Oil pressure gage pegs BEFORE starting

[Full Monte]

This doesn't seem right. I don't think it should read anything until I start the engine. When running, the gage stays pegged at highest reading. It looks suspicious to me. What do you think?

 

[The Warden]

Does it peg before you start cranking?

If it's pegged at 3 with the key ON and the engien not running, my first guess would be a bad sending unit. If the 603 is anything like the 617, the sending unit will be near the base of the oil filter.

Alternately, did this issue crop up after you had the instrument cluster out? Maybe something wasn't plugged in properly?

Just a couple of thoughts...good luck!

 

[Full Monte]

Yes, it pegs before cranking. It was doing the same thing before I took out the instrument cluster. I'm going to investigate the sender unit as you suggest. Thanks

 

[The Warden]

If you unplug the wire from the sending unit, the gauge needle should go to 0 with the key ON. If it doesn't, ground out the wire with the key ON, and the needle should go to 0. If the needle does go to 0 with the wire removed, ground the wire out and it should go to 3 and peg itself. If it does all of that, the sending unit's bad...otherwise, it's a wiring issue (or you got the wrong wire, but I don't think that's likely...I don't think there are any other senders around there).

This is general troubleshooting for a sending unit; I would go out and verify this with my car, but the W123 still used a mechanical oil pressure gauge with an oil line going into the instrument cluster (they switched to electric gauges with the 126)... But, MOST gauges will go to 0 with the wire unplugged from the sending unit, and will peg themselves at the top if the wire is held to the engine block (or other suitable ground). I'm pretty sure M-B gauges are the same way, but knowing me, they probably went the exact opposite just to spite me

 

[Full Monte]

Thanks for the "how to". I'll try it. I'll post results of the test. This w124
seems to need a lot of little fixes, despite how well-maintained it seemed to be on purchase. Funny how you don't notice a lot of things for awhile after buying a used car.

 

[The Warden]

I know what you mean...I've always figured that it comes with the territory. I put about $1000 into my 123 within the first 6 months I had her (wheel bearings, brakes, axleshafts, battery and VR, a few suspension bushings, and a partridge in a pear tree ), but I actually haven't needed to spend too much on her since then.

Once you get the "post-sale" issues stamped out, she'll be a great car!! Let us know how it goes...

 

[towcat]

outside of a powerplant, i feel blessed that my 420 didn't need much else. ok...speakers need to be replaced and the sunroof is starting to act up. aside from that, bug free

 

[Jarlaxle]

Considering its 300,000+ miles, my friend's Euro 300 TDT didn't need much the first year he had it--rear tires, front brake pads, belts & hoses, replacing the cracked tailpipe.

Oh, yeah, and a new clutch, pressure plate, and flywheel. That was a wallet-shattering experience.

 

[The Warden]

Oh, yeah, and a new clutch, pressure plate, and flywheel. That was a wallet-shattering experience.

Ouch..

Was he able to use clutch components from a 240D, or how did he get the parts?