When Parts Collide: VW?And Audi Engine Repair?Information - Engine Builder Magazine

When Parts Collide: VW?And Audi Engine Repair?Information

Nothing makes this truer than the changes in automobile engine design over the last 20 years or so. For example, in the early 1970s, VW/Audi designed a small, efficient and reliable engine that was easy to work on and made use of the then fairly new technology of a rubber timing belt without the possibility of damage if it failed. This two-valve-per-cylinder engine produced excellent power and economy, and really set the standard that many other manufacturers couldn’t match.

The demand for more horsepower led VW/Audi to look for ways to add performance without a complete redesign of the basic engine. An early attempt at multiple-valve technology added complexity to the mix in the form of the 16V engines in the late 1980s and early 1990s.

The addition of more parts in that engine did little for performance, but cost dearly in reliability and durability, causing more than a few of those cars to wind up in the crusher. Many other manufacturers have made this same mistake, and those cars have ­developed reputations as cars to avoid.

Now some carmakers have started a return to reliability as a major focus by redesigning their ­engines with timing chains in place of the maintenance cost of belt replacement. VW/Audi is in the midst of that change with new engine designs going back to chain-driven camshafts, a change that has ­already won the International Engine of the Year award for 2009.

With that said, there are several million VW/Audi cars with the current five-valve-per-cylinder engines. For performance, emissions and economy reasons, these engines do what much larger engines do in other cars. The addition of turbocharging to boost performance is why these engines work, but the complexity of that addition also seems out of place in base models where economy is the prime selling point.

The focus of this article will be the 4-cylinder, 1.8L and 2.0L, 5-valve engines that power everything from New Beetles to midsize VW and Audi sedans. A short road test in these cars proves these engines perform as advertised. With a free-winding horsepower curve and smoothness that is uncommon in a 4-cylinder, it isn’t hard to forget that the car is powered by an engine that is only half the displacement of cars that are more performance-oriented.

Design Changes and Their Effect on Repairs

Though the lower end of these engines can trace their roots back to 1972, there have been many versions and changes over the years. Most of the design changes have been centered on the cylinder head, ­intake and exhaust systems. Starting with the New Beetle, the biggest changes came by way of dual-overhead camshafts and turbocharging, along with five valves per cylinder. Since 1998, this engine has ­become the performance upgrade or standard equipment for VW and Audi base-model cars.

As with many new designs, changes started almost immediately with many components (see Figure 1) being revised without any regard for model year or production location. These engines are made in Mexico, Germany and other engine plants. A quick look at the list of VW and Audi engine codes will make your head spin.

Before starting any repair, you should know the ­engine code (see Figure 2), production date and country of origin. Though some of these engines, in long-block form or cylinder head design, are interchangeable, it is best to consult a machine shop specializing in these engines before attempting a code change.

Since these engines were designed to be installed in two different configurations (transverse or front/back), interchanges are possible only if the correct parts are available to change the configuration of the oil pan and mounts. Two major changes were the relocation of the water pump to the engine block driven by the timing belt, and relocation of the oil pump and drive mechanism.

In the U.S., these engines are turbocharged and ­intercooled. Maintenance mistakes or neglect are the most common reasons for failure of the engine, turbocharger, or both. Leaks of all kinds have been common. Coolant leaks at the oil cooler, mounted on the filter adaptor (see Figure 3, above) and water pump, are common. Oil leaks at the valve cover gasket, timing chain tensioner gasket and filter are typical. The use of substandard oil or extended change intervals leads to sludging problems that contribute to timing chain rattle and failure. Plugged oil pump pickups are also very common and cause early failure due to loss of oil pressure.

Collision Course

Since VW doesn’t specify a realistic change interval for the timing belt on these engines (only vague references are given about inspection and replacement, if necessary), we see these cars with relatively high mileage without belt replacement. The rotational demands of a single belt turning two camshafts, a timing chain against hydraulic tension and 20 valve springs should be a clue that Murphy would be ­invoked earlier rather than later.

A case in point is the subject of some of the photos used in this article. A 2003 New Beetle Convertible with 89,000 miles had almost made it to the top of the hill our shop is located on (two miles of steep climb from 20 feet to nearly 500 ft. in elevation). Since there was a small amount of ice and snow on the road, the slipping and gripping of the tires probably just snapped the belt as the tires grabbed (see Figure 4).

The damage was obvious, as the engine had no compression when cranked. As a second-owner vehicle, it was out of warranty. A call to the owner’s ­insurance company indicated that the damage would be covered, but after removing the valve cover to verify the damage, the cost of the repair exceeded the ­allowed coverage. The finance company refused to loan the owner enough money for the repairs, as the car was already financed for double what the market value indicated. The car was totaled, but we were able to purchase the car for almost nothing!  

Dissasembly Procedures

Rather than go into a step-by-step repair process in this article (the appropriate service manual or online repair information should be available to do this job properly), I will instead focus on things to look out for in the repair process.

1. There are some obvious things to take into ­account before any disassembly is started. Since space is at a premium in both engine layouts, either the radiator carrier (see Figure 5) needs to be moved forward, or the right-side engine mounts need to be removed to ­access the front of the engine to ­replace the timing belt. Depending on the year and engine code, there will be one, or as many as three, accessory belts and their pulleys to remove. Other obvious things to do include draining the coolant and oil, and removing the air filter, housing and intake connections.

