617 Oil pressure gauge instead of idiot light sender? - PeachParts Mercedes-Benz Forum

300 Super D · #1 07-31-2015, 11:24 PM

Has anyone replaced the idiot-light sensor that is on the oil filter housing with one that will work with an aftermarket pressure sensor? I want to add a real oil pressure gauge as I'm always paranoid.

BillGrissom · #2 08-01-2015, 02:10 AM

What car are you talking about? My 84 & 85 300D's have a mechanical oil pressure gage on the dash. But, many cars use a low-pressure switch to a lamp and that also works. The journal bearings work fine as long as they have a good supply of oil, even at 5 psig. The oil pressure indicates how close you are to the flow limit, and indicates when bearing gaps have gotten too large.

Diesel911 · #3 08-01-2015, 09:41 AM

This was discussed in the Oil Pressure Alarm Threads.

5 psi works at idle speed but is not sufficent to lube the Bearings or spray Oil up under the Pistons when you are under a load at higher rpms. That means under those conditions if the Idiot Light goes one it is alreadly likely damage has been done.

My memory is not good on this but I think the Manual has 30psi+ is needed for the Oil Spray Nozzles to open and spray.

What makes the Gauge better if you happen to be looking at it is that it tells you what your Oil Pressure is under load and at higher rpms.

I have not followed the Oil Pressure Alarm Threads but one of the goals was to make one that would alarm when the pressure dropped at higher rpms.

I have a low Oil Pressure Alarm on mine that trips at 7 psi but as I said that is not sufficient to help if an Oil Cooler Line failed on the Freeway. However, it is ok for around Town where you frequently stop and the Engine is at idle speed.

mannys9130 · #4 08-01-2015, 09:50 AM

As is said, there's a realtime pressure gauge. The only idiot light I know of is the low oil level warning light.

The general rule is 10 psi per 1000 rpm is what you want to see to avoid metal on metal contact. Since 1 bar is roughly 15 psi, an idle oil pressure as low as 1 on the gauge is just fine. With Rotella T6 5W-40 my hot oil pressure at idle is 1.5 bar. Also keep in mind, pressure is the resistance to flow, and flow is what you want to keep the journal suspended within the bearing. Pressure is good, but after a certain RPM the oil pump cannot flow enough oil and metal contact will occur at high rpm.

charmalu · #5 08-01-2015, 10:13 AM

I think he has a 84-SD. Then he is referring to the electric oil sender.

The W123 is mechanical and the W126 is electrical.

You could plump in a "T" fitting so then you would have a real time gauge and the Dash gauge will still work.

Charlie

sent from my pos computer

Jeremy5848 · #6 08-01-2015, 11:12 AM

Electrical or not, the sender on the oil filter housing is not an "idiot light sender." These cars do not have a low-pressure idiot light. Many of them do have a low-oil-level idiot light.

The low-oil-pressure warning light I installed in my '95 E300D uses a VW switch that trips at about 1 bar (15 psi). In warm weather it occasionally flashes a couple of times when I slow down at a stop and the oil pressure drops until the EDS brings the idle under control. See this link for details.

Jeremy

MTUpower · #7 08-01-2015, 11:30 AM

Quote:

Originally Posted by Jeremy5848

Electrical or not, the sender on the oil filter housing is not an "idiot light sender." These cars do not have a low-pressure idiot light. Many of them do have a low-oil-level idiot light.

The low-oil-pressure warning light I installed in my '95 E300D uses a VW switch that trips at about 1 bar (15 psi). In warm weather it occasionally flashes a couple of times when I slow down at a stop and the oil pressure drops until the EDS brings the idle under control. See this link for details.

Jeremy

This thread is discussing the 617-96X engine which you do not have. Just sayin'.

barry12345 · #8 08-01-2015, 12:41 PM

Whatever is done you need some system that will alert you in a way you cannot miss if oil pressure sags low. It is highly unlikely for a driver to catch any form of gauge in a critical period.

