Hi all Over the past 12 months i have been rebuilding our old d8h 46a24576, i have gone right through the engine and have spent many $ making sure it will 100%. This included new (cat classic) main oil pump which was purchased through the cat agents over here in Australia. When I got the pump I was shocked to find that the main bolts that hold the pump together were loose, with no locktight or locking tabs on them. After retightening the bolts, the pump was put in, the engine was finished and then test run, with water plumbed up from a drum. Now the engine runs nicely, as expected, but the concern is that the oil pressure is consistently high. From cold it sits at 90psi, and after running up to temp only comes back to 80 psi. Cannot find specs in the workshop manual, but from since reading articles on this site, it seems the oil pressure should be around 40-50. Not sure if this high pressure will cause overloading, excessive wear, or worse, failure to pump driveline. The engine has had all new bearings put throughout, crank has been ground, with 10thou over bearings, clearances were checked, etc. Oil used is 15w-40 I'm worried that this (cat classic) part, has the regulator set wrong, but, I have read that the regulator on the pump is more of a cold start safety valve, set at 90psi With a new (tight) engine and a new pump, maybe the pressure is as it should be, with me just being over cautious Any thoughts would be greatly appreciated John
My earlier s/n service manual for the same 1S4381 pump says 30 psi @ engine rated speed with cold pressure relief @ 90 psi. Appears the pressure regulating part of your pump is not functioning. Maybe stuck plunger?
The CAT D342 engine is fitted with a Positive Displacement controlled oil pump, it is fitted with a Safety P.R.V. that is for cold oil control set at 90 psi, the standard oil pressure of a hot engine via the displacement control valve is 30 psi at full rated engine speed, on this point many will tell you other info, I am just printing the stuff that I know, the oil pump is a 3 section item and can be removed in frame, constant high oil pressure can cause the crank bearings to flake so I do understand your thoughts, it might be worth checking the flow control spool ( its not a relief valve) tctractors
thanks for the info have just been looking at the old pump that was pulled out to refresh my memory of it. It only has the one spring loaded plunger valve on the side of it, which in my manual is refered to as a relief valve. Where is the displacement control valve that you speak of tctractors? Does this valve on the pump serve both functions ( pressure regulating and safety relief)?
Apologies, your correct, the two valve version ended with 46A7433. The 1S4381 pump has only the one relief valve.
Things like this are why it is so important to keep close track of Serial Numbers with Cat or other companies. I have noticed many times where Cat will make a change and it almost seems like after they changed from on type of something they will find they still have a few of the old parts on the assembly line so they change back for a couple days then change again to the new version. One example shown below: So s/n 46A7368 then 46A7370 through 46A7431 are different than the rest of the machines that have the 4H8758 pump? This is why making blanket statements about a machine can get you in trouble
Thanks anyway I decided I will put the engine in, and work it a bit, see if the oil pressure settles any lower, if not, I will pull the plate off the sump, and put the old original relief assembly back in, with a new proper cat spring.
Well here are the spec's on D342 oil pump. I see they are spec'ing it with SAE 10 oil at 195ºF which seams strange for an engine. Especially where the operators manual recommends SAE 30 from 32º to 90ºF.
Any specs available on the relief valve plunger spring?
If we are talking the pump with just one valve the spec's would be here:
Then if we are talking the pumps with two valves:
Thanks kshansen, that info is not in the service manuals, will add to my files.
Even with SIS access it can sometimes be tricky to find that kind of info especially for the older machines!
Thanks kshanson, this will give me a reference, when I pull the valve out