Perkins 4/107 oil pressure

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Richard D

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Motored my new boat home, no wind and after 2 hours of 1600 rpm the oil pressure was at just under 20 psi, which to me seems low being used to modern diesels but it stayed at this till we turned it off after 5 hours, is this pressure acceptable, it sounds just great. Dont want to take the engine out, anyone any experience of putting in an oil booster such as STP or Wynns.

Regards Richard
 
The best test is to rig up a capillary-tube oil pressure gauge in place of the current sender.But that would mean buying one.
Perhaps check the oil pressure relief valve is not stuck slightly open and check all the connections between sender and gauge.

Some instrument set-ups have a voltage stabiliser which can cause erratic readings if faulty and you could always try putting in a new sender unit. Or borrow one from someone whose engine currently reads a higher pressure.

Flow is the major requirement. Pressure being less important. If the pressure read-out had suddenly dropped that would be worrying.
 
Thanks for link but unfortunately does not go into oil pressure, I think only a preevoius owner can answer this question.

Richard
 
When cold it starts at 40 psi, looks lime this is the pressure the releif valve is set and over an hour goes down to just below 20 psi, so dont hink the valve is sttuck. What sort of valve is it, a ball bearing or a conical tube on a valve type seat. Not looked for the reflief valvr is it get atable from the outside ir is it inside the engine.

Richard
 
Sounds like the first thing to do may be an oil change. Then you know you have decent oil that isn't going to go runny when it gets hot (Technical language) and an oil filter that can keep up with the flow.
Pressure is just an indication of flow being high enough to cause back-pressure. Too much flow and not enough oil getting away would be bad as well.

It's ages since I did one of these engines.
Tinkicker may be your man
 
Normal operating pressure is 30/60 psi at working temperature. The pressure relief valve is in the oil pump in the sump.
However there is also a pressure relief ball valve in the oil filter assembly which will open if the filter is clogged. This means unfiltered oil is circulating around the bearings

It's all in the workshop manual Section N (page 80)

.pdf file, takes ages to download.
 
I've got 2 x 4107's in my boat, and both engines climb to just under 50psi when i start them up (takes about 5 seconds to get there) and once warmed up, it drops to about 43-44psi, and if i open the throttles fully, the pressure drops down even more to about 40psi, the port engine always seems to be about 1-2 psi lower than the starboard engine, but i think the gauges are only accurate to about +/- 5Psi


Like Lakesailor said, do an oil and filter change, so you know the condition of your oil and check it again, these engines can suffer split fuel pump diaphrams apparently, and if they do, the diesel leaks straight into the crankcase and waters down your oil which in turn, reduces your oil pressure (and your oil level goes up!)
 
As said before oil and filter change first. My 4107 sluggishly goes up to 60PSI on start but settles down to 50PSI all day at 2000 revs. If I hammer it at 2500 revs it drops to 45ish. Capillary gauge is the way to go for accuracy, you'll get all the bits from Pirtec.
 
Engine oil and filter changed 8 hours ago, no fuel in oil, I was a nechanic and know from my apprentiship in the 60;s that ford cars ran at 40 psi at speed and 10 on tickover and was hoping this engine being of the same vintage ran similar, so I guess engine has to come out.

Richard
 
interesting way to go, what was your oil presure before and also after the cooler mod and how much dif did oil make. How did you cool the cooler?

Richard
 
You 4108/7 should have an oil cooler on it as standard.
My 1978 4108 runs at about 55psi throughout the idle to 1800 rev range.
Yours sounds worn, assuming the correct grade of oil and filter are installed.
It might be a bit smokey as well? I think it's maybe beyond the snake-oil easy cure stage...
Sorry.
 
Richard D said:
the compan who serviced the engine prior tp mr buying it put shell 10w 40 in it.

Richard
Click to expand...

That viscosity may well account for the lower pressure. There is little justification for using less than a 15W in a boat and a 20W might be more appropriate in an older, worn engine. Modern lower viscosities like 10W, 5W and 0W are designed to improve fuel economy and need hardened crankshafts and (mostly) aluminium based bearings to overcome the wear that results. Your engine will almost certainly have neither.
 
Thanks for the info well appreciated, regarding the 20w 50, is this just ordinary petrol engine oil, if so do you not have to change it more often with it having no detergrent qualities. No one has said anything aboiut my question about putting in STP of Wynns oil treatment, any comments.

Richard
 
Richard D said:
Thanks for the info well appreciated, regarding the 20w 50, is this just ordinary petrol engine oil, if so do you not have to change it more often with it having no detergrent qualities. No one has said anything aboiut my question about putting in STP of Wynns oil treatment, any comments.

Richard
Click to expand...

Try a search for 'engine oil', there are countless threads that will give you much information. You need an oil with an API C? Rating. The C stands for compression, i.e. diesel, whereas the alternative S stands for spark, i.e. petrol. Check your engine manual for the grade they recommend but, as you will see as a result of your search, in many cases the recommended oil is obsolete and becoming difficult to source. I don't think you told us what engine you have but in many cases the recommendation is API CD, obsolete since about 20 years ago but available if you try hard.

There is also a page on the topic on my website, under Engine.

As a retiree of a major oil company I will answer your last question with the party line, definitely not! A colleague used to test every commercial oil additive available. He never found a single benefit from any of them.
 
Last edited:
That's a good point about the viscosity range. May explain the dropping of pressure over a period. The same as you would expect if you had fuel in the oil.
Sounds like a change of oil is still the first call and may save a lot of expense.
 
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