Here’s What You Need To Know About Engine Overhauling
What Is an Engine Overhaul?
Many mechanics use the term “engine overhaul” loosely, so it can have different meanings. Some technicians use the term to describe a simple chassis-based rebuild. This means the engine requires a few parts replacements, such as a new cylinder liner or piston rings.
Other mechanics use the term to describe more extensive servicing. In this scenario, the technician needs to remove the entire engine from the chassis and take apart every removable part. Each part is cleaned or replaced with factory-grade replacements.
When a Rebuild Is Necessary
Some car enthusiasts, such as classic car owners, opt for an engine overhaul every few years to keep their older car performing like a newer model. Your car may also need an engine overhaul if you notice some of the classic symptoms of engine troubles. This includes:
- Low oil pressure: damaged valves and broken piston rings may cause an oil leak. This reduces oil pressure, and the car may use oil more rapidly than usual.
- Irregular engine noise: you may hear rattling sounds, which may indicate broken piston rings. You may also hear engine “chattering,” which may suggest a faulty valve train.
- Bad spark plugs: if a spark plug inspection reveals discoloration, then the valve train or piston ring may require replacement.
Considering engine Overhauling?
There are different ways of overhauling an engine. Most workshops do what is called an in-chassis rebuild. This is where you don’t remove the engine from the car, you just pull what you need to do the job of it and do a minor overhaul – replace the cylinder liners, pistons (if they need it), piston rings, replace the big end and crankshaft bearings, lap the valves in and replace the valve stem seals, strip and check the oil pump, replace the gaskets and seals Just what is needed to be done to bring the engine back to factory specification and performance.
A major overhaul or out-of chassis rebuild is much more thorough. The engine is removed from the car (obviously) and totally stripped down – every nut and bolt are removed, cleaned, checked. Most moving parts are replaced with brand new factory stock parts – often the only original parts of an engine that has been MO’ed are the block casting, the head casting, the crankshaft, conrods, flywheel and camshaft. If any of those aren’t in serviceable condition they get switched out too. And the motor gets a fresh paint job. A MO is much more expensive, but it’s like you get a brand new engine back, while still usually costing less than actually buying a brand new engine.
The easiest way to rebuild and revive your engine’s performance is to conduct an in-chassis rebuild. This is basically done without removing the engine from the car. All the defected parts of the engine are pulled out for a minor overhaul. An In-chassis rebuilt may generally consist of replacing cylinder liners, piston rings, crankshaft bearings, valve stem seals, oil pump, and head gasket. Repairing or replacing these components of the engine might help in reviving the engine’s performance to a great extent.
Another sub-category of In-chassis rebuilt is ‘Major Overhauling’ also known as ‘top overhaul’. The major overhauling technique covers inspection and replacement of spark plugs, cylinder heads and vales. A top overhauls proceeds with a compression test. It is important to mention that piston rings are not generally replaced.
The major concept of engine overhauling revolves around Out-of-chassis rebuild. The engine is detached from the car, unbolted totally and thoroughly cleaned and inspected. This overhauling technique involves replacing all the major components of engine with new factory stock components. Other parts such as block casting, head casting, crankshaft, conrods, flywheels and camshafts can also be repaired if they aren’t totally tattered. For a locally manufactured car, an Out-of-chassis rebuild might save you some extra bucks as compared to buying a completely new engine.
Engine overhauling becomes necessary if your engine starts to fail. Overhauling of engine may help in reviving the performance of the vehicle but it may cause some reliability issues in the long run. Sometimes, engine swapping can be a better option as compared to overhauling. In case, you are using an imported car and its engine is excessively worn out, engine swapping can be much more economical as compared to out-of-chassis rebuild.