Normal Diesel Clatter or Impending Doom?
 

I've noticed on my recently acquired '82 240D, that when the engine's cold, there'as a pronouced rattle at idle that sounds somewhat louder than normal. It sounds as if two of the cylinders are knocking louder than the other two. Car has about 170,000 miles. After warmup, it sounds like a normal 4 cylinder diesel.
Should I be concerned?

Happy Motoring, Mark

I'd not worry about it, they make all kinds of noises when cold sometimes, its their way of saying "brrr!!!" ;) Most likely its fine, especially with 170k, if its been at least somewhat maintained, thats very low miles for a 616 4 cylinder engine, they can last a loooong time. Since it sounds fine when warmed up I'd not worry, it may just be worn injectors or something.

mine makes the same sounds, and mileage wise you can swap those 1 and 7 around. 2 days ago it was smoking somewhat right when i started it, but that was because i did not preglow it and just cranked it. then just when i was going to let it rest and turn it off, it fired as i pulled the key. so when i started it again with the preglow it was fine.

i find that it helps to give the gas pedal a short nudge just as it starts, then it does not make that clatter for too long.

Mark-

As long as it starts easily when cold, I wouldn't worry too much about it. Have you checked/adjusted your valves and eyeballed the wear on your timing chain? If you are falling in love with her, you might want to treat her to some new injectors or , at least, a bottle of Diesel Purge.

Rick

So far, she's been starting easily down to the mid '30s, but I always wait till the glow-lamp goes out. Maybe I am 'falling in love'. At least lately, I'm driving her more than I am my '98 Nissan. She's been running so well, I'm afraid to mess with the engine but do plan to check the valve adjustment. There's been no noticeable smoking. Fuel mpg has hovered around 23-24 in mostly local driving.

I did a search and found references to something called 'nailing', but the opinions and remedies were all over the map. Most seemed to recommend new injectors, but then there were discussions about who even makes good injectors anymore- Bosch, India, Italy? I'll check with Phil first.

Happy Motoring, Mark

Engine noise
 

My 77 300d was making noise when cold, and got worse with time, until it was there all the time. This was fuel knock in my eng. and I finally bought and replaced the injector nozzels a few days ago. A world of difference!!
I used the Bozio nozzels. Smooth and quiet. This was the best money that I have spent on my car so far.
To answer your question about cold start noise, a little is normal, just the nature of the beast.
Enjoy your 240, these cars seem to have their own personality.

Those are the Italian ones. How much were they? PartsShop wants about $55 for the Bosch injectors.
I'm not going to rush into replacing them, as long as the cold-clatter isn't something dire.

Happy Motoring, Mark

Mark-

The Bosios run about $29 for the nozzles only. You disassemble the injector and replace the nozzles. Check Diesel Giant's website. I installed them in my 300SD a few weeks ago but haven't driven it much since. Doesn't seem to be emitting a black cloud anymore. It will take some running to clean out the prechambers.

Rick

well, I did a valve adjustment today. What a pain (literally, as I kept smacking the same finger that I injured working on another car last week!) Most of the valves were too tight. I may just be imagining it, but maybe there's a bit more power than before. I've been getting 22-24 mpg city and only 25 highway. Hoping that improves a bit too.

Happy Motoring, Mark

Too tight...someone trying to quiet their diesel? :laugh2:

I have been fighting off the cold-start knock for a while. I notice that there's a very definite lack of power when cold as well. Purge helped, as did a proper valve adjustment, but I'm pretty sure I'm going to have to go the new injector route soon. 175k miles on the ticker, btw.

No power when cold I consider normal. The oil vicosity being thicker seems to take it's toll. I guess how poor would be the hard thing to quantify. On a really cold morning with a 240d there is almost no acceleration. When a friend of mine pulled away it was perhaps zero out that morning or close to it. He did not allow even a minute to warm up. That engine was almost new with normally good power for a 240d standard. Perhaps even exceptional power. Another contributating factor might have been the temperature of the combustion chamber to support the ignition of the fuel. The heat of compression is probably lower than normal as the coldness is infiltrating the ciylinder perhaps. Speaks volumes for using synthetic in these cars in colder climates I suppose. Whatever you do make sure not to pull out into traffic with a really cold 240d using normal oil.

Car was cold when I drove off after the adjustment. (but the temp WAS 70 degrees today!) It seemed a bit more peppy, and didn't need to rev so much before upshifting to second. Hope this translates to better mpg, although even my current figures are a big improvement over most of the gas Benzes I've owned.
I'll check my mileage for a couple weeks, then consider a purge.

Happy Motoring, Mark

23-24?:confused: is urs an auto?

mines a manual with 250K on the clock and i get 28 city and around 33 highway

Yep, mine's automatic. Mileage hasn't been up to what some claim for a 240D, but I'll see if the valve adjustment made any difference before attempting any other improvements. Even 22-24 mpg is slightly better city mileage than my '98 Nissan Altima, so my 240D is still an acceptable alternate daily-driver.

Other question - Is there any adjustment or synchonization required between the throttle plate and injection pump on an '82 240D. Unlike those on carburetors or gas injection, the throttle-plate on this car appears to be designed so that it leaves a wide gap in the opening, even when fully closed. When I got this car, the plastic bushing near the air-filter housing had a deep groove worn in it and the linkage to the throttle-plate was extremely sloppy. I added a brass sleeve to the bushing and the linkage is now much tighter, but I didn't attempt any other adjustment, and as the throttle-plate is designed with this wide gap, I'm not sure if I made any difference.
Of course my Haynes manual provides almost no information on diesel throttle linkage or adjustments. Any opinions?

Happy Motoring, Mark

If what you're callin a throttle plate is the butterfly valve at the intake manifold then its completely irrelevant. The car will actually run fine with or without it open or closed, and linkage there is always sloppy. The diesel develops practically no vacuum of its own, a question of complete fuel combustion of diesel fuel creating its own gasses..... not like mixing gasoline with air for critical ratio with what you're used to driving. And its a direct injection engine, you understand, no mixing of fuel with air in manifolds or cyl head ports.

Cold running engine diagnosis on these beasts is a howling joke - try crankin it up stone cold in the shop and your pals will run to get a fire-extinguisher, swearing the engine will blow up. Normal cold start nailing sounds like ball peen hammer striking steel and is precomb chamber and inject related - nothin to worry about. The noise sounds metalic but it aint metal striking metal at all.

Meanwhile injectors hardly ever wear out because diesel fuel acts as lubricant. Same for injector pumps and bores, rings, valve seats and even guides - one of the secrets of diesel engine longevity.

Gasoline engine mechanics like to sell glow plugs and injectors to diesel customers, dunno why. GP's aint engine performance related and niether GP's nor Inj's ever wear out as a complete set. You can find a bad diesel injector using a stethoscope if 1 or 2 start nailing when *warmed up* after the engine's got 225k miles or so. And then swap the suspect inj to another cyl and nailing will follow it there.

I think that's good advice to use some 'diesel purge' one time only. And then follow up with 4-6 oz DieselKleen per tank for cetane boost and internal cleanliness maintenance. You want immaculate clean piston crowns free of carbon buildup, also clean pre-comb chambers to help with more complete combustion and hence better fuel mileage. And yeah, a city driven 240D automatic can accumulate more then 1/8" carbon on piston crowns that severely robs performance and economy.

And switching to synthetic oil is one of the most performance enhancing things you can do for the 240D immediately noticable and helps with fuel mileage too. Added about 2mpg to mine.