Temperature and oil senders

[Bev & Billy on Sta-sea-dawn]

My Westerbeke 4-108 40 hp diesel has a sender problem, both oil and water.  I bought new gauges and tried to install them.  But the PO's had left both oil and water temperature senders wires disconnected. 

There is a water sender in the block and one in the head...they both have two tabs, parts house employee mentioned a VDO?  The water sender is wired in parallel with 2 wires running to the gauge that were unattached.   
I tried to measure ohms across and continuity to base.  No ohms measure reading but ohm to base seem to work. I connected one wire to meter and it reads temp (120) with key off and below 0 peg with key on...just opposite of what I think it should do. I have the parts house guy  research the senders for possible replacement. 

He got back to me and said it is supposed to be a one wire oil sender and a one wire temperature sender.....75.00 oil and water to be priced (Seafarer marine in Largo Florida.

The oil sender appears to be electric.  I found a sender on the hose manifold for my external oil filter...with a black and white wire, again unconnected.  I have connected the wires to my new oil gauge, I(12v), S(Sender), G(ground). Pegs meter at max.

Before I change them...does anyone have words of wisdom?   Billy

[Jim S]

I was told by an old yachtsman that the W40 and the Perkins 4-108 (same engine) were prone to high oil pressures that would "blow out" the oil pressure sending sensor.  I personally do not know whether this is true but I had two oil senders blow out on my W40.  Does anyone else have any information to confirm or discount this?

[Della and Dave]

I suspect I also have an oil pressure gage problem, and in researching it, the manual says that if poor oil pressure is suspected, put a manual gage on it to verify.  I hope to do that when I get a chance.  Ours, I suspect, it has an intermittent open circuit somewhere, because the needle will drop to zero, then come back in a slit second, faster than the pressure in the oil gallery could drop.  In addition, the low oil pressure alarm is fine.  I plan on pulling the sensor, checking the actual pressure with a mechanical gage, then checking the sensor and the wiring.  On another thread, both Maruska and Journey gave me some good diagnostic advice.  Search for oil pressure and you should find it. 

[Bev & Billy on Sta-sea-dawn]

Thank ya'll...billy...the search goes on...LOL

[jackjanos]

Where on the 4-108 is the oil pressure sender located, I can't seem to find it?  Got a picture? I think I need to install a new sender, but can't seem to find where it goes.

Jack

[Della and Dave]

Take a look at this post.  Journey Talked to that, as well as some good diagnostic advice. 

 
http://www.pearson365.com/forum/index.php?topic=1295.msg7008#msg7008

I think this is ours, but I am not sure.   The big U shaped hose in the picture comes out of the engine coolant heat exchanger, starboard side. 

[SVJourney]

That is indeed the engine oil block.  It is a steel block that is connected to the engine oil system by a hose.   Since it is at the end of a dead ended system, the oil in there can gum up.  Its really old old oil that never gets circulated.  Pull the sensor, crank the engine without starting when it the engine is warm to flush it out a little.  I had to remove it and clean the block and hose with solvent to get a good pressure through there.

The sensor is NOT the standard sensor.  The standard one is much bigger around and has only one wire from it.  Wat you are showing looks more like a pressure switch for a low oil press system.  Look underneath the block for another sensor, that's where ours is. 

$75 sounds like a very steep price for a sensor.  Nothing special about them, get one from Napa if you want.

[PeteW]

Yes, that device in the picture looks very much like a Clixon. Two terminal temperature switches that are NO or NC  until they reach the trip temperature. Check it with an ohmmeter. Pressure and temp senders are resistive. All the ones I have seen or replaced have only one terminal. They screw into ground.

If you have two senders at the same time that are acting up the common cause would be an irregular 12V supply. I test my temp sensors in a pot of water placed on the stove with an ohmmeter and a thermometer.
Pete