PeachParts Mercedes-Benz Forum

PeachParts Mercedes-Benz Forum (
-   Diesel Discussion (
-   -   Low oil pressure alarm. (

barry123400 04-04-2008 02:06 AM

Low oil pressure alarm.
Unfortunatly we had yet another member loose his oil pressure and not catch it in time yesterday. Since I want to build several low oil pressure alarms for myself I wonder if any other people would like to purchase a complete kit? Volume purchases of every component may enable an end price less than the fuel you would burn running around trying to locate all the pieces and then you still have to design a lockout circuit for when the engine is not running.
It strikes me it will have to incorporate a system where it cannot activate without the engine running. Otherwise the high decibel level would drive you crazy everytime you turned on the ignition key or the engine off. Yet it has to be loud to get your absolute attention. Otherwise it is almost worthless in my opinion.
Low decibels could be masked by the radio is an example.On 240ds at speed it is in competition with the engine as well. These devices really give peace of mind in my opinion.
I have had them on other diesels I have owned. I can assure you that you do pay attention if it goes off. Primarily I believe installed for warranty protection by the manufactures. How could you take a seized engine back in and say you did not notice the oil pressure was gone. They are not going to buy it.
I also feel a high temperature coolant limit alarm might be a good ideal for those engines with aluminium heads. They are very simple and it could reduce the amount of cracked heads. These items are now long overdue in my opinion. Any thoughts?

xdjio 04-04-2008 02:16 AM

I must confess that I am somewhat interested! I have a real pressure gauge but I'm not watching it like a hawk all the time.

My previous car (Porsche 944) had the best warning system I've had the pleasure of seeing so far - any critical alarms would cause a huge red exclamation point to light up in the cluster and a super loud alarm would go off. I actually had a low oil pressure alarm go off on that car once, the oil pressure relief valve jammed open and oil was getting shunted back into the sump.

Without knowing or wanting to find out if my 300D has a similar alarm (I suspect not) I wouldn't mind having something to replicate that functionality

bgkast 04-04-2008 02:55 AM

I may be interested depending on cost, but I do not want a big sender tapped into the lid of my oil filter housing.

TylerH860 04-04-2008 03:50 AM

1 Attachment(s)
I agree with Bgkast, but otherwise I'm in.

Many know from my previous posts that I recently surivied a near death experience with an oil cooler hose. Even though I have brand new OEM hoses proffessionally installed, I'm still paranoid.

Perhaps a sound byte of Hillary Clinton for the alarm? That would annoy me enough to pull over.

Feel free to use this picture to advertise... slogan, "THIS COULD HAPPEN TO YOU! NEVER WORRY ABOUT MISSING SUDDEN OIL PRESSURE LOSS AGAIN! Perhaps Joan River's would be available for the infomercial.:D

PatricdeBoer 04-04-2008 04:53 AM

I am totally interested. My dad lost his engine to a broken oil cooler hose a while back and I've been paranoid ever since. Some one once suggested putting a T- fitting in where the original sender unit is and adding the low pressure switch from a VW onto one leg of the T.

Cervan 04-04-2008 05:13 AM

lol... if my engine goes due to no oil.. im slapping a sbc in there and gutting the interior, So ill just redline it till then.

Diesel911 04-04-2008 06:56 AM

Here is my previous thread on a low oil pressure alarm. One member objected to tapping into the top of the oil filter top coverer so if you do not want to do that you will have to find someplace else to tap into the oil pressure. Mine system is a “bare bones” type system. The buzzer sounds until the oil pressure is up above that of the sending unit is set at. There may be another places to get the (+) current from that is only connected when the ignition is in the “run” position but I have not taken the time to look at the wiring diagrams or poked around with my tester to find it. So mine buzzes until the oil pressure is up.
The easiest thing would be to put to put in as switch that would open the circuit while your thumb pushes on the button if you do not want to hear the sound during starting.
But, if your alarm dose not sound during starting how will you know a wire did not come loose or break? You would start up and go thinking your alarm is working.

A new sending unit and a buzzer from Radio Shack should not cost that much.
Another question is how much amperage can go through the sending unit? For instance; a back up alarm for a cars, truck and forklifts could be used and they are certainly loud enough but would the amps pulled burn out the sensor?

funola 04-04-2008 11:16 AM

If your car has an EGR controller, you may be able to tap into the RPM signal to lockout the oil pressure alarm. I say this because my 83 240D has an EGR controller which has circuitry to measures RPM to control the EGR valve and I have tapped into it to drive a tach.

funola 04-04-2008 11:21 AM

TylerH860's, more details please about how your oil lines failed.

[QUOTE=TylerH860;1813810]I agree with Bgkast, but otherwise I'm in.

Many know from my previous posts that I recently surivied a near death experience with an oil cooler hose. Even though I have brand new OEM hoses proffessionally installed, I'm still paranoid.

Mister Byrnzoil 04-04-2008 11:28 AM

Can you splice a T into the line that goes to the oil pressure gauge? Then maybe mount the sensor/sender on the firewall? Seems like the least intrusive way to do it.

Jordan G 04-04-2008 11:33 AM

Some more ideas discussed on here....

and (scroll down to post #24)

vstech 04-04-2008 12:04 PM

um, in race cars we use a large light on the steering colum to tell us when to shift at the correct RPM for max power (kinda hard to do it by ear in 4 or 8 seconds of a ultra high speed run...) how about a simple light on the dash, or a series of them, heck there are at least 3 empty bulb spots on the 123/126 cluster that could be wired in...
I hate buzzers...

hangit 04-04-2008 12:27 PM

I'd be interested in an alarm system of some sort. My wife and daughter do not scan the instruments, judging by the way the fuel gauge usually is pointing to E! :P


Jeremy5848 04-04-2008 12:37 PM

I've looked into alarms too and agree it is a good idea. For 123 cars with mechanical gauges, you could tee the plastic line to the gauge and add a sender behind the instrument cluster, wired to a lamp or buzzer, whatever you want. I have thought about using a hi-brightness flashing LED. There are several spots in the cluster where such a lamp could be placed.

The only problem I've spotted so far is that all of the oil pressure switches I've seen so far make contact with pressure and I want it the other way 'round. That can be fixed with a little bit of electronics, of course, just like a tach signal can be used to activate a loud buzzer, but adds to the complexity.


funola 04-04-2008 12:48 PM

The way I'd do it is add a set of gold plated contacts from a miniature relay to the oem oil pressure gauge, actuated by the needle, the buzzer or light would be lockked out above 1500 rpm, which I think is the trigger point of the EGR controller.

All times are GMT -4. The time now is 01:53 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website