Hey all, I've been using this forum for a while now for tips and DIYs but just now made an account. I had a couple questions for those of you who are long time owners. This is a long post so thanks in advance if you read the whole thing. I really appreciate the help.

Just a little about the car: I bought a 1999 E320 about a year ago. I bought it from my uncle, who took good care of it (changed the oil very frequently etc.), but is not very hands on so he wasn't able to tell me much about it. I don't think he opened the hood more than a handful of times. He had a local mechanic do almost all maintenance and I do not think they deal with that many mercedes or other foreign cars.

The car has been running great with little maintenance since I bought it (other than oil and brakes all I have had to do is change all the tires). The car just passed 180K miles and finally is giving me some minor trouble. The check engine light came on and came up with two codes. P0301 (cylinder one misfire) and P0141 (oxygen sensor).

I changed all the spark plugs and wires (they look like they had never been changed, still had bosch's like the originals but I guess they could have been replacements) and reset the check engine light and so far it hasn't come back on. So I think I solved the first code.

The guy at advanced auto told me the second code was a pending code and was probably not an issue. QUESTION 1: Should I just not just not worry about it unless it comes back on again? If replacing it could help with performance/gas mileage/ or potentially extend the life of the car I would rather just replace it. I hope to have this car for a while longer.

Another issue that concerns me is the first time I changed the oil (about a month after I bought the car) there was a yellow/tan build up under the cap. My fathers very good with cars and told me it is most likely a blown head gasket and that fixing it could cost as much as I paid for the car. However after I did some research, others say that if you take frequent trips in cold weather this is very common. I decided to do clean away the build up and see if it came back. I changed the oil again about 5 months later and there was almost no build up. Recently I added some oil after seeing I was a little low and the build up was back and just as bad as before. It has gotten very cold out again though and I do often make short trips. QUESTION 2: What would your advice be on this? Does anyone have a similar scenario with cold weather/short trips?

The car SOMETIMES (maybe 30% of the time) seems to shake a good deal when in low gear (ie: stopping at a stop sign. Sitting at a red light. My friend who works on cars a lot got in my car and immediately said it was a loose belt. I cant see anything noticeable shaking, or see any belts that are obviously loose when looking under the hood. QUESTION 3: Does this sound like a loose belt? If so, what belt? If not, what might it be?

The car SOMETIMES (again, maybe 30% of the time) has problems up shifting and down shifting. I think its 1st to 2nd but maybe 2nd to 3rd (just judging by the speed it happens at). My previous Ford Explorer had problems upshifting (long delay, rpm's shot up before shift) and not long later the transmission went. This feels a little different though. There is a delay sometimes when upshifting, but the rpms don't shoot up that high. But there is an obvious feeling of it finally clicking into gear and it doesn't feel good. This isn't only when I hit the gas hard. It happens for regular acceleration sometimes.

The downshifting problem is less frequent but sometimes when rolling up to a stop sign or a similar scenario, I let my foot off the gas but it almost feels like the gas is still pressed down. Then there is a shifting or clicking feeling before the car slows down (its a little subtle but the first time it happened I thought I ran over something, so its not that subtle). It's hard to describe because it is infrequent and I haven't experienced it in any other car.

QUESTION 4: Does this sound like the transmission is the issue? If so, is there anything I can do about it? if not, what might it be?

Final question: Do any of you have any tips to increase the performance/gas mileage or life of the car? Like I said, I hope to have this car for a while so i'm willing to put some time and money into in the hopes it helps me out down the road. Some people have suggested changing the coolant, transmission fluid etc. But I'm not sure what will really have an impact. Or just any other tips you might have.

Thanks so much for any help.

 

Mechanic was probably right. If you don't have an OBD II handheld scanner get one. They're cheap (<$50). Check for the pending codes after a few weeks to see if they come back. FYI - Be careful about erasing codes just prior to a smog inspection as the cars computer needs a few drive cycles to re-establish the adaptation values.

The tan buildup under the oil fill cap is almost always due to condensate because the car is being driven short distances in cold weather. It can be a blown gasket but that's less likely.

The vibration while waiting in gear at stoplights is often a sign that the motors mounts have failed. If you shift to neutral most of the vibration should go away if the MM are bad.

These cars were sold with 'filled for life' transmission fluid. Look on the transmission dip stick tube cap. A red locking tab means the system has been open but a black tab means it probably has not. If it has not, you can start by replacing fluid and filter. Be certain to use the correct MB ATF (very important). When the pan is off for changing the filter, examine the bottom for debris. A little small grit is normal but any larger pieces indicate excessive wear. Also, there is a cable which goes from the transmission to the cars computer. If it has signs of AFT on it, replace the o-rings. Based on the results of all of this if you still have shifting issues, have the cars computer system tested for transmission codes. You'll need dealer or indy with MB proprietary computer system to do the check and a fee may be involved. Note - During MY1999 a drain plug on the torque converter was eliminated. With the car on a hoist, rotate the TC to check for the plug. Without the plug you can only drain about 1/2 (4 qts) of the fluid. FYI - Most of the time a AFT change does NOT fix any serious problems.

I suggest that you get everything working as normal. At that point, check the gas mileage over a few tankfuls. With normal driving you should see around 16-19 around town and 27-30 on the highway. Performance and gas mileage are opposites as it takes energy to go faster.

There is quite a bit to learn on the W210 but if you are willing to do proper maintenance they can go 250,000 miles without serious problems.

 

Some good videos about transmission service

 

Thanks for the responses.

I actually just purchased a OBD2 yesterday after seeing how cheap they are. I'm just waiting for it to be shipped. It will definitely be worth it.

Hearing someone else say the build up is just from condensation in cold weather is reassuring.

Next time I notice it shaking a considerable amount I'll shift it to neutral to see if it goes away. I'm sure there is already a thread in here on the motor mounts so I will look for that but if anyone has more information or a link for that I would appreciate it.

I know a mechanic that works on a lot of Mercedes that should be able to read the transmission codes. Hopefully for free or cheap because he's a friend. I think I might take that route first to see if anything comes up.

Those videos are incredible. I just spent almost an hour and half watching the entire series he does on the transmission. I'll definitely watch some of his other series when I have the time. Depending on how the diagnostics of the transmission goes and how much time I have I might follow what he does so thank you for posting that.

 

On the condensation buildup, on mine it helped to renew the thermostat. Try to drive it at least 20 mins on cold days. Also, at some point after 100k you need to redo the valve cover vent seals, and it helps to clear the vent holes and renew the attached hoses (to give some crankcase ventilation).