Heating/Cooling System Related:
* Leaking Heater Core: This is the most likely culprit. A compromised heater core allows coolant to leak into the passenger compartment. The coolant, when heated, will radiate heat directly onto the floor. You might notice a sweet smell (antifreeze) or even dampness on the floor.
* Blocked Heater Core: While less likely to cause *excessive* heat, a partially blocked heater core could cause overheating in the core itself and transfer that heat to the floor.
* Malfunctioning Blend Door Actuator: This controls the amount of hot/cold air that mixes before reaching the vents. A faulty actuator could constantly direct hot air to the passenger-side floor.
* Faulty Heater Control Valve: This valve controls the flow of coolant to the heater core. If it's stuck open, coolant will constantly flow through the heater core, generating excessive heat regardless of the temperature settings.
* Low Coolant Level: Low coolant can cause the system to overheat, leading to increased heat transfer to the passenger compartment. Check your coolant reservoir.
* Incorrectly installed or malfunctioning heater hoses: A hose improperly routed or compromised could cause localized overheating.
Exhaust System Related:
* Exhaust Leak near Passenger Side: A leak in the exhaust system close to the floorboard, particularly under the passenger seat area, can transfer significant heat directly into the cabin. This would be noticeable as a loud, rumbling sound, in addition to the heat.
* Heat Shield Failure: Heat shields are designed to protect the vehicle's interior from exhaust heat. A failed or missing heat shield, especially near the exhaust pipe, would allow direct heat transfer to the floor.
Other Less Likely Possibilities:
* Wiring Issues: While less probable, a short circuit in the wiring harness could generate localized heat, though this is more likely to manifest as a burning smell.
Troubleshooting Steps:
1. Check for coolant leaks: Look carefully under the dash and around the heater core area for any signs of coolant leaks (dampness, staining, sweet smell).
2. Feel the heater hoses: When the engine is warmed up, feel the heater hoses going to and from the heater core. If one is significantly hotter than the other, it may indicate a problem with flow or a blockage.
3. Inspect the exhaust system: Look for any signs of rust, damage, or holes in the exhaust pipes near the passenger side of the vehicle. Check the heat shields for damage or missing sections.
4. Inspect the floor: If there are no apparent leaks or exhaust problems, try checking the condition of the flooring itself. It is possible the insulation has compromised and is failing to sufficiently insulate.
5. Check coolant level: Make sure your coolant levels are within the proper range.
If you cannot identify the cause, it's best to have a qualified mechanic inspect your vehicle. Diagnosing heat problems can be tricky and requires specialized knowledge and tools. Remember safety first – work on a cool engine and wear appropriate safety gear.
