Inside Oil Leak
 

I have a 1984 Mercedes 300D. Recently, I noticed a significant amount of oil on the floor near the gas pedal. I removed the plastic cover underneath the dash and found that some of the insulation was soaked in oil. It looks to be coming from behind the display, either the tach or the oil pressure. What might cause this and what would be the easiest way to fix it without ripping all the guts out from underneath the dash?

Thanks,

Tom

You have a leak in your oil pressure guage, or in the line going to it.

Oil is actually pumped to this guage thru a small hard line to the oil pressure guage. The connection could have been cross-threaded long ago (most likely), or the line could have been crimped and broken (possible, but not as likely), or the guage itself is broken and leaking. Your insulation panel has probably been dripped-on for a long time, and now is overflowing into your floor. There's probably a big mess behind the dash below your guages.

You can access the back of the guages by carefully pulling the whole instrument cluster towards you. They are pretty delicate, with lots of wiring and such, so if you aren't confident that you can repair and replace it yourself, take it to a good shop.

A WARNING: Do not EVER start the engine with the oil guage disconnected, or you will pump oil all over the place and have a VERY BIG mess.


Hope this helps....
Mike

You will need to pull the inst cluster and get to where the oil pressure line ties into the back of it. Do a search on removing instrument cluster. Pretty easy and straight forward once you have done it a time or two. Hopefully, all you will have to do is tighten up the fitting. Takes a 10mm open end wrench. Don't get too carried away with how much you tighten it.

This probably doesn't pertain to your car but I you never know. I used to have a 190E with a 5spd. The clutch was hydraulically actuated and under the dash there was a cylinder which contained brake fluid (part of the breaking system). If your car is a 4spd manual look for the cylinder, it could be leaking.

Placo1

It actually takes two 10mm wrenches. One for the fitting and one for the gauge, the one for the gauge is the counter pressure that keeps you from destroying the gauge (provided it's not the gauge that's bad). If you don't use both you stand a good chance of twisting the innerds out of the gauge.

good catch Mike - I forgot about holding the gauge side fitting :) with the 10 mm.

As someone said , check the clutch cylinder (If its manual). It s just behind the clutch pedal , going through the firewall. A very common leak on a older vehicle.

It shouldn't be hard to tell the difference between engine oil (the gage) or brake fluid (the clutch). Most diesel engine oil is jet black. If the oil on the floor is not black, its the clutch hydraulics.

It's a 300D...Unless it's a rare Euro, there will be no clutch. All American 123s are automatic, right?

Mike