Common Problems after Engine Replacement

Just like humans can’t live without the heart, vehicles can’t function without an engine. For this reason, vehicle owners try to ensure their engines are in perfect working condition. But no matter how flawlessly and sincerely you maintain your vehicle, it can wear due to constant use and age. However, because of the importance of an engine, you can’t just let it stay bad.

You need to repair it ASAP to keep your car running, especially if you don’t intend to get a new car soon. Generally, everyone would expect their vehicle to bounce back to life after replacing a bad engine. However, users have complained of encountering certain problems after engine replacement. This article will highlight the common problems one might encounter after engine replacement and how to avoid them.

pros and cons of replacing car engine

Common problems after engine replacement

While replacing faulty engines guarantees that your car is now in good shape and will perform well, the unforeseen might happen. You might experience certain problems after replacing the engine, especially if there were other components with underlying issues or the installation was not correctly done.

However, knowing these problems will help in tackling the situation on time. This way, you could enjoy your newly replaced engine, prevent damage, and prolong the engine’s life. So here are common problems you might encounter after an engine swap.

01. Weird noises

Your car engine will naturally make some noise when started or driven; most drivers would know the usual sound of their engines. If, however, strange noises start coming from your engine, you need to find the root cause and fix it. Ideally, you may hear different kinds of noises, with each pointing to specific problems.

A thumping or knocking noise, usually felt under the hood, is an indication you have broken seals or the bearings are worn out. Another is a squealing and whistling sound. A squealing or whistling sound that becomes apparent almost immediately indicates a weak fan belt, bad pulleys or rollers.                                      

Another strange noise is a grinding sound, usually irritating to the driver, passengers, and others close to the vehicle. A grinding noise indicates that the front pads are broken or damaged.

02. Unusual smoke

When you start an engine, a white cloud of smoke will pop out from the exhaust pipe, which ultimately reduces as your drive. This smoke is usually white and clear. If, however, you notice other smoke colors—blue or black, there is an issue that needs to be addressed before you continue driving your newly replaced engine. Blue smoke, for example, indicates that the piston rings are bad or valve seals are broken, letting oil into the combustion chamber and burning there.

03. Illumination of the check engine light

The check engine light controls almost all car components, so it will usually alert the driver if any components are faulty. However, if the light turns on immediately after replacing your engine, it could be that the spark plugs were already damaged before the engine swap.

It could also be that the fuel cap was not properly placed after engine replacement.

The CEL could also turn on due to faulty fuel injectors, bad O2 or airflow sensors, a broken thermostat, or a damaged engine coil.

04. Fluid underneath the car

Another common problem after replacing the engine is oil leaking under the vehicle. Puddles of oil appearing under your car are an indication that the engine oil or antifreeze is leaking. A broken hose could cause leakage. But you must make a proper diagnosis to find the real culprit and fix it before continuing to drive to prevent damage.

05. Rough running engine

Drivers may also notice their car not operating to its optimal capacity. Generally, after replacing your engine, you should be able to accelerate and attain speeds smoothly. However, if you struggle to do these or your car vibrates when doing them, something is wrong.

And you would notice these struggles, especially as RPM increases. Engine running rough could stem from faulty spark plugs or ignition coils. In other cases, there is a fuel pressure problem, or your engine needs a tune-up.

06. Loss of engine power

With a loss of engine power, your engine will struggle and not reach its optimal performance level. Generally, loss of engine power will cause your car to shake, stall, stutter, or struggle to drive uphill. Engine power loss is mostly caused by the engine not getting enough fuel or air.

In this case, you’re likely dealing with a dirty fuel and air filter, and a bad O2 sensor, but it could also be other issues. This is why proper diagnosis is needed to ascertain the real culprit.

engine replacement under warranty

How to avoid common problems after engine replacement

To avoid problems after replacing an engine, there are certain things one must do. What to do after engine replacement? Ideally, you only need to check certain components that work in sync with the engine and ensure they are functioning well. This is essential, especially if the car is more than six years old.

