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rkerste219 05-14-2006 03:58 PM

new owner of 1981 MB 240d
Since 1967, the very first time I ever saw a MB Diesel Car, I always dreamed of owning a Diesel car.

In 1985, I did purchase a new Isuzu pickup 2.2 Diesel (C223). After 500,000 miles, and still going strong, I bought a used 1981 240D. Thinking if an Isuzu could run 500,000 then a MB @ 170,000 should last a couple of years +++.

The story behind, the MB is , it was once owned by an uncle in VA. Gave it to his nephew. Nephew, blew engine. Garage replaced with an engine with 70,000 on it.

Since purchase, I have changed oil/oil filter, primary and secondary fuel filters.

Q. Is there a way drain the oil cooler?

Q. On the Isuzu fuel pump, all lubrication is done by the Diesel fuel. It looks like the 240d fuel pump, might use the engine oil some how. So, how does the inline fuel pump get lubricated?

Q. Currently, I am getting 31 MPG city/interstate driving @ 65 MPH. Is this normal?

I work from home and have to dive approx. 175 miles a day, 2 or 3 times a week. Am I asking for problems, if I use this car? My Isuzu does not have air, the 240d does have air, and it works.

There is some body rust on the bottom of all four doors, and some along seams. Had the brakes check, and had to replace pads, and calibers.

Next, I will need to buy some new tires.

I do not think the electric fan for cooling works when the air is on. Is this a problem? In addition, the speed control does not work, is this an easy fix?

Bob new owner!
Fayetteville NC

pj67coll 05-14-2006 04:18 PM

I've owned my first MB Diesel now for just over a month. Also an 81, 4 speed stick with 375000 on it. I think you are probably right about the motor lasting to 500000. That's my goal with mine anyway. My cruise also doesn't work. Havent attempted it yet. My mpg's are only 29 in city driving. Averaging around 50mph. So you are doing real well there. Enjoy the car. I'm loving mine more every time I get behind the wheel.

- Peter.

barry123400 05-14-2006 04:23 PM

Congratulations, sounds like you have a good example. Thirty one miles per gallon is a little above the reported average but good. The majority report less but a few do report 31-32 mpg. Yes pump uses the engine base oil to lubricate it's bottom end. You are lucky as the fan control circuit and motor are quite straightforward compared to the five cylinder cars. . Usually the brushes need changed in the fan motor seems to be the common ailment but check for fuse etc first. Drive the car in a reasonable fashion and change the oil on schedule and it could serve you for a very, very long time. As for draining the oil cooler I do not know. You might want to look in the archives for that. Especially look in the archives regarding your cruise control.

iNeon 05-14-2006 04:24 PM

1) I have no idea about the oil cooler, I have always just run the engine a bit to heat it up then used the drainplug.

2) These cars have fuel pumps? I have always understood that the pump on the engine(IP) pulled the fuel?

3) 31mpg mixed driving is impossible to attain in a 240D, at least it is on mine-- Shlomo has religiously returned 23-25mpg, nothing more, nothing less. I would *not* question the cars getting astronomical fuel economy heh heh;)

4) The cruise not working is a fairly simple fix(if the fix works) wherever you just reheat the solder joints in the amplifier and pray that it repairs what is wrong.

5) Welcome! You'll find anything you need to know here-- except vacuum pump interchange information

Samuel M. Ross 05-15-2006 02:50 AM

my 1980 240D have the same fan problem...
and all I had to do was take it apart, clean it up, a little oil on the bearings and because the brushes still looked good, I put it back together and it worked just fine.

I suggest you give yours, an internal cleaning and inspection, and oiling and while you have it out then bench test it by connecting it directly to the battery with some jumpers.

If the bench test proves it to be OK, then reinstall it and see if it works.

I think you will also find on your M-B that there is a temperature activated switch emersed in the engine's water jacket that also needs to trip before the fan comes on... so check into this too

Good luck... welcome to the "Diesel Discussion" forum.

Sam Ross // Novato, CA

rkerste219 05-15-2006 11:24 PM

thanks and now another question
tires, what size? From what I can find out, the orginial size is 175SR14. On the front I now have 185/70/r14 and on the rear 195/70/r14.

not sure what the differences are and what to ask for when I buy new tires.

81 240D

Skippy 05-15-2006 11:47 PM

Tire Size
A shorter sidewall tends to give better handling at the expense of some ride quality, and can throw your speedo off. A taller sidewall gives better ride quality, at the expense of adding some sidewall squirm and raising the vehicle CG ever so slightly, so you can lose a little handling. You can also use changes in tire pressure to "tune" the car to your driving habits.

