1997 S500 - Oil Pressure Gauge Drops to zero. - PeachParts Mercedes-Benz Forum

bolomiester · #1 12-01-2011, 10:29 AM

I bought this '97 S500 a week ago. When I first drove it I looked at all the gauges while it was idling and everything was good, including the oil pressure at about 2. I test drove it for about an hour and it ran, idled and shifted perfectly. It wasn't until I was half an hour into my trip home that looked down and saw that the oil pressure gauge was at zero. I pulled over immediately but when the car settled down to an idle speed the gauge jumped back up to just under 2. Thinking it was probably a defective sending unit, I started to accellerate and as I did the gauge started increasing until it hit the top and it dropped back to zero. At that point I was sure it was the sending unit so I replaced it with a Mercedes OEM unit. It did not fix the problem.

I have an all data account for this car and found this tech bulletin:

Apparently I need to replace the circuit board. Is this something I can pull out of a salvaged cluster. Does anyone know how to open the cluster up to get at the board?

Baring that, can I install a salvaged cluster without the car's computer system having a bad reaction, like posting a warning on the cluster or refusing to work correctly?

My mechanic tested the oil pressure with a separate gauge and it's fine. I've also taken the car on a 600 mile trip and it ran perfectly, but it sure is scary to look down at the oil pressure gauge and seeing it at zero, plus if something did go wrong I wouldn't know about it until it was too late.

Thanks!

syljua · #2 12-01-2011, 03:32 PM

Agree that is seems like the same fault, but have you checked that electric wire all the way up to the cluster? And, since it says that "Ensure replacement circuit board has a production code of 04/92 or higher", doesn't that mean that this tech bulletin is for cars earlier than 04/92?

br,
syljua

Air&Road · #3 12-01-2011, 03:34 PM

Unlike a typical oil pressure reading problem, this one really DOES sound like the gauge is the problem. MUCH better than what usually causes a low oil pressure indication. Sounds like maybe there is a flaky connection.

pawoSD · #4 12-01-2011, 07:52 PM

agreed, I would check the connections and wire to the sender itself

big dog 2 · #5 12-01-2011, 10:54 PM

Quote:

Originally Posted by LarryBible

Sounds like maybe there is a flaky connection.

Are the other gauges like the tach and clock working OK?

When I had grounding issues with my cluster, the oil pressure gauge would read zero, the tach was a bit haywire and the clock was intermittent. Other gauges were OK.

bolomiester · #6 12-02-2011, 05:41 AM

Quote:

Originally Posted by syljua

Agree that is seems like the same fault, but have you checked that electric wire all the way up to the cluster? And, since it says that "Ensure replacement circuit board has a production code of 04/92 or higher", doesn't that mean that this tech bulletin is for cars earlier than 04/92?

br,
syljua

Wow, that's a good point about the date. It just didn't register on me. Since I only have one car on my All Data account I just automatically assumed it only show me data related to it. My mechanic is out of town through the weekend, but I'll pull the cluster to see what I can see.

All the other gauges are fine. It's just the oil pressure gauge that's wacky.

Can I leave the battery connected when I pull the cluster? I'd like to wiggle the connections to see if it has any effect.

I'm also still wondering if I can swap the cluster with a salvaged without there being a problem. There's one close by that I can buy pretty cheap. Does anybody know?

lee polowczuk · #7 12-02-2011, 08:14 AM

Quote:

Originally Posted by bolomiester

Wow, that's a good point about the date. It just didn't register on me. Since I only have one car on my All Data account I just automatically assumed it only show me data related to it. My mechanic is out of town through the weekend, but I'll pull the cluster to see what I can see.

All the other gauges are fine. It's just the oil pressure gauge that's wacky.

Can I leave the battery connected when I pull the cluster? I'd like to wiggle the connections to see if it has any effect.

I'm also still wondering if I can swap the cluster with a salvaged without there being a problem. There's one close by that I can buy pretty cheap. Does anybody know?

i essentially have the same problem with my 95 e320... one of these days i have to check the connection at he oil filter... i think that's where my issue is....

no issues with the engine, however

bolomiester · #8 12-02-2011, 04:03 PM

All the other gauges are fine. It's just the oil pressure gauge that's wacky.

Can I leave the battery connected when I pull the cluster? I'd like to wiggle the connections to see if it has any effect.

I'm also still wondering if I can swap the cluster with a salvaged without there being a problem. There's one close by that I can buy pretty cheap. Does anybody know?

eddie a · #9 12-03-2011, 11:30 AM

Quote:

Originally Posted by bolomiester

All the other gauges are fine. It's just the oil pressure gauge that's wacky.

Can I leave the battery connected when I pull the cluster? I'd like to wiggle the connections to see if it has any effect.

I'm also still wondering if I can swap the cluster with a salvaged without there being a problem. There's one close by that I can buy pretty cheap. Does anybody know?

Have you looked at your lower harness? ..also called the positive cable? And you dont need to disconnect the battery to remove the instrument cluster..I might have a curcuit board for a cluster, would you happen to have the part number off of the cluster?

big dog 2 · #10 12-03-2011, 04:40 PM

Quote:

Originally Posted by bolomiester

I'm also still wondering if I can swap the cluster with a salvaged without there being a problem. There's one close by that I can buy pretty cheap. Does anybody know?

I have done it without a problem! Just make sure the replacement is for your model year. I also swapped out the speedo on the replacement cluster since the mileage on the odometer was about 100k higher than mine! LOL!

syljua · #11 12-07-2011, 08:34 AM

Quote:

Originally Posted by big dog 2

I have done it without a problem! Just make sure the replacement is for your model year. I also swapped out the speedo on the replacement cluster since the mileage on the odometer was about 100k higher than mine!

Yes, but the 1997 140 class is another beast...

OP, take a look at the connector to the oil pressure sender (behind
the plastic panel, next to the idler arm.), and see if you have good
connection there.

Certainly better to replace the oil pressure sender than the cluster...

br,
syljua, who has recently replaced my oil pressure sender, and know it
can be faulty...

bolomiester · #12 12-12-2011, 06:00 PM

Quote:

Originally Posted by syljua

Yes, but the 1997 140 class is another beast...

OP, take a look at the connector to the oil pressure sender (behind
the plastic panel, next to the idler arm.), and see if you have good
connection there.

Certainly better to replace the oil pressure sender than the cluster...

br,
syljua, who has recently replaced my oil pressure sender, and know it
can be faulty...

We tried a second oil pressure sender and it worked! The first one was supposed to be original but my mechanic said he thought it looked like an after market version. So I contacted the parts supplier and they admitted they were out when my order was shipped so they substituted an after market version. Anyway, they took the bad one back and shipped an original and it's fine.

Cal Learner · #13 12-13-2011, 08:33 AM

Quote:

Originally Posted by bolomiester

...I contacted the parts supplier and they admitted they were out when my order was shipped so they substituted an after market version....

I'll bet you aren't talking about Fastlane Phil.

bolomiester · #14 12-16-2011, 06:09 PM

Quote:

Originally Posted by Cal Learner

I'll bet you aren't talking about Fastlane Phil.

No it wasn't Phil, but the other company is usually very good so I won't beat up on them. I think this is the only time they've ever let me down and they did make good without giving me a hard time.