Replacing timing belts

July 1, 2016
All those vehicles on the road that still use timing belts need experts like you to be ready to replace them. Here’s how to avoid common problems and keep the job profitable – no matter what you’re working on.

In theory replacing a timing belt is pretty straightforward: remove everything in the way, line up the components, replace the belt, set the tension, top up any fluids lost during the procedure and then neatly reinstall everything that came off – no problem in theory.

In reality one mistake or oversight can cause drivability concerns or damage a very expensive engine and it’s quite easy to make a mistake or forget something critical during routine timing belt replacement.

Fact is, the job is usually labor-intensive and can actually be quite complicated with many small, critical steps along the way. Additionally, aligning timing marks and setting tension correctly is critical because catastrophic engine failure can result from tiny errors. And it’s not uncommon for the job to take the better part of a day especially if any mounts need to be removed or bolts are seized in place – and it’s certainly not fun or profitable to have to disassemble everything a second time to fix a problem that you may have inadvertently caused.

(Photo courtesy of Gates Corp.) Most aftermarket sources offer timing belt "kits," providing the technician whith everything he or she needs to do a professional timing belt service.

Therefore is makes sense to avoid the common problems and pitfalls associated with routine timing belt replacement whenever possible, and surprisingly even though engine designs and replacement intervals vary among manufacturers, there are definitely some problems and pitfalls common to all vehicles and it’s important to understand them and plan ahead before anything is disassembled.

Additionally, it’s important to know a few tips to make the job go smoothly and efficiently so you don’t waste time or cause any new problems.

It’s definitely possible to make good money changing timing belts without any unnecessary stress – if you know how.

So here’s how – here are a few quick things to know to make the job go smoothly and leave your customers with a great impression of your work so everyone stays happy and stress-free.

Replacement Intervals

Timing belts are typically replaced every 60,000 - 100,000 miles depending on the manufacturers’ recommendations and also depending on how the vehicle is used. There may be the odd engine that requires a shorter or longer replacement interval (as with most maintenance items nowadays) so it’s always best to refer to the manufacturer’s recommendations and then go from there. Also, it’s usually worth replacing any other related components that have reached the end of their service life when the belt is replaced (e.g. the water pump if it’s driven by the timing belt since it can damage the timing belt when it fails) so that the job doesn’t need to be done again before it’s due.

(Photo courtesy of G. Jerry Truglia) Timing mark alignment is critical on any engine, SOHC or multiple cam.

Some manufacturers, however, don’t actually have a recommended replacement interval. Rather, they recommend inspecting the belt for cracks, loose, damaged or missing teeth (and for other damage or wear) every few thousand miles and replacing the belt if required – which really isn’t very helpful because (from experience) it may be too late to prevent engine damage if the belt has stretched out or has missing or separating teeth since any of those problems can affect engine timing and cause serious problems.  It’s just not worth taking a risk to save the customer money. From experience, timing belts don’t tend to last much past that 100,000 mile interval. It’s best to replace the belt if there’s any doubt rather than guess at its remaining life. This is definitely a case where saving money can end up being very expensive.

Quick Tips

Worried? Don’t be.

Before starting the engine, make sure that:

  • Pulley bolts are tight (including crank)
  • Engine turns over by hand and timing and tension are still OK
  • All camshaft and crankshaft pulleys are correctly aligned
  • Tension and tensioner are set and secured
  • Timing cover is installed squarely, seals are securely in place
  • Engine mounts were retorqued if removed
  • Coolant level is OK
  • Splash shields are free of oil and coolant

Before releasing to the customer ensure:

  • Fan comes on, coolant level OK in reservoir
  • No pinging or hesitation on test drive
  • No DTCs stored
  • Replacement date and mileage recorded
  • Radio stations are set (if battery disconnected)

Whatever interval is recommended, it’s important to keep in mind that as with any belt, contamination from oil or coolant dramatically shortens the belt’s useful life – and the timing belt is not one to just clean off and take a chance with in the hope of saving some money.

Don’t guess, check

No matter what type of vehicle of engine you’re working on, it’s really important to avoid a few common pitfalls that seem to apply to all timing belt replacement jobs – and one of the best ways to do this is by test driving the vehicle before work begins, specifically to ensure there are no pre-existing engine or drivability concerns.

In other words, drive the vehicle and check for any hesitation or pinging noises on hard acceleration, check for any DTCs that may be stored, and listen for any strange noises coming from the engine area since problems like those can be (and often are) caused by a timing belt replacement job gone wrong — possibly by the timing being “off a tooth” or because the tension wasn’t set properly — and you really don’t want to be guessing at whether or not the problem was there before you did anything.

A short drive that includes some hard acceleration really can save hours of headaches later on.

