Cummins 400 Oil pressure & temperature

Hi guys, now this is an easy one..
I have a 400 Cummins small cam.
After fitting brand new dash gauges on the weekend (because I guessed that the old ones were no good) I now find that the oil pressure and water temperature readings are vastly different to what the old gauges said.

1) Is engine oil pressure of 16lb @ 500rpm and 45lb @ 1500rpm OK? Oil is Penrite USA25 (25W60) with 3000km on it. This is how it sits all day after running big loads for a while., warmed up of course. Cold pressure is 65lb @ 600rpm, then drops as it warms. With 15W40 Castrol, the engine was noisy and the old gauge said 5lb. Are these new readings OK?

2) Engine temperature never varies above or below 88 degrees c, the sender unit is just below the thermostat so that would be the hottest part of the engine. It was 32 degress c here today and many times I had a full load lumbering all about the place, but it never ever gets hot. Is 88c too hot, too cold, or just right?

cheers guys,
Bretto

Sounds like it's running pretty much the same as my boss's SAR with a 400 Cummins altho the temp on the SAR runs at a constant 80 degrees no matter what......due to the large radiator.

From what I have seen today Werk, I feel that it has an 88 degree thermostat in it - I'm just not sure if that is an appropriate temperature or not.
Bretto

I'd say it's about where you want itespecially for winter maybe a little lower for summer

I have a new thermostat from Cummins but haven't put it in yet - dunno what temp it is..

On oil pressure - I understand that Cummins run low low oil pressure. Got a mate with a 400 big cam just had a bottom end rebuild done and he only has 10~12lb on idle using 15W40 Delo. If I run Delo I'm lucky to get 7lb! What is the thoughts on using the Penrite USA25 which is 25W60?
Bretto

I have read manuals for other makes that basically say don't worry about low oil pressure at idle. so long as there is something and it goes to where it should be when the revs are up to working speed.
Had an old landcruiser - you could tell when it needed an `oil change because it started to show good oil pressure due to the filter clogging.

Hello,
I think the biggest problem with low oil pressure is how long you let it idle, is the turbo getting enough,
V8 macks seem to suffer from low oil pressure at idle as well, know of a few owners that shut them down as soon as they can, just my 2 bobs worth

Rob

Those figures don't seem all that bad, I was running an Aerodyne with a small cam 350 that didn't have impressive oil pressure at idle when hot. The temps are not bad either, if your getting into the high nineties I'd be a little worried, but if it's staying on 88, that's a good thing.

My old Nissan SD33T has a similar problem with idle oil pressure, seems a few of the old engines tend to slid in pressure at idle.

At least we have pressure gauges and not the warning light system or should that be "the red light of death"



A

hi roadbossman,
i'm an ex 1970's thru 90's cummins mechanic.
your small cam engine should idle around 20-25lb and run at 55-60lb......40 to 45 lb was the spec for big cams.
are you running an electric gauge or capillary type?..if its electric dont trust it...plug an oil gauge into the main oil gallery on the lh side near the camshaft and double check the reading.
water temp at 88c is ok....but....sender unit should be in the water rail on top of the head just before the thermostat housing (usually either rear of front head or in centre head).this is where the water is hottest and gives temp before thermostat opens.

hope this helps,

newto.

Hi newto,
mate thanks for that info !
I use penrite USA25 which is a 25W60 oil. With that oil I have constant 17lb on idle (550rpm) and 44lb at anything over 1400rpm. The gauge is a brand new VDO capilliary plugged in exactly where you suggested.

When I used Castrol RX Super (15W40) I was flat out with 8lb hot idle and never more than 25lb.
I reckon she's is tired but she still does the job and uses about 4 litres of oil between services (which is every 10,000km or 4 months and usually the 4 months come up first because I do a lot of citty running and idling).

The temperature gauge is also brand new but electric, VDO of course. It is also plugged in exactly where you described. She has never got hot, but just making sure that 88 degress is not overly hot.

cheers,
Bretto