What to do When Your Car Engine Overheats

What to do When Your Engine Overheats

Most normal people drive modern cars with computer controlled everything, and they seldom over heat. If you folks are like me (and I know you are because I’m an Eastwood guy too) you likely drive a special car that is more than a few years old and may have a carburetor, purely mechanical forms of engine control (or manual, driver controlled) systems, and a motor butting out a lot more power and heat than the factory ever provided. Some of the common advice for what to do in case of an overheating car works no matter what car you are driving, but older cars sometime require special care.

WARNING: Of course, we all know not to take the radiator cap off of a hot car, right? The guy did it in that Viagra commercial with the first generation Camaro, and we all knew he wasn’t a real car guy. If the car is overheating the radiator cap is usually holding back hot water, steam and pressure, which can spray out if you open it. Pouring water into a hot radiator can cause hot water and steam to shoot out as well, so stand back.

Modern Cars

Briefly let’s touch on why modern cars are so good at not overheating. It really all comes down to the complex computer controls they all have now, which control ignition timing, fuel mixture, idle speed, cooling fan running, voltage regulation, and more. If the computer feels the motor is getting too hot it can turn on the electric fan, raise the idle speed, advance the timing, enrichen the fuel mixture, and more to get things under control. But then, modern cars are already at an advantage because they have computer modeled cooling systems and water jackets so the factory can identify the hot spots before the motor even exists in metal. The old suggestion of turning on the heat if you overheat still works, but not much else can be done. If a Modern car is overheating there is typically something seriously wrong with it.

Our cars

The cars we all know and love tend to be older and simpler, and sometime they just overheat for what seems like no reason whatsoever. Part of the problem is more powerful motors being installed which bring with them more heat, but don’t discount modern stop and go traffic, which is much worse than anything these cars were designed for. When and if the temperature gauge starts to climb, here are some temporary and more permanent solutions to try:

  • Increase the revs – If the car is overheating because you are sitting in traffic and not moving through the cooling flow of air, increasing the revs will at the very least move more coolant through the water pump and radiator. If you have an old school mechanical fan, this will also increase the amount of air the fan draws through the radiator as well.
  • Air Conditioning – If you have an electric fan, and your car is overheating without the AC on, try turning it on. Conventional wisdom will tell you the AC causes the car to run hotter, but if your car is already running hot there is a chance the thermostatic switch or fan relay has gone bad. Many cars have a secondary relay/switch that cause the fan to go on anytime the AC is on, and some even have an extra fan. Turning on the AC may be all you have to do to get the fan going and cool the radiator.
  • Turn on the Heat – Of course we all know your car’s heater core and blower are just a miniature radiator/fan. Some cars don’t even send hot water through the heater core if the heater isn’t on, so open the windows and turn on the heat. Turning the blower up to full blast will draw the maximum heat out of the heater core.
  • Get Out of Traffic – You’ve seen this one while watching auto racing. During long yellows, or close racing the temps will creep up because less air gets to the radiator. Drivers often take a slower line, or move out or formation just to get some clean cool air on the radiator. You can do this too. Fall out of line. Take a right turn instead of sitting at the light. Take 3 right turns through a residential neighborhood instead of waiting to take a left. Get off the congested freeway and take surface streets. You don’t have to make a huge difference, but stop and go traffic with other cars a few feet in front of you really increases temps.
  • Pull Over – There is no real quick fix for an overheating car, sometimes you need to just pull over and have lunch or get a cold drink and let it cool.

Fixing the Problem

If your car overheats all the time it may be a tuning issue, or it may just be an issue with not having a big enough radiator, or the proper air flow through it. Solving the last 2 problems is as easy as ordering and installing a Maxx-Cool radiator, fan and shroud from Eastwood, but the first one if harder. Check the ignition timing, and fuel mixture for something amiss. Pre-ignition can also cause a car to run hot, so try running a tank of high octane, or even race gas and see if there is any improvement.

