My Car Smokes From the Exhaust Pipe. What Does This Mean?

Tuesday, November 22nd, 2005 at 9:28 am  
Leave your comment

Reader Question:
My car frequently smokes from the tailpipe; does this mean I need an
engine overhaul?
Thank you, Don.

Dear Don,

Good question Don. Smoke coming from the
tailpipe is not good news, but does not necessarily mean the engine
needs rebuilding. First, you need to determine what color of smoke is
coming from the tailpipe. The three most common colors of smoke that can
be emitted from the engine and billow from the tailpipe are as follows:

White smoke: White smoke
is caused by water and or antifreeze entering the cylinder, and the
engine trying to burn it with the fuel. The white smoke is steam. There
are special gaskets (head gaskets are the primary gaskets) that keep the
antifreeze from entering the cylinder area. The cylinder is where the
fuel and air mixture are being compressed and burned. Any amount of
antifreeze that enters this area will produce a white steam that will be
present at the tailpipe area.

If white smoke is present, check to see
if the proper amount of antifreeze is inside the radiator and the
overflow bottle. Also check to see if antifreeze has contaminated the
engine oil. You can look at the engine oil dipstick, or look at the
under side of the engine oil filler cap. If the oil is contaminated with
antifreeze, it will have the appearance of a chocolate milkshake. Do not
start the engine if the oil is contaminated with antifreeze, as serious
internal engine damage can result.

How did antifreeze get in the oil or
cylinder in the first place? The engine probably overheated and a head
gasket failed due to excessive heat, thus allowing antifreeze to enter
the cylinder (Where it is not meant to be).

Blue Smoke: Blue smoke
is caused by engine oil entering the cylinder area and being burned
along with the fuel air mixture. As with the white smoke, just a small
drop of oil leaking into the cylinder can produce blue smoke out the
tailpipe. Blue smoke is more likely in older or higher mileage vehicles
than newer cars with fewer miles.

How did the engine oil get inside the
cylinder in the first place? The car has many seals, gaskets, and
O-rings that are designed to keep the engine oil from entering the
cylinder, and one of them has failed. If too much oil leaks into the
cylinder and fouls the spark plug, it will cause a misfire (engine miss)
in that cylinder, and the spark plug will have to be replaced or cleaned
of the oil. Using thicker weight engine oil or an oil additive designed
to reduce oil leaks might help reduce the amount of oil leaking into the
cylinder.

Black Smoke: Black smoke
is caused by excess fuel that has entered the cylinder area and cannot
be burned completely. Another term for excess fuel is "running
rich." Poor fuel mileage is also a common complaint when black
smoke comes out of the tailpipe. Black smoke out the tailpipe is the
least cause for alarm. Excess fuel will usually effect engine
performance, reduce fuel economy, and produce a fuel odor.

How did the fuel get into the cylinder in
the first place? Some of the causes of excess fuel are a carburetor that
is out of adjustment, a faulty fuel pump, a leaky fuel injector, or a
faulty engine computer or computer sensor. If black smoke is present,
check the engine oil as in the white smoke example to make sure excess
fuel has not contaminated it. Do not start the engine if a heavy, raw
fuel smell can be detected in the engine oil. Call your mechanic and
advise him of what you have found.

I hope this helps you determine what
could be causing your engine smoke, and the possible reasons behind the
smoke.

What Should My Tire Pressure Be?

Tuesday, November 22nd, 2005 at 9:21 am  
Leave your comment

Checking Tire Inflation Pressure

When vehicle manufacturers select a tire size for a vehicle, they evaluate the vehicle’s gross axle weights, the anticipated use of the tire, and the tire diameter and width. Adjustments to these factors give the manufacturer a way to improve handling and appearance. This is especially true for performance tire sizes. The size selected is rarely limited to only one capability (i.e. carrying the vehicle’s weight).

The tire usually needs to have additional load capacity as well. This extra capacity is important because without it all of the tire’s performance would be used up just carrying the weight of the vehicle and little would be left for durability at high speeds or responsive handling. For all vehicles produced since 1968, the original tires sizes and inflation pressures (including the spare) are listed on a vehicle placard. This placard can be located on:


  • The driver-side door or door jamb (Ford vehicles on the rear passenger door jamb)


  • Glove box or counsel door


  • Fuel filler door


  • The engine compartment

Additionally, some manufacturers also list the original tire pressure in the vehicle’s owner’s manual. If a car’s inflation pressure has varied from that which was recommended by the manufacturer, it’s likely that the tire’s wear and performance characteristics have also changed.

Under-inflation

If your vehicle’s tires are under inflated by only 6 psi it could lead to tire failure. Additionally, the tire’s tread life could be reduced by as much as 25%. Lower inflation pressure will allow the tire to deflect (bend) more as it rolls. This will build up internal heat, increase rolling resistance and cause a reduction in fuel economy of up to 5%. You would find a significant loss of steering precision and cornering stability. While 6 psi doesn’t seem excessively low, remember, it usually represents about 20% of the tire’s recommended pressure.

Over-inflation

If your tires are over inflated by 6 psi, they could be damaged more easily when running over pot holes or debris in the road. Higher inflated tires cannot isolate road irregularities well causing them to ride harsher. However, higher inflation pressures usually provide an improvement in steering response and cornering stability up to a point. This is why participants who use street tires in autocrosses, track events and road races, run higher than normal inflation pressures.

Effects of Time and Temperature

Tire inflation pressures change due to time and temperature. Tires lose about 1 psi per month due to air escaping through the rubber as it stretches. If you were to check your tires only every six months, it would not be uncommon to find them under inflated by as much as 6
psi. Tire inflation pressures also fluctuate with changes in the outside air temperature. This occurs at a rate of about 1 psi for every 10°F (plus or minus). So the tires you set correctly with an 80°F ambient temperature will be under inflated by 6 psi at 20°F.

If you add the variations of time and temperature together, it is easy to understand why a tire’s inflation pressure should be checked frequently. Improper inflation can cause tires to wear irregularly and can void manufacturer’s warranty.

Another advantage of checking tire pressure frequently is that it allows a slow leak to be found and repaired before it permanently damages a tire. Tire pressures should be checked once a week, preferably before the vehicle has been driven. Spending about two minutes a week will help you get the optimum performance your tires can offer!