2. Depending on the year and code, remove the plastic engine covers, top and bottom. On most of these cars, the intake manifolds can be unbolted after removing electrical harnesses and brackets, leaving the injectors in place and simply pulled out of the way and secured to allow the head to come off. There are a lot of vacuum hoses, secondary air hoses and breather connections (see Figure 6), so take your time to disconnect and save as many as possible. Each hose should be checked for cracks or softening, especially on cars that have any evidence of sludging or driveability concerns, like a code for fuel trim.

3. The rear of the engine (flywheel end) will be a challenge as there are connections for coolant, EGR/secondary air and vacuum tightly grouped and hidden. Look closely at the plastic housings for cracks or heat distortion. It is possible to simply disconnect many of these components and leave them in place, rather than risk breakage by removing them.

4. The exhaust manifold can be removed without removing the turbocharger. Though some of the fasteners have tight clearances, with patience (use a slight tighten then quick break to loosen the fasteners) and the correct wrench, the various brackets can be moved out of the way. On New Beetle and TT models, remove the turbo heat socks and carefully work the boots loose as they will probably be brittle and tear easily.

5. You will need the special socket for the cylinder head bolts (poly drive) to work around the camshafts and lifters; the best ones are several inches long. ­Depending on the type of tensioner, a holder (grenade pin or flat bar-type) will be needed during reassembly. If the timing belt was broken or stripped of teeth, there is no compelling need to set the engine to TDC at this point (it’s too late). After removing the headbolts, pull the head with the camshafts and other components in place.

Inspection Process

1. Bent valves will be obvious  (see Figure 7). You will also be able to figure out where they hit the pistons (see Figure 8). Take the time to turn the crankshaft to TDC for each pair of cylinders and check for evidence of a bent connecting rod. Better to find it now, rather than after the new head is on. The valves are not very substantial (thin stems), so the chance that lower engine damage would occur is remote.

It’s more important to check the position of the crankshaft timing marks (front or rear) in relation to TDC (see Figure 9). If there is any obvious sign that the marks don’t line up, plan to pull the crankshaft sprocket to check to see that it is still keyed to the crankshaft once the front covers and belt are off.

2. After removing the front covers, pull the water pump off for inspection if it is the type driven by the timing belt. Since these pumps fail often (even before the timing belt), they should be replaced any time the belt is replaced. I would recommend a pump with a metal impeller for a lasting repair. A close look at the pumps with plastic impellers will usually show tiny cracks near the shaft from the pressing process, even when they’re new.

3. Cleanup of the block is important for the new head gasket to seal properly since it is a multi-layer steel embossed-type and the sealing surfaces have to be clean, dry and flat to seal properly. Do not use any kind of sealer on the gasket, head or block surface.  

4. At this point, I would set the replacement head next to the old head (see Figure 10) and do a visual crosscheck of ports, mounting tabs, drilled holes, plugs, number of valves and camshaft components to verify the interchangeability of the heads. If you are reusing the head after machine work, make sure you have carefully laid out the removed components (sensors, tensioners, studs and housings), and clean up any dirty or damaged threads.

Refer to a repair manual and remove the camshafts, sensors and chain tensioner, and keep everything in order to be sure the parts are reassembled correctly. You should be able to read all of the camshaft cap markings from the intake side of the head. Pay close attention to the dowel pin sleeves, and transfer or remove missing parts, or remove duplicates.

Reassembly Process

1. Before reassembly, there are some steps you should take to prevent almost immediate failure of the camshafts and valves. I put the lifters in an oil bath and use a socket extension to purge them of as much air as possible (see Figure 11). This takes a little time, but does reduce the death rattle on startup that ­always makes me cringe a little.

2. Read through the assembly ­instructions in a service manual or on-line tech service to familiarize yourself with the proper sequence and tightening torque for the camshafts. The delicate castings for the camshaft caps are very easy to break or distort, and the bearing surfaces need to be lubricated with oil or assembly fluid during installation.

The chain tensioner housing and front double bearing cap need to be coated with sealant, along with the special sealing gasket at the tensioner that is positioned with a dowel sleeve. Do not use silicone sealer for these surfaces, but instead use the special VW sealant or a similar ­alternative made for sealing machined surfaces. The tightening torque for bearing caps and housings is only 7 ft.-lbs. (10 Nm), so use a torque wrench capable of measuring that low. More torque could pull threads out of the head, again causing premature failure.  

3. Set the crankshaft at TDC for cylinder one, then turn the engine backward just enough to allow space in all cylinders for any valves that might be open during reassembly. Clean the head surface of any oil from the lifter installation and clean the mating surface of the block before setting the new head gasket in place.

4. Double-check your chain and cam alignment and then reassemble the engine in the reverse order of disassembly. Before the engine is cranked, turn the engine over by hand at least two full turns to verify correct timing and precharge the oil system (see Figure 12) to prevent a dry start. Use premium-quality engine oil that’s designed specifically for turbocharged engines.   

The shear numbers of these engines in use will provide years of service and repair opportunity. Though complicated and time-consuming to repair, once the maintenance is tuned to the high-performance nature of these engines, they can be made to live to high mileage. From the pattern failures indicated on forums and repair services, most of the failures are directly related to lack of or incomplete maintenance. There are also a number of instances where repairs were done without the extra care necessary to prevent an immediate recurrence.

Larry Bailly is an import specialist contributor to Import Car magazine, Engine Builder’s sister publication. This article originally appeared in the October 2009 issue of Import Carfigure 1figure 2figure 3figure 4figure 5figure 6figure 7figure 8figure 9figure 10figure 11Figure 12

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