Engine problems and repairs are one experience most folks don’t want to experience. Would you?
When a driver starts experiencing complications with the vehicle engine, they move towards trading or selling off the vehicle, thinking it is an expensive repair. Luckily, there are a lot of engine problems that are easier to fix than others.
A rod knock is one of these engine issues that might make you move towards trading or selling off your baby ride.
This article will unveil what rod knock is, the symptoms of a rod knock diagnosis, and how to fix it. We’ll explain in detail what you need to know and how to prevent rod knocks. Before we dive deep into all these, what is rod knock?
What is rod knock
Rod knock is the sound of one or more of your rods “knocking” against the crank as it changes direction through its rotation.
The connecting rod (we’ll just call it the rod from here out) is connected to the crank, and between the two there’s a bearing made from a softer material than either the rod or the crank.
When the engine is built there are gap tolerances (measured in 0.001-inch increments) for the bearing to the surface of the crank journal.
This tiny gap allows oil to enter and remain on the bearing surface. This oil film produces a barrier between the two surfaces.
As the bearing wears, this gap widens and the oil will no longer form a proper barrier, and before you know it you have rod knock.
But it doesn’t have to be normal wear (which can take hundreds of thousands of miles); damage to the bearing or crank journal can also cause premature rod knock.
Loss of oil pressure, dirty oil, and low oil pressure are just a few of the culprits than can ruin your day.
What is spun bearing?
One of the worst failures that can occur inside an engine is a spun bearing. It can happen in a stock engine, race engine, gasoline engine or diesel engine.
A spun bearing is bad news because it usually seizes itself around the crankshaft journal. What happens next depends on the bearing’s location. Spun rod bearings are the most common failure.
A spun rod bearing will tear up the big end bore in the rod, ruin the rod journal on the crankshaft, and sometimes break the connecting rod. That’s really bad news because a broken rod flailing around inside an engine can obviously do a lot of damage!
A spun main bearing will tear up the main bore in the block but rarely will it cause the crank to fail. The damage is usually limited to the main journal surface on the crank and the main bore housing.
A spun cam bearing will tear up the bearing bore in the block (or head in the case of an OHC cam), and possibly snap a timing belt or chain – which may result in one or more bent valves if it’s an interference engine. In some cases, the cam bearing seizure may even snap the cam.
Symptoms of rod knock
Like every other system component in your vehicle, there are a few symptoms that tell you when you have a rod knock. These symptoms are as follows;
Knocking sounds: The most common rod knock symptom is a knocking sound. With a rod knocks in place, you will hear a banging or knocking sound (as if someone is hitting metal on your iron door) when you turn on your car.
The noise will increase as you step on the gas pedal.
Overheating: Excess pressure on the bearing and piston will result in overheating.
Low oil pressure: When engine components like the crankshaft, camshaft, and bearings start wearing out, the engine oil pressure will reduce. This is more noticeable when you first start up the car.
In some cases, it will trigger the check engine light and the oil light to display on your instrument cluster, indicating there’s an issue with the oil pressure.
If these lights go off after a few minutes of idling or running the car and pressure returns, it indicates a rod knock.
What causes rod knock
Here is some point for Rod Knock Causes:
- Defective main crankshaft bearings
- Loose or broken timing belt tensioner
- Failing air conditioning compressor
- Broken or cracked flywheel or flex-plate
- Sticking/ticking valves
- Worn water pump bearing
- Worn alternator rotor bearings
- Bad exhaust leak
How to fix a rod knock
Determining how to fix a rod knock is really the job of a skilled mechanic who understands how to fully evaluate your engine problem. There are several potential repairs that must be performed to resolve a rod knock effectively.
The most common repair to be performed is to replace the connecting rod bearings in your engine. It’s likely that any knowledgeable mechanic will also perform an oil change, replace your vehicle’s cylinder head bolts, swap the seals, and fully flush the engine.
The cooler lines may also be replaced in your vehicle if the mechanic deems that work necessary.
All these tasks may potentially have to be performed to bring your engine back to working order and that’s if more serious damage isn’t done to the crankshaft, the pistons, the connecting rods, or other engine components.
A standard rod knock repair that’s caught quickly can be resolved by most mechanics for between $1,500 and $3,500, depending on the work required, but you must have the problem evaluated by a local mechanic to get an accurate estimate.
FAQs
Can an oil change stop the engine knocking?
If your oil pressure is low or you have a low oil level, you’ll likely hear a splattering, tickling, or ticking noise from the engine. If this noise is from the valves, or lifters, adding or doing an oil change will stop the noise. But unfortunately, if the noise is rod knock, an oil change will not stop it.
Will thicker oil stop the rod knock?
As explained earlier, a rod knock is a sound indicating wear and damage to your engine system. So, changing to oil with a higher viscosity rating (heavier or thicker oil) will help eliminate or at least reduce the rod knock.
It will potentially prolong your engine life. This doesn’t mean you should not diagnose and fix the cause of the knocking.
How long will an engine last with rod knock?
If you have a rod knock in your vehicle, you might also be asking, ‘How long can you drive with a rod knock?’ Regardless of your question, once an engine starts to knock, nothing is too sure to determine how long it will last.
You can have a total breakdown the next time you start your vehicle, or it can keep working for 3-6 months. However, driving with rod knocks for a couple of minutes is not recommended. It can blow up your engine and keep you in the middle of nowhere.
Can you hear the rod knock at idle?
Yes, you can hear rod knock upon engine startup, idling, accelerating, and decelerating. The noise will increase as you step on the gas pedal and decrease as you remove your leg. Disregard anyone who says otherwise. Why?
Rod knock is a loud banging noise upon engine startup and continues until you turn off the car.
What happens when you hear a rod knocking?
Rod knocking is a problem with the internal engine moving parts. Once it occurs, you’ll hear knocking or banging sounds, have low oil pressure, and check the engine light in your instrument cluster.
If you fail to track down the cause and fix it in time, it will result in catastrophic damage to the engine.
Is it worth fixing the rod knock?
A rod isn’t a problem that will go out on its own. You should diagnose and fix the problem on time before it escalates. If you notice and fix the rod knock-on time, it won’t dig a hole in your pocket. So, it is worth repairing a rod knock at an earlier stage.
How Much Does It Cause to Fix A Rod Knock?
Several factors influence the cause of fixing a rod knock. These factors include; the actual cause of the rod knock, how severe it is, hours of labor, service fees, the vehicle makes, and models. However, the cause of fixing a rod knock should be around $700-2500.
Final word
Rod knock is one of those complicated engine problems that many folks overestimate, thinking it’s the end of the game with their car’s engine.
If you notice the problem earlier and take immediate action, your dealership or mechanic might resolve the problem without breaking your budget.
However, if you notice and ignore the signs highlighted above, fixing the issues might cost you a lot. At this point, replacing your engine might be the only option.