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Chevy Silverado and GMC Sierra Radiator and Cooling Questions

Can anyone tell me why the temperature gauge in my 94 GMC Sierra pickup would shoot way up to the red for a few seconds then go back down really low? I have already had my radiator flushed and filled and thermostat replaced and it had not helped. It doesn't seem to matter if the engine is cold or hot when this happens. Also, since this problem has started my heater doesn't work as well either.


  • Hi, I have the same problem with my 94 Suburban. I have also flushed everything out and replaced the water pump, thermostat, and even the radiator cap. Most mechanics I talk to susspect that there is not enough coolant flow through the engine but nobody can figure out how to fix it.
  • My 94 silverado did the same thing with a message of "check gauges" on the dash. I kinda figured with 215K on it the tmp sensor was going bad, so I unplugged it, checked the voltage to it and got a reading from the sensor. plugged it back up and have had no other occurance for about a month now. wiring connection maybe?? the sensor is cheap and easy to replace. i had no trouble codes in the OBD before testing the sensor and had 1 "low coolant temp" afterwards.
  • Can anyone tell me the proper rotation of the water pump. I replaced the water pump and the thermostat with a failsafe and the temperature worked fine for about a week. Now it stay cool
    I know the water pump comes in two styles a clockwise and counter clockwise rotation. I purchased the clockwise rotation, I believe this is wrong. Can anyone help me.
  • I have a 1998 Chevy Z71 and I am having an odd problem with the temperature. I need help if anyone can figure this one out. I start and run my truck just as normal, but when the temperature gauge reaches 190 degrees the problem occurs. At 190 degrees the gauge will drop all the way back down to 100 or below, and also at this time the anti-freeze in the radiator will bubble up or overflow and run out into the reservoir tank. The temperature gauge will never rest or stay at one temperature. It will always rise up and then overflow anti-freeze into the reservoir tank and then cool down. Why is my truck not holding a steddy temperature? Why the overflow? Can anyone help with this? I have replaced the thermostat and that did not work. I have replaced the radiator cap and that did not work. I have checked pressure in all 8 cylinder and they read..
    125, 110, 110, 100, 100, 100, 90 and 90.Does any of this help. Thanks for your help..
  • arkz71arkz71 Posts: 10
    I have 95,000 miles and I am losing coolant I have not seen any on the ground nor leaks on the composite intake manifold. Is there any known problems with the 5.3 have head gasket problems or any other coolant loss problems. I have not had any engine problems out of it or coolant in the oil. Any help would be greatly appreciated.
  • Have had the same issue for the last couple of months, I would have to put in about a pint or less every month and couldn't see it on the garage floor or find it on the truck anywhere, could smell it once in a while. Took the truck in for a 4x4 problem and they discovered the water pump had a small leak, sounds as if you would see that but I never did. Had it replaced and all is good now. Do not let it go too far and get stranded if this is what it is. Hope this helps and good luck!!!
  • arkz71arkz71 Posts: 10
    Water pump has been replaced already, I hope it is not the Intake Manifold gaskets I have read on the internet that they leak. The Intake is composite plastic and since the whole system is under pressure with NO radiator cap (dumb) it is just a pain. I guess the EPA mandated this stupid setup, I have not seen any coolant on the ground and just trying to figure out where it is going.

  • Man if you are not seeing it in the oil and you are not seeing it burning, I'm not sure. How often are you putting coolant in? I have a buddy that has a 02' and he said he loses it in the winter but not in the summer, he took it in and they could find nothing on it either. gotta be going somewhere??? I'll ask a buddy of mine that lives up north, he see's it all in his job, should talk to him tomorrow evening, he's kind of our mister fix it when we cannnot figure it out.
  • ahoronahoron Posts: 30
    Thr intake on your engine does not have coolant running thru it. The throttle body has 2 small coolant lines.
  • arkz71arkz71 Posts: 10
    Thanks a bunch, I added about a 1/4 of a gallon to the coolant tank but the dash will display low coolant, it has 95,000 miles on it. I have an extended warranty and they replaced the water pump about 60,000 because it was leaking around the base of the pump itself. It did not start losing coolant till around 90,000 or so. Plus the coolant was changed, when the other work was done, I would have done the work myself but the warranty deductible was only $100 and it was cheaper than buying the stuff myself.

    It has been a very good truck and I like it just wish I knew if it was the intake or something else.
  • I have a 2001 silverado with the 4.8 in it. Once in a while I can smell anti-freeze but cannot see it. The other day my wife had it and the low coolant light came on. It had not shown any leaks or puddles on the ground until recently. I've read some of the forums here and it suggests the water pump might be bad or leaking. Also the front axle drips a little bit of oil on the ground right where the drive axle comes out of the front differential. Could the seals be bad? What could I expect to pay to have these changed. :lemon:
  • geo9geo9 Posts: 739
    You could possibly have a cracked or leaking heater
    core. Usually thats when you can smell it.
    Do you notice any fogging of the windows?
  • no window fogging, I laid cardboard under it and it leaves small puddles right under the engine in the middle ofthe front wheels as well.
  • chososchosos Posts: 2
    I own an 89 K1500 Pickup. Originally, the radiator was leaking, so we replaced it. In the process, the seal for the waterpump went bad, so we replaced that too.

    Unfortunately, now most of the cooling system has been replaced, but my truck still overheats. I have replaced the thermostat 5 times, thinking it was bad as it was opening late.

    I do know that there were two types of radiator stop leak poured into the system prior to replacing the radiator.

    On my way to work in the morning, it is ~32 degrees F. My truck ussually overhearts quickly if I am driving at ~50-60 mph. However, if I take sideroads, I can do 40 mph and the truck will start to climb up to ~210 degrees and if I pull off and let it idle, the thermostat will eventually open and the system will be fine after that.

    This typically does not happen on my way home from work no matter how fast I drive. The temps going home are warmer ~40-50.

    I just replaced my Radiator cap yesterday, thinking that might be the problem - it wasnt. Then I flushed the radiator - that didn't help either.

    If I let the car idle until the thermostat opens every morning, it drives without a problem.

    I just can't figure this one out. Is my coolant system clogged or gummed up? Is the coolant mixture bad? I know I used 50/50 premix to fill my radiator last night after I drained it and flushed it.

    I have done everything just shy of having my whole system flushed... that was going to be my next step.
  • ricschricsch Posts: 540
    I have a 2006 Silverado with a 5.3 and at 800 miles, the water pump had to be replaced because coolant was seaping from where the metal tube is inserted into the top of the water pump for attaching the upper radiator hose.

    Well, after 2,000 miles, it is leaking once again!!

    If I recall when looking at the new-style '07 Silverado, I believe they did away with the poor design. Wondering if it the new designed water pump will work on my truck.

    Sure don't feel like making a it a habit to have this repaired/replaced at the dealer, especially after the warranty is done!

    Anyone else experience the coolant leak as I described? What was done to correct it?

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