Productive engine service tips

Q: We keep hearing about stretch-fit belt technology on serpentine belts. Does that mean there aren’t any special tools required to install these new belts?

A: Stretch-fit belts are being used on at least some engines by almost all the most popular car makes. While some belt applications may not require any special tools, the overwhelming majority of stretch-fit installations require some sort of tool to safely and effectively route the belt onto its matching pulleys and idlers. When shopping for stretch-fit belt installation tools, line up some training as well so you’re properly prepared to service this new technology.

Q: When diagnosing a suspected faulty head gasket, we usually look for contaminated oil and coolant. Is there anything else we can use that’s more conclusive?

A: Yes, a combustion leak tester helps confirm and pinpoint the presence of combustion gases in the cooling system. First you add a blue-colored fluid to the tester, then insert the tip of the tester into the radiator to expose the tester to potential combustion gases. If the tester encounters any combustion gases in the radiator, the dye will turn yellow.

Q: We’ve heard that removing spark plugs on 5.4L Ford, 3-valve engines is a nightmare as it’s likely the spark plugs will break during removal. Are there any tools that can help save us when facing a “problem child” like this?

A: First, realize that removing plugs on these engines must be done with the engine cool and after soaking the spark plug threads with a recommended carbon cleaner. Still, some plugs break during removal, leaving the spark plug shell behind. When this happens, use a special spark plug remover kit, made specifically for removing the shell from the cylinder head. If the threads in the cylinder head need repairs, there are also inserts for this fix. Take your time and you should have decent success on these otherwise challenging spark plugs. (Check out this month's Tool Briefing on page 18 for more information on spark plug removal and repair.)

Q: When performing engine set-up, we need to easily identify when a cylinder is at top dead center. What tools are available for this?

A: A Top Dead Center (TDC) indicator works best for this purpose, which threads into the spark plug hole and positions a spring-loaded plunger against the top of the piston. As you rotate the engine slowly, watch the shaft of the indicator as it raises to its highest point. You can also use a “TDC whistle” to find top dead center. The whistle also threads into the spark plug hole, and produces a whistle sound as air being pushed upwards by the piston exits the whistle. The instant the whistling stops, you’ve found top dead center.

Q: We’re periodically tasked with owner complaints of low oil pressure. In some cases the oil light comes on and in others the gauge may read low. Is there a quick way to determine the source of the problem?

A: While there’s no quick way to get to the heart of the problem, perform the basics including confirming the oil level and ensuring that the connections to the oil pressure sending unit look OK. From there, consult service information for the oil pressure specification and the recommended access point to connect an oil pressure test gauge, using the proper adapters. With the gauge connected, take one or more oil pressure readings at the specified engine operating speed. Compare the readings to specs and go from there. If the pressure is OK, it usually means a faulty sending unit. Low pressure means you’ve got some further investigation to do, which may require some engine tear-down.

Q: We know warpage is the enemy of reliable head gasket installation, but what do we use to make sure warpage is kept within limits to ensure effective sealing?

A: The flatness of both the head and block must be within limits for an effective seal. To check the head, lay a straight-edge lengthwise on the valve side of the cylinder head and stick the largest feeler gauge possible between the mid-point of the head and the straight edge. Check the deck by laying the straight-edge lengthwise on the block. Generally, a maximum of 0.003” warpage is allowed for 3-cylinder heads; 0.004” for 4-cylinder heads; and 0.006” for (inline) 6-cylinder heads. Warpage specs are for the total amount of warpage for the head and block, not just the head. The block is frequently forgotten when making this check, because blocks usually don’t bend, heads do. Excessive warpage means the head, the block or both may need to be resurfaced.

Q: The techs in our shop have an ongoing debate about how to best find a a weak cylinder. What’s best?

A: A compression test, whether done with a gauge at each cylinder, or electronically with an engine analyzer, reveals each cylinder’s ability to compress air. Car makers differ on the amount of pressure differences they allow, but as a general rule of thumb, the remaining cylinders should read within 10 percent (or about 15 to 20 psi) of the highest cylinder. A power balance test is similar to a compression test, but a power balance test really compares the relative power output between the engine’s cylinders. The test really serves as a quick way to identify a problem cylinder. When you do find a weak cylinder with a power balance test, you still don’t know if the problem is ignition-related (like a fouled spark plug or bad plug wire), fuel-related (like plugged or dead fuel injectors) or a mechanical problem (burned valves, blown head gasket, cracked or burned pistons, cracked head or block, or rounded cam lobes). Sometimes a compression test can give you a clue to what’s wrong, but additional detective work is usually needed to pinpoint a problem. Compression readings alone won’t tell you if the engine has worn rings, worn cylinders, or leaky valves. Even a “wet” compression test, where you take a second set of readings after squirting oil in the cylinders, isn’t exacting enough to confirm the source of the leak.

Q: Since a compression test isn’t very conclusive as to the root cause of a cylinder problem, what’s the next step?

A: If you were to look at a diagnostic flow chart, a cylinder leakage test would represent the last block in the chart. For instance, in the case of an engine misfire, you would test the fuel and ignition systems first, then go to a compression test and finally, end up at the cylinder leakage test. How does a leakage test differ from a conventional compression test? Instead of checking how well each cylinder pumps air, the cylinder leakage test checks how well each cylinder holds air. You do this by applying a controlled amount of compressed air into each cylinder and watching a gauge to see the relative percentage of leakage. Because you’re filling each cylinder with air, you can also listen at different points to find the source of the leak. Since these air leaks are really compression leaks, the signature hissing sound leads you to the source of the cylinder’s problem.

Q: Our shop replaces timing belts on some makes and models right now, but we’d like to go after this market more aggressively than in the past. What do we need to consider?

A: First, consider the vehicles that would represent the highest demand for service. With volume on your side, you can more easily justify the tools you’ll need to do the job. Once you’ve defined your spectrum of vehicles, start looking for the timing belt tools you’ll need to handle that group of vehicles. In some cases, you may find that certain tool companies have timing belt “master kits” that provide a wide range of vehicle coverage, rather than buying multiple individual kits. Like all areas of service, don’t stop with just the tools. You also need to account for the breadth of service information needed to handle that spectrum of vehicles. Consider expanding or rethinking your current subscription if needed. Remember to continue to evaluate during the discovery process, as you may learn that some vehicles may not be worth your while if tool costs are too high and the volume of vehicles you’d see would be too low.


Thanks for checking out this month’s Tool Q&A column. Remember, this is your column, because it’s based off your questions. So, let PTEN know what’s on your mind when it comes to tools and equipment.