And another tip to prevent problems is to check any leaks in the timing belt area before disassembly. Unlike the timing chains that seem to have replaced them, timing belts need to operate in a dry, lubricant-free environment so anything that’s leaking oil or coolant onto the belt should be repaired or replaced before the new belt is installed since it can drastically shorten the belt’s lifespan.

Also be sure to check the protective covers for any signs of cracks and damage from previous repairs (maybe even photographing anything major) in case additional parts need to be ordered or authorized. Noticing anything wrong with the vehicle beforehand can prevent problems later on.

Preliminary pitfalls prevented

When the preliminary inspections are complete, there are a few ways to make sure the rest of the job goes smoothly.

For one thing, my former shop teacher will be very upset if using clean fender covers isn’t mentioned – particularly important for a job like this since you’ll likely be bent over the fender for quite a while and it’s important to keep the customer’s vehicle clean (but we all already knew that).

This 2000 Honda Civic has 160,000 miles on it, so it's ready for a timing belt and water pump replacement. The customer just bought this vehicle (used) and doesn't know if the belt was ever changed — it certainly doesn't look like it.

And along those basics-are-important lines, taking a few moments to review service information, search for service bulletins and check for tech tips before disassembling anything is absolutely critical.

In particular, you need to understand which components must be removed to access the timing belt, what holds tension on the belt and how the tension is released, where all of the timing marks are located, whether or not the camshafts or other components need to be locked in place (and how to do that) – and also to be aware of any other timed and indexed components besides the camshafts and crankshafts themselves. True, some engines aren’t interference-style and can freewheel, but many engines are and need extra care to prevent causing problems during service.

Checking service information is also critical since there may be specific steps you’ll need to take that protect the internal engine components from being damage during service  -- and also there may be updated parts or components available for various reasons. Don’t guess, check and be sure.

Then when you know the critical steps and you’ve got the correct parts you need, proceed to disassembly – but also with a few things in mind.

Disassembly done right

One of the first steps you’ll likely do (as directed by service information) is remove any serpentine belts on the vehicle. Here’s a tip.

To prevent problems from developing (such as odd noises in the engine compartment) mark the direction of rotation for any belts that are removed but are not being replaced (for whatever reason). Belts that suddenly reverse direction after thousands of miles of use may not be happy with the change. There’s never shame in taking a few photos to remind yourself how something was routed or aligned.

True, some take a short cut and pry the op section of the cover from under the valve cover, but taking the time to remove the valve cover and install a new seal is worth the extra effort and fixes the leak.

Also, if you need to raise the engine and support it (such as when a mount is removed or to improve access to the belt or pulleys) it’s important to protect the oil pan from dents and damage. A very common way of doing this is with a block of wood and a jack or axle stand, in particular by using a wide piece of wood to spread the load over a larger surface area.

But there are two important things to be aware of as you do this to prevent problems.

First, avoid putting any pressure at all on rusty or weak oil pans (find another way to support the engine). And second, be careful not to damage any components that are still attached to the vehicle when the engine is forced upwards at a strange angle. Exhaust manifolds can be driven into soft or brittle components if you’re not careful (or the exhaust system itself can be damaged) so be sure to keep an eye out for problems as you support the engine.

Damaging something this early on in the job is definitely a pitfall you want to avoid.

The mount is in the way, so the engine will need to be carefully supported when the mount is removed.

Progressing along

As the job progresses and the as the bolts and components start to come off, here’s a tip to make things go smoothly and avoid problems during reassembly. As each fastener or bolt is removed be sure to inspect it closely to see if it’s identical to the others or if there are slight differences in length or pitch that mean it needs to go back exactly where it came from. This is the time to find out, not later on during reassembly.

Even if the fasteners do seem identical, group them with the component they’re associated with as they are removed and store any easy-to-mix-up components on the bench when possible, not along the cowling at the windshield or on the strut mounts where they can easily be lost. One apprentice here lines the bench with paper floor mats so he can scribble notes next to components as required – smart kid indeed.

And one more tip to ease reassembly, when you do remove the timing belt cover itself see if the rubber seals along the edges are securely in place – if there was an oil leak they may have swollen up or become loose. If they’re loose it may be wise to actually glue them back into place instead of just pushing them onto the cover. If the seal gets inside the cover during reassembly it may bind and cause problems with the timing belt or gears – definitely not good since it can easily be prevented.

Replacing the belt

Once the components and covers are off and the timing belt itself can be accessed and replaced you’ll likely be instructed by service information to rotate the engine and line up the timing marks, then lock anything critical in place, then release the tension and then remove the belt – but there are a few things to be aware of at this stage to prevent problems from occurring.

Generally any timing marks will align when the engine is at top-dead-center (TDC) – but not always, so checking the repair manual for direction is critical. From experience, some timing marks align with the cylinder head, some align with marks on the timing cover, and some even align with marks on the other gears. Some replacement timing belts come with timing marks printed on them to align with marks on the gears, making it even easier to correctly line up the engine. If so, look for any information leaflets that came with the new parts to indicate how to do this critical step correctly.

