(and what to do after your timing belt snapped or slipped)
Back to a4 FAQ list and "how to" index
To see how to remove the turbo only, see 1000q: ALH turbo removal and ALH engine TDI turbo removal (mirrored link from TDIinnovations of TX)
Don't be discouraged by the 4/5 rating- you have to remove the timing belt so that makes it a 3/5 minimum. This project is not technically difficult if you have the proper tools. Add the extra time and complications such as needing parts halfway through the job and rusty/stripped bolts and you have a 4/5 difficult. If the head comes off you will also want to clean the carbon off the intake which also adds time. Cylinder head removal is easier compared to many cars since there's plenty of room in the engine bay. Plan on having the car down for a week if this is your first time, after accounting for complications, finding missing parts, and cleaning the intake. A proper garage could remove and replace the cylinder head in 1 day but machine shop work normally takes a while. Because this is a more advanced procedure, it is assumed that you have the Bentley VW service manual, at least basic mechanic tools, VW timing belt tools, and if you are replacing the head, a competent machine shop or new head.
If you find the tips on this page helpful, please use the donation button at the top so that I can continue to keep publishing great articles for free. The Bentley service manual is about $80 vs. this page with more pictures, color pictures, and greater detail. Thanks in advance!
If you are just changing your ALH TDI head gasket, reuse the old head but I suggest cleaning the intake manifold and intake ports on the head of carbon.
There are two basic possibilities with a broken or slipped timing belt: the camshaft and crankshaft are still synchronized "in time" so there's no damage or they are out of time so the cylinder head is damaged.
It's possible that the timing belt slipped at the injection pump sprocket. If this happens, fuel delivery will be interrupted and the engine will stall. Do not try to continue starting the engine or the camshaft/crankshaft can go out of time! Carefully rotate the engine by hand to TDC. If the timing belt indexing tools fit on the crankshaft and camshaft but not at the injection pump it's probable there was no valve/piston contact. Inspect the lifters and replace the timing belt. If they are all OK then you got lucky.
If the teeth stripped at the camshaft or crankshaft, you'll see it.
Below are two pictures showing stripped teeth at the crankshaft. If you
see this you know there was valve-piston contact because the crank is no longer
aligned with the camshaft.
If the camshaft and crankshaft are not aligned, there is at least one valve damaged through valve - piston contact. When the camshaft valve cover is
off to check for time, carefully examine the valve lifters. Take off the camshaft (see 1000q: timing belt
removal, part 1 for more details) and remove the lifters. The lifters
should appear smooth on the top (mirror like- halo mini scratches in an even circular pattern
on the top from the camshaft is normal) and your fingernail should not catch on
the fine scratches. The reason why the scratches are in a round pattern is
because the camshaft rotates the lifter as it moves across it. If the
lifter does not rotate freely, it's binding somewhere or somehow. If you see a round valve stem shaped dimple on the
bottom or spider
mark cracks on the surface of the lifters, this is a 100% sign that the valves
hit the pistons because the top of the valve was driven into the lifter and left
a mark. Below are some thumbnail pictures of cracked lifters from valve/piston
contact, some from "far cry". They show definite damage and
valve impressions. VW TDI valves go straight up and down and if they hit
the pistons they can be forced up and deform and/or break the lifters and leave
these impressions. Click them for a larger view.
Here are some more pictures of head damage from user jfettig. They are
thumbnails, click to enlarge.
Even though the VW manual states that the head cannot be repaired, there are people out there who can repair even a gouged and damaged aluminum head to like new specs. A member named "Franko6" is experienced with rebuilding these heads, you can at least contact him for more options, here is his forum profile.
Without professional examination and testing, it is impossible to determine if the head can be re-used with some old components, if the head has to be completely rebuilt, or if the head has to be discarded. Be careful because sometimes the valves can bend slightly, get re-bent into the normal position, and then snap off later due to weakening at the bend. The TDI valves are pointing straight down so they oftentimes get mushroomed from piston contact which leads to later failure (instead of getting bent).
According to Franko6" "...if a valve is straight and has a good valve seat, why replace it? I've seen valves that are good in a head with 600,000 miles. That same engine with it's rebuilt head now has another 100k on it. Why am I replacing good components? Just to be 'safe'? That's thowing money at a solution.
The cam follower mushroom up when the valves hit pistons at starter speed. Usually, the valve stem bends above the valve guide if you have mushroomed lifters. You replace valve with bent stems.
Cam followers that are dented downward usually corkscrew the valve stem below the valve guide. That is why measuring the valve stem will indicate a shortened valve length. Replace corkscrewed valves.
But stuck lifters, mushroomed lifters, the valve might be very close to proper height. Once the cam follower is removed, you can see that they are bent toward the back of the head. If valves under mushroomed lifters will slide smoothly out of the valve guide, they are ok."
