Used car shopping: 6 tips for checking the engine

Arif · Aug 15, 2020 07:00 AM

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So, you want to buy a used car. Maybe it’s a project car, a unique car model you’ve always wanted, or a car model that’s not sold brand new in Malaysia. If your reason for buying a used car is a tight budget, you might want to consider other options like public transportation or a motorcycle.

If you’re still here after reading that, we assume you’re serious about this, regardless of your reasons. Well, there’s a long list of things to look out for when buying used cars. In this article, we will be focusing on checking the condition of the engine.

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How deals were closed pre COVID-19 era. Colourized.

Now, before you make an appointment to have a look at the car, MAKE SURE YOU ARE READY TO MAKE AN OFFER. Nobody likes time wasters. Study the market value of the car and know the price you want to offer. Be fair and respectful to the seller. If you’re just casually browsing, don’t waste the seller’s time with an unnecessary “inspection”.

Let’s get on with it.

1. Make sure details on the VOC and the car match

The VOC is the Vehicle Ownership Certificate (Registration Card or Grant). For the engine, you can check the engine number and chassis number on the VOC.

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What can we see from the VOC?

The chassis and engine number. Check if they match with the numbers on the car. If they don’t, there’s a good reason for it. Sometimes the engine head may have been replaced. Sometimes the entire engine has been swapped. This happens for a reason. 90% of the time, the engine has been damaged and fixed.

2. Start the engine (cold start)

If you can’t start the car, it’s usually better to walk away from the deal. The seller might be trying to hide some serious issues that the car has.

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There’s no point in negotiating when you have a vague idea of the condition of the car. There are several possible reasons why a car doesn’t start:

- A blown starter fuse (easy fix)

- A broken starter relay (easy fix)

- A broken starter (moderate difficulty fix); price depending on car

- A weak battery (easy fix)

- The transponder in the key is low on battery (easy fix)

- A faulty fuel pump (moderate difficulty fix); price depending on car

- A clogged fuel filter (moderate difficulty fix)

- Faulty spark plugs (sometimes they’re just loose) (easy fix)

- The car has no fuel (super easy fix)

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If it’s a bad starter and the seller says it’s the only thing you’ll have to fix, it most likely is not the only thing you’ll have to fix. Unless you start the engine, you are unable to diagnose some vital things about the car.

The car will behave differently in cold and warm conditions. It’s usually harder to start in cold.  A good car (in Malaysia) should have no problem starting at all.

If the engine starts with one kick, great.

There are more things for you to check…

3. Check the engine bay as the engine is started

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If the engine twists violently as the car is started, it might be a case of a broken engine mount. Use a torch light and look around the engine bay for leaks and listen carefully for irregular noises.

4. Check the exhaust smoke 

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If it’s blue-ish smoke, it means the car is burning some engine oil. Not good. It might be worn out piston rings, worn out valve seals, or even a head gasket failure. If it’s puffing white smoke, that’s also not good. It could be a head gasket leak.

5. Let the engine idle

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1,500 rpm is a high engine idling speed. Wait until the engine gets warm to see a base idling speed.

A constant high engine idling speed could indicate problems with airflow into the engine or problems with the idle air control valve. Standard engine idling speeds are around 1,000 rpm. Usually the supposed engine idling speed is written on a sticker under the hood.

An unstable engine idling speed could be a sign of a faulty Mass Air Flow (MAF) sensor. Smaller engines (3-cylinders) may rev higher initially but will come down to the designated engine idling speed after a while. The idling speed is regulated by the idle air control valve.

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At the same time, check the radiator fan. The fan is part of the car's cooling system. It usually kicks in when the water temperature reaches 87°C to 89°C. If it doesn’t turn on, it could be a faulty fan motor or a faulty fan motor relay. Not a difficult fix.

6. Turn the engine off and check the engine oil

Make sure the car is parked on level ground. If the car is parked at a weird angle, some leaks can be harder to spot. Check underneath for leaks. With minimal tools, you can check the colour, texture, and levels of the car’s fluids.

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Sludge on oil fill cap. Possible head gasket leak. Bad. Photo:

Check the engine oil fill cap. Check for sludge (Sludge indicates possible head gasket leak). Check the dipstick. Make sure it’s between the minimum and maximum levels. If it’s below minimum, bad.  If it’s above maximum it could be the seller is trying to hide a case of leaking engine oil.

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Metal shavings on the dipstick. Not good. Photo:

Check for specks of metal or froth on the dipstick. If you find any of those two, walk away from the deal. Specks of metal indicate that the engine is already eating itself away. Froth or foam indicate water contamination (and many other possible serious issues with the engine).

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Froth on the dipstick. Froth is only good for teh tarik and beer. Not in engine oil. Photo:

Check the coolant fluid for colour, texture, levels, and leakage. Make sure there is no oil or sludge in the coolant reservoir (Possible head gasket leak).


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In summary, those are the 6 rather basic things concerning the engine that you can check for before purchasing a used car. There are more areas that we will discuss in the future to help you with your next purchase and perhaps give you some added confidence.



Previously an engineer in an automotive manufacturing company and a highway concessionaire. A part-time research student on biofuels and diesel engines. Obsessed with vehicle electrification and the future of transportation.

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