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  

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 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  

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

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 bretto,
the oil pressure is still a little low.
on the side of the oil cooler housing where it bolts to the block there is a large nut (cant remember size but about 7/8 i think) facing outwards.behind that is the pressure regulator and spring.
roadside fix......undo the nut and remove the spring,then pull the plunger out (normally by inserting your finger or using internal pliers)clean the plunger then drop about a 1/4 spacer into it,insert the spring on top of the washer and put it all back in in one piece.
shld pick you up about 10lbs of pressure.
water temp in old language shld be 185F normally & allowed to go up to 195/200 in short bursts.88c is about 190 so thats ok.
cheers,
newto

hi again back,
its not a relief spring,it controls the regulator plunger.
there are 2 pressure regulators and springs,1 in the oil pump and the other in the oil cooler head.the one in the oil cooler allows any excess pressure to dump back to the sump via an internal drilling....but....it still cotrols the pressure right across the range.shimming it shld raise both idle and max pressures.the ideal thing to do wld be to replace both regulators and springs,oil pmp and cooler.if shimming the spring raises pressure then that indicates just general wear and tear in the lube system,if it doesnt then the gremlins could be much deeper.
remember,the spec is 60lb HOT at revs,20/25lb @ idle with 15w/40 oil..your 60lb cold is probably the thicker oil.
just trying to help,
newto

Newto, just to make sure we are taling the same thing, where my oil cooler bolts on there is three bolts about 9/16" AND one bolt which has a 1 5/16" head (a big bolt!). My guess is that is the one - yeah?
Bretto