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Sudden overheating

Discussion in '1982-Present GM Diesel' started by Danno, Dec 24, 2001.

  1. Danno

    Danno 1/2 ton status

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    Location:
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    Today my truck decided to run extremely hot extremely quickly. I fired it up, let it idle for a bit. Left my apartment right after the truck kicked out of high idle, still around 100F on the temp gauge.

    Immediately drove out to Hwy 66 and proceeded to speed up to about 65mph. After about two miles, my temp gauge read just below 240F!!! This was within a matter of two or three minutes.

    I pulled over, and sat idling for about 30 seconds. Temp immediately dropped to about 220F. I turned around to go home (not smelling anything hot, engine sounds normal, etc), and once I got back up to about 55mph, the temp started to spike again. I shifted out of OD to drive, and the temp dropped to 220F pretty quickly. Sped up to 60mph, temp started to go up again. Made it home without incident.

    As soon as I got home, I popped the hood. No smoke, nothing smelled hot, and it was actually very cool under the hood. Valve covers were still cool to the touch. Disconnected and reconnected the wire to my temp sensor. It was reading about 210F after idling for about two minutes.

    Shut the engine off, and felt around. Sides of the radiator were warm to the touch, but not scalding hot. Popped the radiator cap off, very small amount of pressure, nothing else came out. Coolant level was pretty much to the top of the radiator. Felt the center of the radiator with my hand from the fan side, and it was pretty much ambient temp.

    Fan clutch seems to be working, as it is moving a decent amount of air while running.

    What could cause something like this? It's rather strange, if you ask me... Could this be a thermostat sticking closed? Trans about to melt down? The engine appears to run just fine, no knocking, weird smells, excess heat in engine compartment, no smoke or steam. Oil level is at full, ATF is at full, coolant is at full. The truck has never leaked coolant.

    Any suggestions? I had to go to a Christmas gathering, so I just parked the truck and took the wife's vehicle for the day. Just got back. I'll be troubleshooting it tomorrow (Christmas Eve... Joy to the World, bah humbug).

    Thanks... Happy Holidays!

    1984 K5 Blazer 4x4 Silverado
    6.2L diesel, 700R4, 3.42 gears, 31x10.5" tires
     
  2. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    let the truck warm up again and have the radiator cap off and see if the coolent is flowing good if not then take th thermastat out if it still dont you could have a bad water pump or your radiator could be cloged up just a few ideas to try then get back to us with the report and we will go from there

    wheeling videoshttp://community.webshots.com/user/ssmith6333
     
  3. Danno

    Danno 1/2 ton status

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    Thanks for the reply...

    I'll see what happens with the cap off. I didn't think about that when I was looking at it earlier today. Probably won't be able to do much until Wednesday since NAPA will be closed until then. Doh!

    1984 K5 Blazer 4x4 Silverado
    6.2L diesel, 700R4, 3.42 gears, 31x10.5" tires
     
  4. mudhog

    mudhog THEGAME Staff Member Super Moderator

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  5. Danno

    Danno 1/2 ton status

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    Well, here's the lowdown after messing with the truck for a bit today.

    Pulled the thermostat, and took a quick drive. Truck never got over 105F. Went to NAPA and bought a new thermostat. Installed the thermostat, topped off the fluid, and took it for a quick drive. Overheats the same as before.

    That's got me confused. If the truck never overheated without a thermostat, wouldn't that indicate the water pump and radiator are OK?

    I can see a decent amount of fluid pouring into the radiator from the heater return. When I drove around with no thermostat, I had zero heat in the cab. With the thermostat in and the truck overheating, I had plenty of heat in the cab.

    I'm at a loss here.

    1984 K5 Blazer 4x4 Silverado
    6.2L diesel, 700R4, 3.42 gears, 31x10.5" tires
     
  6. calcide

    calcide 1/2 ton status

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    Maybe your gauge is reading wrong. At 210 degrees, you should have pressure in your cooling system and it should all be hot to the touch.

    <font color=red>When in doubt, empty the magazine. </font color=red>
    <a target="_blank" href=http://www.geocities.com/calcide>http://www.geocities.com/calcide</a>
    1983 K5 Blazer Silverado, 6.2L Diesel
     
  7. Danno

    Danno 1/2 ton status

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    Thought about that... Dunno. It's hard to work on stuff around Christmas with all the parts stores I go to closed. I guess I'll just have to take a break for a while before I throw more parts at it.

    I'll try replacing the temp sensor. It's always read around 210F until just recently, so I kinda suspect the gauge isn't what's malfunctioning. Who knows? Thanks for the suggestion!

    Merry Christmas everyone!

    1984 K5 Blazer 4x4 Silverado
    6.2L diesel, 700R4, 3.42 gears, 31x10.5" tires
     
  8. Danno

    Danno 1/2 ton status

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    Just got back from having the coolant flushed from the system, and it's stablized my engine temps. I now run 220F idling, in stop and go traffic, or running 80mph in OD on the highway. The truck doesn't spike up to 240F anymore.

    I'm thinking my water pump is on the way out. All the hoses in the engine compartment are hot, but I'm not getting a lot of warm air from the fan. It's either that, or I need to replace my radiator.

    1984 K5 Blazer 4x4 Silverado
    6.2L diesel, 700R4, 3.42 gears, 31x10.5" tires
     

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