Both my Benzes came to me with Bridgestone Potenza Re930i tires. Old Yeller has them in 195/70R15, and Whitey has 195/60R15. Speedo and odo on Old Yeller are dead on. Whitey's read about 10 percent high. Of late, I've been running manufacturer recommended pressure in the big tires, and 36 in the little ones. Handling with Old Yeller is good but not great. Whitey acts like he's on rails, but he's my commuter, and I drive a five mile stretch of dirt with washboard and embedded rock every day, so after weighing the car (1800 on the steer axle and 1560 on the drive axle, full fuel and no driver), and consulting the TRA Yearbook, I've found I can get away with as little as 26 psi at all four corners. I'll be working my way down in steps until I find the right compromise of handling, ride quality, and rolling resistance.

JimmyL 05-16-2006 12:01 AM


Originally Posted by rkerste219
tires, what size? From what I can find out, the orginial size is 175SR14. On the front I now have 185/70/r14 and on the rear 195/70/r14.

not sure what the differences are and what to ask for when I buy new tires.

81 240D

205/70/R14 :smart: Trust me on that one...

t walgamuth 05-16-2006 05:11 AM

205/70 is considerably larger than stock size for a 240. i have had at least 8 240s. i find they are happiest, imho, with the correct size tires. sharp steering and excellent ride and handling. bigger tires will make it ride harder, your speedo will be off and you will lose gear ratio, so acceleration will be slowed.

the 175r14 is actually a 175/80 i believe, but you can check a tire chart for actual diameter. a 195/70 or 195/65 or 195/75 is the same diameter i cant remember which is the same diameter as the 175r14. whichever is the same diameter is what is the factory optional recommended size. the same diameter is what i recommend after the 175r14 which can be a little hard to find.

i would check your odo against the mile markers on the interstate. your mileage is good and may be just good running or your odo could be slipping and making it look better.

i have found the most common cruise problem is bad amp. i have never tried to repair it myself.

my $.02

yom e

Craig 05-16-2006 08:31 AM


Originally Posted by JimmyL
205/70/R14 :smart: Trust me on that one...

I like 205s on my 300D, but I think that's too big for a 240D. I like 185/75-14 on the 240D, and 195/70-14 has about the same diameter.

JimmyL 05-16-2006 02:50 PM


Originally Posted by Craig
I like 205s on my 300D, but I think that's too big for a 240D. I like 185/75-14 on the 240D, and 195/70-14 has about the same diameter.

YOu know, I agree with Craig and TW on this one. My mind set is always "300" mode, as I don't have the elusive 240 yet. So, don't trust me on that one.....:D

rkerste219 05-20-2006 02:44 AM

no owner's manual in gove compartment..

do I need one? :confused:

Jim B. 05-20-2006 03:21 AM

Need owner's manual?
Yes, they DO really help.
I wouldn't be without one.

Ask your dealer or get one on ebay.

rkerste219 05-20-2006 03:55 PM

new tires from firestone
Went to firestone today and good, bad, or indifferent, came out with 4 new tires:

185/70/r14 turanza series with a 70,000 mile guarantee. Also purchased their ‘for as long as I own the car’ alignment agreement. So I will go back in 5,000 miles.

I have a Sears alignment for my 84 Isuzu and they still honor it.

I went to the store asking for 175/R14 (and of course , this is an old no longer used tire size)..

They recommended the 185/70/r14, will this be ok for my 81 240d with a manual transmission?

I have a hand held GPS system, and when my 240d said it went 2.5 miles, the GPS said 2.42, for a difference of .08 miles. Is this ok?

Firestone did say, I have 30 days to decide if I want a different tire, I could go back and get them with no problems. If I go back, what should I ask for?


Craig 05-20-2006 04:16 PM

This is a handy tire size calculator for comparing different sizes:

According to the manual for my 240D, the original tire size was 175 SR-14 (similar to 175/80-14). Your new tires are 185/70-14, which are 3.3% smaller diameter than stock. This corresponds to the speedometer error that you measured 2.5/2.42=1.033. I use 185/75-14 on my 240D, which are a little taller and almost identical to the stock diameter. Personally, I don't think 3% is a big deal. What you have done is reduced you final gear ratio a little, which will give up a little better low end performance and limit your top speed a little. I would just use the tires you bought and decide if you want to do something different next time. Also, I would keep an eye on the front tire wear, some chain stores don't really know how to do a proper alignment on a benz.

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