The need to change the timing belt is one of the primary reasons the average home mechanic might tear into the front of the engine bay of a 1.8T-equipped car. Like many engines, the 1.8T is equipped with a rubber, toothed belt to transmit the torque of the crankshaft to the camshaft, and to keep these two components rotating at the correct speed and orientation relative to each other.
Earlier cars often used a metal chain, or even gears, to do this job. In modern cars, however, rubber belts have become more and more common. This is for reasons of cost and noise reduction; the downside is that these rubber belts need to be replaced periodically, or at the very least, much more often than a metal chain. If a rubber timing belt fails, it typically does so when the engine is running. If the engine is an "interference" type, meaning that the pistons and valves inhabit the same place within the cylinder, but at different times, a broken belt will mean that these parts will suddenly--and violently--inhabit the same place, but at the same time. Broken parts and expensive repairs are sure to follow.
The 1.8T is an interference-type engine, thus changing the belt is something that must be done periodically--every 60,000 miles is the recommended interval. The tensioner, which is the device that takes up any slack in the belt as it turns over the crankshaft and camshaft sprockets, must also be replaced at this time.
Two elements of this job make it a bit intimidating to the newcomer. First is the fact that it's just to lengthy. That's not necessarily in terms of time, although for a first-timer it's sure to take many hours, but in terms of the number of steps. Adding to this number of steps is the need to move the radiator support panel into the service position first, as well as the need to remove the other accessory belts first. In addition, it's sensible to replace the water pump during the course of the timing belt project, which, while convenient, adds a few more steps to the job.
The second intimidating element is the potential for screwing something up. As with any repair there is the possibility of snapping a fastener or mangling some thread; in this job you can alter the timing of the engine if you don't install the new belt carefully. Care and patience are the key ingredients to doing this job right the first time.
If your A4 is new to you and has more than 60,000 miles, and there is no evidence of the timing belt having been replaced previously, place this project at the top of your priority list. If you do it yourself you can save several hundred dollars over having a shop do the work, but plan to have the car off the road for a few days so that you don't feel pressured to rush the job - that will only lead to mistakes, and you don't want to make mistakes with valve timing.
Before replacing the actual timing belt, you'll need to put the radiator support panel in the service position, as mentioned, and you'll also need to remove the accessory belts from the front of the engine (not a bad idea to replace these too, while you're in there, along with the water pump). Also, disconnect the cable from the battery's negative terminal because you'll need to remove the spark plugs to make it easier to turn the crankshaft by hand.
After you've done all the stuff mentioned above, the next step is to remove the tensioner mechanism for the serpentine belt. It is attached to the alternator bracket with three 13-mm bolts.
As you can see, getting the tensioner out of the way improves access to both the upper and lower plastic timing belt covers, which must be removed to change the timing belt, as well as the components behind the covers.
Two clips on the front of the cover retain the two hoses that cross in front of the engine. The larger hose supplies coolant to the turbocharger, and the smaller hose with the braided fabric covering provides a vacuum signal.
The coolant hose can be pushed up and over the valve cover to keep it out of the way while you work. There's more slack in the vacuum hose, so you can move it out of the way as needed while you work.
At this point you should remove the spark plugs from the engine. This will make it much easier to rotate the engine by hand, as the air that is compressed as the pistons move up in the cylinders will easily flow out through the spark plug hole--in other words, you won't have to fight the compression of the engine in order to turn it over. Follow the instructions in the Changing Spark Plugs project if you're unsure how to remove the plugs. On all but the #1 cylinder (the one closest to the front of the engine) I put the coils back in place to prevent any debris from falling into the cylinders. I rested a long screwdriver on the top of the piston in cylinder #1, inserted through the spark plug hole, in order to provide a visual reference for the position of the piston.
The cam gear at the top of the engine has one tooth that is marked. Once every revolution (every two revolutions of the crankshaft), the mark lines up with the mark on the valve cover, as seen in this photo. Note the yellow paint on the cam gear, which is helpful for finding the mark at a glance.
