Oil pressure gauge

[bgreene30]

I took the car for a drive today maybe 40 miles and the car ran brilliantly.

Had lunch for 2 hours and hopped in the car and drove home.

10 miles or so into the drive home I looked down and the oil pressure gauge was at 0 and car was running brilliantly. I immediately exited the freeway and turn the car off. I started up again and no movement in the needle at all.

I called a tow and cars now in the garage.

Facts:

Oil level Normal before drive and now.
No identifiable mechanical issues or sounds.
Couldnnot see any loose wire or connections
everything else seems normal.

My gut tells me it is not related to actual oil pressure but only testing with a mechanical gauge will tell.

Any thoughts or troubleshooting advice????

THanks in advance.

Bob

 

[gerryvz]

Faulty oil pressure sender or sender wiring interrupt. It's extremely rare that these engines lose oil pressure. It's also less common for the gauges to go out, but that would be the only other issue after the sender.

See this thread. Failing senders often tend to be a bit "slow" in moving the needle up to the proper level, or don't move it up to the proper level at all (meaning the needle will be lower on the scale than it should be). It's probably worth testing your gauge to ensure that the needle is operating appropriately (moves up and down), to eliminate it, before replacing the sensor.

Fuses #5 and #6 in your fuse-box control power to the instrument cluster & related gauges, but if your other gauges are working, then this is probably OK.

I've attached a couple of MB procedures that may help you with diagnosing the oil pressure switch, and separately the oil pressure gauge.

This is what the sender itself looks like



Cheers,
Gerry

 

[gsxr]

Ditto what Gerry said. I'd check/replace the sender first. Another quick check is to remove the oil fill cap with the engine running, if there is oil pressure, you'll see oil flowing on the cam lobes. I'd expect a lot of lifter clatter if there were truly zero oil pressure, so it's very likely just a sensor/gauge issue.

 

[bgreene30]

Thank you Gerry. I appreciate it.

 

[bgreene30]

You're correct. Their is plenty of oil flow so I will order up a new sending unit and seal nThank you for your help. Bob.

 

[gerryvz]

DO NOT order the cheap "Uro parts" brand sender from AutohausAZ.com. Get the "real deal" MB factory part sender through parts.com. The factory part number is on that EPC diagram you referenced in the other thread last night. URO parts are of inferior quality and you will regret buying it.

Cheers,
Gerry

P.S. The Europeans pronounce Euro as "Oy-ro" and "Oy" is definitely what you will be saying if you buy and install an Oy-ro-parts sender....

 

[gsxr]

From this thread:

The part number is 006-542-94-17 and I would also get a new sealing ring part number 007603-012113 to go with it.

Naperville (MB OEM Parts) lists the prices for these items as:

Sender: $68.40 (list price $95)
O-ring: $1.08 (list price $1.50)
Note: Pricing as of Feb-2012.

Sender: $76.96 (list price $104)
O-ring: $0.74 (list price $1.00)
Note: Pricing as of Aug-2018.

​

 

[bgreene30]

thxs

 

[bgreene30]

DO NOT order the cheap "Uro parts" brand sender from AutohausAZ.com. Get the "real deal" MB factory part sender through parts.com. The factory part number is on that EPC diagram you referenced in the other thread last night. URO parts are of inferior quality and you will regret buying it.

Cheers,
Gerry

P.S. The Europeans pronounce Euro as "Oy-ro" and "Oy" is definitely what you will be saying if you buy and install an Oy-ro-parts sender....

I was going to order parts.com. The cheapest part is not always least expensive part!

 

[2phast]

A faulty lower wiring harness is most likely the cause. It's cheaper though to try replacing the sender first.

 

[gerryvz]

A faulty lower wiring harness is most likely the cause. It's cheaper though to try replacing the sender first.

Yes it's why I said to check the integrity of the gauge and the wiring from the sender before throwing parts at it. The fact that the gauge is dead makes me think that it's not necessarily the sender (as mentioned, bad senders usually just give LOW gauge readings, not NO gauge readings) but a bad gauge or bad wiring between sender and gauge will result in a bad gauge. It's not difficult given the factory docs I posted to check the integrity of the gauge/wiring/sender so it's recommended to do some diagnosis work first.... but an extra sender isn't a bad thing to have on hand. Mine at 114K is weak and I've got a replacement waiting for the day it's needed.

Cheers,
Gerry

 

[bgreene30]

A faulty lower wiring harness is most likely the cause. It's cheaper though to try replacing the sender first.

Thanks.

 

[bgreene30]

A faulty lower wiring harness is most likely the cause. It's cheaper though to try replacing the sender first.

Thank you. Do you happen to have the MB Pn handy for the lower harness?

 

[2phast]

Thank you. Do you happen to have the MB Pn handy for the lower harness?

I don't, but you can look it up in the EPC since the US version is free go to the link and sign up.

http://epc.startekinfo.com/epc/

 

[bgreene30]

Thanks. Great advice. What a ton of vital info. Now I just need to get better at pulling the data out!

Cheers

 

[gsxr]

FYI. If the harness was bad, i.e. open wire, the gauge would peg at "3" all the time, even with the key on but engine not running. For the gauge to read zero, the wire would have to be shorted to ground. This could be easily determined with an ohm meter at the sender end of the wire; also you could plug in a resistor between the wire to ground to simulate a reading on the gauge and see if that works.

Photos of the harness (which is 500E-specific) are below. First pic shows my old harness, second two show the new harness. MB # 124-540-27-30, current list price $312.

