The bad news: Your car has been keyed by some psychopath. The good? Our step-by-step DIY guide walks you through diagnosing and repairing the dreaded car scratch.
How to Replace an Oxygen Sensor
Twelve years and more than 100,000 miles have passed under your trusty commuter and the Check Engine light has never, ever, winked at you ... until yesterday, when it coincidentally anticipated your state inspection appointment at the end of the month. Rats! The car will never pass the emissions test with that light on. Now what?
How to Polish Your Headlights Like a Pro
After a few years, polycarbonate headlight lenses don’t have to be scratched to look scuffed and foggy. Neglected headlights get hazy and can develop fine cracks. Here’s how to make them look new again.
6 Ways to Stay Safe in Your Garage ?
A busted knuckle is a badge of honor, and real injuries are easily prevented. Here's the right way to wrench -- without getting hurt.
How to Rebuild a Brake Caliper ?
It's a beautiful spring day, and a perfect time to break the winter seal on the garage and drive around in your classic Corvette, vintage motorcycle or whatever pride and joy you happen to have stashed inside. Off with the cover, and the engine turns over willingly, thank goodness. A quick warmup and you're off for a loop around town.
How to Change a Serpentine Belt at Home ?
There's a squeal emanating from underneath your hood—and it doesn't sound good. The noise started a few months ago, on a gray and rainy morning, but it went away before you even pulled out of the driveway. Problem solved, right? Sorry pal. Unfortunately, the noise was back the very next morning, and this time it lasted all the way to the corner of your block. You lifted the hood and zoomed in on the offending racket—it was the serpentine belt. As the weeks dragged on, your morning commute got noisier and noisier every day. Then you began to hear it on the way home too. Now it's a constant reminder to replace the belt. Soon.
Expert Car Clinic : 7 Car Mysteries Solved !!!
Q:
I've had to replace the radiator in my truck twice and the heater core three times in the last five years because of corrosion. I use fresh antifreeze, but it doesn't seem to help. What's happening here? A:
If fresh coolant, changed every other year, isn't holding the corrosion at bay, look for one of two problems. First, the combustion gases could be leaking into the cooling system through a bad intake manifold gasket, head gasket or a cracked head or block. You can chase that by sniffing the radiator neck with the probe of an exhaust-gas analyzer. If you can detect any carbon monoxide in the radiator, it's a sure sign there's exhaust leaking in. Second, the corrosion problem could be electrical. Measure the voltage between the battery ground and the liquid in the radiator. Just dip the voltmeter probe into the coolant without touching the side of the filler neck. If the meter indicates any more than a few hundred millivolts--bad news, dude. I'd start by replacing all of the ground wires and clamps connecting the battery to the engine block as well as to the frame and body of the vehicle. Remember, you've got a cooling system with several dissimilar metals (iron, copper and aluminum are all common in engines, radiators and heater cores) wetted with an electrolyte. That essentially creates a big battery, and the electrolysis can eat through thin radiator tubes in short order.
Clutching Techniques
Q:
I had to replace the clutch slave unit on my 2003 Ford F-150. The mechanic wanted to know how I drove the truck. I said that when I stop for traffic lights, I usually leave it in gear with my foot on the clutch pedal. He said that this practice might have caused the slave unit to fail. I've been driving manual transmission cars and trucks for some 30 years and have never had a problem with the clutch before. What is the right way to drive a manual truck or car? Leave it in gear with my foot on the clutch pedal or take it out of gear and keep my foot off of the clutch pedal when I am stopped? A:
I dare say most of the vehicles you've driven, unless they were either a tiddlywink-size sports car or a big rig, didn't have a hydraulic clutch like your late-model F-150. So you may not have seen this problem in the past. Most American iron uses a pure mechanical linkage, or maybe a cable. Regardless, keeping your foot on the pedal while stopped, or in motion for that matter, is poor practice. First, there's a safety issue: Leaving the truck in gear might make it easier to lurch into traffic if you sneeze or lose your concentration and release the clutch pedal. On a more mechanical level, the practice keeps hydraulic pressure on the slave cylinder, shortening the life of the seals. It also keeps the throw-out bearing spinning. Unlike any other bearing in the drivetrain, this bearing doesn't have liquid motor oil, ATF or gear lube constantly circulating past it. The throw-out bearing is lubed by a scant spoonful of grease sealed inside. When this bearing fails, the first step in repairing it is to remove the transmission from the car, which isn't easy or cheap.
