After reading through the archives for this forum, I have determined that I need to replace the oil pressure sending unit. I understand that this is a DIY job and that the sending unit is located in the vicinity of the oil filter housing.

With this in mind, I have two easy questions:

1. Do I need to drain the oil prior to changing the sending unit ?
2. Do I gain access to the sending unit from above (under the hood) or below (under the car) ?

Thanks in advance for any help.......

RM92400E,

You don't need to drain the oil, but there will be some in the filter housing. So when you remove the sender, you will get some oil draining out. At most, it will be about 1/2 a quart.

The sender is only accesable from under the engine. You will need to remove the lower engine cover.

The enitre job should not take you more than 1 hr. Once under the car, you can easily see the sender attached to the filter housing.

Good luck!

David,

Thanks for the quick response ! The part is on order and it sounds like I should be able to knock this out myself.....

RM92400E

Hey RM92400E,

I just noticed you are from Raleigh too. Where abouts are you? Im up in N. Raleigh by Falls Lake and Six Forks.

-David

David,

Small world, huh ? I grew up in Wilson, work in Raleigh (Highwoods area) and live in Cary.

While we're on the subject: Where do you take your car for repair for things you don't do yourself ? I just bought my 400E and haven't needed any maintenance work done yet, but you never can tell......

Ray

Ray,

Most of the work I do myself, both on my wife's 300e and my 400e.

I have used an indi shop in Durham twice for emergency work. I believe the name is B & K Motorwerks. EXCELLENT people. High quality work and fair prices. They are off of Roxboro and Hwy 147 in downtown Durham.

Do a search under "Good MB Shops" and there are a few recommendations for a shop in Raleigh. I may try them next time I need some major work.

Congrats on your new 400e.

David,

Thanks for the update on the repair shop - I'll give these guys a try if and when the need arises.

Ray

Looks like I may be in need of a repair shop sooner than I thought.

I replaced the sending unit today with no problems. Connector and wire looked OK. Put everything back together and took it for a test drive. Noticed that when I turned the key to crank the car, the oil pressure gauge pegged to 3 and never moved throughout the test drive. After stopping and restarting the car, the needle pegs to 3 each time, even before the car is cranked.

This can't be right, right ? What's going on here ???

Thanks for any and all help...

RM92400E

Hi,

Well, if misery loves company then we are in the same boat.

I have had exactly the same thing for about 3 months now. I have not taken the time to remove the cluster, but I think the problem is there or a wire.

As I understand it, when the circuit is closed and grounded, it reads 3. When the circuit is open, it reads 0. If you figure it out for sure, I would really appreciate knowing. I have nightmares about going to pick it up after someone spent 8.5 hours tracing a short.

BR,

RM92400E and sschweg,

The oil pressure circuit will read 3 when the circuit is open and 0 if grounded.

I have had this problem on my 400e. It looks like there is a flaw in a check valve located in the filter housing. I believe this is the same valve that causes the timing chain rattle due to a oil leak down.

You can verify the operation of your oil pressure gauge by simply removing the connector on the sender and ground it. The pressure gauge will then read 0.

I have found that the problem happens when I use dino oil. If I run synthetic, the problem does not happen.

Here is something you can try... it worked for me.

Drain the oil. Remove the oil pressure sender. Remove the oil filter and pour 1/2 to 1 quart of fresh Mobile 1 into the filter housing. This will flush out all of the old dirty oil left in the filter housing. Pour until you get clean oil flowing from the oil sender units connection.

Reconnect the oil sender and new filter and fill with Mobil1 synthetic. I use 10-30, but since we are getting into winter, you may want to try the 5-?? Mobile 1 synthetic.

When you turn on your car, you will see that the pressure gauge is at 0. When you start the car, the gauge will jump to 3, it may take a few minutes for the oil to get warm. After the oil warms up, the gauge will show 1.5 to 2.5 at idle.

Good luck!

David,

Thanks for the new information/recommendations. It's obvious that you're in the "been there, done that" category for this problem.

Here are the latest developments:

After the the initial test drive, I proceeded to to take a 120 mile trip (Raleigh/Wilmington) via interstate highway, average speed @ 80 mph. Upon arrival at my first traffic signal, I glance at the oil pressure gauge. Much to my amazement, the needle is sitting between 2-2.5. I briefly put the car in Park and punch the gas - the needle is jumping around between 2 and 3. I would assume this should be the normal operation of the gauge. As soon as I accelerate away from the signal, the gauge moves to 3. After reaching my destination, I turn off the car and turn the key to ACC. Now the gauge is sitting at .7 instead of the initial 3.

sschweg - Have you noticed similar "weirdness" with your gauge ?

Anyway, I intend to follow dSantos' recommendation. I am currently using Castrol 20-50 oil, so this could very well be part of my problem.

I will update this post thereafter.......

OK - the oil was changed to Mobil 1 15-50 and the oil pressure gauge now reads 2.5 at idle after the oil has warmed.

Thanks for the help and advice,
Ray