If they are not in good shape, you may need to replace them. So this means aside from replacing your engine, other replacements may need to be carried out too. This begs the question, what else should I replace after replacing an engine? Here are other replacements to do after replacing an engine.

Replace worn timing belt or chain

The timing belt or chain is an important car component that ensures vehicle valves close and open at the right time. It also aids in the prevention of pistons collision at their topmost positions. Hence, it must be replaced when faulty. So what happens if the timing belt is not replaced?

A failing timing belt or chain will affect your car’s starting speed since they are connected to the pulleys that run the crankshaft. A broken timing belt can also slip on the camshaft, causing the cylinder to open and close incorrectly.

In summary, a worn timing belt could result in complete engine damage, damaged cylinder heads or camshaft, broken valves, and damaged cylinder walls. Therefore, to avoid more engine problems and enjoy your new engine, replace worn timing belts as you replace the engine.

O-rings and gasket

Depending on your applications, O-rings and gaskets serve as sealing devices and are usually used when different components are joined together. They basically help prevent air or gas from escaping from connected components. But when they are faulty, loss of gas and air will be apparent.

With an improper amount of air and fuel in your engine, you may start experiencing issues in engine starting, loss of power, etc. So while replacing engines, replace broken O-rings and gaskets or seal the new engine properly so your engine can work optimally.

Replace broken seals

Seals are placed all over the engine and help prevent liquids from leaking out from their compartments while also preventing things from entering. Typically, seals are always in contact with two surfaces simultaneously. Oil seals, for example, prevent oil from leaving the engine while preventing dust and contaminants from entering.

When these seals are broken, the liquid seeps out. With your engine oil leaking or contaminated, the engine won’t get lubricated enough leading to metal grinding against each other.  So while replacing the engine, ensure the seals are also in good shape.

Replace damaged Sensors

Your vehicle comprises several car sensors that help transmit information around the vehicle for the proper functioning of the vehicle. Some also receive. If they are bad or get damaged during engine replacement, you may suffer from car sensor issues as they won’t be able to carry out their jobs properly.

For example, an oxygen sensor helps measure the air in the exhaust, so it ascertains the amount of oxygen in the cylinder and then delivers this information to the ECM/ECU. The ECM/ECU further uses this information to adjust the air-fuel ratio accordingly. If the O2 sensor goes bad and do its job, the ECU won’t know what to do, leading to an incorrect air-fuel ratio.

Here, you may start to run a lean or rich mixture. This may invariably cause your engine to rough idle, run poorly, cause other drivability issues and result in engine damage. For optimal performance and to prolong your new engine life, check your sensors. Clean dirty sensors and replace damaged ones.

Change faulty spark plugs.

Spark plugs create the spark needed to ignite the air-fuel mixture to start your engine. Typically, faulty spark plugs will cause an almost no-start situation. Bad spark plugs will result in incomplete combustion, letting unburned fuel eat up the cylinder walls.

So while replacing the engine, ensure you replace worn spark plugs so your vehicle can generate enough power to start your car. Changing faulty plugs can prevent engine damage, allowing your new engine to perform excellently.

Change failing water pump.

Water pumps help transport coolant through the engine to cool the engine. A failing water pump, however, will not let the proper circulation of coolant, ultimately leading to overheating or engine freezing during the cold months. So ensure you check and replace faulty water pumps so your new engine can work optimally and last long.

Replace dirty air filters

Air filters help filter air entering the engine, so dirt and other particles won’t contaminate and damage the engine. If the air filter is clogged or dirty, this will prevent enough air from entering the engine.

Too little air in the engine may result in poor acceleration, fuel shortage, and sudden loss of power when driving. So to avoid this, clean or replace the air filter when replacing the engine, else you won’t enjoy your new engine.

Change clogged oil filter.

The oil filter ensures impurities in the oil don’t enter the engine. However, clogged oil filters will not allow enough oil into the engine. This can lead to improper lubrication of rotating engine components, causing metal-on-metal rubbing.

