A balky cooling fan can land you in hot water

  • Article by: PAUL BRAND
  • February 19, 2011 - 3:44 PM

QMy brother has 1995 Corvette he is restoring in Florida. He recently rebuilt the engine and transmission. During his last test drive, it seemed that the car was overheating. He opened the hood and did not see the fans working. He was able to drive it home without overheating, but the temperature gauge was much higher than normal. We have cleaned the fuses to make sure that they are making good contact, and replaced the temperature sensor in the water pump. It looks like the fans are controlled by the ECM. Is there anything else that might be causing the problem?

ANice midwinter change-of-pace question. First, bleed the cooling system to make sure there's no air trapped in the engine. Then with the engine fully warmed up and running, turn on the air conditioning. The primary cooling fan -- on the driver's side -- should come on regardless of operating temperature. Both fans should run when coolant temperatures climb above about 220 degrees.

Is engine coolant actually above 220 degrees? Use an infrared temperature "gun" to check coolant temperature as it leaves the engine.

You are correct that the ECM (engine control module) controls the cooling fans. But before you dig too deeply into the ECM, check all the fuses, relays and grounds in the cooling-fan circuits. These include cooling fan relays No. 1, No. 2 and No. 3, the 30-amp primary fan fuse and 40-amp secondary fan fuse -- all located in the underhood electrical center. There's also a 5-amp fan fuse in the instrument-panel fuse block.

And carefully check, and if needed disassemble and clean, the main ground connection (G117) on the left front frame rail. A poor ground here can interfere with fan operation.

QThe air-bag light in my 2001 Mercury Villager recently came on for no reason and will not stop flashing. The local repair shop said its computer would not communicate with the computer in the vehicle. The flashing continues. Do you have any recommendations?

ATake the vehicle to your dealer. The flashing air-bag light indicates a fault that may prevent the air bags from deploying properly in a serious crash.

When you turn the ignition key to the "on" position, the air-bag warning light should illuminate for seven seconds as the system goes through its self-test. If the light stays on solid for seven seconds, then starts flashing continuously, there is a fault in the air-bag system. If, when you turn the key to "on," the warning light starts flashing immediately and continuously, the fault is in the air-bag diagnostic monitor module.

QI have a 2001 Subaru Outback wagon with 200,000 miles that runs great, but occasionally it gets a raw gas smell that permeates the passenger compartment. It seems to be more evident with colder temps. I did find one small fuel hose that had a leak and replaced it with an original-equipment hose, but my wife occasionally still encounters that smell, which can be overwhelming. Any ideas?

AFirst off, congratulations on reaching the 200,000-mile mark. You've obviously taken good care of a good car.

The most common causes for the odor of raw fuel are a faulty fuel filler cap, or more likely an issue with the charcoal canister or purge valve in the evaporative emissions system. The canister is under the engine compartment and can be drained if full of raw fuel. The canister is designed to store fuel vapor from the tank and vent them into the induction system when the canister control/purge valve, located on the intake manifold, is opened by the ECM.

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