4-108 Oil Pressure Drop After Oil Change.

[phorvati]

I just did my first oil change, I am at about 75 hours after a complete rebuild.
Prior to oil change I was running at 55psi cold, 40psi hot loaded ~ 1900 rpm
No unusual exhaust smoke.

After an oil change I am at 40psi cold idle, 35psi hot loaded ~1900 rpm

Also after long motoring, when i lower rpms to idle(700rpms) and put it in neutral, oil pressure drops to as low as 10psi and I get some while smoke.
I think its just steam. I collected some exhaust water and saw no fuel in it. It also didn't smell like diesel.

I am using DELO 400 LE SAE 15W40 for my oil.

Any cause for concern? Or is there anything I should change to get better oil pressure?

[David M]

What do the manufacturers specifications say? I have seen many engines who idle at seemingly low oil pressures.

Stay with what the manufacturer recommends for oil viscosity. Thicker oil may not lubricate adequately.

[GordMay]

Lube oil pressure should be about 30 to 60 psi at maximum speed & normal operating temperature.
Per page 27 Shop Manual ➥ http://www.marineryachts.com/perkins_manual.pdf

[gjordan]

I dont have an answer for you but the first question is what type/weight oil was put in after the rebuild? Also, did you change brands of oil filter when you changed the oil? On rare occations a filter can make a differance. Those numbers dont sound that bad, but it would be nice to have a little higher idle pressure. Who did the rebuild and what do they say? ___Good Luck_____Grant.

[neilpride]

SAE 40W In the Tropics....

[phorvati]

I kept the same Brand of lube oil DELO 400 LE SAE 15W40, and same brand of oil filter NAPA gold 1515. Did the rebuild myself.
I am mostly just trying to see what others are noticing on new/rebuilt engines.
Interesting observations that at full load, about 2200 rpms I was at about 190F. After an oil change I am at 180F at same load.
But I did not change the condition of the raw water strainer, or anything in the cooling loops. Just a mere oil change dropped the temperature 10F. I guess I was really due for an oil change.

[bobconnie]

I don't know but I was taught to change the oil in a newly rebilt diesel or gas at 1 or 2 hours of running, and to change the filter at the same time ! ya may have went to long if there were any metal floaters in the oil your mains may have been damaged!the filter if ya still have it will tell ya cut it apart and ck for metal!! if ya can't then as said above go to a 40 wt oil and hope for the best !That amount of low oil pressure at an Idle would worry me ! Just sayin it's what ya got ! ya may have to live with it !! sorry could not be of more help !!

[Ex-Calif]

Originally Posted by phorvati

I kept the same Brand of lube oil DELO 400 LE SAE 15W40, and same brand of oil filter NAPA gold 1515. Did the rebuild myself.
I am mostly just trying to see what others are noticing on new/rebuilt engines.
Interesting observations that at full load, about 2200 rpms I was at about 190F. After an oil change I am at 180F at same load.
But I did not change the condition of the raw water strainer, or anything in the cooling loops. Just a mere oil change dropped the temperature 10F. I guess I was really due for an oil change.

Are you sure the fresh water circuit is full? Does the fresh water have a puke tank or just to bilge?

This is certainly perplexing. Steam, lower indicated water temp and low oil pressure would indicate some sort of cooling anomaly. i.e. the engine is hotter than it should be.

I would get an IR gun and spot check the temps on the engine. I would have baselined the temps after overhaul which would have made a nice comparison to now but water under the keel so to speak.

I am not a fan of multi-viscosity oils for boat diesels.

[sailorchic34]

Have you checked your oil bypass relief valve, Could be the ball valve is stuck open a bit

[svHyLyte]

Originally Posted by sailorchic34

Have you checked your oil bypass relief valve, Could be the ball valve is stuck open a bit

Absolutely correct!!

[phorvati]

Originally Posted by bobconnie

I don't know but I was taught to change the oil in a newly rebilt diesel or gas at 1 or 2 hours of running, and to change the filter at the same time ! ya may have went to long if there were any metal floaters in the oil your mains may have been damaged!the filter if ya still have it will tell ya cut it apart and ck for metal!! if ya can't then as said above go to a 40 wt oil and hope for the best !That amount of low oil pressure at an Idle would worry me ! Just sayin it's what ya got ! ya may have to live with it !! sorry could not be of more help !!

There is a pickup screen that would block debree from getting sucked in by the oil pump. I threw away the filter so I wont know if and how much metal floaters were in the oil.
I'll read up more on oil viscosity and pressure and perhaps go with different viscosity oil.
Fresh water is full, I check it regularly. I have an expansion tank. Raw water flow is great.
my 4-108 is westerbeke w40 model. I dont have bypass relief valve.

[Jesse]

You are using the correct oil. And if your engine is equiped with an oil filter it also has a bypass which prevents over pressure in the system (makes oil filters look like cantalope) and with a recently rebuilt engine this is a likely suspect. It isn't unusual to have the ball stick and it's much easier to repair than worn bearings. 1700-1900 rpm seems pretty low for operating a 4108, if 1900 is max rpm at full throttle there is likely an issue with overproping that should be addressed.

[Jesse]

Oops I missread post #6. But 2200 at full throttle is still very low,

[sailorchic34]

Originally Posted by phorvati

T
my 4-108 is westerbeke w40 model. I dont have bypass relief valve.

According to Westerbeke, The W40 model does have a oil bypass, as do most engines, BTW. It's internal to the engine. Generally a ball valve and spring. Sometimes inside the pipe nipple the oil filter spins on. Some times beside it (like on the A4). It's designed to open up to maintain engine oil pressure within normal ranges, generally when the oil is cold.

The Bypass relief valve can get stuck open sometimes which would cause the symptoms your describing.

[DeepFrz]

With a sudden change like this I would check the relief valve and the filter. I always like to go back to "what did I do last" thing because 9 out of 10 things that get screwed up were screwed up by mois...