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Car shop vs DIY: how much can Haynes save you?

10 Expensive Repairs You Didn't See Coming

How much money can you save by doing your own repair instead of taking the car to a garage? Car parts break and wear out, but some cost a lot more to replace than others.

We've used a 2011 2.5 liter 2011 VW Golf as an example below. Costs for other makes and models will vary of course, and labor will differ across the country, but this gives a fair idea of the parts that will leave the biggest dent in your wallet, and how much of the cost lies in the parts versus the labor – very useful information for cost-conscious home mechanics.

01 Catalytic converter replacement

1) Replacing a catalytic converter

Estimated cost: $1780-$1850 • 85% parts, 15% labor
Potential DIY saving: $277.50

Yep. Nearly two thousand bucks. Catalytic converters are designed to give us a greener planet, but you’re going to turn pretty green yourself if you have to buy a new one. The good news is that they should last the life of the car; the bad news is that running over something like an oversized speed bump can damage the cat, as can an engine burning oil, or running the wrong oil or fuel additives. 

You could save a little money by installing the replacement part yourself (and a Haynes Manual shows you how to do it) but most of the cost is in the part, which contains precious metals such as gold, palladium and rhodium. The latter would be another reason you might need to find a new catalytic converter: it's been stolen.

how much clutch

2) Changing the clutch assembly

Estimated cost: $1000-$1400 • 25% parts, 75% labor
Potential DIY saving: $1050.00

How do you know when a clutch has worn out? It starts to 'slip', which means the engine revs more when you're accelerating from a low speed in a high gear. You usually get a good deal of warning before a clutch needs to be replaced. There’s not much you can do to prevent it, apart from adopting a gentler driving style and not ‘riding’ the clutch. There’s no real good news here – new clutch parts can be pretty pricey, and while you can save money by doing the work yourself, changing the clutch on a front-wheel-drive car can be a pain without a lift.

3) A new engine control module (ECM)

Estimated cost: $1200-$1300 • 85% parts, 15% labor
Potential DIY saving: $195.00

Another nasty surprise. Hands up everyone who thought the car’s ECM was a just little black box with a couple of transistors and a circuit board? In fact, a new ECM will cost as much as a mid-range laptop, and you’re not going to save a whole heap of cash by fitting it yourself. But this is a solid-state device with no moving parts to wear out and, in the ideal world, the ECM will last forever.

The world, of course, is not ideal, so while your ECM shouldn’t fail, you shouldn’t rule it out. The computer is usually damaged by someone jump-starting the car improperly, or shorting out something while installing a stereo.

04 Alternator replacement

4) Alternator renewal

Estimated cost: $400-$800 • 70% parts, 30% labor
Potential DIY saving: $240.00

The alternator is one of those parts that you just take for granted, but they do wear out – and when the alternator dies, so does your car’s entire electrical system. Life expectancy varies from 50,000 miles to 100,000 miles or more, but it won't last forever. They’re expensive little beasts too, with not much to be saved by doing the fitting work yourself (unless you go for a cheaper used or rebuilt part).

5) New fuel injectors

Estimated cost: $800-$1350 • 75% parts, 25% labor
Potential DIY saving: $337.50

Remember all the fun we (didn’t) used to have with carburetors, float bowls, needle valves and vacuum gauges? The modern-day equivalent – fuel injectors – are great but stop being quite so fantastic if they go bad and you have to pay for new ones.

What you might have hoped was nothing more than a glorified syringe turns out to be a little more complicated and a lot more expensive. They might last as long as the car, at the very least they might last for as long as you own it. Let’s hope so.

06 Head gasket replacement

6) Changing the head gasket

Estimated cost: $1100-$1400 • 20% parts, 80% labor
Potential DIY saving: $1120.00

Head gaskets fit between the cylinder block and the head, and they keep the combustion chambers, oil and cooling systems sealed and separate – until they fail. That’s when you get oil or water in the cylinders, lots of smoke from the exhaust and a marked downturn in your popularity with the neighbors. It can be worse still if water gets into the cylinders, because water doesn’t compress.

Annoyingly, the head gasket itself is pretty cheap, but the labor involved in getting the head off and milling it (don’t skimp on the head resurfacing) is pretty huge. If you’re lucky, you may not get a head gasket failure for years, but it seems to happen most often with older, infrequently used cars. One way to guard against it to keep your cooling system in tip-top condition.

7) Timing belt renewal

Estimated cost: $650-$900 • 30% parts, 70% labor
Potential DIY saving: $630.00

This is an expensive bit of routine maintenance that you should never neglect. The timing belt is what connects the crankshaft at the base of the engine with the camshaft in the top. If it fails or skips a couple of teeth on the pulleys, the valves and the pistons may collide and wreck the engine. So while it goes against the grain to replace a part that appears to be working perfectly, do it anyway. Your car’s manual or your local garage will tell you when the recommended replacement interval is, so make sure you listen.

If you're lucky enough to have a car with a timing chain, you may be able to get away without having to replace it at all. However, they can stretch over time, so don't think that they're completely maintenance-free.

how change radiator

8) Change the radiator

Estimated cost: $600-$750 • 40% parts, 60% labor
Potential DIY saving: $450.00

Radiators can go on for years without problems, but they can fail easily if your car gets front-end damage or if you neglect to use a proper antifreeze mix when you fill them up. Antifreeze contains corrosion inhibitors and will also prevent frozen water expanding and damaging the radiator.

If your car is losing coolant you shouldn’t immediately assume it’s the radiator, since there are lots of other hoses and joints that can leak, too, and these are simpler, cheaper repairs. So make sure it’s definitely the radiator that’s bad before you buy a new one.

9) Starter motor replacement

Estimated cost: $400-$850 • 75% parts, 25% labor
Potential DIY saving: $212.50

There are few things worse than that horrible moment when you turn the ignition key and all you get is a feeble whirr, a couple of clicks or clonks from under the hood and an extended period of silence.

If you’re lucky, it’s just the battery, which is a relatively cheap and simple fix. If you’re not so lucky, it might be the starter motor. Often, these will go for years without problems, but sometimes they don’t (c’mon, you just had to do ONE thing…).

how much water pump

10) Water pump replacement

Estimated cost: $550-$750 • 25% parts, 75% labor
Potential DIY saving: $562.50

This is a small but vital part of your car’s cooling system that could last 50,000 miles, could last 100,000, and might never fail while you own the car. But, when it does fail, the coolant no longer gets pumped through the radiator and engine, which quickly becomes hot and angry, as will you as you push your car to the nearest repair shop.

Water pump failures can happen on their own, but you can improve the odds by keeping your coolant system well maintained and topped off with proper antifreeze mix.

The final word

Mechanical car parts are perfectly capable of wearing out or failing on their own, but they can also fail prematurely through bad maintenance. Use the proper oils, coolants and fluids and pay proper attention to your vehicle’s recommended service intervals – all of which are shown in your Haynes, Clymer and Chilton Manuals.