Possible Causes:
* Water Pump: A failing water pump is a common culprit. The pump is located at the front of the engine and its seal can wear out, leaking coolant.
* Intake Manifold Gasket: Leaks here can be tricky to spot as coolant might run down the back of the engine.
* Cylinder Head Gasket: This is a more serious issue. A blown head gasket can allow coolant to mix with oil and cause significant engine damage. This often presents with other symptoms like white smoke from the exhaust, overheating, or milky oil.
* Thermostat Housing: A crack or leak in the thermostat housing can cause coolant to leak.
* Heater Core Hoses: While these are usually found inside the cabin, a leak in a section near the firewall could drip down and appear to be behind the engine.
* Engine Block Crack: Less common, but a crack in the engine block itself is a major problem requiring extensive repairs.
What to Do:
1. Safety First: Do not attempt major repairs yourself unless you have significant mechanical experience. Working on a hot engine is dangerous. Let the engine cool completely before attempting any inspection.
2. Visual Inspection: Once cool, carefully inspect the engine bay. Look for wet spots, stains, or trails of coolant. Try to trace the leak back to its source. A flashlight and a mirror can be helpful for accessing hard-to-see areas.
3. Professional Diagnosis: The best course of action is to take your Silverado to a qualified mechanic. They have the tools and expertise to properly diagnose the leak and recommend the necessary repairs. Describing the location of the leak (behind the engine) will help them focus their inspection.
4. Don't Drive It: Continuing to drive with a coolant leak can lead to overheating, engine damage, and even a breakdown. Limit driving to the bare minimum necessary to get it to a mechanic.
Costs: Repair costs will vary greatly depending on the cause of the leak. A simple hose replacement might be relatively inexpensive, while a head gasket repair or engine block crack could be very costly.
In short, a coolant leak behind the engine is not something to ignore. Get it checked out by a professional as soon as possible to prevent further damage and potential costly repairs.