Get out a 19mm, 12-point socket and place it on the crankshaft bolt. Turn the crankshaft clockwise until the timing mark on the pulley lines up with the arrow embossed on the lower timing belt cover. The mark is a little hard to see, but it is there. You could add a touch of light paint to the mark to make it more visible. The #1 piston should now be at top dead center (TDC).
When you've got these two marks lined up, check the cam gear. The mark on the cam gear will either be aligned with the mark on the valve cover, or 180 degrees opposite. If they don't line up yet, give the crank another full rotation. The #1 piston will again be at TDC and the cam gear marks should then line up.
This establishes the correct relative positions of the crank and camshaft and gives you a target alignment after the new belt is installed. Take care not to rotate the crank or camshaft independently when the belt is off and you should only have to make small adjustments to insure the correct alignment.
Don't worry about the orientation of the crank pulley as you remove it. Aside from the four holes for the Allen bolts there is a smaller hole that matches up with a raised mark on the crank gear. This ensures that the pulley can only be reinstalled in the correct position.
There are four fasteners that secure the lower timing belt cover. The two nearest the crankshaft are a 10mm bolt to the left (this is the one with the socket on it in this photo) and a 5mm Allen bolt in the hole just above the crankshaft sprocket.
To the right is a 10mm nut that threads onto a hammer-head bolt that is held in place by the alternator bracket. See the water pump project for more information on this fastener. I removed the fan clutch to get better access to this nut, but you may not need to do so if you can reach it with your tools.
Loosen the central bolt and the pulley is freed from the threads in the cylinder head. Note that you can easily see where the iron engine block meets the aluminum cylinder head in this photo. Keep this in mind if you ever need to keep the timing belt in place while removing the cylinder head
Old pulley on the left, new one on the right. There are three types of tensioner mechanisms for the 1.8 engine, and according to the Haynes manual, this is the type 3 tensioner. As you can see, the new assembly comes with a new securing bolt and bearing.
This is the hydraulic piston that applies pressure to the metal bracket that is attached to the tensioner pulley, in turn applying the proper tension to the timing belt. It attaches to the engine block with two 10mm bolts. This is the upper bolt.
Here the tensioner device has been removed from the block. However, I soon realized that while the replacement part had a new roller, I needed to reuse this 13 mm bolt to attach the new roller to the new tensioner.
Here's the old tensioner on the left and the new one, with its roller, on the right. Note the piston on top, which is extended on the old tensioner. On the new unit, the hole in the body of the tensioner is aligned with the one on the piston and a pin is inserted between them in order to keep the piston retracted during installation. DO NOT remove this pin before you've confirmed the correct installation of the timing belt!
Remove the old belt and install the new one in its place. Attach the tensioner pulley using its central bolt, but don't tighten it all the way down yet. This will allow you to keep the tension on the belt relatively loose while you make any necessary adjustments. Install the timing belt tensioner and the roller but don't pull the pin on the piston yet.
Press the belt against the teeth of the crankshaft sprocket and pull it toward the intermediate shaft/oil pump pulley, and press the belt teeth against that pulley as well. Use a small clip, like a binder clip, to hold the belt in position against the pulley temporarily or, better yet, use a larger clamp to hold the belt against the crank sprocket. Pull the belt up toward the cam pulley and remove any slack in this run. Secure the belt to the cam pulley with another clip.
At this point, all of the slack in the belt should be on the tensioner side, or the left side when looking at it from the front. Make sure the belt is positioned properly over the roller on the tensioner body as well as the tensioner pulley. Rotate the metal tab on the tensioner pulley clockwise to add tension to the belt and tighten down the central bolt on the pulley temporarily to hold that tension.
Remove the clips and/or clamps from the belt and make sure the belt now has enough tension that it won't jump off of the pulley teeth or the crankshaft gear.
Your next step is to confirm that the timing of the engine hasn't changed during your work. I attempted to do this by referencing a mark on the crankshaft gear relative to the engine block, but it turned out that something had already moved. When I checked the timing again after installing the crank pulley, it was off by one tooth.
This shot gives a good look at the crank sprocket. The raised node at 8 o'clock corresponds with the hole in the crank pulley to ensure that it can only be installed in the correct position.
