94 or 95 E320 engine question
 

How long is the usual life expectancy of an engine in a gasoline engine in an E320? Would you buy one with 120,000 or would you expect a lot of issues? I was thinking of buying a diesel wagon but can't deal with the slowness and oldness and think this would be a better fit but want to know if I would just be buying troubles. Thanks, Lance

I bought my wife's '95 E320 wagon a little over 6 years ago with 67K miles. We are just approaching 190K and the engine runs great with no appreciable oil consumption between 5K mile intervals. I had to replace the headgasket at around 120K miles and the wiring harness shortly after that and I think the water pump twice.

The "usual" life expectancy will vary greatly depending on the care of the car. A well cared for 104 motor with 120k should be well within its half life - but the engine is a relatively small portion of the overall maintenance picture. You are likely to be much happier with such a car if you are a DIYer. Better yet would be to be a DIYer on an E420 - which has an even better motor with fewer congenital problems and an even longer life expectancy.

what was the problem with the wiring harness that you had to have it replaced?

Under pressure from environmentalists, MB tried to use a biodegradeable wire insulation. Unfortunately it degraded way to soon. See attached pictures. (one of engine wire harness, one of throttle actuator lead)

So does that mean that if wire harness was repaired that it was repaired with something stronger and you won't have the problem again? Can you tell from looking at it whether it has been replaced or not?

The wire harness is usually not repairable, it has to be replaced. You can check the condition of the wire insulation by striping back the black fabric wire wrap on the wires that attach to the temperature sensors located on the top and or side of the thermostat housing. Sometimes you can also tell by looking carefully at the wire where it enters the temperature sensor connector plug(s). You can also check the wire harness part number tag although it is a bit difficult to find. It is usually located on the wire harness where it runs across the bottom drivers side of the battery area. If you can find it, Phil at FASTLANE PARTS (sponser of this web board) can tell you if it is made with the new non biodegradeable insulation. If so, you should not have any more problems. Some of these harnesses (and also ac evaporators) were replaced by the dealer under warranty, This warranty replacement seems to have been more common in cars that began life in the Southern States, probaly because the warmer climate caused earlier failures. A friendly and helpful dealer service department can look up the VIN number to see if this has been done. There is really no way to tell by looking if the throttle actuator has been replaced. Only proof would be maintenance receipts or partial disassembly.

I was supposed to go see the car today but chickened out because of this issue. How much is it to replace, wire harness and/or throttle actuator for a E320 by an inde shop? I'm afraid to ask but where is the wire harness once you open the hood? Is it by the battery somewhere?

For some reason I love this year of wagon and had a '95 previous but had everything but the harness and throttle actuator go and finally got tired and regrettably traded it off. Now I would like to get another but am afraid as these cars get older that the problems might get worse. It seems like people either have a lot of problems or very few. I guess it's just one of those things that we can't control and have to roll with it. I have owned a lot of cars and Mercedes are by far my favorite, doesn't matter the model or year!!!

And you are looking at $700+ and labor, rights?

You can do the wiring harness yourself, it's not difficult. On the M104, it starts behind the battery, runs underneath the battery tray, around the back of the engine, under the air intake along the driver's side of the engine and eventually to the front. There's various connectors that come off the harness, one to each pair of spark plugs, EGR, etc.

Lay out the old one on top of the engine and as you unplug the old connector, plug in the new. Should only take an hour or two.

Never done the throttle actuator on my car, but I probably should. No idea how easy it is to do.

as far as M104 engines go - I got 285,300 miles and it still runs like a dream. The engine is worth the investment. Get the transmission fluid changed before you do anything. 30,000 mile interval.

I think the wire harness is closer to $800. It takes a competent mechanic about an hour to install. A rebuilt throttle actuator is around $600, also takes about an hour to install.

lws1: I wouldn't let this wire harness issue scare you to much. If you are not a hands on DIY type, you might consider a pre purchase inspection. A good mechanic who is familiar with these cars will be able to tell very quickly if the wire harness is bad or not. He will also be able tell if the head gasket is leaking. If the throttle actuator has been replaced with a rebuilt unit, He should be able to tell by looking at the connector plug. As I mentioned in a previous post, there is really no way to tell by looking if a throttle actuator has been replaced with a new unit.

I have 200,000 miles on the engine in my 94 wagon, and, now that the common issues have been dealt with, I expect to get another 100,000 relatively trouble free miles.

J. M. van Swaay

By the way, there is a how to article on the engine wire harness replacement with lots of informative pictures. Here's the link. http://www.peachparts.com/Wikka/M104WireHarness

M104
 

I would not even hesitate on a car equipped with an M104 engine! They are absolutely amazing and will last forever, providing you simply change the oil and coolant when you are supposed to! I have never had a single problem with any M104 engine, and I have had them in 6 different models! I love the engine's smooth acceleration power and responsive torque. If you are a knowledgeable DIY'er and you utilize this website to its fullest, a Mercedes Benz (especially with an M104) will be the BEST ownership experience of your life.

Don't be afraid of the wiring harness issue, It is not a big deal to replace or buy a new one. If you are scared about an $800 dollar part, you better get used to it.:)

<<I would not even hesitate on a car equipped with an M104 engine! They are absolutely amazing and will last forever,>>

Yeah..we don't even know how long they will go yet b/c they are all only old enough to be running in the 250k + range ....with the original valve seals, rings, valves, timing chains , etc...if it wasn't for the original headgasket problem, they would be in the Rock & Roll Hall of Fame.
They might go 1,000,000 miles...

Even with my limited abilities (oil changer), that looks like it might be a bit fun! I'm rethinking this now. Appreciate all the info!!!!