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Mercedes-Benz 300-Class, Engine, Fuel System, Diesel, Coupe, Sedan
#1876 of 2332 surging and transmission shifting hard
Jan 31, 2008 (8:03 pm)
Hey, I have a couple of questions about my 1990 300D 2.5L turbo. I'm new to the Mercedes diesel. The car has 227000 miles on it.
1. The car changes gears very hard and often "clangs" into overdrive. Is this due to a vacuum modulator?
2.There is also a plastic cam like piece on top of the valve cover that rides against two small wheels. The wheels are worn out. Is this a valve that controls the vacuum to the transmission? What is this called?
3. The motor surges at idle,if in gear it runs smooth. Is this normal for mileage and just a characteristic?
Thanks for your help
#1877 of 2332 Re: surging and transmission shifting hard [allman1313]
by MrShift@Edmunds HOST
Feb 01, 2008 (8:49 am)
I'd say all your problems are related yes, to either vacuum leaks somewhere or a badly adjusted throttle linkage that's getting worn out.
#1878 of 2332 rustprofing
Feb 05, 2008 (8:34 am)
im thinking of having my 300D turbo rustprofed and undercoated to stop it from rusting out any suggettions
#1879 of 2332 Re: rustprofing [swash9]
Feb 05, 2008 (10:11 am)
Well.....You may just be covering up rust that's already there. Without seeing the car it's hard to say, and not knowing where your from also doesn't help.
#1880 of 2332 Re: rustproofing [swash9] [burdawg]
Feb 05, 2008 (7:23 pm)
Swash is right; it's too late to rust proof if rusting has already begun, even if the rust isn't yet visible. So, unless the car has resided in the South or Southwest, and away from the coastal areas, since new, chances are rust proofing would be a waste of money.
#1881 of 2332 Re: rustproofing [swash9] [burdawg] [hpmctorque]
Feb 06, 2008 (6:43 am)
Even out here in dry southern California, I've never seen an old Benz without some rust somewhere.
#1882 of 2332 newbie looking for guidance
Feb 15, 2008 (7:55 am)
Hello all, I have recently begun researching the mid 80s 300D series. I seem to be reading a lot of good things about the reliability/safety of these cars with some concerns of cost of maintenance/repairs. I am hoping someone can either point me in the direction of further researching resources or give me some ideas of specific things to watch out for. Disclaimer: I have no real experience working on cars, however learning how is one thing I am sorta looking forward to ( with some reservations about the learning curve). I have seen several listings for cars with less than 180K miles for under $3000 and many for cars with 200-260K miles under $2500. I have read that it's not unusual to be able to hit 300-450K miles with a 300D. Does anyone here think that is accurate? I live in North Carolina so don't have a ton of cold to contend with. I would be driving the car less than 5 miles one way to work each day and on weekends when I go out for errands for a few hours. One of my objectives with buying this type of car would be to get rid of my monthly car payments, but I am wondering if I go this route if I am likely to end up with never ending expensive repairs instead. Any advice for a newbie would be welcome!
#1883 of 2332 Re: newbie looking for guidance [smerkinb]
by MrShift@Edmunds HOST
Feb 15, 2008 (8:16 am)
We could talk for hours about this-- --- but my two cents is that with this type of car you should buy the best, cleanest, best documented car you can find and NOT buy a "fixer-upper". There is no upside to a fixer-upper because the values are low and they aren't going to get much better except for the cleanest and best cars.
Any car on earth can go 400K miles, even a Yugo. All you have to do is keep pouring money into it. I think you will find that any old 300D with 400K has a lot of investment in it.
What is remarkable about them is their build quality. Where most cars literally fall apart at 400K, a 300D can still look good, not rattle and not shred its interior. But that doesn't mean they don't break down mechanically or wear out just like any other car.
Your average taxi cab can run as long as a Benz but it won't look at good, is my point.
As for things to look out for:
NEGLECT -- greasy oily engine, rusted body, dents, mildew, balding tires, filthy trunk, broken lenses, etc. Stay away from cars like this
ENGINE -- many 300D engines are tired. Look for danger signs such as lots of oil in the air filter (blow-by) and hard starting when cold. A 300D engine should a) start up quickly and b) peg the oil pressure gauge when cold---that oil needle should literally click as it hits the highest number and the needle stop
NOISE-- a rattly engine, noisier than usual (they aren't very quiet normally) could mean bad injectors.
SMOKE -- 300Ds smoke a bit on acceleration but it should NOT be clouds of noxious smoke. This could be bad injectors or bad injection pump timing.
HEAT/AC --- notoriously unreliable controls. check for ALL functions before you buy.
CRUISE CONTROL -- notoriously unreliable. Almost always a bad amplifier located behind the console. About $100 to rebuild + labor.
REAR SUSPENSION -- sagging back end, front end up in the air? You have a failed hydro-pneumatic compensator. Fairly big bucks.
CLUNKING ON TURNS? -- bad CV joints in the rear axles
HARD SHIFTING -- hard shifting is normal. Buy a neck brace, you'll need it. But LATE shifting could mean a vacuum leak or bad vacuum modulator
DOOR LOCKS -- these are vacuum operated by little motors in the door panels. They often get slow. The motors are rebuildable and don't cost too much.
BEST CAR TO BUY? --- Definitely choose the TURBO models. Do not pay extra for the coupe, they aren't worth more and they are less practical.
always use fuel conditioner every fill up
use anti-gel for the fuel in cold weather
change your fuel filters (two of them) FREQUENTLY
make sure the valves have been adjusted at least once in the last 30K miles
change the oil every 3,000 miles come hell or high water
FUEL MILEAGE -- you will hear all sorts of silly claims but in fact you will get about 18-22 mpg city driving and about 22-26 highway driving
TOP SPEED -- diesels this old don't like to rev. 75--80 mph MAX is more than enough for this car. Drive faster and you'll crack the cylinder head sooner or later.
PARTS-- lots of stuff on the Internet, and the MB dealer still carries an amazing number of parts for this car
REPAIR MANUALS -- you can't beat the 3-volume factory manuals, but you'll pay over $300 for them.
SPECIAL REPAIRS -- you cannot work on the fuel injection pump. This goes to a specialist and costs about $1,500 to repair. They are very rugged and should be fine if nobody messes with them.
#1884 of 2332 Re: newbie looking for guidance [smerkinb]
Feb 15, 2008 (8:22 am)
The only other thing I might recommend is to check out a low miles/big $$ 300DD so you'll know what a good one is like. This way you can discount the 'they all do that' line from someone trying to sell you a junker.
#1885 of 2332 Re: newbie looking for guidance [Mr_Shiftright]
Feb 15, 2008 (9:58 am)
That reminds me, the other day I got behind a powder blue early 80s 300CD turbo coupe in very nice condition...on a highway on ramp. I prepared for the worst, but the car barely smoked upon acceleration, and it was up to 60mph like any other car. It was refreshing to see one like that.