At this stage I recommend installing the lower timing belt cover and the crankshaft pulley. You only need to install a couple of bolts into each. This will give you a more accurate look at the cam and crank positions relative to each other. Turn the crank through two full rotations (one rotation of the camshaft) and make sure the marks line up.
If the timing is off, remove the pulley and lower cover again, loosen the belt, and move the crankshaft or camshaft sprocket slightly in the direction that will correct the problem. Replace the belt and double-check the timing again. Once everything lines up correctly, you can install the lower timing belt cover and pulley for real.
Finally, reinstall the upper timing belt cover. Note that the serpentine belt and its tensioner are already installed in these photos, but it is not necessary to install those first. It's easier to do it without these parts in place, but the upper cover can be installed either way.
Once the cover is in place, snap the two metal clips back onto the valve cover and place the two hoses back into the brackets on the front of the timing belt cover, with the vacuum line getting in place first.
Snap the coolant hose in place and you're done with the timing belt change. Remember to replace the spark plugs and ignition coils, replace the accessory belts, connect the battery, and put the radiator support panel back into its home position.
Comments: thanks for this information, it's very usefull for me.
August 25, 2014
Comments: should the camshaft, crankshaft, and the oil pump seals be replace during timing belt replacement as preventive? Are the three seals the same part number?
Excellent write up to follow; keep up the good work,
June 19, 2014
Followup from the Pelican Staff: I would replace any seal behind the timing components when servicing it. I am not sure of the part numbers. Give our parts specialists a call at 1-888-280-7799. They can help you find the right part.
- Nick at Pelican Parts
Comments: Very low compression after replacing timing belt 28-40 lbs Re-checked timing belt position and is still good although 1/2 tooth off. Any ideas about what can cause this? Pressured up each cyl with air while at tdc and holds air pressure, so no bent valves, right?
June 1, 2014
Followup from the Pelican Staff: 1/2 tooth wouldn't drop compression that much. Either you have incorrect timing or valve damage. I would double check the timing marks. - Nick at Pelican Parts
Comments: These were the most concise and complete instructions describing an automotive procedure i've ever gained access to. Thanks so much!
May 25, 2014
Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
Comments: I did this job on my 2002 Passat. One of the crazy things about the engine is that I could not find a good way to get all the coolant out of the engine. The radiator can be drained, but the block still contained a lot of coolant. Lots came out when the water pump was pulled, but still there was a lot in the engine. I never swapped out that coolant did not flush it so there is old coolant in there during the change. Not a nice feeling, and makes me wonder why there was no drain plug in the engine.
Also, I have done 4 timing belt changes on various cars, and never put the engine at TDC. If you use a sharpie or white-out to mark crank pulley and the cam pulley such that the teeth and the belt only have one mark on them at each cam so that it can be reinstalled exactly... then place identical marks on the replacement belt so that it can be put in exactly... then you know that the cam and crank are in correct position. It is a good practice to do this anyway in case the cam gets moved somehow albeit that is difficult.
I took my time and it took about 12 hours total. If I did it again, it would likely take about 8 to 10. It's a big job, but even buying all OEM stuff parts including water pump, saved about $1000 from what VW charges. Hugely rewarding when all back together... I highly recommend this repair to the budding shade-tree mechanic.
February 21, 2014
Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
Comments: Looking at image 26. I don't know of another way to align tdc with the crank on this 2002 1.8t automatic. No plug I can find to see the crank. Is this the only way to set it to tdc?
Using the straw method I can tell I am close but I cannot be sure.
January 16, 2014
Followup from the Pelican Staff: Follow the instructions in the tech article. That is the best way to line it up. - Nick at Pelican Parts
Comments: What I have ro do if i miss the mark on the crank
December 9, 2013
Followup from the Pelican Staff: I am assuming you mean the belt is installed but your marks are not aligned. Put the engine back to TDC and remove the belt, the realign your marks. - Nick at Pelican Parts
Comments: Very good write up. Did you also change the water pump? The water pump replacement is almost identical with the TB change, as you know.
December 6, 2013
Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
Comments: How much torque for the three bolts on the serpentine belt tensioner?
May 29, 2013
Followup from the Pelican Staff: The torque for the serpentine belt tensioner is 23 Nm. - Nick at Pelican Parts
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