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85 C20 overheating

Discussion in 'Chevy Trucks' started by owen, Aug 30, 2003.

  1. owen

    owen Member
    from florida
    Messages: 34

    Great site!:D You plow guys know these trucks better than any forum I've found. I did some searching and decided to replace my clutch fan and thermostat from what I read. Still have some questions though:

    85 C20 3+3 454 TH400. The truck is missing that plastic air tube going from the grill to the air cleaner snorkel. I live in Florida where the temp was 93 degrees today and I was pulling a 21' boat.

    Within 15 min of normal running the temp sits about 210 or just above. When I turn off the engine the temp rises and is in the red (260+) after about 5-10 min of sitting. I know it should get hotter with no circulation, but should it go that high?

    When I go to start it it feels as if the battery is dead and had one good start left to fire it off.

    If I wait till the temp drops back down to 210 or so then it starts normal.

    While dicking around at the boat ramp and doing a lot of idling the temp would be at 260 and just about in the red. Once I got it back on the road the temp came down a bit, but stayed around 230-240.

    Any input on that?

    Also, what is the range of available thermostats. Which temp should I buy?
  2. wyldman

    wyldman Member
    Messages: 3,265

    Always run a hot t-stat.The t-stat has nothing to do with the max operating temperature,only the minimum.Use a 195 stat.

    The plastic air tube will not have a major affect on engine temperature.

    I'd do the clutch fan and stat first,and let us know if it's fixed.
  3. Chuck Smith

    Chuck Smith 2000 Club Member
    from NJ
    Messages: 2,317

    It sounds like the starting problem if only when hot, is the fact that the starter solenoid is so close to the exhaust. GM used a heat shield on some big block motors. YOu can buy one, make your own, or relocate the solenoid up and away from the exhaust.

    Do you have an aux. trans cooler? If you plan to do a lot of towing in that heat, I suggest one.

  4. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    Hot starting problems are common on big blocks,a starter shield goes a long way here,you may be able to get a factory one,if you know where to look. After doing what Chris said,id suspect the radiator is plugging up with corrosion,or sediment.With a 195 stat the truck should run about 195-205. The fins could also be full of bugs .especialyl in Fla. You can powerwash it out,very gently,or you bend the fins up.
  5. owen

    owen Member
    from florida
    Messages: 34

    Thanks for all the great info:drinkup:

    I'll go to work now.

    The dishonest guy I bought the truck from said it was a brand new radiator, and it looks new. He was obviously troubleshooting a cooling prob.
  6. owen

    owen Member
    from florida
    Messages: 34

    New HD thermal fan clutch & t stat. Problem solved. It has yet to even hit 210 degrees:)

    Also put a new starter on. Big improvement!

    Thanks guys
  7. wyldman

    wyldman Member
    Messages: 3,265

    Great,good to hear it's fixed. :drinkup: