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Old 01-10-2011, 04:34   #1
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Why an Oil Pressure Alarm ?

My elderly Westerbeke diesel began chirping after running for a short while though the gauges were normal. I was told that the low oil pressure (or high temp.) alarm was most likely failing. I bought one of each and began looking for them on the engine block. I eventually found one of them in a position that looked impossible to access for replacement without removing the engine or my shrinking to half my size.

So my question is, why the alarms? The gauges read normal and I don't think gasoline engines have shrieking alarms. Are diesels in more danger than their gasoline cousins from low oil pressure? Why not just disconnect the alarm speaker at the panel or perhaps replace it with a small bulb of some sort as long as the readings are ok?
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Old 01-10-2011, 04:47   #2
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Re: Why an oil pressure alarm?

If you read though the forum long enough you will find a lot of engine oil leak stories. I don't know if boat engines are more prone to the problem, but it seems to happen. Boats also rock and a low sump is more an issue that for a car.

So it is up to you whether to fix the alarms or to just go on the gauge readings.

Did you thoughy check all the wiring for the alarms as there's a good chance is a bad connection/wire? Run a jumper wire from the switch to the gauga and see if problem goes away.
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Old 01-10-2011, 05:32   #3
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Re: Why an oil pressure alarm?

Auto engines have idiot lights and not usually audible alarms.

But your sensors are easy to check. Follow the wiring up from the sensor. It usually will come to a connector. Break open the connector and find the wire to the sensor. These sensors almost always make to ground when activated, ie high temp or low oil pressure.

So with an ohmeter check the resistance from the sensor wire to ground. If it is very low then it is bad.

Whether you decide to replace it or live with it is up to you. Ages ago autos only had gauges, but nobody looked at them. Will you?

David
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Old 01-10-2011, 05:42   #4
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Re: Why an oil pressure alarm?

Thanks for the comebacks. If I could get at the sensors I'd replace them but as I mentioned, they might require engine removal. Very tight space in my Nonsuch.

As for the marine v automobile environment issue I can understand that but there are marine gasoline engines and I didn't think they bleeped like the diesels. Or do they?

Replacing the alarm with a light mounted at the wheel could be an alternative.

Thanks again.
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Old 01-10-2011, 05:58   #5
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Re: Why an oil pressure alarm?

on a gen set one most often starts it and then ignores it how would you know there was a problem? On a main at least one is at the helm where the gauges are
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Old 01-10-2011, 06:05   #6
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Re: Why an oil pressure alarm?

Quote:
Originally Posted by HarveyN View Post

Replacing the alarm with a light mounted at the wheel could be an alternative.

Thanks again.

How does this change anything? Uses the old sensor and wiring.

You need to check the wiring. much more likely to be the problem than the sensor.

If the sensor is really bad look around the engine. Some engines (like mine) the oil gage sensor and the low oil pressure alarm sensor are located in different spots. If you can get to 1 of them maybe you can install a tee fitting and install both at the same location. Just leave the old sensor you can not get to installed and abandon it.
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Old 01-10-2011, 06:43   #7
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Re: Why an oil pressure alarm?

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Originally Posted by Don Lucas View Post
How does this change anything? Uses the old sensor and wiring.

You need to check the wiring. much more likely to be the problem than the sensor.

If the sensor is really bad look around the engine. Some engines (like mine) the oil gage sensor and the low oil pressure alarm sensor are located in different spots. If you can get to 1 of them maybe you can install a tee fitting and install both at the same location. Just leave the old sensor you can not get to installed and abandon it.
It took looking in a small mirror just to be able to see one sensor, let alone get at it. I trust the gauges so if I'm alerted to check them I'd like to then ignore the alarm. Perhaps a switch at the alarm is a better answer.

Thanks
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Old 01-10-2011, 06:48   #8
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Well, having burned up two car engines with gauges (hole in oil pan while 4 wheeling, and an overheat), I believe in alarms. Just installed an exhaust over temp sensor/alarm on my Lehman. Wouldn't run without the bells and whistles!

My $.02 worth...
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Old 01-10-2011, 07:09   #9
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Re: Why an oil pressure alarm?

Loss of oil pressure is a very bad thing and can cause the engine to seize in very short order. The purpose of the alarm is to notify the operator in the event they are running the motor while not near the engine gauges and for some reason have a major loss of pressure.

Oil pressure and water temperature alarms and gauges are critical and should be maintained in good working order.
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Old 01-10-2011, 07:43   #10
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Re: Why an oil pressure alarm?

Agree with everything noted. The alarm on/off switch will be left on unless I can verify that it's a false alarm according to the actual gauge readings. Thanks all.
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Old 01-10-2011, 08:15   #11
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Re: Why an oil pressure alarm?

Audible alarms for low oil pressure, and for high coolant temperature are not to be discounted, but you have to be able to hear the alarm over engine noise. Had an oil cooler line rupture earlier this year and failed to hear the alarm for several minutes --- just a new buzzing sound against the background noise of the engine. That was a Ho Lee Sh!t moment. No harm done as it turned out (apart from an engine compartment and bilge covered in diesel engine oil). Make sure the alarm is LOUD, and maybe supplement it with a bright red flashing light visible in the sun. But the main lesson is to check and replace oil lines at the first sign of chafe, cracking, or embrittlement.
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Old 01-10-2011, 08:17   #12
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Re: Why an oil pressure alarm?

Good advice
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