Oil Pressure Drop On Perkins 4108

[S Y Tuppenny]

Hi all,

I have an interesting situation, I have a reconditioned Perkins 4108 with about 550 - 600 hours on it.

It has been sitting on the hard in Malaysia for about 19 months.

I have now run it a couple of times and for the first 50 mins, the oil pressure reads 50psi, which is normal, then for the last 10 mins it slowly drops to 20psi, where it sits. This is at just above idle. if I put the Revs on, it will rise to 30 psi.

The engine temp is running at approx 80 Celsius, which is also normal.

I have just put new oil 15/40 in and new filter. can anyone suggest what the problem might be and how to solve?

thanks for your input.
Gillie

[leftbrainstuff]

Have you confirmed the pressure drop with another sender and gauge?

Oil pressure relief spring sticking open slightly?



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[mike d.]

I would think 50 psi at idle, after warm up is a high, 20 to 30 sounds more normal. This from a truck driver for 36 yrs. We have a Volvo/Perkins 50 hp. which runs at cold 50-60 psi, then drops to 20-30 after warm up! this takes about 10 minutes, at 1k rpm. Also note we are fresh water cooled. So it takes a bit longer to reach normal temp. Hope this helps. Best!!!!!

[SimonV]

What you have sounds normal. my 4108 idles at about 20psi and 40psi at 1500 and 60psi at full noise.

[S Y Tuppenny]

Hi leftbrainstuff,

I do not have any other gauges to test it with, and not sure how to check if pressure relief spring is stuck.

mike d. Thanks for your input, seems like I am worrying for nothing, so great, as have plenty more stuff to contend with.

SimonV. great to know thanks, feel a lot happier, now have to tackle other issues but relieved that engine doesn't seem to be one of them.

Thanks for the help, much appreciated, till the next time, fair winds.

[Cadence]

I would have to go with leftbrainstuff. Replace the sending unit, I have experienced it.

Not with that engine. Has this been the case or did you just get it. What does the manual say. You may not have a problem.

[Cheechako]

My 4-108 was pretty low at idle , maybe 15-20...and ran strong psi at higher rpm. My guess is you don't have an issue.

[Smourt]

Damn, if you have an issue so do I!!! Out of interest what was it like before? Mine appears to do as you have described.

Regards

[kelbylinn]

Both my Detroit 453 diesels do the same thing. Cold they run around 40 to 50 and once warmed up, idle at about 20, or running at 1500 rpms at about 30 to 40. Think it is a normal happening...

[a64pilot]

What you describe is normal for most engines, the PSI is high until the oil warms up and thins out, then it drops.
I don't know what is normal for your engine, some run higher than others

Actually I went back and re-read your post and I want to retract what I said, if it is high for almost an hour then drops, well that's not normal, it doesn't usually take 50 min for an engine to warm up, more like 5, not 50.

[Cadence]

Originally Posted by kelbylinn

Both my Detroit 453 diesels do the same thing. Cold they run around 40 to 50 and once warmed up, idle at about 20, or running at 1500 rpms at about 30 to 40. Think it is a normal happening...

I had a pair of old 671s that scared me at about 8 lbs. at an idle till I read the manual. 30 to 40 at 1500. When all else fails read the manual.

[tinkrman69]

40 to 50 cold is normal once wormed up 20 to 25 at idle is normal. if it's taking 50 minutes to worm up you might have a thermostat issue....stuck open or missing.80 C is a LITTLE on the cool side. That engine is made to run 82 to 87 C

[peter57]

Originally Posted by SimonV

What you have sounds normal. my 4108 idles at about 20psi and 40psi at 1500 and 60psi at full noise.

I agree, I had a 4108 for ten years and similar to Simon V pressures, before and after a full rebuild. Also when running for many hours then dropping back to idle the pressure alarm I installed would go off. After disgusing this with many diesel mechanics that had extensive dealings with 4108's these are normal pressures when oil is hot and is even written in print in one of the manuals as it was pointed out to me.

Cheers.