donehickman

My '84 300TD and I are experiencing our first winter together. It's a great car. I have no complaints but a question or two. when the temp outside drops to around the freeezing point it seems like the fuel echonomy drops by %10-15. Is this just to be expected?

The engine temp reaches about 80 degrees after about 10-15 minutes. I have heat long befor that and lots of it if I want it but usually don't even need to adjust the climate control setting from 22.

The front end sounds like a cage full of finches. There are all kinds squeeks. The front shocks are especially squeeky. When the outside temp is milder the squeeks dissappear. Is this typical or do I have a problem I should be concerned about.

johna1

I was just about to post a similar question.

I have an E320 CDI and have noticed that the fuel (diesel) comsumption is much higher when the engine is cold.

Does someone technical know why a diesel would use more fuel when it's cold? The owners manual warns this will be the case, but doesn't say why.

sph17

Welcome to the wonderful world of MB W123 diesels. I have had three W123 (240D, 300D, & 300TD) over the last 20 years and have put over 600K total miles on them. They all went over 200K. I still have my 84 300D which has 230K miles now. Other than changing the clutch plates twice on the manual 240D, and the rear axle support rusting/wearing out on the 240D, I haven't had any major engine/suspension problems. Most of your questions are things I have dealt with.

Disclaimer: I am not a mechanic, but I do most of my own basic maintenance. Take my suggestions with a grain of salt, as I know others on this forum disagree with me on some points.

Regular Diesel fuel will gel at colder temperatures. To prevent this, during the winter most places "winterize" their diesel fuel. They can put in additives, or cut it with kerosene. Kerosene has less energy per gallon, so if your diesel has kerosene added to it, you will get lower fuel milage. If you are going to be in very cold temp (my rule of thumb is below 20F) you need to do even more to winterize your fuel.

You can add up to a 50/50 mix of kerosene and diesel. I believe this is one of the recommendations in the owners manual. Remember your fuel milage will be substantially less, the more kerosene you use. Instead, I add one (only one) gal of gas to a full tank of diesel (added in the middle of filling up, to mix well with the diesel fuel). This was taught to me by an old MB mechanic. I have never had a tank gel on me, and I have driven in -20F weather in the mountains of WV. Others on the Forum argue that there are petroleum distillates in gas that will damage your engine. In addition, you can by commercial diesel anti-gel and add it to your tank.

I put in-line fuel heaters in my W123s as the fuel usually gels in the fuel filters, and the in-line heaters (gets heat from the engine coolant) warms it just before it goes to the filters. MB also offered free engine block heaters to owners who asked to have them installed. Plugging in a diesel overnight may make the difference between starting a diesel in below Zero temp, it also helps it start much easier in cold weather, is easier on your starter, and helps you get heat faster. If the original owner didn't put in the free block heater (look for an electric cord tucked into the front passenger side of your cars engine compartment or under the front passenger side bumper) an inexpensive but inconvienient solution is the heated dip stick that you can buy at any Auto Supply store for $5-$10.

Another reason you get lower fuel milage is that diesels like warmer/hot temperatures so you will use more fuel in cold temp as the engine has more resistance with cold oil and cold moving parts and in addition, the engine has to warm itself up.


In regards to your heater, there is a hose that comes off the engine on the passenger side goes to an in line water pump and then goes back to the firewall to the infamous "mono-valve". If you have problems with your heating system, most likely the silicone diaphragm in the mono-valve is ripped. Its easy to check, four screws secure the electro-magnet with the mono-valve and actuator to the housing. Pull the unit out and check if the diaphragm is ripped. The diaphragm, mounted on the actuator costs about $35 to replace. In the olden days you could buy the diaphragm alone for under $5.

My right front suspension was squeaking big time last winter. I sprayed about a can of WD-40 on every part of the suspension and finally got the squeaking to go away. This spring, when I tried to get a wheel alignment, Sears told me that I needed to replace my lower ball joint and a tie rod. I was able to do the tie rod myself, but had to pay someone to do the ball joint. I don't know if the squeaking was related to the parts I had to replace, but you might want to have someone you trust check out your front suspension, if you just got this vehicle recently.

Bottom line: These cars will go for a very long time if you trat them properly. Diesel has sulfur in it, and as you drive your engine builds up sulfuric acid in the oil. Change your oil religiously every 5,000 miles maximum, or sooner if you drive hard/city driving or if you are a low milage driver. Follow MB recommendations for oil changes!! Also change your ATF and filter every 30,000 miles also.

Good luck!!