Outmoded
Q:
What's the replacement for Type A transmission fluid? A:
Type A automatic transmission fluid (ATF) was a GM specification for transmission fluid back when they still used buggy whips. Well, not exactly: It was first used in 1947 when GM started selling cars with modern automatic transmissions. Type A ATF was superceded by Dexron in 1967, and then by Dexron II and Dexron III. Some power-steering units, convertible-top hydraulic systems and even outdoor power equipment still specify Type A. You should be able to substitute Dexron III in most applications that specify Type A. If you're really compulsive about an older vehicle's diet, you can find true Type A from some smaller manufacturers if you hunt around. Underhood Turbulence
Q:
My wife has a 1990 Lincoln Town Car, which she loves. Recently we've noticed an engine vibration you can feel in the gas pedal. Yet it goes away when we're parked. Is this an engine problem or a transmission problem? A:
Probably neither. If you're feeling the shake through the accelerator pedal and not through the steering wheel or the car's body, then I'd hazard a guess that a motor mount is broken or loose. This will allow the engine to shift under acceleration. When the engine's torque is just right, the mount lifts away from the frame. Feather the throttle just a bit, and the engine's weight holds the mount down. But too much throttle and the motor mount will top out, and things are free to shake. The shaking is then transmitted to your right foot through the accelerator cable. Time to replace that broken mount. Shiftless
Q:
I have a tough transmission question for you. My '93 Mustang GT sometimes won't go into gear. If I'm sitting at a traffic light in neutral with the clutch pedal released, then push the clutch in to put it in gear, the shifter won't go into that gear (or any gear) until I wait to the count of three. At that point, it will go in and out easily--until I let the clutch out with the transmission in neutral again. The clutch cable is adjusted correctly, and I have no problems shifting once the car is moving. I can't figure this one out, and I'm a professional mechanic (albeit for Benz, so we only see maybe a dozen manual trans cars in a career). It's really stumped me and my co-workers; any ideas? A:
Sounds perfectly normal to me. You've got a clutch disc, input shaft and the front half of the transmission spinning along merrily at idle speed, driven by the flywheel and pressure plate. When you step on the clutch pedal, that rotating mass doesn't stop spinning instantly. It takes a second or three to slow down. The 1-2 dog ring in the transmission won't mesh with the first-gear engagement ring until it's nearly stopped. The synchronizers use friction to slow down (or speed up when downshifting) all the whirly bits to allow gear changes. That resistance you feel in the shifter is the synchronizer matching speeds. When that synchro starts to wear out, you'll get a crunching noise. Best practice is to always depress the clutch a few seconds before trying to shift into first gear. This will let the parts slow down on their own. Dead Mule
Q:
I have a 2006 Kawasaki Mule 610. This winter it just wouldn't start--no matter what I tried--choking, no-throttle, quarter-throttle or full-throttle. The battery had enough juice to turn it over, but there was no spark (sometimes just a ppfst, ppfst, ppfst sound). A Kawasaki mechanic told me another spark plug should work. He said, "If it gets flooded, that will ruin the spark plug. It takes a new one to allow the engine to turn over. Just cleaning the old spark plug won't do it." How can flooding an engine permanently ruin a spark plug? A:
When the choke is on, especially when air temps are low, the fuel going into the cylinder tends to remain liquid rather than evaporating, wetting the plug's insulator with fuel. Only fuel that's evaporated and mixed with intake air will burn. After the engine starts and warms up, the fuel gets atomized much more completely--no problem. But until then, all that liquid fuel just soaks everything. The little combustion that actually happens is incomplete and will plate the entire inside of the combustion chamber, including the plug, with a sloppy film of gasoline and carbon and moisture--which is conductive enough to let the spark trickle down the side of the insulator instead of jumping the 0.028 of an inch to the ground electrode and lighting the charge that comes in on the next intake stroke. Continued cranking and partial combustion just makes it worse. A fresh plug fixes that. As far as your mechanic's assertion that the plug will never work again, he's partially right. The oxides and carbon can't really be removed, unless you use a spark plug cleaning tool. I have one. And I've have had it for 35 years. It's just a small sandblaster (although I fill mine with glass beads) that scrubs away all the goop. Problem is, it also rounds off the edges of the positive and ground electrodes, and those work best when the edges are sharp, not rounded. The electrons in the spark like to jump off pointy things, not rounded ones. When plugs had steel electrodes, I used a file to dress the electrodes and then gapped them back to the correct gap. Modern plugs mostly use precious-metal electrodes that don't take kindly to that. I haven't gapped a plug in a new car for years.
I've had engines in motorcycles and cars and power equipment that would consistently take two sets of plugs to get started on cold days. I'd pop in a fresh set to light the fires, warm up the engine, and then put the originals back for the rest of the day. Of course, I had less money and more time back then. Ignition systems are a lot better than they used to be, but sometimes not good enough.
Synthetic Leakage?
Q:
I heard from several "not too reliable" sources that once you use synthetic oil in your crankcase, you should never change back to regular motor oil. I have difficulty believing that, but would appreciate your response. A:
A generation ago, when synthetics first hit the market, there were a lot of complaints about leaky engines. In spite of claims to the contrary by the purveyors of these new, premium oils, they didn't have the same seal-swell characteristics as mineral oils. Mineral oils generally have an additive package that makes rubber and cork seals swell up slightly, promoting a tight, oil-free engine. When you switched to synthetics, the seals would shrink, ever so slightly, and oil would weep. Exacerbating this condition, the synthetics were generally much thinner in viscosity, and would find smaller gaps to percolate through. The result? Speckles on the driveway. Other brands of mineral oil had less seal-swell. These engines didn't leak when filled with synthetic--but the seals and gaskets compressed and wore out in their swollen state. Change back to low-swell oil; the seal contracts to its former, less turgid state, and out it gushes. Fortunately, the petroleum industry seems to have a better handle on that today. Don't worry. Change back and forth as you deem necessary.
How to Troubleshoot a Tire-Pressure Monitoring System ?
It's hot. Real hot. Fortunately, the new car you bought right before that Arizona spring-break road trip has air conditioning that works great, in spite of the heavy pop-up trailer and loaded roof rack weighing it down. You pull in for gas and lunch, and carefully check the pressure in the trailer tires with the gauge that lives in your glovebox. The tires on your crossoverare fine though, because all new cars have a tire-pressure monitoring system that will tell you if your tires are low from the comfort and safety of your driver's seat. The desert beckons, and 40 miles of heat-shimmered asphalt later, a tire blows. What happened?
After swapping in the spare, you continue your trip at a more sedate pace. The TPMS light is on, and you stay well under the speed limit until you can check the tire pressures with a gauge. Surprise--they're all low. Surprise No. 2: The TPMS light remains on after you top off the tires to the correct pressure, at least until you can get a replacement tire mounted later in your trip.
Be Prepared
A Department of Transportation study dating back to 2001 says that 60 to 80 percent of cars on the road are running tires underinflated by as much as 10 percent. Worse yet, they say that 20 to 50 percent are being driven with tires down in pressure by as much as 20 percent. Yet, here's the scariest part: If your tires are low, even falling into that minus 20 percent category, your TPMS won't tell you--ever. The TPMS warning light is only required to illuminate when the pressure gets 25 percent below the correct value, which is enough to reduce fuel economy, lower the available grip (especially in wet conditions) and make tires run substantially hotter.Bottom line: Don't trust the TPMS. Once you understand how your TPMS system works, you'll understand why it doesn't obviate the need for regular tire-pressure monitoring.
The Easy Way
There are two types of TPMS on the market, direct-reading and indirect. Indirect systems use only software and readouts from the individual wheel-speed sensors used by the antilock brake system. If all four tires are properly inflated, they will all rotate the same number of revolutions in a stretch of road. If one tire rotates more than the other three, it has a shorter rolling radius because the pressure in it is low.The indirect type of system is inexpensive, because the only real part that must be added to a car is the display on the dash and some extra code in the vehicle's operating system. Properly inferring tire pressures this way can be a problem when the tires are unevenly worn, or if you replace only two worn tires instead of all four. You can reset the system to allow for wear when all the tire pressures are correct. The procedure varies from vehicle to vehicle, and this one won't necessarily work on yours. Persistent TPMS warnings can often be cured by setting the tire pressures properly and then resetting the TPMS somewhere in the menu on the driver's display, or perhaps with a scan tool. If the system isn't reset this way, TPMS warning lights will also crop up after a normal tire rotation, or if you're replacing tires with ones of a different size from the old ones.
