Updated date:

How to Mechanically Check a Used Car Yourself Without Tools. And Then How to Negotiate to Buy The Car Cheaply

Checking a car out isn't difficult. Here's how to check the engine and transmission plus bodywork

how-to-mechanically-check-a-car-out-before-buying

Preparation

Before buying a car it's critical that the car hasn't been started and warmed up. So if you see a car that interests you, and you want to check it out, phone the advertiser and make an appointment, but say to them, please don't start the car before I arrive. I'd like to check it out when it's stone cold.

The reason for this is that when cars are cold they may, for example, be difficult to start. But also it's an ideal time to check the oil. When cars are warmed up the oil level changes. Also engine rattles can disappear. Transmissions run fine etc - when everything's cold all is revealed.

The only tool you'll need in your kit is a torch and pen and paper.

Also, so as not to waste your time. When you first make the appointment to view. Ask for them to please have all service records available. I've sometimes forgotten to ask this and being held up forever with 'I'm sure Bob put them in this draw, but they're just not there." Service records are really important for a genuine car.







The 20 Point Checklist

  1. Engine oil
  2. Engine oil color
  3. Engine/Transmission leaks
  4. Coolant level
  5. Checking rubber cooling hoses
  6. Head gasket
  7. Power steering oil level
  8. Battery
  9. Timing belt/ Timing chain
  10. Hoses
  11. Auto Transmission
  12. Starting the car
  13. Suspension
  14. Steering
  15. Clutch
  16. Transmission synchromesh
  17. Brakes
  18. Handbrake
  19. Exhaust
  20. Rust

So, we'll check these off one by one. With your pen and paper, take a note and mark them out of ten. Ten being the best.





Engine Oil Dipstick

how-to-mechanically-check-a-car-out-before-buying

Checking Quantity of Oil

As in the photo above, all cars have an engine oil dipstick to tell you how much oil is in the engine. It’s always best to check this while the engine is cold. At that time all the oil is sitting in the engine sump and that’s where the rod with the indicator level is sitting. If the engine’s warm or hot, oil is transferred all around the engine, as it should be, so the indicator at that point is inaccurate.

All cars have a dipstick. Older cars just have a rod with a bent loop but newer cars have a stick like in the photo with a plastic handle that may be yellow, red or green but it will be prominent and sticks slightly out of the side of the engine.

Have a small tissue or cloth ready and slowly pull the stick out. At the bottom 6 inches of the stick you’ll see the oil. Wipe that off with your tissue and you’ll see two marks on the stick. One is for minimum oil level and the one closer to the plastic handle is the maximum oil level. Take a note and put the stick fully back into the hole again. Give it a twist to make sure it’s fully inserted. Then withdraw it again and see where the oil level is.

If it’s under minimum this should throw out a red flag. It likely means the car hasn’t been serviced regularly – but this needn’t be the end of the world.

If the car has done a fairly hefty mileage - say 120,000 miles plus, then it likely will burn through a bit of oil and needs more top ups than newer cars. If the car is cheap enough, well, if you have to tip a pint of oil in every six to eight weeks, it’s not that much money.

Engine Oil Color

how-to-mechanically-check-a-car-out-before-buying

Checking Engine Oil Color

Next take a look at the oil color on the stick. If its blackish then it hasn’t been changed for some time, or, there are issues internally with the engine. If the oil is transparent then that’s great. That’s how it should look. But if the oil is transparent and also at the minimum level, I’d be worried. To me that’s saying oil is getting burnt out the back, or, it’s leaking like anything out the bottom or the side of the engine.

Engine Oil Leak

how-to-mechanically-check-a-car-out-before-buying

In the photo the sump is the lower part of the engine, featured here in silver

how-to-mechanically-check-a-car-out-before-buying

Spotting Engine Oil Leaks

Reverse the car a few yards and turn it off and have a look at the ground where the engine was above and see if there’s any oil lying there. As the car’s been cold, it’s likely the car has been sitting there for at least a few hours if not more. Obviously the preference is for no oil leaks at all. A few drops is acceptable. A pool of oil of say 4” square, I’d walk away from the car. That’s quite a loss of oil and will only get worse. While driving it you could literally run out of oil, unless you’re regularly checking it, and the cost of that will be a blown engine.