If the overheating just happened suddenly, you likely have a new problem that need to be addressed. Here are some of the common issues and solutions:

  • Coolant Leak – This seems obvious, but if it is a slow leak you may never notice it until the car runs hot. Once the radiator and motor are cooler, fill to the top with the correct color of antifreeze. If you don’t have any, just fill with the cleanest water you can find. Bottled water is better than tap water, and tap is better than river water, but any of them will keep the motor alive until you get where you are going.
  • Clogged Radiator – You should flush and fill your cooling system periodically to prevent a buildup of gunk and corrosion that will lessen its ability to cool. There is really no way to tell if this is the cause of the overheating. You can do a simple flush anywhere with a hose and water if you have a bucket to catch all the coolant (antifreeze is toxic, and also tastes very sweet to animals, so you don’t want to just drain it on the ground). Then instead of just refilling it, take the bottom hose off and rinse it out with fresh water. Replace the hose and refill with the coolant from the bucket, and top off with water.
  • Bad Water Pump – The impeller on the water pump can sometimes come off the shaft, and the seals on the bearing or the bearing itself can fail. Unfortunately there is no simple fix for this and replacing a water pump can be a 30 minute job or a 4 hour job, depending on the motor. Plus you need a new water pump.
  • Thrown Belt – Older cars had 1 belt that turned the fan and water pump, and several other belts that ran other things. Throw the fan belt and you could keep driving for a while, but the temp would creep up. Modern cars have 1 belt which runs everything; it’s called a serpentine belt because it has to snake in and out of all the pulleys. If you lose a serpentine belt you are pretty much getting a tow. If you lose a fan belt you can sometimes make a temporary fix with a pair of pantyhose, or any stretchy synthetic fabric.
  • Bad Fan (Electric) – If the electric fan or fans don’t come on it can be for any number of reasons. As I mentioned before, it may be the temperature switch, or the relay that is controlled by the switch, or the fan motor itself may be bad. A good sharp tap of the relay with a screwdriver will sometimes make it work again, though often this works better when it gets stuck on, not off. If you are comfortable with electricity you can easily jump the relay and turn the fan on manually, with just a short piece of wire (you will have to turn it off manually when you get where you are going, too). If that doesn’t make the fan work, the likely problem is the fan motor itself, and that can’t be field repaired.
  • Bad Fan (Fan Clutch) – As old school and untrick as it seems, a mechanical engine driven fan with a thermostatically controlled fan clutch does a great job and is super simple. However fan clutches do fail, and when they do just let the fan rotate freely not pulling through much air. There is not much you can do in the field to fix a bad fan clutch, but you may be able to rig it to spin with the motor temporarily. You are on your own as to how to do it though.
  • Stuck Thermostat – The thermostat closes off the motor so it can reach operating temperature faster. When it fails the hot coolant from the motor usually can’t reach the motor at all, though some do have a bypass so a small amount can flow when it is closed. If your car overheats just a few minutes after getting warmed up it likely is a stuck thermostat. In the field you can fix it by taking out the thermostat, if you have a few tools and can get to it. Don’t drive longer than you have to before replacing it though, because some motors need that restriction in the cooling system to work properly.
  • Retarded Timing – Very few people run points type ignition systems these days, even on nearly stock cars, but the distributor can still slip out of time for some reason, or one of the advance mechanisms can fail. Spark plugs firing too late can cause an engine to run hot, and a failed vacuum advance unit, or other issue can be the cause. If you have the proper wrench you can adjust the distributor for a few more degrees on the road. I recall my dad pulling over and using a few taps of a hammer to advance the timing on the family station wagon while on a road trip once, but don’t try that if you don’t know what you are doing.
  • Lean Fuel Mixture – Various things can cause a lean fuel mixture all of a sudden. If a fuel pump is going bad, or a fuel filter is partially clogged you may be sucking the float bowls dry with extended cruising at large throttle openings (like going up a hill). If you have a good fuel filter the chances of getting a plugged jet are pretty slim, but it does happen and will also cause a motor to run lean.
  • Bad Head Gasket/Cracked Head – These are really the worst case scenarios. A crack or a bad head gasket can just happen while driving, but a common cause of both is driving an already overheating car too hard. When the needle starts to climb think about how much money you spent getting the motor built, or buying that trick set of aluminum heads. Prevent these expensive problems by spending a little time and money installing a high performance cooling system. The Eastwood Maxx-Power Tri-Flow radiators, with matching fan shrouds, fans, radiator caps, and switches make that easy to do, with an almost universal fit and minimal fabrication.


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