My brake pedal is low when I step on it, but it comes up when I pump the brakes. Do I need new brakes?

A low brake pedal that has to be pumped repeatedly to bring a vehicle to a stop may be due to a low fluid level, drum brakes that need adjustment or air in the lines. It usually has nothing to do with the condition of the brakes and certainly isn't grounds for a brake job.

If the pedal feels "soft" or "spongy" instead of firm, there's probably air in the system. This will require "bleeding the brakes" to remove air from the lines, calipers and wheel cylinders.

The first thing that should be checked is the fluid level in the master cylinder reservoir. If the level is low, there's a leak somewhere in the hydraulic system that must be found and repaired. Adding fluid will only cure the symptom, not the cause, and sooner or later the level will be low again creating a dangerous situation. So check for leaks around the master cylinder, wheel cylinders, brake calipers, rubber brake hoses and steel brake lines.

If the fluid level is okay, the adjustment of the rear brakes should be checked next (assuming the vehicle has drum brakes in the rear -- if it has drums all the way around, check the front drums first, then the rear). The shoes should be close enough to the drums to produce just a hint of drag when the wheels are rotated by hand. An excess of slack probably means the self-adjusters are either frozen or fully extended.

If adjusting the drum brakes fails to eliminate the low pedal, the wheel and drum will have to be removed so the adjusters can be freed up or replaced, and/or so the worn brake shoes can be replaced.

If the vehicle has rear disc brakes, the adjusting mechanism in the rear caliper pistons that maintain the correct pad-to-rotor clearance may be corroded, frozen or worn out. In most cases, the piston assemblies cannot be rebuilt and must be replaced.

If the fluid reservoir is full and the brakes are properly adjusted, but the pedal is low (or feels spongy), there is probably air in the brake lines. Air is compressible, so every time you step on the pedal, the bubbles collapse instead of transferring pressure to the brakes. The cure here is to bleed the brake lines following the factory recommended sequence.

Brakes are usually bled in a specified sequence (always refer to a shop manual for the exact procedure for your vehicle). Usually the rear brakes are bled first, then the ones up front on most rear-wheel drive cars and trucks. But on front-wheel drive cars and minivans, the hydraulic system is split diagonally so the brakes are bled in opposite pairs (right rear and left front, then left rear and right front). Following the proper sequence is important so air doesn't remain trapped in the lines.

On late model GM and Ford cars with quick take-up master cylinders, the quick take-up valve takes about 15 seconds to reseat after the brake pedal has been depressed. If the pedal is pumped too quickly while manually bleeding the system, you may never get the pedal to firm up. Most professionals use pressure bleeding equipment to bleed the brakes because it is faster and easier.

I've heard that using a temporary spare will disable my ABS system. Is that true?

Yes. On many cars equipped with ABS and a temporary spare, an electrical connector inside the trunk or luggage compartment is attached to the valve stem on the spare tire. If you have a flat tire and remove the spare, you have to unplug the connector. This tells the ABS system that the temporary spare is being used, causing it to temporarily disable itself.

The reason why the ABS system shuts itself off when the temporary spare is in use is because the spare tire has a smaller diameter and narrower tread than a standard tire. This causes the tire to rotate somewhat faster than the other tires, and to brake differently. Were the ABS system not disabled, the difference in wheel speed and braking friction caused by the temporary spare would probably cause the ABS system to kick in unnecessarily when the brakes are applied. So disabling the ABS system prevents this from happening.

The important thing to remember here is to reconnect the ABS connector to the spare tire when it is returned to the trunk. If this is not done, the ABS system will remain disabled and unable to prevent skidding when braking on wet or slick surfaces.

When I replace the tires on my vehicle, do I have to use the same size as the originals?

On ABS-equipped vehicles, all vehicle manufacturers recommend using the same size and aspect ratio tire as the original. ABS systems monitor the rotational speed of the tires through individual wheel speed sensors. Changing to an oversize tire with a taller diameter than stock would cause the tires to rotate at a slightly slower speed relative to vehicle speed than the stock tires. Changing to a low profile tire with a shorter diameter would cause the tires to rotate at a slightly faster speed relative to vehicle speed. Though the difference either way isn't much, it may be enough to upset the calibration of the ABS system and have an adverse effect on its ability to detect and prevent skids.

