W163 ML270cdi Turbo Replacement
Im not a mechanic albeit I have a considerable amount of experience in removing and rebuilding engines (Skoda Estelle 1.2/1.3, Rover SD1 2.6/3.5) and many associated components of cars, such as differentials, gearboxes etc. I would call myself a competent amateur mechanic and as such the guide has been written with similar minded people. No doubt professional mechanics will know short cuts etc, so please feel free to add your comments and tips, especially if Ive got something wrong (typo, missed info etc).
This thread will be split up into many small components (according to character posting limits) and will contain a plethora of photos to aid in visualising what work is to be done.
1. Ensure engine is up to normal running temperature (ie. 80-90'c) before commencing work. It is recommended to drain the engine oil and fill with new oil before commencing this procedure as oil is a crucial component of a turbo-charger and your previous turbo could have failed due to poor oil or its circulation.
2. Park car, apply handbrake and engage in gear (Park for Auto). Chock the back wheels. Jack the car front up, place axle stands or heavy-duty wood between the floor and the solid engine /suspension cross beam, about 30cm under the front bumper. Place additional supports all round and under the car as the ML is one heavy beast!
3. Remove the plastic engine cover, 4 bolts on cylinder head (black with Mercedes written on), 2 bolts over inlet manifold (silver with manifold indentations). Be careful when lifting as the two plastic components are interconnected and it you don’t keep it straight, you could break the interconnections.
4. Remove the 3 bolts from the air filter. Just in front of the air filter is a brake vacuum sender, lift this up as it’s on a rubber grommet and move it (strap it) to the side. Remove air filter cover. Remove air filter.
5. Remove 2 bolts from inside the air filter box connecting it to the cylinder head. Remove two screws, on the outside/underside of the air filter box. Loosen clamp connecting air inlet (oblong shape) to air filter box, then gently push off concertina pipe from air inlet silencer and completely remove the air inlet pipe. Remove connector from the Air Mass Sensor (MAS) and strap it to the side. Loosen jubilee clip on interconnect pipe from the air filter box to turbo-charger at the air filter end, and then do the same at the turbo charger inlet end. Remove pipe paying particular attention to the sleeve like seal (#23) on the turbo charger inlet, which may have stayed inside the pipe (remove and replace). Remove air filter box. If the unit looks dirty/oily, swill thoroughly with Isopropyl Alcohol - be very carefull not to touch the innards of the MAS with any object/fingers other than the alcohol. Place it in a clean location safe from damage until ready to re-assemble. Should the MAS require cleaning, refer to Parrot Of Dooms excellent article: http://forums.mercedesclub.org.uk/sh...ad.php?t=18298
6. Squirt copious amounts of spray copper grease or rust penetrator onto the 3 bolts holding the Turbo to the exhaust manifold. These bolts can be difficult to extract, hence getting the engine warm and spraying at this time.
7. Remove under body protector covers - the 3 going from centre to front of car - middle of car protecting transfer case and gearbox, under engine and engine front. All use a plastic rivet (#43), where you have to pull the centre out, then the main rivet. They cost about 50p each, so if you break any, not the end of the world - NB. Make sure when you reassemble you replace ALL of them!
8. Remove right wheel (drivers side in the UK), then remove right wheel arch inner cover. This involves unscrewing the mud flap then all the plastic nuts fastening the plastic cover under the wheel arch to the body. Once all are removed, have a bit of patience and wriggle out the cover so as not to damage any paintwork. (NB. this part is important, because without the aid of hydraulic lifting gear, getting to several of the bolts holding the Turbo/Catalyst is very difficult).
9. Use spray grease or rust penetrant and spray onto the two bolts holding the Pre-Catalyst to the engine block, as seen through the right wheel arch.
10. Remove the exhaust clamp between the Turbo and Pre-Catalyst (#5,#7). This is best done through leverage, using a steel wedge and a wood block, pushing the wedge just under the clamp and the wood just under the clamp to create a seesaw arrangement. Use a wood block from the ground up to the Catalyst to support it whilst removing the clamp.
11. Accessing through the right wheel arch, or from underneath the car, remove the Pre-Catalyst to secondary catalyst exhaust clamp (#28,#29) using same method as above.