If, however, it’s a few drops, grab your torch and get under the engine as much as you can to see how wet it is underneath, or, on the sides of the engine. This can just be a sump gasket leak if it’s a few drops. That’s an easy and quite cheap repair. Generally in the region of $120.00. If the engine is wet with oil above the sump then it’s coming from somewhere else and could be expensive to repair.

Coolant Level

how-to-mechanically-check-a-car-out-before-buying

Checking Coolant Level

The Coolant tank should be obvious when you open the hood. It should be on the right side up by the windscreen and be quite a large prominent plastic clear tank. The coolant fluid is generally green can also can be a reddish color too.

The level it should be is usually a plastic indent on the tank. It will show its minimum level.

Older cars don't have coolant tanks but radiators right in the front of the engine. They're a large tank that go nearly between each headlight and down deep - more than a couple of feet. The car should be cold, as advised when you're first checking it out, but if the car has been warmed up and it does have a radiator here's a safety waring. Don't open the radiator cap until it's cooled right down. Many many people have undone that radiator cap and got a face full of boiling water.

So, if the car does have a radiator and no coolant tank and it's cold, unscrew the cap. Ideally, colored coolant should be visible. If there's none to be seen, be wary, either the owner has neglected to check this and it's run down, or, the car has a leak somewhere in the cooling system.

how-to-mechanically-check-a-car-out-before-buying

Checking rubber cooling hoses

Take your torch and have a look at the larger black rubber hoses around the engine. There's not that many of them so it won't take long. Look more towards the end of them where the retaining clips are. This is normally where thy can develop a split which will lead to pressure loss and therefore coolant loss. If a split isn't visible you may still see a dry fluid mark, whiteish in color that tells you there is a leak in that hose.

Also give the hoses a squeeze. They should be quite firm. If they're soft then they'll need replacing. This is only a minor expense. Perhaps $30 a hose at most. You could usually do this yourself but you'll have to look up how to do this. It's not tricky but you have to get rid of all air bubbles in the system. Best to look this up on the net.

Head Gasket Check

The head gasket fits over the engine block and seals up with the cylinder head. If the engine becomes overheated it's usual that the the cylinder head will slightly warp with the heat and then a pressure leak will develop in the gasket. This causes coolant loss.

An owner who has had this problem will have seen his temperature gauge rise alarmingly as the car runs right out of coolant. This almost always happens in urban areas when traffic is crawling, as that's the time when the car doesn't get any added and natural cooling through the front grill when moving at speed.

Many cars get sold with this condition. The only way to repair this problem is to remove the cylinder head/s and install a new gasket. On some cars this is a full days work.

So the owner will sell the problem to someone else, simply by refilling with coolant and knowing that during the test drive, if from a cold start, the problem won't appear until the coolant gets hot, and that's unlikely for the first 20 minutes.

However, there is a simple test for this. Take the cap off the coolant tank and get someone to start the car. Watch the coolant very carefully. Get the person to rev the engine from 1000rpm to say 3000-4000 rpm. If the head gasket is blown (mechanical terminology for needing a new gasket) the coolant will start to bubble when revved. Also look for white smoke coming out of the exhaust. This will happen under revving when the engine is warmed up.

Unless the car is going incredibly cheaply - If you've got a blown head gasket and you can't repair it yourself - I'd walk away. Gasket repairs can be anywhere from $500 -$1500.

Power Steering Fluid

how-to-mechanically-check-a-car-out-before-buying
how-to-mechanically-check-a-car-out-before-buying

Power Steering Oil Level

Look for a small reservoir on the top and at the front of the engine with the strange round cap. This is the power steering reservoir. Undo the cap and you'll find underneath the cap is a mini dipstick. This shows the minimum and maximum oil levels. Wipe it with a cloth or paper towel and dip it in again to read the level. Take a look at your cloth and check the color next to the photo above as to the age and quality of the fluid.

Car Battery

how-to-mechanically-check-a-car-out-before-buying

How to Check a Car Battery

First thing is to find the car battery. It will either be on the left or right side of the engine, but more likely to be in the trunk.