But even though manufacturers usually supply timing marks and service information can tell you where they are located, timing or index marks may not always be visible or easy to use, especially on older engines, engines that had oil leak on to the marks, or engines that were exposed to the elements.

It's important to make sure the engine splash shields are free from oil and coolant after the timing belt is replaced so that customers don't mistakenly think their vehicle had developed a leak. Even the smallest amount like this could cause problems.

In those cases (or even in all cases if you’re paranoid like I am) white-out or touch-up paint can be used to make your own index marks. Actually, marking components in two places can prevent problems and ease reassembly. This should be done before releasing tension or removing the belt – it’s not fun to try to do this afterwards.

Also, it’s also worth taking a moment to feel the tension on the belt before you loosen it off so that you’re more likely to notice problems or irregularities when you set tension on the new belt. One very old tech I used to work with told me that if a timing belt had correct tension you shouldn’t be able to twist the longest length of the belt 90 degrees – which is definitely not the way to set belt tension (always refer to the repair manual for specific belt tension and set it accordingly) but it is a guideline to know if the belt is far too loose. By checking the existing tension before removing the belt you’ll at least have an idea of what to expect as you set the tension on the new belt.

When the old belt is off and the new one is installed, tension on the new belt needs to be set correctly. A very common pitfall of timing belt replacement is allowing camshaft gears to slip or jump out of place when the tension is set so it’s important that nothing be allowed to jump out of place at this stage. Check with the service information, but generally rotating the engine by hand a few times after setting tension and locking the tensioner (if needed) then rechecking that tension is still correct and the timing mark are still lined up correctly can save a world of problems. If they’re correct, that’s good. If not, find out why before proceeding any further.

Catching problems at this stage is preferable to catching them when everything has been reassembled.

Actually, there are a few things to be aware of when setting the tension to prevent problems.

For systems with automatic adjusters, unless the manufacturer recommends otherwise, making sure the adjuster is in good condition, works well without binding and rotates freely should be all that’s required.

But for those with manual adjusters, there’s a bit more to it.

Setting the tension too tight may cause the belt to whine when the engine is running and may also cause idler or tensioner bearings to wear out prematurely – and possibly the belt to fail causing engine damage. Setting the tension too loose will cause the belt to hit the timing belt covers and may even cause the engine timing to be slightly off, resulting in engine performance or drivability problems – which may worsen over time. So tension needs to be set correctly to prevent problems, according to the manufacturer’s recommendations.

One last tip, no matter the vehicle configuration or drivetrain orientation, replacing the timing belt is usually a labor intensive process so while everything is apart, that's the time to replace any leaking seals, worn timing belt idler or tensioner bearings, and anything else that can affect the belt not lasting to the end of the next replacement interval. Don’t let something small ruin all your good work.

Reassembly and finishing touches

When everything is back together and you’ve started the vehicle – and it seems to run well – be sure to test drive the vehicle and bring it up to operating temperature (in other words, until the fan comes on). You may want to do this in an area without much traffic since you’ll need to get back to the shop quickly if there is indeed a problem.

There are two reasons for this test drive.

First, just as on the preliminary test drive, you want to find out if the vehicle pings or hesitates under load and then check for any stored DTCs to verify that the job was done correctly or to find any problems before the vehicle is released to the customer.

The coolant reservoir in particular needs to be topped up after replacing the timing belt and water pump because when the engine cools down, any air trapped in the passages will displace and coolant level will drop.

And second, as the vehicle cools down after the test drive the engine will draw in coolant from the coolant reservoir and displace any air pockets that may have developed when the water pump was replaced and you’ll want to be sure the level in the reservoir is within specifications since the coolant reservoir is definitely an “appearance item” that the customer can see.

For that reason it’s wise to top the reservoir up with the correct coolant, and ensure that it’s at the correct strength to reinforce that a professional worked on the vehicle and left it in great shape. A small mistake here can leave a bad impression.

And another tip along those lines is to be sure to clean any fluids like coolant or oil off of the engine splash shields so the car doesn’t stain the customer’s driveway or parking spot – that’s just bad advertising for your business and it can easily be avoided.

Finally, as a professional courtesy and nice touch, record when the belt was replaced someplace obvious so that the countdown to the next replacement can be accurately planned. No one like to guess if a belt needs to be replaced, and after taking everything apart, to find the belt is still in great condition.

Conclusion

Engines and vehicles vary among manufacturers but there are still problems and pitfalls common to all routine timing belt replacements, such as not noticing pre-existing problems, mixing up critical bolts, setting timing or tension incorrectly and even just leaving a highly-visible mess by not topping up fluids or cleaning oil and coolant off the splash shields.

By knowing a few tips and being careful to avoid common pitfalls you can keep the job trouble-free and profitable and look like a pro doing it – and keep your customers happily returning to you for repairs.

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