True or False? A brake shoe adjusting gauge is an inside-outside measuring device used to initially adjust the expanse of brake shoes before the brake drum is installed.
When conducting an oil pressure test: Technician A says that lower than normal pressure can be caused by faulty piston oil rings. Technician B says that lower than normal oil pressure can be caused by excessive engine bearing clearances. Who is correct?
a. Technician A
b. Both A and B
c. Technician B
d. Neither A nor B
The Correct Answer and Explanation is:
Answer to First Question: True or False?
True.
A brake shoe adjusting gauge is an inside-outside measuring device used to initially adjust the expanse of brake shoes before installing the brake drum. This tool ensures that the brake shoes are properly set close to the drum surface, improving initial brake performance and reducing the need for further adjustment once the vehicle is in use.
Answer to Second Question:
Correct answer: c. Technician B
Explanation (300+ words):
When diagnosing low oil pressure in an internal combustion engine, it’s important to understand how oil circulates and the factors affecting its pressure. Oil pressure is primarily generated by the oil pump and maintained by the clearances within the engine components — such as crankshaft bearings, camshaft bearings, and lifters.
Technician A claims that low oil pressure can be caused by faulty piston oil rings. However, this is incorrect. Piston rings serve to seal combustion gases within the combustion chamber and to control oil consumption by scraping excess oil off the cylinder walls. While worn piston rings can lead to oil consumption and smoke, they do not directly affect oil pressure. Oil pressure is measured in the pressurized lubrication system, not in the cylinder walls or combustion chamber, so defective piston rings won’t lower oil pressure.
Technician B states that low oil pressure can be due to excessive engine bearing clearances, which is correct. The engine’s oil pressure system relies on controlled clearances between moving parts. Bearings — such as the main and rod bearings — are machined to precise tolerances. If these clearances become too wide (due to wear over time or poor machining), oil can flow through them too easily, leading to a drop in oil pressure. This happens because the oil pump cannot maintain sufficient pressure due to the rapid escape of oil at the bearings.
In addition, excessive bearing clearance increases the volume of oil needed to maintain pressure, and if the pump is not capable of delivering that volume, pressure drops. This condition can eventually result in engine damage due to inadequate lubrication.
Conclusion:
Technician B is correct. Excessive bearing clearance is a well-known and documented cause of low oil pressure. Technician A’s explanation is not supported by how oil pressure systems operate. Therefore, the correct choice is C. Technician B.