Modern car batteries have a much longer life than batteries from decades ago. These days they have to power quite a bit more stuff too like computers that weren't around until the late 1980's.

The real test for a battery is starting the car. But you really want to hold that off until you've done your 20 point check. But when you do, if the battery is in good condition it will crank the car engine over quickly. If it's slow to start then the battery is old and likely on its way out.

So, get your torch and take a good look at the battery. They generally have a birth date on them so you can see how old it is. But it also should look good. If it has any spillage by the terminals or down the sides, it likely has a crack in it and it's leaking fluid. Also look for bulges in the plastic casing. They shouldn't be there.

New batteries aren't the end of the world - $90-$200.

how-to-mechanically-check-a-car-out-before-buying

Checking the Timing Belt

The timing belt is critical. It's what drives the camshafts on the engine. Its flexible rubber with teeth as in the above diagram. If it breaks it can in an instant cause enormous and expensive damage.

Most US and European manufacturers BMW, Mercedes etc run with timing chains not belts. Chains mainly last the lifetime of a vehicle. Generally the chain tensioner should be checked every 150,000 miles and that's that. If the tensioner needs tightening you can usually hear a little knock in the front of the engine when its idling indicating this. Being a chain they're heavier than a belt of course. Tensioner's are not expensive or difficult to tighten up.

But getting back to timing belts. Most Japanese manufacturers use them. They're generally not visible and unlike a chain you won't detect any noise if there's an issue with them. If they're old they'll snap without warning.

It's recommended by manufacturers to have them replaced about every 60,000 miles, but most service garages will recommend every 50,000 miles to be safe.

The cost is generally around $500.

You can check them with aid of a Phillips screwdriver and taking off the front plate but I wouldn't bother. Normally service dealers will write somewhere on the engine in indelible ink at what mileage they've replaced the belt. If its not there then ask if it's in the service receipts of the car. Be very cautious about this one. If the car has done close to 50,000 miles then this is definitely a negotiating issue if it hasn't been replaced. If the car has done 65,000 miles plus it's very definitely a negotiating issue and if you do buy it I'd very carefully drive it to the nearest garage for replacement. If the owner says he's done it himself, then get him to take some plates off to prove it. Feel and look at the teeth on the underside of the belt for new depth. An old belt these will be well worn.

Coolant hose

how-to-mechanically-check-a-car-out-before-buying

Checking the Coolant Hoses

Check the coolant hoses on the radiator and coolant tank for softness. Only do this for safety sake when the car is cold. Squeeze the rubber and see if there are cracks along the way. If so they may not be leaking yet but it's a matter of time. They will need to be replaced. Take a look at where they connect to the radiator and coolant tank where the hose clips are. There shouldn't be any seepage here - it will be a whiteish color if it is leaking.

Hoses are not expensive but if they fail in a traffic jam for the sake of $15-$20 spent if you don't see your temperature gauge on red hot you can destroy your engine for the sake of so little money.

Auto transmission selector

how-to-mechanically-check-a-car-out-before-buying

Checking Auto Transmission

Okay now it's time to turn the car on from cold.

Right so, before checking certain things in the engine, turn the car and fire it up. Wait about 15 seconds for the engine to settle down. The engine should be smooth by this time. If it's a good engine there will be no vibrations that you can notice or hear. If there's vibration, then the engine is running rough. Not a good sign but possibly easy to fix too.

Now put your foot on the brake if the car has auto transmission and while keeping your foot hard on the brake, switch the gear shift selector into reverse. When you hit reverse there shouldn't be any hesitation, you should immediately know you're in reverse. But, also the rear of the car should only rise a very small degree. If it lurches up, you've got an issue with the transmission. Once the transmission is warmed up, this lurching may go away but you're still left with this issue and to repair it will require an expert to pull it apart or replace the transmission. Either option is expensive.

However, if the car is going to be a cheap run around and you don't really care about its resale, then this issue won't get too much worse over time. You'll find the forward gears are usually fine so if you can bring it to the sellers attention you should be able to knock the price down a lot. As I said, once warm this reverse gear issue usually doesn't appear again anyway.


