outlet temp there.
Today, it was 0F out. I let it idle for almost 10 mins and drove 5 miles to the shop. Had basically no heat the entire time and temp gauge barely moved from the far left.

In short... I'm pretty sure I'm/We are correct. Thermostat is bad. Did some digging in the trucks records and a 379-187 motorad stat is in the truck now from last year.
They only had the truck for an hour. Just had them do an oil change and pull the codes. They said they "would need more time to check it out fully but think its heater core related"

What do u guys think?

Sent from my SM-G975U using Tapatalk

 

[OR VietVet]

I think you are closer with the thermostat than they are. Yes a temp drop is expected when running the fan. If the heat and fan is not on the hoses should be close to same temp. Should be hard to hold on to with a bare hand. A bad/clogged heater core will never effect the temp gauge. The basics say start with the thermo from here and check after. You may still need heater core replacement but at least get the heart of the system to work correctly with a quality part.

 

[UmmScott]

I think you are closer with the thermostat than they are. Yes a temp drop is expected when running the fan. If the heat and fan is not on the hoses should be close to same temp. Should be hard to hold on to with a bare hand. A bad/clogged heater core will never effect the temp gauge. The basics say start with the thermo from here and check after. You may still need heater core replacement but at least get the heart of the system to work correctly with a quality part.

Fully agree.
Ill get it changed as soon as i can. Its Cold here!! Lol

Sent from my SM-G975U using Tapatalk

 

[UmmScott]

Update.

Got thermostat changed. Heres a pic of them the new ACDelco one is on the bottom and the motorad one that was in the truck is on the top.

Anyhow...put it all back together, filled the coolant back up, and test drove it.
While it was not as cold today, only 27F instead of 0F lol, Im pretty sure I have a big difference. I have lukewarm to mild heat right before the temp gauge even starts moving past 160F.
Before with the old stat i had practically no heat even when the temp gauge started moving.

We will see. Ill let it cool completely down and see how it does on a really cold day.
[emoji106][emoji106][emoji16][emoji16]

Sent from my SM-G975U using Tapatalk

 

[Splorg]

Glad to hear you think you've gotten it licked!

Not sure what the other guys experience is, but my Yukon can sit and idle for quite a long time and not generate heat. Since I replaced the water pump and thermostat, though, if I start driving it it only takes a few minutes to have some sort of heat. Idling it doesn't seem to help at all, still.

I'll cross my fingers for you that it completely resolves your problem! Now that mother nature has decided that winter might not be a bad idea you're going to need it!

Sent from my SM-S727VL using Tapatalk

 

[OR VietVet]

I see the new thermo has the vent hole in the thermostat. Did the old one?

 

[JonnyTahoe]

Fully agree.
Ill get it changed as soon as i can. Its Cold here!! Lol

Sent from my SM-G975U using Tapatalk

Unless its really cold you should be getting heat just starting the engine and letting it run. The computer does all the rest (as we all know). It's completely normal for the engine to run a bit rough for a minute or so especially if it's really cold but it should stay running on it's own. I actually wish it would run at the start-up rpm longer before slowly coming down to the normal idle.

 

[JonnyTahoe]

Faulty Fan Clutch very common. Been running with No Fan since Nov. started out as a radiator hose replacement project and turned into an experiment. as long as its below 20 degrees outside engine temp will never go much past the 1/4 mark at idle and yes my cooling system is all new. had it running almost an hour one time. Pics coming soon.

 

[OR VietVet]

Faulty Fan Clutch very common. Been running with No Fan since Nov. started out as a radiator hose replacement project and turned into an experiment. as long as its below 20 degrees outside engine temp will never go much past the 1/4 mark at idle and yes my cooling system is all new. had it running almost an hour one time. Pics coming soon.

Even on warm days, if you are driving on the freeway at speed there is enough air flowing over the radiator, if it is in good shape and no debris in front of it, the engine should not run hot or overheat. It is even less critical when cold. In cold weather you used to see people block some of the air flow to get the engine temp higher. At idle and at low speeds, if in the warmer temps, you better have good flow across that radiator.

