NOTE:  If you are not comfortable leaving the radiator cap off during warm-up then you can accomplish the same thing by leaving the radiator cap on and allowing the car to cool down after step four and then repeat steps one through four again, making sure the overflow bottle is maintained full.  The heating and cooling cycle will push the air out through the overflow bottle and then suck coolant in to replace the air when the engine cools.  The car must remain inclined for the whole procedure.

When should I check my cooling system

The best time to inspect your heater and radiator hoses is cooler weather.  Less obvious signs of decay can be seen and felt by grabbing hold of a cold radiator or heater hose and giving it a good squeeze. Brittle or cracking material, a spongy feel, or a hose sticking to the inside of itself are bad signs.

WHy is my car overheating?

There is no one answer for this question but here is a list of places to start to isolate the problem.

1.       Before you do anything else, tune up the car. Many overheating cars are out of tune, running lean or with retarded timing. A lean fuel mixture will overheat your car. If your engine runs lean you can chase your tail looking for problems in the cooling system and never figure it out. The easy way to do this is richen your jetting a couple of steps. If the overheating is better, you're on the right track.

2.       There is a lot of misinformation about ignition timing and cooling. Retarded timing contributes to overheating. Advanced timing helps cooling. Advance your initial timing a few degrees and see if it helps the car run cooler. However, if you advance to much you risk detonation and that too will cause you to overheat.  If you start to detonate back off the timing. Overheating cars should always run vacuum advance. Vacuum advance helps cooling.

3.    Radiators: Your radiator is the primary means to bring the engine temperature back to the optimal temperature.  They can be dirty, clogged, poorly designed, too small for the engine, fin dsnsity too great for the low rpm airflow...you get the picture. We know al little bit about radiators; visit The Brassworks FAQs page for more information.

4.       Airflow.  Inadequate airflow can cause overheating. You have to get the air through your radiator and out of the engine compartment.  Obstructions to that airflow can cause a cushion of hot air to build around your block and engine compartment. A properly fit fan shroud sealed to the radiator helps to channel the air through your radiator.

5.       Inadequate coolant flow. If your overheating at idle, stop and go traffic, on grades or towing you might benefit from higher flow rates through the radiator.  Hi Flow water pumps and hi flow thermostats allow more water to pass through the radiator where it has a chance to cool.

6.       Modified gear ratios: Generally  speaking lower ratios give slower acceleration, higher top speed and less braking power – Higher ratios give more acceleration, less top speed and more braking power.  Changing gear ratios may generate more heat in the engine and potentially cause overheating.

7.    Coolant composition. A 50/50 mixture does not help cooling it raises the boiling point. Run 100% distilled water with water pump lubricant or distilled water with about 15-20 % antifreeze. Both cool better than 50/50 and still lubricate the water pump to prevent corrosion in system. When the weather cools return to 50/50.

8.    Cooling the transmission is added work for a poorly constructed radiator.  Do not obstruct airflow or heat the air by placing the cooler in front of the radiator where it will overheat the cooling air. Transmission and engine oil coolers constructed within the radiator can also tax your cooling system.  Using external coolers may help.

9.  The elusive manifold vaccuum leak. Trouble at idle may point to a manifold vaccuum leak. If you find you're too fast an idle speed, rough idle or stalling, misfiring on acceleration or adjustments to your carburetor seem to have limited effect than you may have a vaccuum leak causing overheating.

10.  Use a better grade of gas. If you are not running premium fuel and experience overheating a higher grade may help. If there is no improvement, try advancing your timing a few degrees. A little extra octane will allow you a little extra timing without getting into detonation. Earlier engines were designed for better gas than is sold today.       

11.   Head gasket leaks from the cylinder to the water jacket are a definite cause of overheating. That's bad news and a whole lot of work.

12.   A stuck thermostat. Many thermostats are designed to fail in the open position but thermostats have also been known to stick partially open and impeed coolant flow.

13.   A slipping water pump belts can slow flow rates from the water pump and impeed coolant flow resulting in overheating.

14.   A fan blade with insufficient blade count or incorrect pitch may not draw enough air resulting in overheating.

15.   Headers without thermal coating can cause overheating.

16.    A stretched timing chain or belt can cause overheating.