Oil consumption is something nobody wants. So, how can worn engine bearings make it worse ?
Engine oil consumption past rings, will only get worse, when engine bearings begin to wear out.
So, oil consumption with no apparent oil smoke, often indicates, collapsed oil control ring expanders or worn oil control rings.
Oil consumption past rings, happens all the time, but some cases are worse that others. The bottom piston ring’s sole duty is; to scrape excess engine oil off the cylinder and back into the crankcase. Poor lubrication can cause modern piston rings, to overheat and lose their tension as well.
Worn out bearings will flood the cylinders, because of the excess oil the bearings are throwing off. So, as long as there’s a steady flow of clean oil, the bearings will generally keep moving along fine.
When the oil is dirty, or suffers lack of lubrication, that’s when the problems start.
While on the one hand we’re trying to reduce oil flow to the piston rings, on the other hand; the oil film must reach the very top of the cylinder wall.
Worn Main Bearings Causing Oil Consumption
So, worn main bearings throw off an excessive amount of oil. The amount of oil throw off, increases rapidly when bearing wear increases. For instance, if the bearing is designed to have .0015” clearance for proper lubrication and cooling; the throw off of oil will be normal; as long as this clearance is maintained and the bearings are not damaged.
However, when the bearing clearance increases to .003”, the throw off will be five times normal. If the clearance is increased to .006”, the throw off will be twenty-five times normal.
So, when the main bearings throw off too much oil; the cylinders are usually flooded, with more oil than can be controlled, by the piston rings. As a result, this causes burning of the oil, in the combustion chamber and carboning of, pistons and rings.
In a conventional full-pressure lubricated engine; a large loss of oil at the main bearings, may starve the downstream connecting rod bearings of lubrication; to such an extent that sometimes; especially at low speeds; insufficient oil may be thrown on the cylinder walls. This will cause the pistons and rings, to wear to such an extent; that they will not be able to control the oil at high speeds. So, the effect of main bearing wear, will be high oil consumption.
Worn Connecting Rod Bearings, Causing Oil Consumption
Clearances on connecting rod bearings, affect the throw off of oil in the same proportions; as mentioned for main bearings. What makes this worse, is that the oil throw off is thrown; directly into the cylinders.
Worn Camshaft Bearings – (OHC Engines)
Large quantities of this oil, may flood valve guides resulting in, increased oil consumption.
Symptoms Of Worn Engine Bearings
Problems with engine bearings, will usually result in some sort of knocking noise, coming from your engine. The type of knocking noise that you hear, will usually give you a good idea; of which bearing is faulty:
Main Bearing Sounds
- A rumbling or thumping sound, deep in the engine, when accelerating.
Rod Bearing Sounds
- The knocking noise sounds more like, two hammer banging together and increases in intensity, as you accelerate. Poor maintenance, is a major cause of this problem. The oil gets dirty and grit can wear the surface of the bearings. As a result, the noise you hear, is a knock towards the bottom of the engine.
Low Oil Pressure
- Many times when a bearing is beginning to fail (or has failed); you will noticed signs of, decreased oil pressure. This is usually more evident, upon first starting the vehicle. In many cases, a bad rod bearing, will lead to a “check engine oil” light being displayed on the dash.
Signs Of Worn Piston Rings
Excessive Exhaust Smoke
- If there is a lot of exhaust smoke coming out of your vehicle; this could be an easy sign that you have bad piston rings. This smoke will look very thick and have gray and white colors to it. When you have bad piston rings, engine oil, will start leaking into the combustion chamber. Once that happens, the oil will burn and create; thick gray and white exhaust smoke.
Excessive Oil Consumption
- This symptom has the same result, as the first symptom listed here. When you have worn piston rings and oil leaks into the combustion chamber; it will cause added oil consumption. This means you’ll have to, regularly add oil to your vehicle; rather than wait the standard 3,000 to 5,000 miles before you do it. If you find yourself adding oil more often than you should; then have a mechanic inspect your piston rings.
Low Engine Power
- When piston rings suffer wear or get damaged, your engine will lose power; because there is less compression taking place. This means when you put your foot on the gas pedal to accelerate; the vehicle will take a long time to speed up. In this case, you will need to have your piston rings replaced to fix the problem.
In some cases, car maintenance, is straightforward and simple. A lot of parts give us ample warning, before they give up the good fight. Unfortunately, we enjoy no such insight, when it comes to engine bearings.
Thank You !