I'm very excited. I just got a 1984 300d. I have an awful lot to learn here and love the site.

So couple newbie question:

1. On the front passenger side of the car, behind the wheel there appears to be an oil line of sorts that is leaking. The clamp must be gone or loose. The fluit coming out appears dark read. From my experiance oil from diesels is black - I will take a picture in the day light but is this an oil line or something else? Its a metal line basically right behind the wheel that you easily see without taking the wheel off.

2. Tachometer does not work - the the MPH - spedometer (??) part does. With a friend following me home, the car appears to show 7-10 miles per hour slower then the car is actually driving. Ok?

3. The oil pressure pretty much stayed at 45 - at the top at full throttle - ok?

4. The temperature on the highway stayed a tick under 180 during the trip - normal?

I'm sure I'll have more questions.

Thanks.

Pappa G.

1. Red would be transmission fluid. I don't know how transmission fluid is getting behind the passenger side wheel. The only fluids back there are coolant (whatever color is in the engine) and brake fluid (should be clear but discolors with age and use). If it's right behind the wheel, it would be a brake line!

2. Do a search on "cigarette butt" as a shadetree fix for the tachometer.

3. The oil pressure gauge should peg high anytime above idle. Should idle at about the halfway point or higher at operating temperature. Pegged at idle is fine.

4. If my math is right, 180*F = 82*C which is spot on per the thermostat spec. If it takes more than 10 minutes of driving to get to that temperature or is more than a tick below 180*F, check that the thermostat is in good shape.

Sixto
87 300D

^ Agreed, transmission fluid is red, oil is black and old brake fluid is dark yellow.
That car has a tach that picks up the signal from the transmission, not the amplifier unit, so the cig butt trick won't work.
Temp is right too.
Nice car, enjoy, ask away.

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83 SD

84 CD

First thing to do to troubleshoot the tach is to check the Over Voltage Protection (OVP) relay. If this relay fails, it will not feed power to the Exhaust Gas Recirculation (EGR) control unit. The EGR control unit passes the tach signal to the tach, and it needs power via the OVP relay to do that.

The EGR control unit is under the passenger side kick panel next to the door. It's the big black thing in there. Pull the connector and use a voltmeter to check pin one on the connector - the wire should be black with a blue stripe if you can see the wires going to it. The connector may have the pins numbered as well. With the key turned to the run position, you should have battery voltage at pin one. If not, check fuse 14 - this supplies power to the OVP relay. If fuse 14 is good and you don't have power at pin 1 of the EGR control unit connector, then you likely need to replace the OVP relay. The OVP is located near the air vent on the passenger side. Since you already have the passenger side kick panel off, you should be able to see it by just looking up between the air vent hose and the fender. You might just check the voltages on the OVP relay connector as a double check that all the voltages are present.

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mjk

'84 300SD 119KMi (Liesl der Diesel)
'84 300D 326KMi when the oil left (former parts car)
'82 300SD 253KMi (new parts car)

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