 | |
| 1. TPMS senders are usually attached to the valve stem, although some are banded to the wheel's drop center. These units can cost over $100, but replacements for most domestics can be found on the aftermarket for $50 or less. They're prone to damage from tire-mounting machines, so get your tires mounted by a knowledgeable technician. | 2. In an attempt to reduce the sensor's mass and keep the wheel in balance, the metal stem of the sender is commonly made of aluminum. Soft aluminum. Use a torque wrench on the inch-pound scale to tighten these, because it's really easy to strip the threads by overtightening. Ferrous-metal valve caps may interfere with the electronics, so stick with OEM-style plastic valve-stem caps. |
The Better Way
There is a much better (read: more expensive) technology to monitor tire pressures. Higher-end vehicles use a direct-reading system of battery-powered senders mounted inside the tire, communicating with the TPMS by means of small antennas in each wheel well. Every few minutes, the TPMS will interrogate the senders in the wheels, acquire a "true" pressure reading and transfer the message to the in-car display.But what's to keep the system from reporting the tire pressure of the car next to you at a traffic light? In order to keep things straight, the individual senders have a unique serial number to transmit to the vehicle. And that keeps individual wheels on each corner of the car properly sorted in the TPMS's tiny little brain. On many vehicles, there's even a sender on the spare tire. The TPMS is initialized with the position of the four (or five) tires when the car is new. Eventually, those tires could change position, through normal tire rotation or as the result of a flat. That's why there is a procedure to resynchronize the system. For most vehicles, it involves the use of a special tool that communicates with the vehicle and the sender to make everybody play nice. This device knows which wheel is which because it's held next to each valve stem in turn as the system is programmed. Your car dealer will have one, and some independent repair shops might as well. Unfortunately, they're different for every brand of car, and they cost plenty, with basic models going for $600 to $800, and those that work on a variety of vehicles running up to $2500.
Fortunately, it's rarely necessary to use the factory-style tool. Each manufacturer has its own tool and procedure. Look in (surprise!) the owner's manual.
And all of this has to happen within 2 minutes, or the learn mode times out and you'll have to start over. Also, if anyone nearby is adjusting tire pressures on a car with TPMS sensors, the system may be confused. If your vehicle's TPMS includes the spare, burrow into the trunk and get access to the spare first. Don't forget to top off the tires to the correct pressure.
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| 1. The definitive correct tire pressure is on this sticker on the door frame. This info is also in the owner's manual. Ignore what's printed on the tire sidewall. Your car manufacturer has determined what pressures will make your car handle properly. The pressure on the sidewall is the maximum pressure for any vehicle. | 2. Tire pressure should be checked in the morning on cold tires, not after you've driven to Starbucks. Tire pressure changes 1 psi for every 10 degrees of outside temperature. A change from 70 F to 40 F will lower the pressure 3 psi, enough to affect wet braking and fuel economy; check your pressures monthly. |
On some GM cars you can activate the wheel sensors with a simple, powerful horseshoe magnet. GM has a special tool for this, but I'll bet a nice strong magnet from RadioShack would work. On Toyotas, apparently the only way to activate the sensors is with the Toyota TPMS tool or scan tool. Your mileage may vary. You'll need to find out exactly what procedure your vehicle needs any time you rotate tires or install winter tires. Consult your owner's manual, or the factory service manual. Be wary of advice on TPMS from enthusiast websites: A lot of the procedures I saw there were wrong or just plain out-of-date.
Special Considerations
If you ever need to replace a valve-stem core, use stainless steel rather than brass to avoid corrosion. It's one thing to replace a $2 rubber valve stem and something else entirely to replace a $100 TPMS sensor. And always use that cap. Water, road salt or mud could affect the sensor.One last thing: That can of aerosol flat-fixer in your trunk may damage the sensor. Yes, it says "Sensor Safe" on the label, but experience in the field says it's a bad idea. The hole-filling compound may well plug up the hole in the sensor that checks pressure. If you must use one of these products, take the vehicle to a properly trained tire technician as soon as possible to have the hole plugged properly from the inside.
Here's a typical procedure for teaching the TPMS system which wheel is which:
1. Place the ignition switch in the "ACC" position.
2. Simultaneously press the keyless entry transmitter's lock and unlock buttons until a horn chirp sounds. This will put the system in "learn mode."
3. Starting with the left front tire, increase/decrease the tire pressure for 5 to 8 seconds, then wait for a horn chirp. The horn chirp may occur before the 5-to-8-second pressure increase/decrease time period has been reached, or up to 30 seconds after the 5-to-8-second pressure increase/decrease time period has been reached.
4. After a horn chirp has sounded, proceed as in step 3 for the next three sensors in the following order: right front, right rear, left rear.
5. After the LR sensor has been learned, a double horn chirp will sound, indicating that all sensors have been learned.
How to Change a Tire?