Improper lubrication of engine parts could also lead to the failure of other parts like the exhaust manifold, timing belt, etc. So if you want your new engine to perform optimally, try cleaning or replacing clogged oil filters.

Other components to replace

Aside from the components stated above, what else should I change after replacing an engine? Other common engine repairs or replacements to do after replacing the engine include repairing or replacing:

  • worn fuel pump
  • Car sensors
  • Failing exhaust manifold
  • Worn/broken hoses and vacuum pipe
  • Broken thermostat


How long will a car last after engine replacement?

A new engine can last up to 20 years. But technically, the engine alone does not define how long a car will last. Several components work collectively to ensure the smooth running of a car. So, how long a car lasts after engine replacement depends on the condition of other components.

If the car has been used for long and its components weak, it may not last longer. For example, if a car was rated to last 200,000 miles and you replace the engine at 150k miles, the car will still need to be scrapped at 200,000 miles. It won’t last longer than rated because you changed the engine.

So the right question will be, how long does a replacement engine last? Replacement engines can last as long as the OEM engines if maintained properly, whether rebuilt or manufactured. For example, if the original engine hits 150k miles, the replacement engine can also hit another 150k miles.

What should I look for after replacing my engine?

True, a new engine will give your car a different feel. However, if you want optimal performance, there are certain things you must do or look at after engine replacement. So you may ask, what should I do after engine replacement? You need to check some components working together with the engine and replace them if faulty.

You may need to change dirty fuel and air filters, damaged timing belts, failing crankshaft and camshaft sensors, faulty fuel and water pumps, etc. These components work together with the engine to drive well. If they are not in good shape, you may encounter certain problems as engines replacement by-products. So what are the types of replacement problems you may encounter?

You may experience loss of power or no start situation due to failing spark plug not igniting, or there is a shortage of fuel due to bad fuel filters or sensors. You may also notice strange noises from your car due to broken seals or bearings, faulty fan belts, or worn brake pads. So try to check and fix these components immediately after replacing the engine.

What happens when you replace a car engine?

Replacing a car engine will bring your car back to life on the condition that other car components are still in good shape. It will even increase your car’s value, especially if the engine is well-built and the installation is done by a professional, and the car still runs smoothly. While it won’t give you the feel of a new car, it’s better than driving a deadbeat car.

So you may ask, is getting a new engine like getting a new car? No, getting a car is different from getting a new engine. With a new engine, you save costs in many ways. First, you can get an engine replacement under warranty. Secondly, engine replacement doesn’t push up your insurance premiums.

New cars, however, are expensive and come with other expenses. You will need to pay for vehicle registration as well as increased insurance premiums. So basically, buying a new engine is an efficient way of saving costs. If, however, the entire car is close to the end of its service life, you may need to retract. A new engine won’t help it perform better in this case.

How long does it take for a new engine to settle?

How long an engine breaks in or settles depends on the application—check your owner’s manual. But as a general rule, you should let your engine settle for at least 500-1500 miles before speeding things up.

By settling down, we mean allowing your engine to get used to the car and other components before testing its limits. New engines are delicate, so it would take time to get used to your application before working to its optimal capacity. So for the first couple of miles, you would need to take things easy.

It is recommended that during the break-in period, you should not exceed 4000rpm, idle for longer periods, maintain a certain speed for too long, etc. While driving normally during this period might be tiring, it’s a good way of enhancing performance and prolonging engine life.

Is it Ok to buy a car with a replaced engine?

It is OK to buy a car with a replaced engine. But ask yourself, where did the engine come from, and who did the installation? If the engine is new or just fairly used with the installation done by a professional mechanic, it’s a good buy. If the replacement is new or, say, a fairly used engine, it means that the engine has recorded less use than the OEM, and therefore, there are chances it will last longer.

If, however, the installation was done by an amateur with the engine gotten from a junkyard, then reconsider. Engines from such places are usually too used and won’t last long, even if the installation was done correctly. So ideally, you would need to check the condition of the engine.

