Cooling system problems usually fall into two categories for collision repair shops – those that are incredibly easy to diagnose and those that are extremely difficult. Vehicles with front-end damage with radiators leaking coolant are in the first category. Vehicles with which, at first inspection, the system appears in fine shape with no damage, corrosion or other problems, yet the engine runs hot or overheats are in the second.
In either case, one needs a diagnosis as soon as possible to add to the estimate. Complicating matters, one needs to determine if the collision caused the problem. If a shop is operating lean and blueprinting its work, creating a system to solve cooling problems is even more essential. Consider the following steps to create an effective checklist:
Step 1: Examine the obvious. Check the coolant level. In some vehicle models, significant overheating can result from coolant levels that are only slightly below vehicle recommendations. Also, check the cooling mix, and examine the coolant for oil because this can indicate a leak from the engine or transmission, which signifies engine or transmission damage.
If a vehicle is overheating and not losing coolant, there are two other prime culprits at which to look. The vehicle could be using the wrong grade of engine oil or might have a broken temperature gauge. To address these, check the vehicle service history. For the latter, talking to the customer can quickly resolve a potentially time-wasting, expensive mystery.
Step 2: Examine the radiator to locate punctures, tears and corrosion. Start the search by washing and rinsing the front of the radiator carefully using a soft, nylon brush and warm soapy water. Doing this might solve the problem because leaves, bugs, dirt, debris and small rocks can lodge in radiator vents, preventing the radiator from working properly.
Step 3: Examine the radiator cap for problems such as corrosion, swelling or damage. Defective caps are the source of cooling problems frequently, so much so that some shops replace them as a normal part of cooling-system maintenance.
Step 4: Spend extra time examining hoses. Check the lower, manifold and bypass hoses. Look for leaks, cracks, collapses, dry areas or areas with oil, which can make a hose swell or sticky and soft. Oil damage also can come from within the hose. If the hose becomes swollen, odds are there is excessive oil in the hose. When this happens, check the transmission system for leaks into the radiator coming from the transmission cooler. Check each clamp connection for leakage. Tighten loose clamps and replace any defective ones.
Because of cramped conditions in modern engine compartments (particularly those in compact and subcompact vehicle models), hoses are exposed to more heat and other potentially damaging conditions than previously. Even a little compression in the compartment from a collision can put a kink in a hose or push a hose against a hot or sharp engine part that can damage it – sometimes in mere seconds. While a slight kink might not seem important, kinks can cause serious cooling problems because they reduce coolant flow.
If a damaged hose is the problem, route the replacement hose(s) away from any potential points of contact and provide some extra protection for the hose by wrapping a protective sleeve around the new hose at the point of contact.
Step 5: Make sure the thermostat isn't sticking. Constant low temperature readings or peaks between high and normal temperatures are signs the thermostat needs replaced. Another obvious indicator is if the vehicle runs hot while the radiator remains cool.
Step 6: Examine the belts and fan. Even a light hit can knock cooling system hardware loose. One critical area is the fan belt and its tension. Readjust the tension if necessary, and verify the fan works. A fan that remains running after the engine is shut off drains the battery. The likely causes of this are a bad thermofan switch or faulty fan relay.
Step 7: Perform a pressure test. A pressure test can uncover any remaining potential problems with the radiator cap and reveal leaks or blockages. Look for coolant seeping into the passenger compartment because this is a sign the heater core is damaged. You may notice a strong coolant smell but not see seepage.
Step 8: Rule out any problems with the radiator, radiator cap, hoses, thermostat, belts and fan. The sources of overheating and/or coolant loss problems are, at this point, engine related – a bad water pump or a faulty head gasket. Pinching the top radiator hose closed with your hand while the engine idles will determine if the water pump is bad. Then release it. If the pump is working properly, you should feel a surge of coolant. Don't perform this test on a vehicle if the engine is hot.
Also, you can test the water pump by draining and refilling the radiator. With the radiator cap removed, start the vehicle and watch the coolant level. If the level quickly drops, then the pump is doing its job. If it is possible to perform a visual inspection of the pump (for vehicles with the water pump not run by the timing belt), check the pump hardware for damage, particularly the belt. You should be able to roll the belt drive smoothly with your hands.
If the water pump is fine, the vehicle probably has considerable internal engine damage. Check for this damage the same way you'd look for evidence of a blown head gasket – check for coolant in the oil reservoir or white smoke coming from the vehicle exhaust. You also can perform a compression test.
Cooling problems related to collision damage run the gamut from ordinary to catastrophic. Pinpointing relatively simple causes can be difficult but is much easier when a methodology is in place.