Once the head is off, inspect the pistons and check piston protrusion to make sure no piston rods were bent. On the ALH and similar engines, the lower end is normally OK but the cylinder head is normally damaged when the timing belt breaks or slips.
You will also need a new timing belt kit with all new rollers, tensioners, stretch bolts, and water pump.
Some aftermarket head gaskets have slightly different and smaller coolant holes. This was done to retrict flow and improve coolant performance. As long as you have the correct gasket, it's OK. Here is a .pdf from elring. and the forum thread which discusses this change.
Caution - I would not buy the or any other of this seller's copycat websites heads. These are almost certainly low quality copycat parts! It's not worth saving $75 when it can result in thousands in engine damage and labor! In my experience, he sells poor quality parts, has bad customer service, and lies about product descriptions. I had a bad experience with this seller and many others report the same, so never again.
Full metric tool set, sockets, wrenches, etc.
new head bolts (quantity: 10) VW# 068 103 384 a
new gasket set - note - check the number of holes punched in the head gasket, it must either match the old gasket or you must measure piston protrusion and order the respective "number of holes" gasket. An incorrect gasket will change your compression. See your Bentley manual for more details. Because the gaskets have different part numbers they are not listed here. If you shave the cylinder head during a rebuild it doesn't change the compression or piston protrusion since the head is flat. The valves must keep the same relationship to the pistons and check valve seating and relief.
engine oil and filter
new turbo oil feed line VW# 038 145 771 ah
full timing belt kit, see 1000q: timing belt
removal, part 1 for part numbers and detailed procedures
VW# 038 103 351 b (link is AMC brand) - new, rebuilt head, or head repair components (as needed)
hydraulic lifters (as needed)
valves, valve springs, valve keepers, valve guides (as needed)
misc intake and exhaust gaskets
PB Blaster or Liquid Wrench - penetrating lubricants that helps loosen rust - they're not WD-40
Feel free to sign up and ask a question about this article at the forums here: myturbodiesel.com forums
Secure rear wheels with chocks, jack up front of car, and make sure the front of the car is safe and secure before doing anything else. Remove the engine bay lower belly shield/skid plate, upper engine cover, and engine lower side shields, both driver and passenger side.
Disconnect and remove the battery. Note - in some rare cases this causes the immobilizer light to come on. The immobilizer is an anti theft device that won't let your engine stay running. If it's tripped then you might need to go to the dealer unless you have the proper tools and SKC. See 1000q: immobilizer FAQ for more details. You can use a 12V battery tender in the cig lighter outlet to prevent disturbing the system but it should not come on.
Because you will spend some time under the car and the engine bay is probably dirty, take this opportunity to clean the engine bay. It will help prevent dirt from falling into your face and eyes while working under the car. Always wear eye protection when working on your car, especially when under your car.
To clean the engine bay, remove the battery and cover all major electrical switches and the alternator, air filters, etc. Make sure that you do not get water into the intake tract. Clean with water, degreaser, etc, as necessary. Do not get degreaser on the alternator. Always blow dry all electrical switches and anywhere there may be water. The TDI engine stands up well to washing because there are gaskets that protect the electrical plugs but it's still best to blow dry spots of standing water.
Remove driver's side plastic cover blocking access
to battery tie down (2 phillps screws) and remove battery tie down bracket (top
red circle, may be 13mm) Remove battery box (5 bolts, other red circles)
Cover the alternator with a plastic bag if you have not done so yet. Spray oily areas with degreaser, brush as necessary, and let soak. Rinse off with water thoroughly. Make sure to clean the undercarriage and any areas where dirt may be hidden. Use compressed air to dry, pay attention to electrical connectors and areas of standing water.
While you are under the car, you will be glad that you cleaned most of the dirt
off. Under the car, remove white plastic inner CV boot heat shield (2 bolts circled
Spray PB blaster on the 3x 13mm turbo exhaust downpipe nuts (2 nuts marked by solid yellow arrows, 1
is hidden, marked by dashed yellow arrow) and turbo oil supply union/line (hidden
on top, marked by red arrow), let soak, you will loosen them later. Wear
safety goggles at all times. The turbo oil supply line may get twisted
during removal, I suggest having a replacement if you want to minimize car down
time. If it gets twisted at all, do not reuse it. The best way to
avoid twisting it is PB Blaster on the union and counterholding it while loosening the
Here is another view after turbo removal.
Spray PB blaster on turbo oil return line (outlined in red) and turbo
support bracket bolt (outlined in yellow), let soak, you will loosen these
later. Wear safety goggles at all times.