12. Accessing through the right wheel arch, remove the two nuts, which secure the Pre-Catalyst to the engine block.
13. Remove the Pre-Catalyst (#30), gently working it out.
14. Examine the clamp and the carbon seal from both the Pre-Catalyst to Turbo and Pre-Catalyst to secondary catalyst. Replace if needed (replacing both is recommended, especially if your car has done 50+K miles since it was last done).
15. Disconnect the vacuum pipe, which goes into the diaphragm actuator on the turbo underside and strap it out of the way.
16. Remove the compressed air expansion chamber to turbo bracket, 2 bolts.
17. From underneath the vehicle, remove the two bolts securing the compressed air expansion chamber to alternator.
18. Pull the compressed air expansion chamber forward to separate it from the turbo compressor outlet. Remove the rubber sealing ring ( #8 ) and replace.
19. From underneath the vehicle, or through the right wheel arch, remove the bolt between the support bracket and the turbo charger. Loosen the bolts of the support bracket, as you need some leeway when removing the turbo.
20. Put cloths underneath the turbo, then remove the bolt (#13) securing the high-pressure oil feed line into the top of the turbo. Remove the bolt securing the high-pressure oil feed line into the cylinder head. Remove the high-pressure oil feed line. It is recommend to buy a new high pressure oil feed line (#15) and hollow feed bolt (#13), most certainly, you need to replace the rubber seal located at the end which enters the cylinder head (#17). If you re-use the old oil feed line, soak it in turpentine or white spirit until all the grime inside has dissolved, and run an abrasive through to dislodge any carbon deposits.
21. Loosen and remove the three bolts holding the Turbo charger to the exhaust manifold. Use a long TorX or hexagon spanner (depending upon what has been used on your turbo) and ensure it is perfectly square with the bolt as they will be very tight. The front bolt you can access easily, the two behind, you need to put the spanner from the direction of the car rear, behind the manifold. Plan only to move them a few millimetres at a time. If they wont come loose, get some heavy-duty rust penetrant, soak and leave overnight. Use shock tactics if the bolts are tight, ie. Tap the spanner with a dead hammer in short quick blows.
22. Lift the turbo out of the vehicle. NB. The low pressure oil return line (#20) is still connected between the turbo and the engine block, but this is only a push fit and the oil line stays attached to the turbo as you remove it.
23. Place the turbo on clean plastic or wax paper surface and remove the 2 bolts securing the low-pressure oil return line to the turbo. Thoroughly clean the oil low-pressure return line. It is recommended to replace the seal which sits in the engine block where the low pressure oil line is located (#21).
Cleaning of the Intercooler (recommended if your car has done 50+K miles)
The intercooler is located at the very front of the car, what appears like a radiator. Below it you will see a small radiator used to cool the oil from the transmission and behind it you will see 2 different radiators.
1. Remove both headlight units. 1 bolt secures the light at the top of the engine bay, 2 nuts secure it at the bottom (you will need to remove the plastic body colour strip which sits between the bumper and the headlight). Gently ease them out and disconnect the 2-3 connectors at the rear. Store them in a safe place!
2. Remove the 8 bolts holding the crash strengthening plate, which sits just above the radiators, which is usually body coloured. Remove the crash strengthening plate.
3. Remove the two bolts holding the Intercooler onto the air-con/radiator, 1 at each side at the top of the intercooler. Once the bolts are removed, pry off the clips.
4. Loosen the jubilee clip on the left hand side pipe and pry off the pipe (this is the pipe connecting to the compressed air expansion chamber).
5. Loosen the jubilee clip on the right hand side pipe and pry off the pipe (this is a short pipe, connecting to the engine manifold inlet chamber).
6. Unclip and strap to one side, the charge air temperature sensor connector, located at the middle right hand side of the intercooler. Remove the sensor from the intercooler, spray with isopropyl alcohol and put in a safe, clean place.
7. Pull forward the top of the intercooler, sufficiently to clear the loosened pipes, and then pull upwards. The intercooler is held in place at the bottom via a ledge in which it sits.
8. Using Isopropyl alcohol, washing up liquid etc, thoroughly clean the innards of the intercooler using agitation. Drain, then refill and repeat until fluid in = clean fluid out. Using very hot water, swill and agitate the water through the innards of the intercooler until NO signs of alcohol or washing up liquid can be seen (NB. washing up liquid contains salt, so it is very important to swill excessively). Run a cold-water hosepipe through the intercooler for 10-15 minutes, to be sure all has been flushed out. Leave until dry.