 

[jano]

The pressure sending unit has come up a few times in the last several months.. wiki it? It's an easy fix albeit a bit awkward to get to, recommended to be done during an oil change while oil is out.

 

[Jelmer]

If noone else feels like making a wiki entry out of this info, I could try and do it?

 

[bgreene30]

FYI. If the harness was bad, i.e. open wire, the gauge would peg at "3" all the time, even with the key on but engine not running. For the gauge to read zero, the wire would have to be shorted to ground. This could be easily determined with an ohm meter at the sender end of the wire; also you could plug in a resistor between the wire to ground to simulate a reading on the gauge and see if that works.

Photos of the harness (which is 500E-specific) are below. First pic shows my old harness, second two show the new harness. MB # 124-540-27-30, current list price $312.

Thanks Dave. I will have a look at it this weekend on my friends lift. Bloody impossible without getting the car in the air.

 

[gerryvz]

What was the result of this? Did you solve the problem with the gauge reading? What was the cause?

Cheers,
Gerry

 

[ccc]

Yes, i think follow up answers and "completing" posts is an important
tool for all of us. On this one, i wonder what simple test one can do on the side of the road, to tell if one still has adequate oil circulation/flow in the event one is not sure in an event such as this?

For example, if he had just pulled off the oil cap and started the engine,
should there be oil squirting about? (I have never tried this). Any other tips? Maybe listen somewhere for flow? Soemone once mentioned to listen for oil flow over the valve cover, but i heard mechanical sounds when i put ear too valve cover via stethoscope.

A roadside oil flow test would have saved him the towtruck hastle.

Chris

 

[Johnnybenz500e]

hey guys.. I just had the same problem happen to me tonight. Oil gauge worked at beginning of the day and now it's at 0. With full throttle pressed it goes up to about.. .75-1. Then drops. Oil is about 4k old on mobile 1 syn. Oil pressure switch was changed LAST oil change. Removed oil cap and oil is visible. Any info would be great.

 

[Johnnybenz500e]

Update: car started up great, oil pressure at 3 bar for about 1 min then shot down to about .25. Went on the highway and under acceleration gauge did hit about 1.5 but when cruise was set it went down to about .75. Strange thing was after 15 min on the highway as I exited the pressure gauge moved less on the streets.

 

[gerryvz]

Need to replace the sender again. Be sure to get a VDO sender or MB OE sender.

 

[Johnnybenz500e]

The replacement was an original part.

 

[gsxr]

Has your lower wiring harness been replaced? An original/old harness may cause problems with the oil pressure reading. Very unlikely a new OE sender has failed since the last oil change.

 

[Maui]

It could also be the gauge itself. If you have an extra gauge cluster laying around you could try that.

 

[Johnnybenz500e]

Not sure, but main harness is from 2006.. how do I tell if it's bad or old/orig

 

[gsxr]

Not sure, but main harness is from 2006.. how do I tell if it's bad or old/orig

Look at the date code on the tag, same as on the upper harness. Check the Wiki when the forum starts working again. If you don't have a record of replacement, very likely is original. Look for insulation flaking off at the oil pressure/level sender wires.

http://www.500eboard.com/forums/wiki_index.php?title=Lower-Wiring-Harness

 

[Trae]

Being lazy here, but does anyone have the part # to a M104 oil sender?

For my 94' wagon.

 

[J-Sauce]

Johnny texted me and says he is using 10/30 oil. I suggested moving to 15/40. Though, I still have a sneaking suspicion that the guage is on its way out.

 

[Maui]

It is not uncommon for the lower harness to be original even if the upper has been replaced. I just replaced my lower. I wasn't having any issues but I knew it was just a matter of time.

 

[J-Sauce]

Luckily if Johnny does need a harness, the prices were down last I checked from when I purchased mine in 2009.

I was under the impression though that if a harness is shorting, it would cause the car to read 3 bar at all times. Am I wrong?

 

[Johnnybenz500e]

thanks for helping out guys.. I have a spare cluster that's first to try..

 

[Maui]

Disconnect the battery before pulling the cluster and make sure you know your radio code before disconnecting the battery.

 

[gerryvz]

Being lazy here, but does anyone have the part # to a M104 oil sender?

For my 94' wagon.

Same part as for the M119, as shown here: http://www.500eboard.com/forums/showthread.php?t=4287

The oil pressure sender on the M104 is much more of a PITA to replace than on the M117 and M119, however.

Cheers,
Gerry

 

[Johnnybenz500e]

any idea how much this part is costing

 

[gsxr]

I was under the impression though that if a harness is shorting, it would cause the car to read 3 bar at all times. Am I wrong?

Shorting to ground reads zero. Open (disconnected) reads max 3 bar.

Trae, the sender p/n is the same for all W124 engines. OE or Hella/VDO only.

 

[gsxr]

any idea how much this part is costing

what part? the harness is ~$250, see link in post #29 above with part number. 500E harness is not the same as 400E, btw.

 

[Johnnybenz500e]

Thanks gsxr!
Trouble shooting to begin soon this week.

 

[J-Sauce]

Shorting to ground reads zero. Open (disconnected) reads max 3 bar.

Awh! In that case I definitely would go with the harness. It's not hard to check, simply get under the car and check the insulation on the wires going to the alternator. If you see any cracked insulation, or no insulation at all, you've found your culprit.

I stick with my recommendation to move to a thicker oil even if that's not causing this particular problem.

 

[Johnnybenz500e]

if it is the wire harness is this a emergency asap fix or can I get a little out of it to collect funds to do other things as well in one shot.