My backhoe (cat 426) has just recently started to bring the oil light on after maybe 30 seconds of running. The engine has maybe 100 hours of running after a complete rebuild with no problem. I pulled the sending unit and inserted a mechanical gauge and the engine will run about 60 p.s.i. For about 30 seconds , then drop to maybe 5 psi. The engine runs great with no abnormal sounds etc. If the engine is left sitting for a time the process repeats itself. I am leaning towards a faulty relief valve but I would appreciate any input before I pull the pan. Thanks in advance for any help Sam
Who rebuilt the engine? Someone reputable?
Could the oil pump pickup screen be partially plugged (from excess gasket sealant)? I had a 3204 in a d4h that tested the same way. Pickup screen was 95% plugged (albeit for a different reason).
I would remove the oil pan. I would bet there is debris or a rag that gets sucked up restricting flow. Then you shut it off and the debris falls off. I seriously doubt it is a relief valve if it comes and goes like that. Also is the oil not returning to the pan? Not sure on that engine because I have not had mine apart but on some vehicles I have worked on if you put the head gasket on incorrectly it can block/restrict some oil return passages. So the pan basically runs dry.
The engine was reliably rebuild and was faultless for about 100 hours so if a head gasket was improperly installed the problem would have surfaced long before now I thank you for the input and will keep you posted Sam
If this is the case, isnt there some kind of warranty on this rebuild?
I agree that it is not a head gasket installed incorrectly. The tidbit of info makes all the difference. I would be looking at debris floating around in the oil pan and blocking the pickup screen. I have been in the repair business for over 35 years. Almost always mechanics/technicians use way to much sealer, thread locker, RTV etc when reassembling. This stuff come loose eventually and causes issues. Get the pan down and check it. If you wait it could end up blocking an oil passage. I have seen this before in automotive engines. RTV is near impossible to get rid of once it is floating in the passages. I have seen it cause a main bearing to not get lubed enough and wipe out a crank.