9. Clean all pipes, using rags (non-lint based) or swill out as per above. ie. Air inlet pipe, air filter to turbo pipe, compressed air expansion chamber and pipe.
10. Re-assemble in reverse of above.
Re-assembly of Turbo
1. Prepare/clean all surfaces, exhaust manifold, primary catalyst, secondary catalyst and apply a little copper grease (copper grease withstands temperatures up to 1100’c) to all removed nuts and bolts.
2. Assemble low-pressure oil return line onto turbocharger, using a new gasket ( #18 ). Lightly tighten the bolts, ensure that the low-pressure oil line is free to turn.
3. Ensure sealing ring (#21) in the engine block, where the low-pressure oil line will sit is clean and renewed.
4. On ML270’s, no gasket is fitted between the Manifold and the Turbo-Charger (#4). Most other 270 engines have this gasket. It is recommended to install one, so that any irregularities in the manifold are compensated by the gasket.
5. Install turbo-charger into engine bay, locating manifold bolts (insert 2 bolts, no need for gasket at this point) and ensuring that the low-pressure oil return line is located into the engine block gasket from 3 above. If the turbo won’t fit correctly, slacken further the turbo support bracket bolts (point 19 in disassembly above).
6. From underneath the vehicle, tighten up the 1 accessible bolt, which tightens the low-pressure oil return line to the turbo-charger.
7. Remove the 2 bolts holding turbo to the manifold, remove the turbo. Tighten the remaining bolt on the low-pressure oil return line to turbo-charger. This procedure is necessary, as you cannot access both bolts whilst the turbo is in the vehicle and it is difficult to line up the oil return line when the Turbo is on the bench.
8. Re-install turbo-charger into engine bay, install exhaust manifold gasket (#4) and the 3 bolts, tighten to finger tight.
9. From underneath the vehicle, install the bolt between the turbo support bracket and turbo charger. NB. On my vehicle, this component was bad fitting and as a consequence, the turbo turbine was in tension, which may have led to its failure. The bracket hole had been worn wide due to the tension. There should be NO tension when the support bracket is tightened up and the bolt from the bracket to the turbo is tightened up. If there is tension, observe how the bracket hole sits square in relation to the thread on the turbo, remove bracket and file out sufficient so that when the bolt is inserted, there is no tension.
10. Fill the Turbo up with oil via the high pressure oil feed until overflowing with high quality synthetic oil. Fill the high pressure oil pipe with synthetic oil and do your best to keep the oil from running out. Place a new seal onto the cylinder head high pressure oil feed outlet (#17) and install the hollow bolt (#13) into the turbo side of the high pressure oil pipe. Offer up the pipe between the Turbo and the cylinder head and tighten the hollow bolt (#13) and the cylinder head pipe retaining bolt (#16).
11. Ensure that all manifold bolts, turbo support bracket bolts and oil pipe bolts are fully tightened.
12. Place the carbon sealing ring ( item 5 ) (this should be new if your car has done 50K+ miles on the old ring or the old ring looks worn) onto the lip on the turbo turbine outlet. The smooth rounded side should face outwards towards the exhaust or rear of car.
13. Place the carbon sealing ring ( #28 ) (this should be new if your car has done 50K+ miles on the old ring or the old ring looks worn) onto the lip on the Pre-Catalyst outlet (opposite end to turbo). Use a little gaffer tape to hold it in place (ie. Between the lip and the sealing ring).
14. Offer up the Pre-catalyst (#30), lining it up with the secondary catalyst inlet and the turbo outlet, ensuring the rings are square on and the bolt holes securing the Pre-catalyst are mated to the bolts on the engine block. Lightly tighten the nuts on the Pre-catalyst to engine block bracket.
15. Place a support (a piece of wood from the ground) onto the Pre-catalyst inlet (at turbo junction). Using a new clamp (#7) (you can use the old clamp if it hasn’t done much mileage, but without the installation bracket which opens up the clamp, it wont be easy) push hard and firmly onto the junction between the turbo and pre-catalyst. DO NOT HAMMER, only use muscle power because you could damage the catalyst. When the clamp is fully on, the installation bracket which opened up the clamp will come loose so just remove and store in-case you ever have to take the clamp off again. NB. The clam has front fingers with upward turns on, these fingers should be facing towards the pre-catalyst.
16. Place a supporting block of wood under the secondary catalyst inlet between the inlet pipe and body subframe. This is necessary so that you don’t flex or strain the secondary cat when you put the clamp on. Using a new clamp (#29) and using muscle power only, fingers of the clamp pointing towards the turbo, locate the clamp on the junction between the pre-catalyst and secondary catalyst, push hard and firmly until the clamp is fully over the junction and the installation bracket comes loose. Remove the installation bracket and store for potential later use.
17. Tighten the pre-catalyst to engine block bolt.
Re-connect the air expansion box, but first ensure a new sealing ring ( #8 ) is installed between the metallic lip inner and the plastic compressed air expansion box. Push it onto the turbo compressor air outlet. Install bracket, accessible from top, which holds this pipe into the turbo (2 bolts).
19. From underside of vehicle, install 2 bolts which hold the compressed air expansion box to the alternator.
20. Reconnect the vacuum pipe which comes from the Boost Pressure Control Valve Transducer (item 15 in disassembly) onto the Turbo vane actuator.
21. Verify that everything is tight and connected. ENSURE NOTHING IS LOOSE near the turbo compressor inlet, keep everything well clear of it. Start the Engine BUT DO NOT REV IT. Check that no leaks are coming from the pre-catalyst to turbo exhaust junction, the pre-catalyst to secondary catalyst junction and the turbo compressor to air expansion box junction. Allow the engine to run for around 10 minutes at idle to bed in the turbo oil feed. Check that no oil leaks are occurring at the cylinder head high pressure oil outlet, turbo oil inlet, turbo oil outlet and engine block inlet. Any problems, stop the engine and rectify.
22. After bedding in, gently rev the engine (using the bulk head mounted accelerator cable, left side of engine) and verify that the turbo actuator is moving back and forth according to revs. Re-verify leaks as per 21 above.
23. Switch off engine.
24. Re-install the air filter housing (2 bolts from inside of air filter to cylinder head), air filter and air filter cover (3 bolts).
25. Install pipe from Air filter to Turbo. NB. There is a sealing ring which goes between this pipe and the turbo compressor inlet, if you install this part incorrectly, expect a damaged turbo! I left it off because it is a sod to get on and after 13K miles, it is still showing no signs of being needed. Basically, if your insistent on installing this sealing ring, YOU MUST install the ring onto the turbo compressor inlet, then push the pipe over the ring. Tighten the clamp on the turbo compressor inlet and on the air filter outlet.
26. Re-connect cable to MAS and re-site the vacuum sender (item #4 in disassembling).
27. Re-connect the concertina air-pipe from the air inlet silencer to the air filter.
28. Re-verify everything is installed correctly then start engine and check for leaks/noises etc. There should be no noises other than the sound of the diesel and a faint turbo whine when revved.
29. Re-install the wheel arch cover and wheel.
30. Re-install engine cover (item 3 in disassembling).
31. Road test, BUT GENTLY DOES IT! Treat the turbo with respect until its bedded in (ie. Try to keep below 2000rpm).
Below is the complete part list for replacing the Turbo, along with exhausts components should any be found to require replacement.
# Part Number Description Quantity Must Change
For Turbo Charger:
1 A 612 096 00 99 Turbo - engines upto 963 30 044707 1 Yes/or
1 A 612 096 02 99 Turbo - engines upto 963 30 044707 1 Yes/or
1 A 612 096 05 99 Turbo - engines from 963 30 044708 1 Yes
2 A 612 096 00 45 Support Bracket - Exhaust to turbo-charger 1
3 A 611 098 14 39 Bracket - Charging airline to turbo-charger 1
4 A 646 142 00 80 Gasket - Turbo-charger to exhaust manifold 1 Yes
5 A 000 492 04 81 Sealing Ring - Pre-catalyst to turbo-charger 1 Yes
6 A 011 990 23 01 Screw - Support to turbo-charger 2
7 A 000 993 26 15 Spring - Pre-catalyst to turbo-charger 1 Yes
8 A 012 997 22 45 Sealing Ring - Turbo-charger air outlet 1 Yes
9 N 000000 003161 Screw - Turbo-charger to exhaust manifold 3
10 N 910143 006000 Screw - Charging airline to turbo-charger 1
11 N 910143 008000 Screw - Support to crankcase 2
12 N 910143 008006 Screw - Support to crankcase 2
13 A 001 990 11 63 Hollow Screw - Lubricating oil line at turbo-charger 1 Yes
14 N 007603 010406 Seal - Lubricating oil line at turbo-charger 1 Yes
15 A 611 180 01 20 Lubricating oil line to turbo-charger 1 Yes
16 N 910143 006001 Screw - Lubricating oil line at cylinder head 1
17 A 023 997 85 48 Seal Ring - Lubricating oil line at cylinder head 1 Yes
18 A 611 187 06 80 Gasket - Oil return line at turbo-charger 1 Yes
19 N 910143 006001 Screw - Oil return line at turbo-charger 2
20 A 611 180 01 22 Oil return line turbo-charger to cylinder crankcase 1
21 A 611 187 05 80 Gasket - Oil return line at cylinder crankcase 1 Yes
22 A 006 997 26 90 Jubilee Clip - Turbo air inlet 1
23 A 612 094 00 51 Seal Ring - Turbo air inlet 1 Yes
24 A 163 492 08 41 Bracket - Pre-catalyst to crankcase 1
25 N 910143 008000 Screw - Bracket to crankcase 2
26 A 140 990 07 50 Nut - Bracket to crankcase 1
27 A 603 990 09 51 Nut - Front exhaust pipe to exhaust manifold 2
28 A 000 492 05 81 Seal Ring - Exhaust pipe to catalytic converter 1
29 A 000 993 25 15 Spring - Exhaust pipe to catalytic converter 1
30 A 163 490 47 14 Pre-catalyst - Front exhaust pipe 1
31 A 163 490 53 14 Secondary Catalyst 1
32 A 129 490 00 44 Plate - Front exhaust pipe to transmission 1
33 A 163 492 00 41 Bracket - Bracket to transmission case, left 1
34 N 000934 008006 Nut - Front exhaust pipe to transmission 2
35 A 140 990 07 50 Nut - Front exhaust pipe to transmission M8 2
36 A 202 492 00 18 Base plate - Front exhaust pipe to transmission 1
37 A 163 492 02 18 Rubber pad - Front exhaust pipe to transmission 2
38 N 914007 008010 Combination Bolt - Front exhaust pipe to transmission 2
39 A 163 490 47 01 Exhaust Muffler 1
40 A 163 490 00 37 Suspension Ring 2
41 A 163 490 08 27 End piece - Tail pipe 1
42 A 163 492 00 44 Suspension Ring 1
Underside Cover Protectors:
43 A 163 990 02 92 Rivets 1++
Picture 1 - Turbo to Pre-Catalyst Clamp
Picture 2 - Turbo Turbine to Manifold - These bolts can be difficult to remove.
Picture 3 - Turbo Turbine to Manifold - different angle.
Picture 4 - Air inlet silencer. Concertina pipe goes from it to air filter housing.
Picture 5 - Air filter housing - Lid and filter removed.
Picture 1 - Air filter to Turbo compressor inlet hose. Connects to MAS (not shown).
Picture 2 - Turbo compressor inlet.
Picture 3 - Secondary Catalyst inlet - looking up from ground into engine bay.
Picture 4 - Turbo removed.
Picture 5 - Turbo removed, look at high pressure oil pipe top right.
Picture 1 - Air inlet silencer, boost pressure control valve transducer (top left), air vacuum reservoir (top right, round object).
Picture 2 - New turbo installed.
Picture 3 - Installation of Turbo to Pre-Catalyst clamp - note the installation bracket on top of clamp, this comes loose and is removed once clamp is in place.
Picture 4 - Different angle on Turbo to Pre-Catalyst clamp.
Picture 5 - Union between secondary catalyst and pre-catalyst (picture middle).
Picture 1 - Close up of Union between Secondary Catalyst and Pre-Catalyst.
Picture 2 - Close up of Turbo to Pre-Catalyst clamp.
Picture 3 - Turbo to Pre-Catalyst clamp, installation bracket removed.
Picture 4 - Supporting the vehicle using tressels and wood on the engine support cross member.
Picture 5 - Pre-Catalyst to Secondary Catalyst clamp installed.
Picture 1 - Air filter to Turbo compressor inlet, connected at turbo side.
Picture 2 - Different angle on picture 1.
Picture 3 - Heat shielding around Turbo (heat shielding is attached to air filter housing).
Picture 4 - Turbo to Pre-Catalyst and Pre-Catalyst to Turbo clamps (they are different sizes).
Picture 5 - Turbo support bracket, looking from under vehicle. Note the bolt hole has been filed to ensure no tension in turbo once mounted.
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