Should You Buy a Car With a Replaced Engine? (Full Guide)

Many people send us emails asking should they buy a car with a replaced engine. And what are the common problems after engine replacement? The answer to these questions really depends on the situation. So, let’s elaborate.

If the car has a replaced engine does not necessarily mean that this is a bad car. On many occasions, it is a much better idea to purchase a car with a replaced engine than a car with a high-mileage engine.

I’ve been in this situation before, I have purchased a Mercedes CLK 230 Kompressor with a replaced engine and I don’t regret it. Mainly because I got a vehicle with a low-mileage engine. And the engine itself wasn’t the problem of that car, the previous owner was.

But there are also some common problems after engine replacement, especially if the engine that was installed in the car isn’t new or if the person swapping the engine doesn’t know what they are doing. Let’s cover those problems.

Common Problems After Engine Replacement

Now that we learned that getting a car with a replaced engine is not a bad idea, we can move on and cover the common problems after engine replacement.

There are some problems that can pop out after you do an engine replacement. This is why it is worth covering them in great detail. So you get the perspective of what to expect.

The Engine Doesn’t Want To Start

One of the first problems when you install a new engine is ignition problems. Small electric or ECU problems can cause permanent or intermittent ignition problems.

Many people think that installing a new engine is a really straightforward thing. They install it without caring much about how they connect things and leave some things behind. Especially beginners who are doing engine swaps at home.

For an engine swap, you need to take a lot of things into mind in order to make this a successful job. For example, with older engines, you need to know how to set up the carburetor in order for the engine to work correctly.

This means that you need to adjust the carburetor manually. And this is something that not a lot of people these days know how to do. So, it can be tricky.

For modern engines, it is a similar story. The engine carries a lot of sensors and equipment and if you don’t connect everything correctly to the engine’s wiring harnesses, the engine will not start. The electronics and coding in the new engine is the main challenge.

When buying a car with a replaced engine, make sure that the engine of the car you’re buying was replaced by a professional.

Strange Noises Appear

Another very common problem on our list of common problems after engine replacement is strange noises. Stay with us, we know this sounds silly.

Engines are usually replaced due to high mileage, poor maintenance, or because the engine in the car had problems straight from the factory (it’s more common than you think). Make sure that before you buy a car with a replaced engine, the seller tells you exactly why the engine was replaced.

Make sure the new engine doesn’t already have symptoms of a rod knock, lifter tick, timing chain rattle, or improper valve adjustment, all these issues will trigger different kinds of noises.

In most cases, these noises indicate a problem with the new engine. So, if the noise comes from inside the engine, it means that the new engine has problems.

But there can be noises if you don’t install the engine correctly. There can be exhaust leaks if you don’t tighten the bolts at the recommended spec. So, hissing noises can be present if you don’t connect the exhaust in the proper order.

Check Engine Light

The check engine light is a common culprit with cars with a replaced engine. The check engine light for those who don’t know is a special light that tells you that you have a problem with the car’s engine.

The cause for the ignition of this light can only be diagnosed with a special OBD2 scanner tool. With this tool, you can read the trouble codes that are reported by the computer, and every modern diagnostician should have one of these scanners.

Nevertheless, this check engine light is often triggered because something in the process of engine swapping wasn’t done right.

If everything is good and plugged in properly. The only way around this problem would be to diagnose it with a scanner and move on from there.

Maybe one of the sensors is not working correctly and is reporting codes, or there is something else wrong with the engine, anything is at play. So, proper diagnosis is key in this case to uncover the problem correctly.

Unusual Smoke

Another on our list of common problems after engine replacement is the smoke that it develops.

Usually, every new engine that is installed produces a cloud of smoke when you first start it up. Many people are scared and think that this is something really bad, and the engine is broken.

But this is not the case, everything is normal, and the engine can smoke for a while but eventually, the sensors will start functioning properly. The engine’s air-to-fuel ratio will adjust and everything will get back to normal after a couple of minutes.

So, don’t immediately panic if the engine starts smoking after you fire it up for the first time. It doesn’t necessarily mean that it is bad.

But if the engine keeps on smoking, there might be a problem with the carburetor if it’s an older engine, and you will need to learn how to adjust it.

Or if it’s a newer engine, there could be a problem with the sensors and the wiring harness. Something might not have been well connected and this is happening because of that.

Rough Engine Idle and Operation

Rough engine idle is also common on replaced engines. The engine will start up and usually works pretty roughly.

It will not be happy at first, and it could turn off if you don’t give it more gas. This is a completely normal thing to happen.

As we noted, the carburetor if it’s an older engine has to be adjusted, as well as the ignition timing.

If it’s a newer engine, the engine should adjust its work automatically with no issues whatsoever if everything is plugged in properly.

Fluid Leaks

Fluid leaks are also common after engine installation, especially if on the engine there were some modifications done. If some seals have not been installed correctly, there can be oil leaks.

Also, if the cooling system was not bolted on correctly, there can also be coolant leaks coming from the hoses if there are loose clamps. Make sure you check everything over, twice!

Loss Of Engine Power

Engine power loss was also noted, especially on older classic engines that people know how to install but don’t know how to set them up.

These engines require an understanding of ignition timing and carburetors. So, you will need to learn how to do these things in order to get the most out of these engines and not deal with power loss and frequent drops in power.

How To Check If The Car Has A Replaced Engine?

The easiest way that you can check if a car has a replaced engine is to grab the VIN number and do a VIN check.

A VIN check will tell everything about the model you have, data like paint code, engine number, and other important information is readily available.

Another way is by looking into the registration papers of the car, if the engine was replaced, there should be information on this service being done to the car.

If you have a classic car, you need to find the VIN plate and learn how to read this VIN plate. Then check if the VIN contains the engine code that is stamped on the block.

Does Replacing The Engine Reset The Mileage?

Replacing the engine does not reset the car’s mileage, the odometer is not directly connected to the engine.

So, if you install a new engine, the mileage should be the same. Resetting the mileage is an illegal thing in 99% of the jurisdictions. So, if you buy a car with a rolled back odometer, the seller can get in big trouble with the authorities.


Overall, when it comes to whether you should buy a car with a replaced engine, the answer is yes. If the engine swap was done professionally and if the engine that was installed is low mileage, you should have nothing to worry about.

If you’re buying a car that had an engine replaced because the car’s engine has an inherent fault from the factory, make sure that the new engine in the car had that problem taken care off.

Common problems after engine replacement include oil and fluid leaks, loss of power, smoke coming from the engine, check engine light, and inability to start. Most of these problems that occur are normal unless you start to hear noises from the engine. This means that the new engine has something going on inside and is probably broken.

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