Starting the Car

Okay, now the car's running you can check a few things under the hood while it's warming up.

First thing is to listen for a ticking noise inside the engine, or, where it appears to come from. If you hear a reasonably loud ticking noise almost like a loud clock - walk away. You've got piston damage internally and the engine can go at any time.

But, this shouldn't be confused with a ticking noise at the top of the engine. If the engine has done a fair mileage then this ticking (sorry, I know this sounds confusing - but the ticking at the top is very different). The ticking at the top is likely to be what's known as tappet noise and can be corrected quite easily by a good mechanic. He may not get completely rid of it as it may have worn valves, but he should be able to quieten it right down. However, you should ask some questions to the seller about this. How to make certain it's the tappets is to borrow if possible if you haven't got one yourself, a long screwdriver from the seller and use it as a stethoscope by placing the sharp end on the top of the engine while the engine is idling (be careful of moving parts like the front fan and belts) and the other end on your ear. It should be quite distinctive.

Also check for noises from the moving belts. Make sure there's no squealing from them. Get inside the car and turn the steering from lock to lock fast while listening to sounds under the hood. If the belts and power steering are okay there shouldn't be any added noise.

Suspension

Turn the car off again. The suspension is better tested while out on the road, but first take a long look at the car while standing back, from the front, back and each side. The car should be even all around in height. If it's slightly dropped on one corner then that'll likely be a suspension issue on that corner. It may or may not be an expensive issue to fix. It also could be an indicator of rust on that corner, which could be very dangerous to drive and very expensive to fix.

Next, go to each corner and push the car up and down as hard as you can. If it squeaks, it's old and tired and will need refreshing in the suspension with new bushes, and possibly shock absorbers. Yep, can be expensive as any mechanic will tell you if you do one side for safety sake you've got to do the other side at the same time.

If you have got one raised corner more than the other corners, as I said that's dangerous. When you take it for a test drive, for your own safety don't push the car hard into corners or braking, you may end up upside down in a tree. Take it easy. It might be something simple though. If you love the car, well just get it checked out properly to confirm.

Steering

how-to-mechanically-check-a-car-out-before-buying

Steering problems

So now the car's warmed up and you're off for a test run. First test for the steering is find a smooth longish road. Get up to a cruising speed - say 50mph and keep it steady there. Now just slightly take your hands off the steering wheel maybe say an inch or two above it, so you can grab it quickly if you have to.

While the car is steering itself, does the wheel move either off centre say slightly to the left or to the right? The car should be going deal ahead - but to be fair to this test there should be no camber, so the road should be even and no bumps.

If it's moving to one side or the other it may be something easy to fix - your tire shop is likely to have a machine that they can replicate this problem on called a wheel alignment machine. They'll put it up there and adjust it to run straight again.

But, it could be caused by the car been in an accident and the chassis has been bent on one side. If you like the car, take it to the wheel alignment place and they'll be able to tell you pretty quickly if this has been the case. Depending on the severity of the accident they may or may not be able to fix it. If not, a panel shop will likely have a chassis straightener that can do this. At this stage you'll be spending dollars. If the car's cheap enough to warrant this go for it, otherwise I'd walk away. You might be opening up a can of worms.

Another test while you're out there is to see if there's any vibration from the wheels/tires. You can do this from a standing start on a long straight road. Slowly ( and I mean slowly) build up speed all the way to say 60mph or more if it's allowed. On the way see if any vibration comes through the steering. It usually happens like this - you'll get to say 40mph and at a steady speed there you may get a constant vibration, but by taking it up to 50 or 60 mph, the vibration ceases.

What it is likely to be is a wheel that needs balancing ( one for the tire shop and not expensive - $15-$20) or, it could be a faulty tire. If it's a faulty tire the vibration will likely be constant right through the speed range. If that does happen, I'd pull over and check all four tires for safety before continuing. Check to see if any of them has like a bubble coming out the side. If so, I'd slowly drive it all the way back. That's a soft spot and could blow out on you.

Of course, it could be a tire that's a lot flatter than the others. You should be able to visibly see this. Go get them all pumped up at your nearest garage and continue. But if one is pretty flat check it again before returning in case you've got a puncture - which you likely have, even if it's a slow one.