 

[UmmScott]

Pretty much everything on this truck is original.
Original hoses and radiator for sure. Fan clutch and water pump I believe were replaced by previous owner.

I did this job quick. Just popped off the lower rad hose and then thermostat and replaced it.
Then filled back up.
Im thinking since this truck is 20 years old, this summer I might go ahead and replace all the hoses. Dont need them busting open on me thats for sure. What u guys think?

Sent from my SM-G975U using Tapatalk

 

[UmmScott]

I see the new thermo has the vent hole in the thermostat. Did the old one?

Old one had a jiggle pin but not the vent hole like this GM one

Sent from my SM-G975U using Tapatalk

 

[JonnyTahoe]

Even on warm days, if you are driving on the freeway at speed there is enough air flowing over the radiator, if it is in good shape and no debris in front of it, the engine should not run hot or overheat. It is even less critical when cold. In cold weather you used to see people block some of the air flow to get the engine temp higher. At idle and at low speeds, if in the warmer temps, you better have good flow across that radiator.

Last spring I let my Tahoe run half in the garage with the door open and it was about 40 degrees out had not put the fan back on yet (dummy) the motor went into''over heat mode'' read your owners manual it's a real mode I looked at the temp and it was almost pegged. I jumped in and took it for a cool down drive to get some air through the radiator which did cool it down but at the cost of cracking the left side radiator tank. I noticed a big difference in the engine operating temp when I installed a Brand New Radiator. I have never purchased a new radiator we use to just take them to a radiator shop and have them fixed (Harrison four core) I was surprised they are just a single core(row) and affordable.

 

[OR VietVet]

Last spring I let my Tahoe run half in the garage with the door open and it was about 40 degrees out without the fan on and didn't think nothing of it till the motor went into ''over heat'' Mode, read your owners manual it's a real mode I looked at the temp and it was almost pegged I jumped in and took it for a cool down drive to get some air through the radiator which did cool it down but at the cost of cracking the left side radiator tank. I noticed a big difference in the engine operating temp when I installed a Brand New Radiator.I have never purchased a new radiator we use to just take them to a radiator shop and have them fixed. I was surprised they are just a single core(row).

Radiators made with aluminum dissipate heat so quick that they don't need as many rows as they used to. The tank cracked typically because as the coolant drops and it is replaced with super heated steam, hotter than hot coolant, that will crack the tank or if just hot coolant the seam gives from the hot pressure.

 

[OR VietVet]

Pretty much everything on this truck is original.
Original hoses and radiator for sure. Fan clutch and water pump I believe were replaced by previous owner.

I did this job quick. Just popped off the lower rad hose and then thermostat and replaced it.
Then filled back up.
Im thinking since this truck is 20 years old, this summer I might go ahead and replace all the hoses. Dont need them busting open on me thats for sure. What u guys think?

Sent from my SM-G975U using Tapatalk

Replace the hoses asap. That old are way ast when should have been done. They break down from the inside out.

 

[Splorg]

So it's a bad thing that my 2001 has a top rad hose that is marked 10-31-00?

It's on my list of stuff to do. It's a long list.

Sent from my SM-S727VL using Tapatalk

 

[UmmScott]

Replace the hoses asap. That old are way ast when should have been done. They break down from the inside out.

Any kind in particular? Or just gates hoses from oreillys?

Sent from my SM-G975U using Tapatalk

 

[JonnyTahoe]

Pretty much everything on this truck is original.
Original hoses and radiator for sure. Fan clutch and water pump I believe were replaced by previous owner.

I did this job quick. Just popped off the lower rad hose and then thermostat and replaced it.
Then filled back up.
Im thinking since this truck is 20 years old, this summer I might go ahead and replace all the hoses. Dont need them busting open on me thats for sure. What u guys think?

Sent from my SM-G975U using Tapatalk

I just did all my Hoses about a month ago in a cold garage with no heat. I have the same year truck you do with all original hoses ( GM numbers on them) who knew they can last 20 years +. I got my Yukon last September when it was in the 70's. I wish I would of replaced them then but that would of made to much sense.