Low oil pressure

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Low oil pressure

Home > Discussion Forum > Mechanic's Corner (general)

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All Messages in Thread	Author	Date
Low oil pressure	Debbie	6-3-08
We have a MCI with an 8V71 Detroit diesel. The engine overheated in Mexico and had to be rebuilt there. It ran perfectly all the time we were in Mexico and we made it back as far as northern Florida without a problem. We stopped in a rest area on I-10 and as we pulled in, the oil buzzer went off and the pressure was at zero. We chacked the oil and it was full so revving up the engine to full throttle only produced 20 lbs of oil pressure. Several shops we talked to wanted $1,000 just to give an opinion. We left it at a friends home and rented a car. The engine sounds and runs great. Any suggestions?
Re: Low oil pressure	BUBBA THE BUS TECH	6-4-08
Where did you read the pressure? Off the front guage? It is not to be trusted. Off the the mechanical rear guage, That may be a little better, But the best way is using a master guage you know is correct. Do the following, OIL sample. This will tell you if you have metal or other debries in your oil from a failure and maybe more important if you have large amounts of fuel in your oil. Test kit about $50 bucks where I am and test back in a week. Get from most heavy duty supply stores. I used to get mine from the local oil testing house direct. But they only sold me 24 at a time. Is the oil over full? Good sign that you hae an internal fuel leak. Very comon problem on these older engines after overhaul. Either way an oil sample will tell the tale. Good Luck
Re: Low oil pressure	Joe	6-4-08
These Detroit engines never had great oil pressure. They would idle at 3 to 5 lbs, and wide open have 35 to possibly 55 lbs. First thing I would do is check for water in the oil which would make it turn to sludge. If not, next, remove the oil filter and cut it open. Look for metal or even fiber like from a ground up shop rag. If you find metal, stop right there and have the engine looked at by reliable shop. If you find fiber, the pan should be removed and find the source. Lastly if nothing shows up, possibly....just possibly one of the two relief valves could have come loose or even fallen off into the oil pan. That would show the condition you mentioned also. Good luck.
Re: Low oil pressure	Debbie	6-5-08
Why would they have such low oil pressure and still work ok? Our friends neighbor is a mechanic so he drained the oil and cut open the filter. He said the filter was perfect, but after he drained the oil, he poked around in the oil pan with a coat hanger and he said he hooked on to something large that klunked when he moved it. Could that be the valve you mentioned?
Re: Low oil pressure	Erik	6-8-08
This may sound too simple but have you checked the oil sending unit or the plug/wire to the 'buzzer' if the line is frayed or the connection is oily it will send a faulty signal to the guage or buzzer. I would check the oil sending unit before going into any extensive or expensive repairs.
Re: Low oil pressure	Joe	6-6-08
Those engines depended on oil volume more so than pressure. Most important is consistant pressure. If it only ran 35 psi down the road, and it always stayed the same, that would be normal pressure for your engine. As far as what's rattling around in your pan, nothing should be doing that. My best guess is that the capscrews for an oil pressure relief loosened up or broke off. Investigate immediately before running it again. Let us know what you find. Good luck.
Re: Low oil pressure	Debbie	6-9-08
Thanks Erik, but something loose in the oil pan wouldn't have anything to do with a sending unit. There are two guages on the coach. One on the dash, and one in the engine compartment. They both read low. And the buzzer is on it's own sender. The final outcome was bolts not tightened on a relief valve. The relief valve actually was in the pan. We got it going over the weekend and drove it home yesterday. Thanks everybody for all your help. I know it would have not been cheap if we just handed it over to somebody that didn't know. All it cost us was some oil, a filter and a new pan gasket.