One more thing, apart from a suspension problem it could be a warped or damaged brake disc. That could have been caused by the seller wacking it into a kerb at speed. That could be expensive to repair as all sorts of things might need replacing along with a whole new brake disc.

Clutch Pedal

how-to-mechanically-check-a-car-out-before-buying

Checking the Clutch on a Manual Transmission

If the car has a manual transmission and you're on your test drive. Here's how to test if the clutch is okay. Make sure you test the clutch when the car is cold and also at running temperature.

First, unless it's a performance car, it shouldn't be heavy to push in.

When you first start the car, deliberately push the clutch in slowly, listen carefully for any noises on the way. It should be free of any noise whatsoever.

When you slip the car into first gear the clutch shouldn't 'grab' grabbing is when it suddenly catches and you have little control over its smoothness. You should be able to control the clutch and make a smooth take off. Without wanting to sound discriminatory, older people are generally the worst for clutch problems. They tend to just ride around town and keep their foot resting on the top of the clutch in case of emergency. That heats the clutch up and that's when all those issues happen - noises and grabbing. If the car has those issues, you're in for a new clutch. Bank on at least $500.



Manual Transmission

how-to-mechanically-check-a-car-out-before-buying

Checking Manual Transmission Synchromesh

Make certain to be sure that you check the manual transmission synchromesh while the car is started when cold and also at running temperature.

Synchromesh wear is when you change from gear to gear and there may be a grouching feel and sound.

You're unlikely to feel it going up the gears but if they're worn you will hear and feel it going down the gears. The transmission will be reluctant to select the gear you decide.

Mostly this will be second gear as it's the most used car in town on a car with manual transmission.

A performance car is very likely to have these problems as it's likely been driven hard. Italian cars are notorious for worn synchromesh, because they're so much fun to drive. Old people with manual transmission are also suspect as they tend to get a bit lazy and not use the clutch or have the for muscle for the clutch.

You should test when warm and use the gearbox as hard and fast as you can changing up through the gears and down through the gears.

If you've got worn synchro's that means gearbox out and then generally a replacement gearbox put back in. Much cheaper than having the synchro's replaced. Bank on $1000 plus.


Checking the Brakes

So, you're on this long straight road still. You want to be doing about 30mph as that's a relatively safe speed if anything strange happens. Now if you've got anyone else in the car with you make sure they've got their seatbelt on and warn them that you are about to test the brakes on a very sudden stop. Look behind you to make sure that no other car will be about to pile into your trunk on this test.

Count down for the sake of your passengers. 5 4 3 2 1 and now bury your foot hard onto the brake pedal. If the car lurches slightly off centre - to the left or right, immediately take your foot off the pedal - you'll be in danger of losing control.

With your foot hard on the brake if you feel a strange vibration, that's normal if the car (and these days even older cars are likely to have this) has ABS which is an anti lock braking system. It's designed through the software on the cars computer to pull up straight - especially in wet conditions if you hit the brakes hard and it will help you not get into a violent skid.

If you stop even with a squeal of tires in a straight line then all sounds good. If the car goes off centre you've got one brake working well and another on the other side either worn or not catching at the same time. That's going to be a repair. If it's brake callipers - maybe $200. A new disc - about the same. Brake pads - $100-$120. Although the mechanic is bound to say - we have to do both sides to be sure even though one side seems okay. So, you can double these prices.



Handbrake

how-to-mechanically-check-a-car-out-before-buying

Checking the Handbrake

Firstly, the handbrake should be working when you pull it up a distance of say 4-6 inches. If it doesn't work until it reaches about 8 inches. It requires adjusting. That can only be done at the rear wheels. Not expensive for a mechanic to do it. Maybe half an hour labor only.

If the car has a manual gearbox, then as a safeguard the handbrake is quite critical. On a step hill you can still use first gear when parking it to act as a brake but if it got a tap from behind, it could jump out of gear and if the handbrake is ineffective well your car is off on a trip of its own.

A car with automatic transmission the handbrake is not as important as generally the car has 'park' in it selection range to act as a secure handbrake even parking on a steep hill.

