1968 Pontiac Firebird Runs Hot HWY Driving


Asked by Aug 12, 2011 at 02:56 PM about the 1968 Pontiac Firebird

Question type: Maintenance & Repair

1.) I am considering buying a 1968 Pontiac Firebird. The owner mentioned the car runs hot on the HWY because it has 4/56 gears or because it needs a larger cooling fan.  I thought maybe a more efficient radiator may solve the problem.
2.) The owner mentioned the real seal leaks oil.  The car sits for long periods of time. He said when the car heats up the seal swells and that seals the leak.
3.) Short of changing the 456 gears I would think a 5 speed or 6 speed transmission would compensate for the higher gears.
I only saw pictures of the car so far and spoke with the owner. From the pictures the car looks very nice.
I don'd mind replacing the fan or the radiator, or eventually replacing the 4 speed with a six speed.  I don't want to have a major problem after buying the car.
Looking for advice especially with the hot running car on the HWY.

6 Answers


4.56 gearing will not cause the overheating. It's normal for these cars to over heat. There are methods available to fix this issue. For example, fan shroud and a flex fan or clutch fan and a/c filler panels should be enough to cool her down. Older engines will have a real seal leak. The seal available back in the day do not last much more than 10 years. You might need an engine rebuild at this point anyways so it can be fixed then. Heat WILL NOT seal it up. You want to focus on the condition of the sheet metal. Rust is your worst enemy! Come see us on the fgf forum for more info. www.http://firstgenfirebird.org/forums Brian

1 people found this helpful.

Brian thank you for your help and response. Greatly appreciated.


If the timing is to far advanced on a Pontiac engine they tend to run hot. Check the ignition timing first.


Dennis thank you for your advice.


put on a set of dual fans with manual switch


sounds like its probably time to do some work on the top half of the engine but if you want to band-aid it ,a good flush and replace with performance radiator fluid , twin electric fans (might wanna install a automatic switch instead of manual , Dont fool your self its easy to forget to turn it on) and a performance thermostat , dont ever ever ever use any kind of miracle cure in a bottle unless "lucas" makes it and use as directed

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