In order for the miracle of the automotive cooling system to march on unabated all the components must be able to hold up under pressure. The heavy hitter in this equation is the radiator. Inside the radiator are coolant passages. Connected to the passages are the cooling fins. As hot engine coolant passes through the radiator heat gets wicked away through these fins and into the air. Neglecting the cooling system can cause corrosion and even rust to build up inside the radiator until one day it literally cracks under pressure and makes like an underhood Old Faithful. Pressure and tempers are lost along with engine cooling.

Coolant Crusted

A regular check of coolant level will indicate if the system is holding its own. Check the coolant only when the engine is cold, and on a level surface by removing the radiator cap and peering inside the filler neck. Never open a cooling system when the engine is hot. If the coolant level in the radiator or coolant reservoir is below normal, or if there are the tell tale signs of coolant leakage on the garage floor first inspect the radiator and heater hoses and water pump for leaks. Take a good look at the hose clamps and make sure they're snug. A leaking system cannot maintain the pressure required for coolant circulation. The engine will run hot as hot as a boiling kettle and eat itself up.

Core Issues

If a look inside the radiator reveals coolant the color of iron oxide then it might be time for radiator replacement or repair. The radiator is comprised of a core and surrounding tanks. The core contains the coolant channels and fins that transfer heat away from the coolant and into the air. The tank surrounds the core and holds everything together. Older cores are made of copper and brass. More modern cores are made from aluminum. Tanks can be made of brass, copper, aluminum, or plastic depending on if the car was made recently or long ago. Inspect the finned surfaces and seams where the fins join up with the surrounding tank for leaks. Obvious leaks mimic a bright green Vesuvius. Other leaks are harder to locate and may require pressure testing of the cooling system along with removal and testing of the radiator itself.

Repair or Replace?

We get asked this question all the time and we're going to answer it by saying yes, radiators can be repaired. This is good news to motorists who like us have cars manufactured on the Island of Misfit Toys, for which there is no replacement radiator available. If the radiator is in good shape overall both core and tank leaks can be repaired. If the core is rotten but the end tanks appear OK a local radiator shop can install a new core in no time. For composite plastic and aluminum radiators the best bet may be replacement, but even these can be repaired. Each type of setup presents its own repair challenges. The one way to keep the radiator and entire cooling system in good shape is to change and flush the coolant according to manufacturers recommendations. Neglected coolant becomes corrosive and can cause a myriad of problems.

Temporary Fix

While cracking eggs and pouring ground black pepper into the radiator filling neck, or applying JB Weld may or may not temporarily stop a radiator leak, the problem will be sure to return. A good radiator repair shop will be able to tell whether radiator repair is an option, or if a replacement radiator is the answer. It may be more cost effective to actually replace the radiator in some cases. Another option to consider is getting a heavy-duty or three-row core installed in place of a rotten two-row core for improved cooling. Removing and replacing a radiator is well within the scope of the DIY mechanic. Repairing or recoring a radiator is a job best left to the radiator shop. Use those eggs for an delicious omelet instead. Black pepper to taste.

Stuff You'll Need:

· Your Friendly Neighborhood Radiator Shop
· Hand Tools to Remove the Radiator
· Catch Container to Drain the Coolant
· Some Cash to Pay the Radiator Shop
· Distilled Water and Engine Coolant

Obvious symptoms of a leaking radiator are coolant spraying forth or steam. Subtle signs of a leaking radiator are discoloration and crusty dried coolant deposits. Upon removal this radiator revealed the source of a slow leak. Off to the radiator shop.

Expansion plugs are installed into the inlet and outlets of the radiator. These plugs seal things up so a pressure cap on the filler neck can pressurize the radiator with air.

Into the soup. The radiator is submerged and then pressurized. Any leaks will reveal themselves by a stream of air bubbles escaping from the radiator.

Once out of the soup some flux is applied to the leak area in preparation for the repair.

With some flame, solder, and more flux the radiator will soon be good as new.

The radiator goes back into the tank and is pressurized once again to test the repair. Success! Take it home and put it back into the car.


Replace a Radiator or Heater Hose; Replace a Thermostat; Replace a Water Pump; And You Will Know Us by the Trail of Parts [Internal]