On your test drive if there are any hills at all in the vicinity you might like to park the car and test the handbrake out by leaving the car running and keep your foot on the foot brake, then pull the hand brake up, release your foot off the foot brake and see if the handbrake is working effectively without the car creeping forward.

Checking the Exhaust for different Colored Smoke

how-to-mechanically-check-a-car-out-before-buying

Checking the Exhaust

Best when you're ready to start the car from cold, get someone else to start it for you. Maybe the seller or a friend. Not too important.

Before they turn it over, so to the rear of the car and fix your eyes on the exhaust. Get them to start it and give it some quiet revs on the accelerator. Not hard revs at this stage. When an engine is cold you've got to let it warm up slowly. Revving hard straight away is never good for an engine.

Okay so what you're looking for is the color of the exhaust smoke (if any). If blueish color smoke comes out that means the engine is burning oil. I'd pretty much walk away at that point unless you want to go to the expense of reconditioning or replacing the engine. Be prepared to pay around $3000-$4000 if that's the case and you still want to buy it.

If quite a lot of grey smoke comes out that is likely to mean the car has a blown head gasket (as discussed earlier up the top). This is serious too. The owner has run dry of coolant and could have warped the cylinder head. Bank on $2000-$3000 to fix if this damage has been done.

But if the car is fairly much free of colored smoke, well that's a great sign.

One more test though that won't show up until the car is warmed up. When you're out test driving it, periodically look in the rear view mirror while either revving it, or, accelerating. See if there's any smoke you can see then. This could be still burnt oil coming through, or, if the car has mostly had city miles and running it could be water trapped in the exhaust silencer, that is now hot and turning that water to steam on the exit. That's not a bad thing but the end result, unless it's a stainless steel exhaust system, is that the water will eventually corrode through the silencer and that will require replacing - $200?

Looking for Rust

Checking for rust in cars is difficult. A lot of it depends on where the car is and its history. If it's been by the sea well I'd get a specialist to put it up onto a hoist and thoroughly check underneath. All these States put salt on the road in winter:

Connecticut, Delaware, Illinois, Indiana, Iowa, Kansas, Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Nebraska, New Hampshire, New Jersey, New York, North Dakota, Ohio, Pennsylvania, Rhode Island, South Dakota, Vermont, Virginia, West Virginia, Wisconsin.

If the car is located in any of these states or has been - you've got to have it checked out underneath. Salt kills them. They may look fine in the body and you can't see any rust anywhere, but if it's attacked the suspension points or chassis in any way that's going to be dangerous.

You might be fine. Some owners are fastidious in those states knowing the damage it can cause, so will thoroughly clean it, or, they don't drive them in the winter. So it could be good. But just be wary.

Rust can also be caused by leakage from the battery. Batteries are usually hidden in one side or the other in the boot. Take a torch and check this out. Usually these days batteries don't leak like they used to but you never know until you've checked.

Rust repairs are incredibly expensive. Examples are insurance companies. Even with brand new cars, if there's flood damage - they just write a car off their books, they don't even try and get them cleaned up, as it might come back to bite them later on.

how-to-mechanically-check-a-car-out-before-buying

How to Negotiate on the Car

Okay well now you've done the 20 point mechanical check. One thing you have done is impressed the seller with your knowledge. If he had anything to hide, it may still be there, but if you've carefully checked, then that's doubtful. At the least he'll think you're very knowledgable.

Out of the 20 points you may have picked up a couple of things which aren't that serious and you can either still keep driving the car or get it fixed, but you can use any faults to drive the price down.

Buying the car with large faults is up to you. If it's a great classic car that's value will go up then if the engine's about to fall apart and you can knock $5000 off the price, it still might very well be worth buying.

But if it's like a 5 or 10 year old Honda etc, be wary what you pay for a car with faults. All modern cars are on a price slide downwards. If that's what you're after any major issues, unless the car was an absolute bargain to begin with and you can still knock a lot of money off it - I'd walk until you find a better one.

But hopefully this 20 point mechanical guide will be some help and save you money having to drag a mechanic along.

Related Articles