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  1. #1
    Member C4ME's Avatar
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    Jan 2004
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    Huntsville, AL
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    Corvette(s)
    1986 Z51 (Al heads), Auto
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    Default What is normal...safe operating temp?

    I have an 86 with aluminum heads and the heavy duty radiator. I have only had the car a few days and ran it only in the driveway (Long story why). I noticed that the temp was hovering around 230ish and peaked at 240 and I shutdown immediately. There is plenty of fluid and the fan was running no a/c on. This seamed a little hot to me but I am a newbie so it may be jitters. When should I be REALLY concerned about the temp?

    Also (and this is cheating a bit as I did not mention in the title), is it normal to have a 30 psi oil pressure swing?

    Thanks

  2. #2
    WNH
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    The main fan is controlled by the ECM [the electronic control module] and it starts the electric main fan at about 228.
    Also, the auxilary fan kicks in at about 238.
    Other members can correct me if I'm wrong.
    Anyway it should not go too far above 240, that's too hot.
    Start by checking when both your fans start, let it idle till it gets hot, look at your dash coolant temp.& see exactly when they start.

  3. #3
    limomanb
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    And yes....my Oil pressure swings from the low 30's to the mid 60's...quite normal.

  4. #4
    Member c4cruiser's Avatar
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    Feb 2002
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    Corvette(s)
    87 Gold Z52 Coupe 02 EB Z51 Supercharged Coupe
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    One of the most common problems with C4 cooling is debris clogging the radiator. Cooling air come up from the bottom and all sorts of junk can be picked up; paper, leaves, twigs, Hondas... You should be able to look at the front of the radiator by looking thru the gaps in the radiator shroud on the passenger side.

    Use a hose to direct a stram of water from the fan side through the fins. Also check the front of the A/C condensor by looking at it from under the car.

    The main fan should come on around 228 and run until the temps cool to 200 or so. You may also have a bad thermostat in that it may be stuck closed. It's easy to replace and use a 180 degree stat as a replacement. Another possibility is the lower radiator hose collapsing due to age. If the hoses look original or feel very soft, they should be replaced.

    Do a coolant system flush at the same time and refill the system with a 50-50 mix of ethelyne glycol (green) coolant and distilled water. Distilled water is available at grocery stores for less than a buck a gallon.

    For the oil pressure swing, a difference of 30psi at an oil temp of around 200-210 it should be OK for a motor with some miles on it. If it's something like 20psi at idle and 50psi crusiing, you should be fine. Use a good 10w-30 grade oil and a quality filter and change oil every 3000 miles or so.

  5. #5
    Bob Yates
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    Hey C4ME....I've got a 86 with aluminum heads on a summer day when I'm roll'in my temp stays about 190 with AC on. When I stop and idle it goes up to 225,the fan kicks on and it cools down to 205.... it will do this till I start roll'in again. I installed a 180 thermostat and cleaned between the AC condensor and radiator. To really clean it good you have to remove the cover that is over the radiator. Believe us there is more junk there than you can imagine. As far as your oil pressure get a GM manual. It will tell you what the oil pressure needs to be at certain rpm and if it is in that pressure range your OK. I don't have my book handy and I don't remember the pressure. Let me know if you can't find it and I'll look it up for you. You never mentioned how many miles were on the clock. This may be a factor too. But be sure to clean between the radiator. Look in my past threads and you will find how to make a screen to keep out trash from your radiator. Good luck ......Bob Yates

  6. #6
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    1988 35th Anniversary Edition
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    My radiator had accumulated some leaves and even a few small twigs, but the biggest blockage was from Cottonwood tree seeds. Those little white fuzzy things had blocked around a third of the spaces. The only way to get them out was to remove the radiator and gently brush the fins.

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