Another reason for not changing tire sizes is because it can affect the speedometer, odometer and transmission shift points on a vehicle with an electronic automatic. Oversize tires will make your speedometer read slower than normal (which may get you a speeding ticket unless you have the speedometer recalibrated to compensate for the change in tire size!). Smaller diameter tires will make the speedometer read faster than normal, and increase the mileage readings on your odometer at a faster than normal rate.

All this doesn't mean you can't change tire and wheel sizes, however. If you maintain the same overall tire diameter as before, you can switch to larger wheels with a shorter aspect ratio tire. This is the basic idea behind "Plus 1, Plus 2" tire and wheel sizing.

Replacing a stock 14-inch wheel and 70 series tire with a 15-inch 60 series tire would be Plus 1. Plus 2 would be moving up to a 16-inch wheel and possibly a 50 series tire. Plus 3 would be going to the new 17-inch tire and rim combination -- which could turn out to be a Plus 4 application if the vehicle originally had 13-inch wheels.

Aspect Ratio

The "aspect ratio" of a tire is the ratio of its section height to its section width. The smaller the number, the shorter the sidewall and the wider the tire. Low aspect ratio tires started with 60 series some time ago, then progressed to 50 series and now 45, 40 and even 35 series tires.

Shorter aspect ratio tires (60 and less) are usually considered to be performance tires because they lower vehicle ride height, have a wider tread and put more rubber on the road to improve handling. But the shorter the sidewall, the harsher the tire rides.

A tire's ability to support a given load depends on its air volume. If you go to a lower aspect ratio tire with a shorter sidewall, the tire must be wider to maintain the same air volume. If you just go to a shorter aspect ratio tire without increasing width, the load carrying capacity goes down. That's why when you go from a standard wheel to a Plus 1 wheel, the rim is usually wider to accommodate a wider tire.

It's important to follow the tire manufacturer's recommendations as to load capacities when going to larger wheel and tire sizes. There's no hard rule that says you have to drop 10 points in aspect ratio when increasing wheel size one inch, but that's the general recommendation.

How do I know when my car really needs a brake job?

You need a "brake job" when your brake linings are worn down to the minimum acceptable thickness specified by the vehicle manufacturer or the applicable state agency in areas that set their own requirements. The only way to determine if new linings are required, therefore, is to inspect the brakes.

You may also need a brake job if you're having brake problems such as grabbing, pulling, low or soft pedal, pedal vibration, noise, etc., or if some component in your brake system has failed. But if the problem is isolated to only one component, there's no need to replace other parts that are still in perfectly good working order.

There is no specific mileage interval at which the brakes need to be relined because brake wear varies depending on how the vehicle is driven, the braking habits of the driver, the weight of the vehicle, the design of the brake system and a dozen other variables. A set of brake linings that last 70,000 miles or more on a car driven mostly on the highway may last only 30,000 or 40,000 miles on the same vehicle that is driven mostly in stop-and-go city traffic.

As a rule, the front brakes wear out before the ones on the rear because the front brakes handle a higher percentage of the braking load -- especially in front-wheel drive cars and minivans. So many service facilities advertise $59.95 brake job "specials" that replace the linings on the front brakes only. Doing the front brakes only is okay and can save you money as long as the rear brakes are in good condition. But if the rear brakes need attention, they should be relined too.

One of the problems with the brake specials you see advertised in the newspaper is that the price is very misleading. A person typically goes in expecting to spend $59.95 for a brake job, but usually ends up spending considerably more because the brakes need more than the minimum amount of work to restore them to like-new condition. The price of a brake job depends entirely on the work that needs to be performed. So any advertised special is not a firm price, but only an estimate of the least amount of money it might cost you to get your brakes fixed. A price should not be quoted until after the brakes have been inspected. Then and only then can an accurate determination be made of the parts that actually need to be replaced.

How do I know when my car really needs a brake job?

You need a "brake job" when your brake linings are worn down to the minimum acceptable thickness specified by the vehicle manufacturer or the applicable state agency in areas that set their own requirements. The only way to determine if new linings are required, therefore, is to inspect the brakes.

You may also need a brake job if you're having brake problems such as grabbing, pulling, low or soft pedal, pedal vibration, noise, etc., or if some component in your brake system has failed. But if the problem is isolated to only one component, there's no need to replace other parts that are still in perfectly good working order.

