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Help, My Car Run Hotter On The Highway

Discussion in 'The Hokey Ass Message Board' started by sled51merc, Aug 18, 2009.

  1. Hi all, I'm having a problem with my car running hot on the highway and once I'm back in town it slowly cools down. The car I'm speaking of is not your traditional hot rod or custom. It's a '68 Buick Riviera. I though I would post this problem here because I really don't frequent any other message boards and the knowledge is great here! I don't have a temp gauge with #'s, just cold to hot with the marks in between. My fan clutch recently went bad so I went to Checker and got one from them. My car has always ran about a quarter of the way up on the gauge and not much higher than that. It seems it started running warmer after replacing the fan clutch. I thought maybe I got a bad part from Checker and went to Carquest and got a heavy duty one for the engine in my car. I took it down the highway today and same thing. It got as high as the middle point between halfway and 3/4's, on the hot side. I had the radiator boiled out last year and just replaced the thermostat. There isn't a spring in my lower radiator hose so I'm wondering if it's flattening out at the higher rpms on the highway. Any suggestions would be greatly appreciated!


  2. yah the lower hose will suck flat at high speed need to change that out and should be fine and replace the thermostat while ur at it
  3. Mr48chev
    Joined: Dec 28, 2007
    Posts: 27,214


    Ok, I don't want to sound like a smart ass but I don't put much faith in the accuracy of electric gages. I'd suggest putting in a mechanical gage to get a more accurate temp reading. You could hide it down below the dash somewhat out of site except to you.

    Is the radiator/ac condenser free of bugs, dirt and what not?

    Is the thermostat opening when it should?

    Are any hoses kinked?

    And after reading Skenny'schopshop's post yep make sure that the bottom hose isn't getting sucked flat.

    The fan clutch and fan should be pretty well out of the picture at highway speeds as long as there is good coolant flow through the cooling system and good air flow through the radiator. If it was cool out on the road and then hot at slow speeds I'd suspect the fan clutch as the problem.

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  4. ChevyRat
    Joined: Oct 12, 2007
    Posts: 575


    I agree with Skenny's - get one with the coil in it. What temp thermostat did you have before and did you replace it wih the same?
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  5. Ghost28
    Joined: Nov 23, 2008
    Posts: 3,157


    It sounds like you have an air lock or bubble in you cooling system that needs to be purged. I say this cause at highway speeds or under load it is getting hotter this makes me think it is a flow problem...John
  6. The radiator is pretty clear of bugs a few here and there. No kinks in the hoses. I put a 195 degree thermostat in it. That's what Napa said the book called for. I guess I'll pull the thermostat out tomorrow and replace the bottom radiator hose. Do you guys know if I could just buy a spring and put it in the hose, it's not that old. Or do I have to buy a new one?

  7. Mr48chev
    Joined: Dec 28, 2007
    Posts: 27,214


    It should just run at operating temp with that thermostat if it is what the specs call for.

    I see way too much of this stuff of guys looking at a temp gauge and just because it reads a tad higher than they think it should they think the car is running hot. What I am saying is that up past the middle mark may not be hot for that engine and it may just be running at normal operating temperature.

    I've always had the theory that if it isn't puking coolant it isn't hot. That has held good for me for the past 46 years of driving.

    If the car didn't have a thermostat before or it had a 160 or 180 yes it will show a bit hotter but that should still not be "too" hot.

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  8. It pukes plenty of coolant, in fact I can smell the coolant as I'm going down the highway. It just seems weird that all of the sudden it's running condsiderably warmer.

  9. its the hose change it out have to get new one dont think u can get just the spring because u say it cools down in town is bescause u arnt go ing over 35 in town so it dosent have thet much suction but on freeway ur probly running 70-75 then it is flowing more coolent so it going to suck the bottom hose shut then restrict the flow thus over heating
  10. TooManyFords
    Joined: May 21, 2008
    Posts: 553

    from Peotone IL

    Sounds like a bad radiator to me. Really dont need the fan clutch much over 40 miles an hour. I shoot for a new radiator. 195 sounds hot for a car of that vintage. I would run 180.
  11. dalesnyder
    Joined: Feb 6, 2008
    Posts: 397


    Please don't take this the wrong way, but it is an easy mistake to make.. When you put the old fan blade back on the new fan clutch are you sure it is facing the right way..
    Put a peice of paper against the front of the rad and see it sticks..

    Sometimes you just have those kinda days..
  12. tommy
    Joined: Mar 3, 2001
    Posts: 14,758

    Member Emeritus

    Every time I've encountered this phenomenon it was a partially clogged radiator. It's not too uncommon on a cross flow radiator. The lower tubes get blocked off by sediment and it heats up under a load. One of those "ray gun" temp readers can confirm if the lower tubes are not as hot as the upper tubes on a cross flow. You might be able to tell just by touch. I've found recently that you can often find a replacement radiator cheaper than a radiator shop will charge you to clean and repair your old one. Check around.

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