As summer approaches and temperatures soar to record highs, we would like to focus on your Corvette’s cooling system. Although it may seem more important to check the A/C system to keep you cool, you also need to make sure the cooling system is working properly for optimum A/C performance. As engine temperatures increase, A/C performance is affected adversely.
There are a few things that every Corvette owner should check annually to determine if further maintenance is necessary. 53-82 Corvettes have a basic cooling system in which radiator cooled air flows through the grille opening. Obvious large road debris should be removed from the front of the radiator. A garden hose can be directed through the radiator from the fan side of the radiator to flush out debris and dirt that has accumulated.
84 to present Corvettes are more susceptible to road debris because of their bottom feeding radiator opening. 84-89 Corvettes make debris removal difficult and should be checked every other oil change to prevent major accumulations. There is no good way to remove debris without removing the top of the radiator housing once a major accumulation of debris has occurred.
90-96 Corvettes have a window to look between the radiator and A/C condenser on the passenger side of the radiator housing where the A/C aluminum lines connect to the condenser. A garden hose can be directed to the front of the radiator through the window to remove debris . If this is neglected and major debris accumulates, removal of the upper radiator housing will be required for proper cleaning.
Whether you have an early or late C4, the major concern is debris buildup between the A/C condenser and radiator. The debris accumulates over time and elevates temperatures slowly until the engine finally overheats. At first the elevated temps will be most noticeable at idle. If you see leaves and grass coming out the bottom of the radiator housing, most likely you have a major accumulation of debris and radiator housing top cover removal is necessary.
97 to present Corvettes are less prone to debris between the A/C condenser and radiator but like their C4 predecessors, debris builds up at the top of the condenser.
Now we move on to the fan clutch, which all Corvettes before 84 use. Fan clutches were made two ways: centrifugal and thermostatic. GM used thermostatic fan clutches on all applications for optimum idle cooling. The idea is that when the hot air passes through the radiator, a thermostatic spring located at the front of the clutch heats up and directs the viscous fluid to engage the fan. Centrifugal fan clutches engage at low speeds and as RPM increases, disengagement occurs regardless of engine temp. Centrifugal clutches are an inexpensive alternative to thermostatic fan clutches and have no spring at the front of the clutch to detect heat which can adversely affect cooling, especially at idle.
So how do you know when the clutch is worn and requires replacement? Three simple tests will tell you the condition of the clutch. The first test starts with a cold engine: try to wiggle the fan. It should be stable and any looseness indicates worn bearings and imminent failure. Then while the engine is cold, try rotating the fan. It should spin freely when the ambient temp is above 85 degrees. If it feels stiff and hard to rotate, the clutch is seizing up. The final test: warm up the engine to operating temp, shut the engine off and watch the fan. It should stop within 3-4 seconds maximum. If the fan keeps spinning, the clutch is not engaging and will cause elevated idle temps. If needed, we have all the correct thermostatic fan clutches available for your early or late Corvette.
What condition is the coolant itself in? Has it been two years or more since the coolant has been changed? The idea that less use requires less maintenance is not the case when coolant is concerned. 53-73 Corvette cooling systems have no coolant recovery tank, allowing air to enter the system on a regular basis. When the Corvette isn’t driven a lot, the constant air eventually leads to rust forming where the coolant isn’t touching the components, causing sediment to drop to the bottom of the radiator and engine block. On the other hand, Corvettes with recovery systems usually get driven and the temps are higher than early Corvettes, depleting the coolant of the very important corrosion inhibiting chemicals.
74-96 Corvettes with coolant recovery systems can also have corrosion and it can be severe. You can check the recovery systems operation by simply watching the flow in the recovery tank as the engine warms up. The coolant level in the recovery tank should increase as temp rises and then the level should drop as the engine cools. If the coolant level stays the same through the hot cold cycle, there is most likely a leak in the cooling system or the cap itself is bad.
You should always check the coolant level in the radiator or expansion tank at every oil change to assure that the cooling system is filled and not full of rust. Recovery system Corvettes should have coolant at the top of the filler neck when the cap is removed which indicates the recovery system is working properly. Non-recovery system Corvettes should have the coolant level two inches below the filler neck for expansion. Filling to the top of the filler neck will cause a puddle of coolant on the garage floor.
The final check concerns the cooling system hoses. They should be pliable with some resistance. Spongy hoses are trouble. Rigid hoses that make a cracking sound when squeezed are bad news. They usually have a coating of rust and the squeezing breaks the rust and sediment off the hose. The hoses and cooling system should be immediately serviced. Check the upper hose carefully for ballooning, especially near the radiator connection when the engine is up to operating temp. This is a warning that you may be walking soon. If the upper radiator hose is under pressure when the engine is up to operating temperature, that’s a good indication that the cooling system has no leaks or minimal leaks and is working properly. If the upper hose stays soft you most likely have a leak and corrosion is next.
Servicing the cooling system including coolant replacement should be done every two years to prevent major engine work. As your mileage approaches 75,000 you should consider complete cooling system hose replacement to prevent that long wait for the wrecker on the highway. We can supply you with the necessary cooling system components for minor or major service including high flow water pumps to help keep the engine temp in control at low speeds when you’ve added those extra ponies. Plus we have electric fan systems, aluminum radiators and electric fan control switches to turn fans on quicker to help keep you cool.
We also have a convenient digital mini thermometer that can keep tabs on the cooling system efficiency and verify your temp gauge accuracy. You simply point the mini thermometer at the location to check temp pull the trigger and the temp is displayed. You can check the radiator efficiency and check for hot spots indicating flow problems. A few simple checks can make your summer driving pleasurable and avoid costly repairs. In the shop, the cooling system is the most neglected area and problems can lead to major engine work. So here’s your chance to preserve your Corvette and keep you rolling on the highways with a smile.
This article was written by Chris Petris for Corvette Central.