Coolant leaks: When to fix it or just live with it

Q I have a 2002 Olds Alero with the V6 engine. Recently I noticed that coolant is leaking. I have been told it is a slow leak from the intake gasket. My mechanic recommended that I get the leak fixed to avoid having the coolant mix with the oil. Is there a way to tell whether the leak is external or internal? If it's external, do I really need to fix it?

The car has about 95,000 miles on it, but my mechanic says that with this fix, some new plugs, wires and regular maintenance, the car will go 200,000 miles easy. Do you agree? Should I spend the $800 to $1,000 for the intake fix, new plugs, and new wires?

A Coolant leaking internally from the intake manifold gasket or cylinder head gasket can end up in one of two places: mixed with the engine oil or burned with the air-fuel mixture in the exhaust. Coolant mixed with oil is bad news because ethylene glycol doesn't work well as a lubricant. It doesn't take long for contaminated oil to destroy an engine.

Coolant leaking into the combustion chambers. where it vaporizes and is carried out the exhaust. doesn't sound so bad, right? In very small doses, it isn't. But any significant coolant consumption can strip oil from cylinder walls and etch or corrode aluminum pistons.

Relatively simple, inexpensive tests can identify specific internal coolant leaks. A visual inspection of the oil, oil dipstick, oil filler cap and PCV valve may show a white, milky film of homogenized oil and coolant. An increase in oil level or the bittersweet smell of ethylene glycol on the dipstick are solid evidence of a significant internal leak.

The smell of coolant and/or a whitish cloud of smoke from the exhaust at startup can be an indicator of coolant in the combustion chambers, which can be confirmed by a chemical test for exhaust hydrocarbons in the coolant. Pressure-testing the cooling system and starting a cold engine with the radiator cap off to see if coolant is immediately pumped out can also confirm a leaking cylinder head gasket. Engine overheating or fluctuating coolant temperatures are also indicators of coolant loss.

External coolant leaks can be identified by residual coolant odor after shutting down the engine, coolant smoke or steam wafting from the engine compartment or drips, puddles and stains on the garage floor.

While I tend to agree with your mechanic, although 200,000 miles might be a push, I would suggest trying a quality stop-leak product like Mendtite or SilverSeal added to the cooling system. I've had remarkable luck stopping intake manifold gasket leaks with these products, but even if they don't work as a permanent fix, you can still have the lower intake manifold gasket replaced.

The bottom line: As long as the coolant leak is relatively small, doesn't contaminate the oil and doesn't allow the engine to overheat, try the stop-leak product first. If the leak is beyond these simple parameters, have the repair done professionally.

Q When I changed the transmission fluid on my 2005 Impala, a 4-inch "clip" with a V in the middle fell out. I don't know what it's for or where it goes. I think it was near the transmission filter. I'm going nuts with this one.

A It is the "thermo element," which is retained by two pins so the "V" is in contact with the thermo element plate. This component is designed to restrict oil flow to the pan until the oil is up to temperature. It needs to be reinstalled and properly adjusted.