If you can’t, have a professional check the car to ascertain the condition of the replacement engine. These people have the right knowledge and tools to do this. Lastly, aside from the engine, you may also need to assess the condition of other components. If the engine was replaced, chances are that other components may also need replacement.

Does replacing an engine devalue the car?

Whether or not replacing an engine will devalue a car depends on certain variables. A used car with an old engine will sell for less than an old car whose engine was replaced. This is true because the new engine does not have wear like the old one. However, if the replacement engine is old and doesn’t run efficiently, the car will lose its value.

However, understand that a car losing its value it’s not only dependent on just the engine. So if you’re trading a car with a replaced engine, you may also need to consider other things. What kind of replacement engine did you use, and what is the engine replacement cost compared to the overall car cost? How much is the vehicle sold at with or without a new engine?

You may also need to consider the overall condition of the car. A car whose components are already failing and close to its service life will still lose its value even with a new engine. Generally, a new car engine will not devalue a car. The overall car condition will determine if the car has lost its value or not.

Does the miles reset with a new engine?

No, the miles do not reset with a new engine. Your odometer, which records your car’s mileage, is not connected to the engine but to the front wheel hub. So there is no way the odometer will reset after an engine replacement.  If the miles reset, then someone must have reset it manually.

Generally, the odometer helps record how much you’ve traveled, and altering this is illegal in the United States. Through the odometer, you can track when certain things were done in your car—oil change, wheel alignment, etc. So if you’re replacing your engine, you should record the miles at which the engine was replaced. This will give someone an insight into what they are getting if, eventually, they buy your car.

Say you’re trading a car with a replaced engine, and a buyer wants to know how much mileage the new engine has recorded in two years. All you need is to deduct the mileage at which the engine was installed from the current mileage.  So you see, vehicle owners know the importance of recording miles and, therefore, won’t let your miles reset with a new engine.

How do you drive a new car engine?

Typically, cars with a new engine have a break-in or settling period, usually between 500-1500 miles. So while you may be urged to test the new engine’s limit, you need to take it easy. In this period, you must drive your car a certain way to avoid engine wear. So how do you drive a new car engine?

During the first 500-1500 miles, keep your RPMs below 4000, so the engine can break in properly. After this, you can increase your RPM gradually. Secondly, do not maintain a certain speed for too long; drive at changing speeds even if you’re on the highway. This allows your pistons to seal correctly, minimizing premature engine wear. Thirdly, avoid idling for longer periods.

Fourthly, try to change gears at lower RPM and accelerate gently. Avoid short trips since they don’t let the engine warm up properly. Also, avoid towing heavy loads. For safety, try adjusting your driving styles because aside from the engine, other components like the tires, brake pads, and suspension also need to settle in. While doing these may look tiring, they help boost fuel economy, performance, and engine lifespan.

Does replacing an engine affect the transmission

The engine is directly connected to the transmission. However, while replacing an engine isn’t supposed to affect the transmission, something may have been done wrongly. This is true, especially if the transmission and engine assembly was removed during replacement. Chances are they may not also add the transmission fluid back to the transmission.

The most grievous damage would be damaging the transmission pump by not properly lining it up before putting them together.

If the above is true, some transmission problems after engine swap you may encounter include car jerking when trying to accelerate. You would also be unable to remove the car from gear.

Because of a stuck gear, no matter how much you press the gas, the car won’t move; instead, it will keep reviving. So if you keep experiencing these after an engine swap, you may need to take your car back to the mechanic that did the swap unless you did it yourself.

Final Words

This article has highlighted and offered solutions of common problems after engine replacement many car owners face. These include weird noises, excess smoke, fluid leakage under the car, engine running rough, engine losing power, etc. All these problems stem from underlying issues with the vehicle parts before the engine swap.

So even after replacing the engine, you will still face these issues if these faulty components are not fixed. Some of the things to check and possibly replace include air and oil filters, water and fuel pump, thermostat, hose, etc. You risk damaging your new engine if these components are not fixed before driving your car.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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