Jump to content

2003 Sierra overheats after coolant flush

Nemesisdawn

Recommended Posts

Nemesisdawn Enthusiast

Nemesisdawn

Posted
Posted

I did a coolant flush on my 5.3 '03 Sierra and changed the fluid from green to Prestone orange coolant. I had mild overheating issues prior to the flush, so I figured flushing the coolant and changing to orange Prestone might help (I did the same exact thing in my '04 GTO with LS1 and haven't had overheating issues since forever).

 

Now the temp always goes above midway, and here's the thing... It does the same thing even on the HIGHWAY with fans on high speed, and it sometimes goes down in traffic only (basically when I'm not giving the engine any acceleration).

 

I changed the coolant again with dexcool, and did an air bleed, changed the temp sensor and thermostat two months ago, and cannot see any leak from the pump but still nothing is helping.

 

I'll note that the green coolant didn't look dirty when it I flushed it out, and that it only heats up when I'm accelerating.

carkhz316 Enthusiast

carkhz316

Posted
Posted

So you had overheating issues before the coolant flush and exchange? Are you losing coolant regularly or any other issues? You should do a cooling system pressure test to verify. What about the coolant temp circuit? If you already replaced the sensor, the wiring can still be an issue.

Colossus Senior Enthusiast

Colossus

Posted
Posted

Plugged radiator and what brand of thermostat are you running? 

 

Logan Lanfear Enthusiast

Logan Lanfear

Posted
Posted

Either a bubble in the system or you partially plugged your rad.  Wouldn't surprise me if it was both.  Could be a sensor or just an unrelated issue as well.  

Nemesisdawn Enthusiast

Nemesisdawn

Posted
  • Author
Posted

I'm positive it's not an air bubble because I changed the coolant twice and the issue didn't change. I tried splashing water on the radiator when it's cold to get any dirt out, still nothing.

 

But I'll have to note that the coolant temp sensor cable looks so thin and fragile, could it be that it's sending a wrong reading when the engine is accelerating?

20181109_221458.jpg

Nemesisdawn Enthusiast

Nemesisdawn

Posted
  • Author
Posted

I swapped my clutch fan for electric OEM ones with a harness from JustChevyTrucks. What happens is that when I'm driving, the temp gauge suddenly goes above midway, and I hear the fans kicking on high, and then turn off after a while due to what I think is a shorting stopper that's in the harness, and then the car gets too hot because the fans are off. All this happens when I'm accelerating, or just cruising on roads.

Nemesisdawn Enthusiast

Nemesisdawn

Posted
  • Author
Posted
On 11/8/2018 at 6:00 PM, carkhz316 said:

So you had overheating issues before the coolant flush and exchange? Are you losing coolant regularly or any other issues? You should do a cooling system pressure test to verify. What about the coolant temp circuit? If you already replaced the sensor, the wiring can still be an issue.

No I did not lose coolant before, and no, there's no white smoke or milky oil. I've had mild overheating problems with the green coolant, but nothing that stopped me from driving the truck. I've posted a picture of the wire above, do you say it could cause all of the problems I'm having? I can see some exposure near where the wire meets the plug.

carkhz316 Enthusiast

carkhz316

Posted
Posted

Well, since that is a thermistor circuit, a short circuit would show overheating temps, whereas an open (high resistance) would show cold, so if you suspect the wiring, I'd look for pinched wires somewhere. Also, I re-read your first post, and you mention that the gauge goes just above midway. Could it be that there's really no issue, or do you think it's still overheating?

Nemesisdawn Enthusiast

Nemesisdawn

Posted
  • Author
Posted
11 minutes ago, carkhz316 said:

Well, since that is a thermistor circuit, a short circuit would show overheating temps, whereas an open (high resistance) would show cold, so if you suspect the wiring, I'd look for pinched wires somewhere. Also, I re-read your first post, and you mention that the gauge goes just above midway. Could it be that there's really no issue, or do you think it's still overheating?

Well I bought a new wire with a pigtail that I'll install tomorrow, and I'll see if that fixes my problem. Whenever I need to push on the gas, or the car has to go up a hill or downshift, the gauge goes above midway, and I can hear the fans kicking on high but then turn off after a minute. And then the car gets seriously hot and lose all its power. The car behaves normal in traffic or idling, but whenever I'm seriously driving it the temp suddenly increases, fans go on high then turn off, and then the car gets seriously hot because the damn fans are off.

 

One thing I noticed is that when the fans turned off while it was still above midway, I fiddled with the lousy temp wire, and then the temp gauge suddenly decreased without the fans even coming on. I'm no coolant expert, but I don't think coolant can become colder suddenly in a running car with no fans.

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Latest Articles

  • Posts

    • Chuck FB
      2 speed transfer case optional now?

      By Chuck FB · Posted

      Yes, and also pulling heavy trailers or a large camper up steep grades as well as descending grades such as the more rustic off road camping locations and using engine braking with that low gearing as well as soft ground can just suck the power . I realize pickups these days tend to have an over all lower first gear ratio compared to automatic transmission pickups from years back so that has helped a lot in its ability in high range but there comes a point if in four wheel drive the torque runs out at the wheels, certainly with a gas engine. They don't put two speed transfer cases on pickups for a cool factor, they have a function if one needs that massive torque to the wheels that high range can't deliver. 
    • Grumpy Bear
      Grumpy Bears 2015 Silverado 2WD

      By Grumpy Bear · Posted

      Notes 7/18/2026   3,400 miles on this batch of Mobil 1 Euro 5W40 since the GDI pump replacement. Alcohol runs very clean when ring seal is tight and the sump isn't getting hosed with fuel. Checked oil level at fill up today as is my practice and grabbed a white Kleenex to look at the color. What color?  I was going to change it but.....  
    • Another JR
      2 speed transfer case optional now?

      By Another JR · Posted

      4 low is really nice on steep boat ramps. 
    • Chuck FB
      Gas Prices

      By Chuck FB · Posted

      Interesting, I suspect I would have fueled up in Lee Vining as the day prior I would have filled up either in Laughlin or near there and maybe again before I entered Death Valley and once out the other side late that evening as I kept on driving into the night up near Lee Vining. Next morning I most likely fueled up in LV before heading over Tioga Pass into ( as I refer to it as "Yose .... Mite" 😁 ). And again that was 19 years ago but the price then must not have jumped out at me like the 5 bill a gallon theme of nutty cult hippy country Big Sir or head so far up their rear Aspen. I'd be curious to know where the highest prices are in the lower 48, I probably would not be far off to guess somewhere in Cali forn ie. Coldfoot and Prudhoe bay may have those prices beat but that is a whole other world up there and when prices are more normal elsewhere that is about what they can be up there I believe in no mans land. Anyway interesting that the 395 corridor is hosing people and the thing is, its tourist season and its not like there are a lot of competition options when driving up that highway from what I could see. Yup, big ole Boaterhomes and various other RV's ahead and behind me at the Yosemite entrance gate and they have to get their fuel somewhere.  
    • Atlas
      Gas Prices

      By Atlas · Posted

      Those can be high, as well as the big California cities. The ones that will pop your eyes out are the 395 corridor on the Eastern side of the Sierra Nevadas. Lee Vining, $7.19 for regular and $8.89 for diesel is what the Google said right now.

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...