Preparing a Car For MOT

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The MOT test is a scary prospect for a lot of drivers but most of the checks the tester will carry out you can also carry out at home. Checking your car before it goes in for it’s annual test may save you money and time!

Today, we will be checking out my Mercedes W202 C240 Sport.


Firstly we are going to do the interior checks. First turn your key to the second position so all of the warning light illuminate on the dashboard.


Your SRS/air bag light should go off after a couple of seconds but the rest should stay on. If one doesn’t come on then you may have a bulb out.

Now turn the car on and they should all go ff! (the one on the right of my dashboard is the light to tell me my parking brake is on. That goes off when the parking brake is off)


Now press the horn and make sure that works.

The final check we need to do inside the car is check the seat belts are all in serviceable order. They should all look like what is pictured below. Any frays or splits threaten the strength of the belt and should be replaced ASAP!


Also just pop the belts into the buckles and release them again to make sure they are ok.

The next thing to check is the lights. Most MOT failures are on the lights which is mad as they normally aren’t that hard to change and they are a super easy thing to check. First thing to do is pop your hazards on. On most cars that hazards light switch is marked by a red triangle or is a red triangle.


Do a walk around of the car and make sure all the bulbs are working. Once they are confirmed to be working jump back in the car, turn the hazards off and test each individual side on the indicator stalk. The indicator will click fast if there is a bulb out but it’s best to manually check each bulb at this stage too just in case.

If an indicator bulb isn’t working most cars including the W202 require a PY21W/581 bulb in the front and rear and a 501a in the wings or wing mirrors.

Now we’ll do the front lights! Most cars have three bulbs (or two bulbs with the headlight having two elements) in the headlight cluster. The regular/dipped headlight:


(skill getting the indicator flash exactly right!!)

The side light which is a tiny little bulb:


The full/main/flash beam:


If any of these are gone, these are the Euro Car Parts links to the bulbs you will need for a W202:

H7 Dipped Headlight
H1 Full Headlight
434 side light

These are the bulbs that go into the W202, other cars are different though so check before buying!

At the rear each corner should have a brake light, two tail lights, an indicator and a fog or reverse light depending on which side you are looking at. 90% of modern cars also have a central brake light which, on the W202 saloon, is at the bottom of the rear windscreen and on most cars is at the top of the tailgate.

Either get a friend to press the brake pedal or check the bulb is working whilst you press the pedal.


(again with the indicator!)

Also check the number plate lights whilst you are there.


If any of the bulbs have gone here are the Euro Car Parts links to the bulbs you will need for a W202!

Tail Light Bulb
Brake Light Bulb
Number plate light

Now all the lights are sorted we’ll check the wind screen. Any visible chips or cracks should be sorted sooner rather than later before they get worse. The big issue is the window wiper though. If your wiper leaves streaks or makes a noise as it’s moving across the screen then it’s time to replace it. you can also check it manually by lifting the arm away from the screen and running your finger along the base of the rubber. If there are any noticeable cracks, bits missing or if the ends are starting to come away then it is also best to replace them.


Euro car parts do a wide range of Wiper Blades here: Wiper Blades

The windscreen washer jets also have to work for an MOT. If they don’t the most likely reason is that these little jets are blocked with dirt. To unblock simply put a pin down them to clear the blockage.


If not then maybe you are out of washer fluid which brings up to our under bonnet checks!

On a W202 the bonnet release is a red lever under the drivers side of the dashboard. Most cars have one either under the drivers side or passenger side of the dashboard or in the footwell. Some French cars have it in the passenger side door shut. There will then either be a little thing to pull out of the bonnet to open it or a switch under the bonnet that will need moving.

Once we are under here we will start with the screen wash bottle. On a W202 it’s a huge plastic reservoir  and you can clearly see how much is in there. Other cars may be tucked away. If you can’t see the level then it’s worth topping up.


Screenwash is super easy to top up. There’s no minimum or maximum to worry about so just pour it in until it gets to the top. Screen wash can be purchased from Euro Car Parts. If you get concentrated screenwash make sure you mix it with deionised water.

Other underbonnet checks are pretty much making sure all the hoses and places where the hoses connect to are dry and that all the affiliated jubilee clips are on tight.


It’s also worth checking the rocker cover gasket(s) for signs of oil leaks and the head gasket(s) for signs of coolant leaks.


That’s all we need to do for under the bonnet! The next big thing cars fail on is tyres. The legal minimum tread depth in the UK is 1.6mm. The easiest way to test your tread depth is to put a 20p coin into the tyre. If you can see the outer band then the tyre is below the legal requirement. Put the coin into tread at multiple locations around the tyre and down the depth of the tyre to make sure the tyre is wearing evenly.


Now to check the suspension. Most of your car’s suspension is held in place by rubber bushings. As the suspension moves about the components move about in their bushings. Over time these get hard or wear away which causes bits to move about in ways they shouldn’t which can have an adverse effect on your car’s handling.

The wheel and hub also spin on a bearing that can fail over time and break apart which causes a bit of wheel wobble. To test the integrity of both the bushes and inner bearing jack the car up (and put it on a jackstand) then try to rock the wheel left to right and back and forth. A little play is acceptable but any major movements should be looked at.

It’s also worth popping under the car and make sure there is no movement on the anti roll bars or any other suspension components.


At the back it’s worth checking the diff mounts for movement…


…as well as checking the CV joints (the rubber boot that mates the out shafts to the diff) for play.

Also whilst the car is up in the air it’s best to have a look over the exhaust for deep corrosion and holes. The joints between the pipes and muffler or cat are normally susceptible to rot. You can buy a stuff called Holts FG1RP 150g Firegum Tube” target=”_blank” rel=”noopener”>Firegum that you can use to plug holes in the exhaust. It’s only a temporary fix though and is no substitute for welding of a new bit of pipe or a whole new exhaust.

Once the car is back on the ground it’s time to check the brakes. Most modern cars will have a light that lets you know when the material on the brake pads is getting thin but it’s best to check it for yourself. The W202 has disc brakes front and rear. Some cars have drum brakes but I can’t comment on how they work or how to check them as I’ve never had anything to do them.

A brake pad should be at least 3mm thick. It’s the material that sits between the caliper and brake disc. 26907009_10215222050248354_1666887348790669711_n26991789_10215222049288330_7004211368901337245_n

As you can see this vehicle has plenty of life left in the pads. Ignore the dirt and surface corrosion on the discs. The car hasn’t been driven for a few days. When its taken out a couple of sharp stops will get rid of that.

The only thing that isn’t so easy to test on your driveway is emissions. If the catalytic converter is visually in good condition and the car is running alright then emissions shouldn’t be a problem but it might be worth putting a bottle of Redex Professional Complete Petrol System Cleaner 250ml” target=”_blank” rel=”noopener”>Redex through it just in case.

Then that’s it! You should be covered for your MOT.

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