Overheating at Highway Speeds

Discussion in '96-04 - 4V Specific' started by ShaneOMac4109, Apr 15, 2020.

  1. ShaneOMac4109

    ShaneOMac4109 New Member

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    My 97 Cobra temps are fine during town driving, around 200*. Once on highway temps start climbing slowly up to around 215*-220*(stopped before temps increased anymore). Not sure what the issue is. Bad radiator/water pump maybe?

    Stock Radiator
    Unknown Water Pump
    Brand new 180* Thermostat
    Recent coolant change
     
  2. ttocs

    ttocs Legend

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    on the bottom of the core support there is supposed to be a small piece of plastic in the shape of a "C" that attaches to it. It creates a low pressure behind the rad that helps it to suck the air through the rad. With out it the car will overheat while rolling as you say. Its just called an air deflector and cj's or or am muscle has them for I think $20.

    https://www.google.com/search?q=94+.....69i57j0l2.4289j0j7&sourceid=chrome&ie=UTF-8
     
  3. evilcw311

    evilcw311 Most Evil Mod! Staff Member Staff

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    I don’t know if that’s really true though. I drove mine for a few years without that and never had an issue. After the wreck it’s one of those parts I never bothered ordering or replaced.

    A leaking head gasket can cause this though. When a head gasket is first starting to leak it can cause it to overheat under the sonata the load of highway driving. To be safe check your oil and check your coolant.


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  4. Jakespeeds

    Jakespeeds Member

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    Are you using the factory electric fan and shroud? Or have you put on an aftermarket one? I have seen the exact condition when people install aftermarket fans and has them running while going down the freeway. It restricts airflow.

    Jake
     
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  5. ShaneOMac4109

    ShaneOMac4109 New Member

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    I do not have the air deflector, although it didn’t have one when I bought the car either, which was 5 years ago. It just started overheating this year.(I’ve driven the car 3 times this year so far, I park it over winter.) I put in the 180* stat hoping it was a bad stat it helped a little bit but it still is running hotter than it should for a 65* day outside. Also I still have the stock fan on the car.
    As far as the head gasket goes, will there just be coolant in the oil? Is the only way to check it to do an oil change?
    Thanks.
     
  6. evilcw311

    evilcw311 Most Evil Mod! Staff Member Staff

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    Look for milky oil or see if theirs crud in the coolant. Also, with the car running looks for bubbles in the coolant. Coolant will also smell like exhaust


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  7. ShaneOMac4109

    ShaneOMac4109 New Member

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    When i changed the oil last year, it was not milky. And as far as the coolant goes it was a little dirty (Green with a hint of brown/yellowish) but nothing alarming as far as old coolant goes. I also don't see any smoke from the exhaust either, a little when it warms up but nothing after that. There where bubbles when i burped the system but they pretty much cleared up throughout the burp process. It doesn't seem to be pointing towards a head gasket. Could my radiator just be partly bad, which would explain why temps are good at low rpm but bad at high rpm?

    Thanks
     
  8. clubcart84

    clubcart84 New Member

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    I just went through this. 1996 cobra was running hot and thought it was a fan problem. Went on many forums and researched it. Temps would go up to 225 and no fan. Replaced sensor, thermostate, radiator. Still got hot with no fan coming on. Tested fan with 12v and it worked great. Did a leak down test and found #5 & #7 was leaking. Air bubbling in cross over tube. Pulled the engine and replaced the head gaskets, new long tube headers and water pump. Burped the coolant system was a pain but finally got all the air out and the thing runs like a new car. The heads and the iirc plates were full of sludge so I cleaned them as well. Checked all electric motors that open iirc plates and all was good. Never thought head gaskets where bad but in my case replacing them made all the difference. think steam keep my fan from coming on as well
     
  9. ShaneOMac4109

    ShaneOMac4109 New Member

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    Although my fan is still working, when your coolant was bubbling in the tube. Was it a lot of bubbles or just small subtle bubbles? Like would I question whether I see them or not? Would it be obvious?
    Thanks
     
  10. evilcw311

    evilcw311 Most Evil Mod! Staff Member Staff

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    Depends on just had bad the gasket is blown out so far. I had a car once blow a gasket but it woudnt bubble. Kept driving it here and there and eventually it got bad enough that I started seeing noticeable bubbles.


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  11. clubcart84

    clubcart84 New Member

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    It bubbled very little in the cross over tube like it was burping but larger bubbles. when I did the leak down I was good on #1 thru#4. I thought I was in good shape until I got to #5, soon as I put air to the cylinder the antifreeze looked like it was boiling. #7 did the same
     
  12. evilcw311

    evilcw311 Most Evil Mod! Staff Member Staff

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    Yep. Like I said. Blown head gasket.


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  13. clubcart84

    clubcart84 New Member

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    best thing that could have happened. After I pulled the engine and went thru everything and cleanened the hell out of the intake and heads the car has never run better since I had it.
     
  14. evilcw311

    evilcw311 Most Evil Mod! Staff Member Staff

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    Gonna do any upgrades while redoing the gaskets or just get it back to running?


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  15. clubcart84

    clubcart84 New Member

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    just put new long tubes on it while I had the engine out. Its pretty much stock other then headers. I have 6 more mustangs that are built nice (450rwhp to over 800 hp)
     
  16. evilcw311

    evilcw311 Most Evil Mod! Staff Member Staff

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    Where the hell is the thread for each of those?!?!?


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