whereto find valve adjust info for 240D ?

adjust valves .004" intake, .012" exhaust, cold.

Beginning of injection- 24 degrees BTDC no. 1 cyl. Bill Ditmire Ditmire Motorworks,Inc.

425 White Horse Pike Absecon,NJ 08201 609-641-3392

Diesels don't get traditional "tune-ups" but do have a maintenance schedule that ought to be followed. 5K engine oil & filter change, 15K valve adjustment, 30K engine air & fuel filter, automatic transmission fluid change & transmission filter.

I'll post valve adjustment instructions for a 300D Turbo, but will apply basically to your 240D but you need to check your engine's valve adjustment gaps.

As 617 powered M-Bs are acquired by new owners the question of valve adjustment arises increasingly. This modest instruction attempts to cover the basics of a DIY valve adjustment. Old hands may have suggestions that differ and those are encouraged to enrich the archives. >>

Until the mid 1950s all auto engines used mechanically adjusted valves; thereafter hydraulic valve compensation was adopted for most US engines. (I bet many "valve and carbon" jobs were done for neglected valve adjus- tments.) Thereafter only Detroit's high performance engines and imports retained mechanical valve adjustments. >>

Mercedes-Benz cars were designed for top performance with the cost being more maintenance intensive until the 1980s. Better car design and increased competition reduced maintenance and its costs. But that leaves the need for DIY owners to know how to maintain these vintage four and five cylinder diesels, all of which should have their valves adjusted every 15,000 miles. >>

The valves in an engine look like mushrooms that are raised from and lowered into their seats. The contact area between the valve and its seat in the cylinder head is quite small and, though hardened, wears over the miles; the wear allows the valve to recede into its seat. That means the valve moves closer and closer to its cam lobe until the cam prevents the valve from fully closing and sealing. To prevent this and to ensure its complete closure and seal the engineers put a safety gap between the cam and valve. The adjustment is to restore the correct safety gap between the cam and the rocker arm and hence its valve. >>

Adjusting valves is not hard physical work but is rather a fastidious task that requires some time (2 or 3 hours for the first time) so have the time available and be in a patient mood for the job. You need a good drop light, a new valve cover gasket, two thin 14 mm straight open ended wrenches or better, the Hazet 14 mm offset valve adjusting wrenches, and a blade feeler gauge. Doubled latex gloves are a helpful option. >>

You need to be organized and methodical. There are ten valves to be checked (8 in a 240D); typically only a few will need to be adjusted. The intake valves' gap should be set to .004 INCH and the exhaust valves' gap should be set to .014 INCH; both specifications are for a COLD turbo diesel engine (60 - 70 degrees F.) that, ideally, has stood overnight without having been started. >>

YOUR engine's specification may be different, check before starting work. >>

Remove the throttle linkage from the top of the valve cover. The sockets are pried off their pins with a flat bladed screw driver. Just get the linkage out of the way and let it hang. Remove the valve cover, also known as the cam box. It fits tightly but lifts off with some vertical lifting and wiggling. Set it somewhere clean, upside down. Before you is the camshaft and ten very black valve springs and rockers. >>

It's now time to stop and make a check off list for these valves all look the same after you've checked a few and you don't want to omit any, or work on the same one twice! >>

Make a layout sketch like this (from the RIGHT side): I=intake, >> E=exhaust >>

Remember, the turbo's Intake valves' gap should be .004 INCH and the Exhaust valves' gap .014 INCH. That's why a guide and check off list is needed to avoid confusion between the specs, not omit any valves or duplicate your work. >>

I'm right-handed so I stand on the car's right and reach to the left; I also remove my engine's air cleaner for better access to its valves. >>

OK, it's time to begin. Look at the cam from the front of the car and find a lobe that's pointed at 1:00 o'clock - that puts its lobe about

180 degrees opposite its rocker arm. (First pick one that's easily ac- cessed so you can concentrate on the valve, rather than the struggle to reach it!) >>

Determine if that valve is an I or a E and slip the appropriate feeler gauge blade between the cam and its rocker arm. It should be snug and take a bit of a tug to move it through the gap. It's OK if the blade slides through the gap with resistance; if so, mark it "OK" on your check off list. >>

The valve is too tight if you can't get the gauge into the gap and needs to be loosened. Conversely, if the gauge is really loose the gap should be reduced. Bear in mind that most adjustments are only about .002 to .004 INCH or about one eighth of a turn of the wrench so start with modest expectations - of making a fine adjustment. When in doubt, looser is better than tighter, but too loose = tapping. >>

Below the rocker arm and above the valve spring are two nuts. The TOP or cap nut adjusts the valve's gap, the LOWER nut is the lock nut. These are firmly snug, not very tight. Hold the cap nut and loosen the lock nut, then turn the cap nut tighter or looser as needed, check the gap and, if OK, hold the cap nut and while you snug the lock nut. Check the gap again. You can turn the valve spring with your fingers (wear double latex gloves) if needed to get the wrench onto the nut. That's one valve done so X it off your check list. (I note which valves I adjust so if, there's a problem, I only need to check those, not all.) Turn the engine by touching it with the starter and look for a cam lobe that's opposite its rocker arm. >>

Officially one is supposed to turn the engine by placing a 27 mm socket onto the crankshaft pulley's nut. Sometimes you can also turn the engine by putting a wrench onto the power steering pulley bolt but be sure to turn it the CORRECT direction or rotation. Use a ratchet to ensure correct rotation. >>

While the cover is off you can also check the timing chain's stretch. Between the chain sprocket and the front most camshaft support or tower is a thrust collar; it has a notch. On the driver's side of that front most cam tower, is a horizontal mark cut into its exterior at the mid point of the camshaft. Turn the engine until the collar's notch and the groove are exactly aligned. That puts the camshaft at TDC (top dead center). Now read the degree scale on the crankshaft balancer. ( 00 degrees is TDC on the crankshaft's scale.) (You'll need to clean the dirt off the crankshaft's balancer and its reference pointer to read the angle.) >>

The timing chain should be replaced if the crankshaft reading is 5 degrees or more ahead of the cam (now at TDC) for that indicates the chain's worn and stretched and the greater these are the greater are the odds of the chain breaking. When it breaks the valves and pistons collide and another engine will be needed for repairing the resultant mess is much more costly than a used engine. Chains last a long time but a new chain can be installed DIY if necessary. >>

After all the valves have been checked and adjusted as needed it's time to install a new gasket onto the valve cover, install the cover and torque its nuts to 11 ft lbs. Reassemble the throttle linkage and lubricate each socket with a few drops of ATF and snap them together and check that the linkage moves freely. >>

Job complete. Inventory your tools and mark the date and mileage on your check off chart so you'll know when it's next due. >>

I hope the job creates an appreciation of the precision and reliability that "old mechanical systems" can achieve. No computers, no lasers, just some personal attention. Afterward you know how it works and what you've accomplished. >>

Thanks to all for the thorough help.

Gratefully,

Courtney

T.G. Lambach wrote: