Oil consumption is something nobody wants. But, worn engine bearings can make it even 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. Furthermore, poor lubrication can also cause modern piston rings, to overheat and lose their tension.
Also, 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. However, 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. Then, the throw off of oil will be normal. That is to say, 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. Usually, 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 carbon on the, pistons and rings.
In a conventional full-pressure lubricated engine, a large loss of oil at the main bearings, can cause major damage. Because, this may starve the downstream connecting rod bearings of lubrication. Consequently, to such an extent that sometimes, especially at low speeds, insufficient oil may be thrown on the cylinder walls. This will cause the rings, to wear quickly. As a result, 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
Most often, when you have problems with the main bearings, the rod bearing follow, with the same issues. However, sometimes, its the rod bearings, then the main bearings. Either way, both add to oil consumption and damage.
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.
Using high-viscosity oil in a new engine reduces the lubrication and cooling of low-tension piston rings. And, can be a serious problem on today’s turbocharged, high-performance engines.
Another issue with using high-viscosity oil, is that it might prevent low-tension piston rings from contacting the cylinder wall. In addition, this can increase oil consumption.
As mentioned above, oil slinging off the crankshaft not only lubricates the rings, but cools them as well. Since high-viscosity oil reduces oil flow through the connecting rod bearing, cylinder lubrication and cooling will suffer.
Worn Camshaft Bearings – (OHC Engines)
Large quantities of this oil, may flood valve guides resulting in, increased oil consumption. When the bearings develop a problem, the camshaft may start moving improperly. Because, it is not getting the required support.
This may lead to increased friction between the engine parts. If the friction is too much, the engine may start burning more oil than usual, resulting in more oil consumption. The oil may also leak into the engine’s combustion chamber, causing excessive exhaust smoke.
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, lower 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, on the dash.
Signs Of, Worn Piston Rings
Excessive Exhaust Smoke
- If there is a lot of exhaust smoke, this could be a 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 engine, before the standard 3,000 to 5,000 miles. 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. So, when you put your foot on the gas pedal, 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 !