Undercar: Diagnosing And Repairing Wheel Bearing Noise
Power to the People: An independent repair shop has a handful of engine replacement options available: a used engine, a quality rebuilt, a remanufactured or new OE engine.
emature wear and, occasionally, catastrophic bearing failures caused by clogged oil pump screens or oil galleries. Heavily sludged engines may also tend to have application-specific lubricating problems in some areas of the engine, including valve and camshaft oiling.
Insufficient oiling, on the other hand, often results in the overhead camshaft seizing in the cylinder head, the timing belt breaking, and interfering intake and exhaust valves bending. Insufficient oiling also may cause crankshaft damage and severe piston scuffing.
Many shops lose money because they estimate a partial, rather than a complete, engine replacement. Under-estimating the engine replacement usually causes the shop to write off many billable hours in order to resolve these otherwise avoidable misunderstandings with the customer.
Since a replacement engine is usually priced at a very low profit margin, and considering the warranty liability, the long installation times and other contingencies that go along with an engine replacement, profitability can be very low or, in some cases, non-existent.
The true profit in an engine replacement is found in the add-on items required to restore the engine support systems and drivetrain to like-new performance.
For example, during the estimating process, extra time should be included for cleaning parts, removing broken studs, refinishing warped manifolds and road-testing the finished product. In addition, a wheel alignment should be included if the front suspension is disassembled or the engine cradle is removed during the replacement process.
When estimating an engine replacement, it’s important to remember that oxygen sensors may be contaminated with antifreeze or oil from the old engine. If the old engine was severely overheated, it’s a safe bet that the calibration on the temperature gauge and engine management coolant sensors has also been ruined. Along the same lines, don’t forget that new spark plugs, wires and, if applicable, distributor cap and rotor are recommended, especially if the engine is a 1995 or newer model equipped with an OBD II misfire monitor.
The catalytic converter also may be ruined from a misfire condition or contaminated with antifreeze or oil, so it’s wise to leave the estimate open for such contingencies, especially when operating in an area that requires an annual emissions test.
When the intake manifold is removed, the exhaust gas recirculation (EGR) passages should be cleaned to make sure that the EGR flow is adequate and distributed evenly among the cylinders. If this basic procedure isn’t
performed, the on-board diagnostics may later discover the fault, store an EGR failure code and illuminate the Check Engine or Malfunction Indicator Light.
Other Pricing Notes
Be sure to include expendable items like timing belts, drive belts and tensioner pulleys in the estimate. Many reman engines, for example, are shipped without timing belts. If the engine is used, a timing belt replacement is recommended, especially with the engine out of the chassis. If the engine is a valve interference type, a technician simply can’t afford not to replace the timing belt with a fresh unit simply because of warranty considerations.
Also, if the old engine has suffered catastrophic bearing failure and is equipped with an engine oil cooler, the probability is very high that the cooler itself is heavily contaminated with metal particles. The best option is to replace the oil cooler to avoid ruining the new engine.
Cooling Off Period
Cooling system component sales usually are neglected because a shop is trying to keep the cost of an engine replacement affordable. While it’s true that every job has to balance affordability with reliability, it’s also true that a clogged radiator, badly deteriorated hoses or a worn water pump can cause the new engine to overheat and possibly fail.
Radiators are always a prime candidate for service or replacement, since the old engine may have been overheated. When overheating occurs, sediment from the engine’s water jackets may partially clog the radiator core, which reduces the cooling capacity of the radiator. While this condition may not be obvious at first, it may come back to haunt the engine installer on a hot summer day. In the extreme case, the engine replacement may be ruined, especially if the driver doesn’t keep an eye on the temperature gauge.
At the very minimum, the radiator should be cleaned externally and flushed before doing the engine installation. In addition, the correct mix of factory-recommended coolant should be installed to ensure against the coolant boiling away or a freeze-up occurring during the cold days of winter.
After the new engine is thoroughly warmed up, always make sure the engine cooling fan(s) activate when the coolant approaches specified maximum outlet temperature. In some cases, the cooling fan may have two speeds, with the slower speed activating when a normal temperature increase occurs, and the second speed activating when the coolant temperature exceeds a specific threshold or when the air conditioning is turned on. When all systems are “up and running,” the complete engine replacement is ready to roll out the door with your full confidence that it will perform to the original manufacturer’s specifications.
Prepping the Block
Engine blocks are generally resistant to heat and lubrication damage. More commonly, an engine block might develop fatigue cracks between cylinders or around main bearing journals, which renders the block unserviceable. A worst-case scenario might include spun main bearings, which requires the main bearing journals to be align-bored.
Unfortunately, align-boring, like excessive block and head milling, reduces centerline dimension between the crank and camshafts, which retards camshaft timing.
Although over-boring the cylinders can cause overheating and excessive oil consumption, most remanufacturers now hone the cylinders to accommodate piston oversizes amounting to much less than the standard 0.030” oversize bore.
Torque plating, which duplicates the stresses and distortions in the cylinders caused by tightening the cylinder head to the engine block, involves installing a heavy plate resembling a cylinder head gasket to the engine block. Torque plating is critical for correct cylinder refinishing on some engines that use low-tension piston rings.
The most common oversight in cylinder block preparation is the failure to remove hardened accumulations of core sand and sludge in the cylinder block water jackets, which can cause future overheating and radiator clogging problems.