Here is another angle - this oil return line is different because it sits
under the turbo bracket. If you have this style of return line, loosen it
as much as possible. When you start to pull off the exhaust manifold, you
will have enough clearance to loosen the return line all the way and remove it.
If you want to remove the intake or exhaust manifold separately, spray everything with PB blaster. The intake and exhaust manifolds can be removed with allen and regular sockets, see the below pictures. Some of them may be damaged or get stripped, have some EZ-out/bolt-out tools handy in case.
These are thumbnail pictures,
click them to see the enlarged pictures with more detail. See 1000q:
intake manifold removal for more details.
It can be easier to remove the head with intake and exhaust manifolds attached.
Above the car...
Remove air intake box and it's accordion hose, vacuum ball, vacuum lines, fuel injector lines (17mm) , glow plug harness, etc. I suggest a touch of PB blaster on the fuel injector line unions. If you don't have a 17mm flare wrench, you can take a cheap wrench and cut a groove in it to get around the fuel line.
Drain coolant, see: 1000q: how to coolant flush and drain
Drain oil, see 1000q: how to change your oil
The next steps are identical to timing belt removal part 1. You have to remove the timing belt or at least remove the belt from the camshaft sprocket. Refer to: 1000q: timing belt removal: part 1 for more details. You may not have to remove the motor mount and support the engine if the belt is not coming fully off. Most of the time, a bad cylinder head is from a broken timing belt, in which case you would have to remove the motor mount.
Make sure the tensioner is removed or else there won't be clearance to remove the head. You can also choose to remove the tensioner stud to check for straightness. If you don't have a stud remover, use 2 nuts tightened against each other and use a socket to turn the nuts.
Unbolt exhaust downpipe from turbo (10mm x3 bolts), as pictured above. This is where the PB blaster was needed. An air wrench will come in very handy here for quick removal of those bolts. If you didn't clean the engine bay earlier, there will be lots of dirt and rust chips flying down from the air wrench. Always wear safety eye goggles.
Remove turbo oil return line and turbo support bracket as pictured before. If your car has very high miles replacement of the oil return line is optional. It's unlikely to break but sometimes it does happen because it's a flex line.
Disconnect EGR cooler hoses and other coolant hoses. See 1000q: EGR removal for more details. Make sure to label them for fast identification later.
Disconnect all remaining lines to cylinder head - electrical wires, glow plug wires, fuel supply/return lines to the injector pump.
You should now have adequate access to remove the turbo oil supply line. Although the service manual says to replace the oil feed line each time, it's possible to reuse it if it's clean and clear. If the insides have buildup or if it gets twisted at all during removal, do not reuse the oil feed line. Do not try to untwist it because once it's bent it's not possible to unbend it without having an internal restriction. The journal bearings in the turbo must ride on a layer of pressurized engine oil. It goes from the banjo fitting on the oil filter housing, counter clockwise around the engine, then down into the turbo, held with a union. Use a mirror to examine the line before trying to remove it. If it gets twisted, just bend it and cut it behind the bend (to prevent metal shavings from entering the oil line), to make it easier to remove. In the below picture, after I removed the oil supply line, I put a piece of plastic under the union and tightened it a few turns to hold the plastic in place. This will also help keep dirt out of the turbo bearings and oil line. Note the labels on the various hoses, lines, etc - after a week of sitting you'll forget which line goes where.
Below left is a thumbnail, click for a larger view. Below right is a
new oil line, The white plastic thing on the end is to hold the washers in
place until it's installed.
Use a stubby 17mm wrench on the oil line nut while counterholding the oil
union. There isn't enough clearance for a normal
wrench to counterhold so Herm TDI found you can cut a notch in a 12 point head wrench (so
it can go around the oil line, like a flare wrench). This method is
the least likely to twist the oil line.
| eddie1 found
that if your wrench is short enough it may fit (shown right).
While you could use a 7mm allen wrench or square punch wedged between the oil union and turbo exhaust housing side to jam the oil union, it only holds 1 side and could strip the union if it's rusty or too tight. If using a allen wrench I suggest placing it on the cast iron exhaust side and not the aluminum side. A stubby wrench or a crow's foot wrench on an extension (shown right) can reach the upper 17mm oil line "nut".
Again, if the oil line gets twisted it's no longer usable. Just cut it off for easy removal and cap the end so dirt doesn't fall into the turbo oil line.
After the oil line is removed wad some plastic or a paper towel into the oil union to keep the insides clean.
Also remove the oil line banjo bolt at the oil filter (1x 17mm) and the 2
brackets holding the oil line (1x 10mm bolt on each bracket). If the oil
line is still good, just loosen the bolt, pivot the oil line out of the way, and
hand tighten it to hold the line.
Above the exhaust manifold:
Remove valve cover (7 allen bolts, marked in yellow below.)