So has to be a light that you cannot ignore or an audio alert. There is still a better chance to save an engine if an oil cooler hose or oil pump chain fails than without one. .

People do not really watch gauges all the time. I suspect even if tried you would tire of it. Or if a person does not want to expend the effort improving the oil pressure gauge system. Make sure the oil cooler hoses are in great condition. My guess is they are at maximum stress when you are out on the highway. That is also where the majority seem to fail. In my opinion a lot do fail. It seems to go in cycles on this site still the vast majority of owners still do not use this site.

I always liked the expression of stick a fork in it as it's done. Goes well all too many times when an oil cooler hose lets go.

Because the consequences are so severe it is not the brightest ideal to be driving around with really old oil cooler hoses anyways.

Jeremy5848 · #9 08-01-2015, 11:47 PM

Quote:

Originally Posted by barry12345

Whatever is done you need some system that will alert you in a way you cannot miss if oil pressure sags low. It is highly unlikely for a driver to catch any form of gauge in a critical period.

So has to be a light that you cannot ignore or an audio alert. There is still a better chance to save an engine if an oil cooler hose or oil pump chain fails than without one. .

People do not really watch gauges all the time.

Absolutely right! I suspect that's why Mercedes eventually (in the W210 and other mid-1990s models) dropped the oil pressure gauge entirely. What surprised me was they didn't at least provide an idiot light. Maybe too often people would drive the car anyway!

Jeremy5848 · #10 08-01-2015, 11:43 PM

Quote:

Originally Posted by MTUpower

This thread is discussing the 617-96X engine which you do not have. Just sayin'.

You are correct, of course, but my alarm design can still be used in the OM617 engine (and other OM61X engines).

300 Super D · #11 08-02-2015, 04:53 AM

I wanted to know what the pressure actually is when needed, and my intent was to also put one of these on the dash.

Very cool LED warning BEEPING light
https://www.youtube.com/watch?v=LdU6u8bfxa4

2 Pcs AD16 16SM 16mm 12V Red LED Indicator Flashlight Signal Flash Buzzer Beep | eBay

Jeremy5848 · #12 08-02-2015, 11:30 AM

Quote:

Originally Posted by 300 Super D

I wanted to know what the pressure actually is when needed, and my intent was to also put one of these on the dash.
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That's a nice product. I wonder if the beeper can be heard over engine sounds, radio, etc? My alarm is similar except it has no beeper.

leathermang · #13 08-27-2015, 07:19 PM

Quote:

Originally Posted by Jeremy5848

That's a nice product. I wonder if the beeper can be heard over engine sounds, radio, etc? My alarm is similar except it has no beeper.

That is nice... they claim 80 db volume ..... which I think would be enough..
so a properly calibrated sending unit mated up to it.... very important that important warnings be AUDIBLE.... all the important ones on airplanes are...

mach4 · #14 08-27-2015, 08:00 PM

It would not be too difficult (relatively speaking) to implement a microcontroller-based engine warning system. I'd envision sensors for oil pressure, coolant level, oil level and fuel pressure. My first cut on system logic would be to have it chirp when the key is turned on to alert the driver that the system is live but not throw warnings until it recognizes that the the engine is actually on. I'd use oil pressure (as normally used in Hobbs meters) as the indicator that the engine has started. A RGB LED would glow Blue until the engine is on and sensors are normal at which point it would glow Green. A fault would sound an audible alarm and turn the LED Red and flash 1,2,3 or 4 times to signify which sensor had tripped (unless a gauge is present for that sensor). A pushbutton would silence the alarm but the LED would still flash. Since it's a microcontroller the trip points could be programmed as desired.

Junkman · #15 08-27-2015, 06:22 PM

I'd like one in the SDs for oil pressure & on the Cummins for fuel pressure. How do adjust the pressure at which the alarm is triggered?

The Ram already has a mechanical fuel pressure gauge. I could splice into the line & run a pressure switch then up to the light but haven't seen a switch that can be set to 10#.