Safety First
Pull your car into a safe spot, even if it means driving on the flat tire. Driving more than a few feet with no air pressure will ruin your tire and maybe even the rim. On the other hand, being rear-ended by a high-speed vehicle that couldn't see you because you were parked on the road around a curve will ruin more than that. Try to pick a spot that's flat and dry, and has solid support.
This Is Supposed to Be Easy, Right?
The spare tire, jack and lug wrench that came with your car will make it technically possible to change a flat. You might want to carry around a few extras. I do.
First problem: The spare is flat, too. You check the air pressure in your spare tire regularly, right? Throw an inexpensive 12-volt air compressor into the spare tire well. This might let you add enough air to get you home to change the spare at leisure in your dry, well-lit garage. I also suggest carrying disposable Tyvek painter's overalls, some gloves, rags and hand cleaner. And a flashlight--one with batteries that work.
First Things First
I'm going to give you some homework to do this weekend--before you get a flat. Go out to your car and loosen all of the lugs a half-turn, and then retighten them. Odds are that the last mechanic to work on your car used an air gun to tighten them, and you'll need to struggle with them. Loosen the lugs one at a time and tighten them to the manufacturer's specified torque, generally between 75 and 100 lb.-ft. I strongly recommend the use of a torque wrench (about $25) to do this. Do not simply tighten them until they squeak and throw off little clouds of rust. And loosen and retighten in a star pattern, not going round and round in a circle.
Oil or Not?
Some car manufacturers use a proprietary coating on their lugs, and say that no lubrication is necessary. Others specify they should be lightly lubed. I prefer to lubricate, because then the torque you're so carefully applying to the lugs will be far more accurate. A small dab of grease or engine oil will make it much easier to break the lugs free when you have to. And no, it won't make your lugs spin off by themselves, at least not if you've torqued them properly.
By the Side of the Road
Okay, your tire is flat and you've parked off the road surface on flat ground. Set a safety triangle or a flare 75 ft. behind your car to warn traffic. Start by using a couple of pieces of wood or a roadside rock to chock the wheel opposite the flat both in front and back. Set the handbrake and leave the gearshift in Park (or Reverse if you have a manual).
Remove any hubcap or trim. Loosen the lug nuts or bolts. They're movable, right? The lowest-tech solution is to use a piece of water pipe as an extension on the lug wrench's handle. Around 3 ft. of pipe makes the tightest lug a one-hand job. No pipe? Try standing on the end of the wrench and bouncing up and down. Unfortunately, this is likely to cause the wrench to pop off the lug and whang your ankle, so be careful.
We carry an old-fashioned four-way wrench. Because you can push with one hand and pull with the other, the socket stays planted on the lug and you can generate lots of torque.
Leave one lug on--one near the top of the wheel--a couple of turns from tight. Put the others someplace where you won't scatter them into the weeds by accident.
Upsy-Daisy
Lift the vehicle until the wheel is unloaded, run off the last lug and pull it free.
What? The wheel won't budge? Sit down on the ground and kick the sidewalls with your feet, alternating left and right until it pops loose, but not so fiercely as to knock the car off the jack. Still stuck? Put two lugs back on fingertight, and then -loosen them one turn. Remove the jack, and drive back and forth a few feet three or four times while slamming on the brakes to break it loose.
Together Again
Now is the time to clean any foreign matter from the mating surface and centering ring of the hub and wheel to ensure the wheel runs true and stays properly torqued. Wire brush both surfaces and apply a light coat of antiseize compound to prevent a stuck wheel in the future. Thread all the lugs back on fingertight. Spin the wheel a couple of times to center it, and tighten the lugs slightly with the wrench.
Now you can lower and remove the jack. Tighten the lugs again, in a crisscross rather than a circular pattern to keep the wheel true. The last step is to tighten the lugs to their final torque.
(1) Chock the opposite wheel with scraps of wood, tree branches or partially flattened soda cans.
(2) Stock lug wrench is often inadequate to the task of un-torquing lug nuts. Use a pipe extension. Leave wheel on ground to keep it from spinning.
(3) Jack will have someplace to peg to its intended location on the bottom of the car.
(4) This jack attaches to the frame rail while others may have a small recess on the pinch weld along the bottom of the body.
(5) The owner's manual should show where to place the jack, and some vehicles even have a decal on the jack itself or on a tag in the tool bin.
(6) A little grease on the jack's screw will reduce effort. Don't overdo it or the grease will get on everything.
(7) On soft ground or hot asphalt it's a good idea to use a chunk of 2 x 6 to keep the jack from spelunking down.
(8) Toss the old tire under the car in case car falls off the jack. Clean the hub before mounting the new tire.
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