To avoid damaging the camshaft, slightly loosen the camshaft cap bolts (10 bolts marked in blue below) in the suggested order of: 1, 5, 3, 2, 4, and gradually in stages before you loosen them completely. Remove the caps and then the camshaft. Make sure to label which cap goes to which spot! They must go back in the same spot. You can use a sharpie permanent marker for this.
The reason for removing the camshaft is so that all the valves are closed during head removal. This prevents any damage to the valves or from them catching somewhere during removal. It also gives a little more room to maneuver the head them since the valves will be closed and the cam out of the way. It is optional but recommended. (Thanks for the tip Growler!)
Loosen the head bolts in sequence and in stages - they are stretch bolts and are not reusable. Bolt removal order is different from the bolt reinstallation order. Loosen each bolt slightly first before loosening them all to avoid warping the head. Loosen and tighten all the head/cam bolts in stages!
Lift off the head. If any coolant or dirt is present, clean it off. Cover the exposed head with a piece of plastic and tape down to keep it clean. If you leave the head exposed for a while, coat the exposed surfaces with some light oil to prevent rusting.
Clean the exposed surfaces. Make sure that there is no fluid in the head bolt holes - fluid pooling in the bolt holes could hydrolock and crack the block when you torque down the head bolts! No gasket sealer should be used on the head gasket. The gasket letters and numbers should face up.
Which head gasket you need is determined by
piston protrusion above the block. The Bentley manual says that
you only need to measure piston height if you change the crank, pistons, rods,
block, or bearings, etc. but it couldn't hurt to check the piston height
anyways. If your timing belt broke you definitely want to do this
measurement to make sure the engine didn't bend a rod. Use a dial gauge or
at least some feeler gauges to compare them at the same spots on the piston
face. Make sure to clean any carbon off so that it doesn't change the
If you're sure it's fine, count the
punch holes in the gasket and get another one with the same hole count.
On the ALH gasket, there is an oblong hole and some circular holes, only count the circular holes on the ALH engine. When you get the new gasket the holes will look the same. Not having the correct thickness head gasket (indicated by the number of punch holes
you have in the gasket) will change how high the head sits and change
compression. Here are the measurements for piston protrusion and head gasket thickness for
an ALH engine.
0.91-1.00 mm (.0358-.0394 in) = 1 hole gasket, 1.55 mm (.0610 in) thick
1.01-1.10 mm (.0398-.0433 in) = 2 hole gasket, 1.63 mm (.0642 in) thick
1.11-1.20 mm (.0437-.0472 in) = 3 hole gasket, 1.71 mm (.0673 in) thick
When you torque the bolts, tighten them hand tight, then tighten them gradually in the order suggested above by 30 ft lbs each, then 44 ft lbs each, then each 1/4 turn (90o). Then turn 1/4 turn again for the final torque (90o). Tighten in stages and in order to prevent head warping. I've heard of very lightly oiling the head bolts and washers by dipping them in oil and letting drip dry to get the proper torques but I can't find it in the service manual so I would assume they are dry. See 1000q: torque wrench FAQ for some tips on torque wrench use.
VW uses a special tool to guide the
head onto position, you can use old head bolts with the bolt head cut off. Wood dowels
as guides will also work. Jfettig looped some rope around the lift point
and exhaust stud to make it easier to handle.
If you have to replace only one bolt for whatever reason, you can loosen that one bolt only, it won't warp the head. If you have to remove more than one bolt, make sure the others are tightened while you work on one bolt at a time only. Again, the bolts are not reusable after tightening them to their final torque. If you have to loosen the head bolts or remove the head again, do not reuse the new headgasket, get a new gasket every time the head comes off.
Install timing belt, see timing belt part 2 - installation (exclusive content for forum members, please join us for free and confirm your account to view), how to refill engine coolant , and how to change engine oil as needed. Make sure you put copper crush washers on the turbo oil line unions.
When installing the oil line, snug up the union first but don't counterhold it when tightening the oil line nut. Just tighten the nut and it will tighten the union. You only have to counterhold the union when loosening the oil line. This assumes that the union can move freely and isn't rusted.
The rest of installation is the reverse of removal.
turbo oil return line banjo bolt - 30 ft lbs
turbo oil return line turbo side - 11 ft lbs
turbo/exhaust manifold - exhaust downpipe bolts - 18 ft lbs
exhaust manifold bolts - 18 ft lbs
intake manifold bolts - 18 ft lbs
head bolts - first hand tight each, then 30 ft lbs each in it's required order, then 44 ft lbs each, then each 1/4 turn. Final tightening, another 1/4 turn.
If you have any more questions on replacement or what to do after your timing belt broke, please ask in the VW TDI forum. You can also search below: