15. Tip: 240 GD replace Cylinder head gasket - replacement engine with 200.000 km mileage, 2000 km with Rapeseed-oil

Last update 16.07.2005 Copyright Dr. Hans Hehl, translated: Klaus Hold (www.gwagen.de)

Impressum gem. TDG 6

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All work on the G requires special knowledge, competency, special tools and the strength to not overestimate your own abilities, or better go to the service dealer for repair or maintenance. All information here at the best knowledge, but without guarantee! Data is for 240GD My 10/1979, BM 46031017000518

Replacement engine Nr. 616 010 8302/80 - June, 08, 1984, disassembled June, 11, 2003
Motor Motor Motor Motor Motor Motor
Engine assembled Disassembly of the environment Engine open and the other side Cylinder head removed Not bad after 200.000 km
Motor Motor Motor Motor Motor Motor
Head on its own, not cleaned yet Rocker arms removed Head without rocker arms Cleaned surface Cleaned head Detail
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Chain tensioner gasket Thermostat gasket Cylinder head gasket
y-branch gasket
3 different head screws Top too long
bottom new
Old and new
Overview: top back to the Top

Replace cylinder head gasket
Get spare parts
Stretch measurement
1) All starts: remove cooling fluid
2) Remove air filter
3) Remove injection rails
4) Remove rocker arms
5) Remove camshaft wheel
6) Remove camshaft
7) Remove cylinder head
. 8) Lift cylinder head
9) Clean cylinder head
10) Attach cylinder head (screw on)
11) Test chain tensioner
12) First start
13) Old piston: defect
14) others: Diesel filter
Replacing the cylinder head gasket: top

The replacement engine has had more then 200.000km on the clock, runs perfect, but on the left side, cooling fluid is leaking. In the front, oil is draining outside. Replace the gasket! It is interesting how an engine after 200.000 km looks like and if the 250 l rapeseed oil has left traces.

Get spare sparts top

You need the following sealing and gaskets:

1. Cylinder head gasket: A 616 016 20 20 - 38,60 Euro incl. Tax
Leave the gasket in the wrapping (Light and Ozone sensitive

2. y-branch gasket: A 615 142 05 80 - 8,35 Euro incl. Tax
cylinder head / Auspuffkrümmer
3. Chain tensioner gasket: A 617 052 02 80 - 0,70 Euro inkl. Tax
4. Thermostat housing: A 616 203 02 80 - 0,64 Euro inkl. Tax
5. Eventual Valve head gasket: A 615 016 00 80 - 7,97 Euro inkl. Tax
Kettenspanner-Dichtung Thermostatgehäuse-Dichtung
Because the cylinder head screws had to be replaced (M12, Inside geared) if expended too much you should have 2-3 replacement screws of the 3 screw types available. Maybe they are enough, because not all of the screws are expanded equally.
Stretch measure (measured by head underside face to the screw end). top

8 long screws: A 615 990 02 12 - length: 144 mm, max. length: 145,0 mm - 3,03 Euro incl. Tax
6 middle screws: A 615 990 03 12 - length: 119 mm, max. length: 120,5 mm - 3,90 Euro incl. Tax
4 short screws: A 615 990 01 12 - length: 104 mm, max. length: 105,5 mm - 2,78 Euro incl. Tax

cylinder head screws
The upper one of both lying together screws crosses the permissible stretch measure, the lower screw is new and 104 mm long.

One needs a long inside head tool M12 of e.g. Hazet No. 990, M12 SLg or from Mercedes: No. W 617589001000 / 15,42 Euro incl. Tax

For two of the four M8-socket screws a long 6 mm inside hexagonal tool is required, e.g. by Hazet No. 986, 6 SLg. Magnetizing the tools (repeated touching with a magnet) is recommended, then the screws get stuck at the tool.
screw too long M12 Innenvielzahn/Zylinderkopf 6 mm Innensechskant lang /Zylinderkopf
Start: The engine must cool down first (best would be over night).

1. remove cooling fluid top

The coolant is let down (screw at the side in the engine under suction elbow). Because it is obvious to renew the coolant now in general, below the screw is also opened in the cooler. However, in addition the bush bar be unscrewd before. The old coolant is caught (toxic) in a tub and is decontaminated at DC
2. remove air filter, suction pipe, exhaust elbow, thermostat housing and the valve bonnet with throttle wire.

Unscrew first complete ait filter, then suction pipe with exhaust elbow (both screws in the exhaust flange). Both thick cooler tubes are unscrewed from the thermostat housing and the upper tube bell is completely screwed off the short connecting pieces. Then the thermostat case (two screws) can be removed. There follows the cylinder head bonnet.
3. Remove the injection rails and the main diesel filter. top

Four injection rails are unscrewed, the leak oil pipes are drawn off from the injection nozzles and also the tube to the first injection nozzle. On loosening of both screws the diesel filter is moved a little bit away.

4. Remove of the rocker arms with support blocks

The camshaft is so put that the rocker arms are relieved. Attention: In addition not the camshaft is turned, only the crankshaft (27 nut, short lengthening and wrench) must be turned in rotation direction of the engine. Otherwise a danger for the tensioner blade exists.

Both rocker arms group are removed (socket screws) and front and rear are marked for the correct reinstallation.
engine engine
5. Preparation: remove camshaft wheel top

First the tension screw in the camshaft wheel is loosened (easily done, it is tightened only with 80 Nm / 8 kpm ), but not unscrewed. One can counterhold with a screwdriver by a hole of the wheel.
Then only the crankshaft with the rattle as long as is turned clockwise, until the first cam of the camshaft (if one stands in front of the engine) horizontal points to the right, the set mark (notch) on the balance disc (disc behind camshaft wheel) with the mark (line) in the 1 camshaft support block (see arrow) must be inline. Because the balance disc has two notches, the degree mark of the crankshaft must stand, in addition, on OT of the 1st cylinder (zero-degree mark in the hole middle of the footbridge). Then the first and the 4-th piston completely stand on top. Motor
Now the crankshaft may be turned no more. Now camshaft wheel and timing chain are firmly connected with a wire by a hole or one marks the postion to each other. With a clean steady cloth close the openings, so that no part can fall into the engine. The The screw of the sliding rail unscrew and by means of hit-extractor pull out the support bolt of the engine case (M6 thread) and infer sliding rail upwards.

6. remove camshaft

will be continued
7. remove cylinder head top

To avoid shape distortion of cylinder head, the screws must be released in the reverse order like the assmbly, thus also with the same working steps. The screws are tightened very hard. It is useful to work with a lenghtening (3/4").
1. Step: start at screw 18 towards screw 1 with 90 degree loosening
2. Step: another 90 degree loosening
3. Step: remove the screws. Eventually remove the injectors.
4. Step: M8-head screws (a) with 6 mm wrench.
8. remove cylinder head top

The cylinder head mostly sticks a bit, you can help a bit carefully with an iron-bar at the corners.If the gasket has freed itself, you can remove with an assistant the head and see hopefully nothing unusual. Engine mileage: 210,000 km exchange engines in 1984, since a half year 2300 l rapeseed oil with 2-3% of diesel). On the left in front the head gasket leaked water, you see the rust!
Motor Motor-Kolben
The white scab formations in the overhanging ball heads of the pre-chamber are normal after 200,000 km with diesel). Zylinderkopf
9. Clean Cylinder head and Engine block

Now the rests of the destroyed gasket are removed with a sharply polished scraper carefully (create no grooves!). Beside that, you're your time and do not fill your oil channels with the gasket rests. I have cleaned the head with a wire brush.
Motor Motor
10. Muont cylinder head top

The head will be put back, two studs on the engine block are ensuring correct postion.

Fastening torque and angle (cold engine!):

Attention: use an indicator (grease crayon) to indicate the screws that has been pre-tightened to avoid mistake.

1. Step: start at screw 1 to screw 18 with 40 Nm.
2. Step: use the same order for the 70 Nm.

Pause 10 Minutes, because of the seating of the gasket.

3. Step: same order of screws, turn by 90 degree.
4. Step: same order of screws, turn again 90 degree
5. Step: tighten the M8-socket head screws (a) with the 6 mm tool.
11. Chain tensioner check top

The chain tensioner should only be possible to be compressed with a lot of force. In the disassembled position oil was leaking and the tensioner was easy to be compressed. Then a 1 litre can is filled with 10series oil and with a drilling machine supporting stand or similiar tool oil is filles into the upside down laying tensioner. Compress and release (6 to 8 times) slowly to refill it with oil. Then the chain will not make noise when first start. Assemble the tensioner with a new gasket. A replacement is expensive (A6150500811): 171,56 Euro incl. Tax.
Kettenspanner Motor
12. First Start: top

Install the rocker arms, adjust clearance of the valves.

After everything is assembled correct, cooling fluid is refilled, it is getting exciting. First of all, the injection rails are connected to the injectors (only loosely). The leak oil pipes are connected, the last small cap is missing. Now pump with the hand pump diesel until diesel is getting out of the end of the leak pipes. If the diesel is getting outside, the injectors are filled with diesel and you don't need to crank a long time.
Finally put the valve cover back (maybe use new sealing), the last wire from the Relay to the first glow plug not connected yet turn crank the engine for approx. 2 sec. After that tighten the injection pipes and connect the wire. After pre glow the engine started immediately. Let the engine run warm, check the level of cooling fluid and oil. Motor
13. Old piston from original-Engine 10/1979:

Interesting is the comparison of the pistons of the dissambled replacement engine with the defect piston of the original engine. The previous owner used to drive the 240GD mostly on the highway and perhaps has too many thermal incidents. The old piston had special slots within some cracks.
Motor alter Kolben
14. Other parts: see Filter 240GD

Diesel filter: A 001 092 04 01 - 10,07 Euro incl. Tax
Oil filter: A 617 180 00 09 - 11.95 Euro incl. Tax

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