Engine not reaching operating temperature

[Matahoe]

What kind of coolant are you using and is it pre mix? I run Dexcool mixed with distilled water and my truck starts warming up within a block of leaving my house, but I do have efans..I do not put tap water in my cooling system because of the corrosion it causes.

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Same here. I use distilled water with Dexcool 50/50 as stated in the service manual. I put two quarts into an empty Dex jug and then add two quarts distilled. Shake it up for about 15 secs and use. I make it a habit to always mix my coolant right away 50/50 if I remove the cap and seal on the Dexcool jug. That way I always know that if it is opened ...it has already been mixed.

 

[Fless]

I got the replacement thermostat and housing in the other day. So I removed the one in Tahoe today and put in the new one. Just for grins and giggles I put the old one in a pot of coolant on my stove. It opened up at about 190-195F. The replacement opened at the same temp. Didn't notice any foreign material or corrosion with the old thermostat. I did notice a slight difference in the spring thickness. I also noticed the rate at which they closed was different (because of spring diameter?). That's either a good revision of the previous design or a someone just threw in a substitution which could be hurtful to performance. Time will tell. I'll report back soon. Could be a few days or so until the last bit of air is purged.

@Matahoe, this purge sequence worked great for me when I replaced my water pump, thermostat, and some hoses. I did it on level ground, although I have heard that having the radiator higher helps to purge air.

 

[Matahoe]

There seems to be lots of advice regarding cooling system bleeding on our engines. It's actually not that difficult to understand looking at the hoses under the hood. With our style cooling system the surge tank does all the work. The surge tank is a sealed system with an extra air space hose connected to the radiator that provides a path for escaping air. Essentially there is no special procedure to bleed the cooling system. Just drive the vehicle like normal.

From service manual:

Surge Tank:

The surge tank is a plastic tank with a threaded pressure cap. The tank is mounted at a point higher than all other coolant passages. The surge tank provides an air space in the cooling system that allows the coolant to expand and contract. The surge tank provides a coolant fill point and a central air bleed location.

During vehicle use, the coolant heats and expands. The increased coolant volume flows into the surge tank. As the coolant circulates, any air is allowed to bubble out. Coolant without air bubbles absorbs heat much better than coolant with bubbles.

 

[SnowDrifter]

TBH I've never had an issue with bleeding these things. It's a pressurized, circulating reservoir. They bleed themselves.

Fill it up, drive it, top off. Once its at operating temp, few revs to dislodge any stray bubbles and you're done

 

[Angelo217]

having this same issue. replaced thermostat and coolant temp sensor. mines running in the middle of operating temp and cold. a few times ive seen it get up to 210 where it should be while I was in stop in go traffic on a highway, thats about the only time ive seen it. the hoses feel hot to the touch, enough to burn after more than a second, so maybe it could just be a bad gauge, but I don't hear much of the gauges going out in these 03-06 Tahoes.

ive been seeing some things about not having a restrictor in the radiator, from a cheap aftermarket, not sure of the history on that because I just got this car. and the previous owners don't wanna be straight up with any issues it had/ past maintenance.

so both upper and lower rad hoses get hot enough to burn me, the truck runs fine, just doesn't quite get to where it needs to be temp wise on the gauge itself. do y'all have any pointers? thanks.

 

[Fless]

@Angelo217 I would say put a cheap OBD reader on it to verify what the engine coolant temp sensor is reporting for temp.

The stepper motors that drive the gauges are a known issue on these instrument clusters. In other words, don't count on them to be accurate until they've been verified. If they haven't been updated, they should get some attention.

 

[2006Tahoe2WD]

@Angelo217 I would say put a cheap OBD reader on it to verify what the engine coolant temp sensor is reporting for temp.

The stepper motors that drive the gauges are a known issue on these instrument clusters. In other words, don't count on them to be accurate until they've been verified. If they haven't been updated, they should get some attention.

Good thought. I'd like to hear someone had these gauge reading issues or similar and then got the cluster renewed - and the readings were normal.