There is no specific mileage interval at which the brakes need to be relined because brake wear varies depending on how the vehicle is driven, the braking habits of the driver, the weight of the vehicle, the design of the brake system and a dozen other variables. A set of brake linings that last 70,000 miles or more on a car driven mostly on the highway may last only 30,000 or 40,000 miles on the same vehicle that is driven mostly in stop-and-go city traffic.

As a rule, the front brakes wear out before the ones on the rear because the front brakes handle a higher percentage of the braking load -- especially in front-wheel drive cars and minivans. So many service facilities advertise $59.95 brake job "specials" that replace the linings on the front brakes only. Doing the front brakes only is okay and can save you money as long as the rear brakes are in good condition. But if the rear brakes need attention, they should be relined too.

One of the problems with the brake specials you see advertised in the newspaper is that the price is very misleading. A person typically goes in expecting to spend $59.95 for a brake job, but usually ends up spending considerably more because the brakes need more than the minimum amount of work to restore them to like-new condition. The price of a brake job depends entirely on the work that needs to be performed. So any advertised special is not a firm price, but only an estimate of the least amount of money it might cost you to get your brakes fixed. A price should not be quoted until after the brakes have been inspected. Then and only then can an accurate determination be made of the parts that actually need to be replaced.

Is it better to maintain my engine's oil level at the full mark or wait until it reaches the "add" mark to add oil?

Most vehicle manufacturers say it's okay to wait until the level reaches the add mark to add oil. The add mark But considering that the crankcase capacity on most passenger cars today is only four quarts, running the engine 25% low on oil (one quart) may not be wise. Here's why.

Oil not only lubricates the engine's internal parts, but also helps cool the bearings. The total amount of oil in the engine, therefore, serves as a heat sink to help control heat. Under normal driving conditions, running a quart low probably doesn't make much difference in terms of bearing temperature or overall engine lubrication. But during extremely hot weather, when driving at sustained highway speeds and/or when towing a trailer, running a quart low may increase the risk of accelerated engine wear and/or damage.

The best advice, therefore, is to add oil whenever the dipstick reads low. Don't wait until it is down a full quart. If it needs half a quart, add half a quart to bring it back up to the full mark.

CAUTION: Do not overfill the engine. Adding too much oil can overfill the crankcase. As the crankshaft spins around, it can whip the oil into foam if the level is too high. This, in turn, can cause a drop in oil pressure and loss of lubrication to critical engine parts. Also, too much oil may cause leaks as the extra oil is forced past seals and gaskets.

Follow your vehicle manufacturer's guidelines for the type and viscosity of oil to use in your engine.

My engine is leaking oil past the valve cover gaskets. I've tried tightening down the valve cover bolts, but it doesn't seem to help. What should I do

Bite the bullet and buy a new set of valve cover gaskets. Most cork valve cover gaskets usually cost less than $20 and are fairly easy to install on many engines. You may have to disconnect and remove some plumbing or other accessories to get to the valve covers, but on many engines the job is usually within the capabilities of a do-it-yourselfer. If the valve covers are buried or access is difficult, then let a professional replace the gaskets for you.

Tightening the valve cover bolts or screws will rarely stop an oil leak because the gasket is usually cracked, crushed or has lost its natural elasticity. Cork gaskets only last about four to six years before they age harden, become brittle and start to leak. Molded silicone rubber gaskets, on the other hand, (which are used on many late model domestic and import engines) often last the life of the engine. But molded rubber gaskets are a lot more expensive than die cut cork gaskets. That's why cork gaskets have long been used by the vehicle manufacturers.

Some engines do not have gaskets, but instead use a rubbery-glue called "RTV silicone sealer (the "RTV" stands for Room Temperature Vulcanizing). If this is the case, you can remove the valve cover, scrape off all the old RTV, and either apply a fresh bead of RTV silicone sealer to the valve cover flange or head mating surface or install a conventional gasket.

CAUTION: Do not let any pieces of rubber or debris fall into the engine. Also, if you decide to use RTV sealer and your engine has an oxygen sensor (which almost all 1981 and later engines do), make sure the RTV sealer is the "low volatile" variety that is approved for use with oxygen sensors. Some types of RTV give off silicone vapor that can be sucked through the crankcase and contaminate the oxygen sensor.