Jumpy Oil pressure gague - PeachParts Mercedes-Benz Forum

#1 03-11-2003, 12:42 PM

My oil pressure gague seems very "jumpy"

Suppose when I ma stoppedat lights with the selector to N the gague will be dancing from 1.5 to 2.5 when warm.

The other times it may settle at 2 and stay put.

Any ideas on why I seem to get such an erratic reaging.

Is it engine an engine issue (runs fine), a sensor issue or a gague issue?

Thanks,

John

1981 500 SEL (converted to a 300 SDL)

Wasuchi · #2 03-11-2003, 01:40 PM

I think this is fairly common.... mine does it. You should be safe as long as it stays above 1.5 at idle and goes all the way up when you step on the accelerator pedal.

The Warden · #3 03-11-2003, 01:41 PM

My 300D did that for a while after I first got it, but it stopped after I got back to California...I was told that it's pretty common, and is a gauge issue, and isn't a big deal.

Hoiwever, I've got a 123, which has a pure mechanical gauge...dunno about the 126...

#4 03-12-2003, 03:59 AM

cheers guys, appreciate the replies.

shear2001 · #5 03-12-2003, 07:07 AM

Check the little o rings on the stem that houses the oil filter. I read somewhere that if they're cracked or worn it makes the needle jump at idle...

airfoill · #6 03-12-2003, 08:06 AM

Shear2001,

The orings would not make the needle jump around. Those little orings are to prevent oil from leaving the oil filter canister when the engine is off.

The problem with the fluctuating needle may be an indication of a malfunctioning pressure sensor. If it were me, I would replace that first to see if that fixed the problem.

Herb
'82 240D
'87 300SDL
'92 300D 2.5 Turbo

Stevo · #7 03-12-2003, 11:44 AM

heywood970

Best replace those o rings like shear2001 said, they are cheap.

autozen · #8 03-12-2003, 11:09 PM

I'll cast my vote with Airfoil. After working on these beasts for 30 years as a professional mechanic, I have never seen rock hard seals cause any erratic readings, however, the seals should be replaced to prevent leak down. I believe you have an electric sending unit which has never proven to be as reliable as a mechanical pressure gauge, but hey it's the cheap American way. I'd check the sending unit.

Good luck,
Peter

Piotr · #9 03-13-2003, 03:38 PM

had the same problem in my 190D AND my Grand Wagoneer. Both times it was a sending unit. $24 and 1/2 hour to replace in the 190D, $7 and 5 minutes in the Jeep.

The Warden · #10 03-13-2003, 03:43 PM

Quote:

Originally posted by Stevo
heywood970

Best replace those o rings like shear2001 said, they are cheap.

Just wondering, where can the O-rings be gotten from? I don't remember them being in the kit with the oil filter, and I'm sure that mine could use replacing...

Thanks! This is actually perfect timing, as I'm about due for an oil change...

autozen · #11 03-13-2003, 09:32 PM

Warden,

You will have to get them from the dealer. They are both the same and can't cost that much. I can't remember the part # offhand, but they should be able to figure it out.

Peter

Stevo · #12 03-13-2003, 10:25 PM

Wadden

The o ring part # is 015- 997-94-48 Seems like the cheapest thing to try first.

Stevo

Ridge · #13 03-14-2003, 01:29 AM

Pull the connector off the sending unit on the engine, wipe the oil off the tip of the sending unit and do the same for the inside of the connector. Plug it back together and start engine, I'll bet it works fine. Same thing has happened to me two or three times and this aways clears it up.

Ben

Stevo · #14 03-14-2003, 01:42 AM

Thats even cheaper than the o rings

Steve

autozen · #15 03-14-2003, 10:01 AM

Steve,

You missed my point. Those o rings need to be replaced in every engine when they become rock hard regardless of what the gauge does.

Peter