Oil Pressure Problems
 

So I got my boat on the water yesterday with a fresh engine. Ran fine for a while, but after a 20 sec. run at 4500 the oil pressure dropped. The gauge barely moved at idle and read about 20 psi at 3k. So I limp back to the trailer and call it a night. Tonight, I change the filter (had a throw-away fram on it) and fire it up on the hose with a mech. gauge. Had 20psi at idle so I run it for 5 minutes, shut it down and drain it. Refill, another new filter, and run it. Ok at idle still, so I run it at 2k for about 30 secs (30 psi). Return to idle and the pressures gone. WTF? I dont have a temp gauge but I wouldn't think it would get very hot without a load. Any Ideas?

tj,
First of all, if you have not already done so, do NOT throw away your original oil filter that was on the engine when the problem started. You need to get it cut open to see if there is any evidence of bearing material etc. You should do this before you run the engine even another second. If there is a problem, every second you run it is going to make it worse. I have seen the inexpensive filters come apart and the filter paper get into the oil system and clog things up. Does your setup have an oil cooler ? Was it replaced with the fresh engine ?

In case you have not realized my point yet .... DO NOT run the engine any longer until you find out what the problem is. Unfortunately in this case it sounds like its time to pull the engine and get the pan off to take a look. If a bearing is starting to fail it might still be repairable but if you keep running it you might go past the point of no return :( If you want to do any additional testing, pull the distributor and use a pre-oiling tool, dont run the engine.

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

I second what bill is saying,cut your original filter open if its still around,if you find any metal (and you probabl are going to) pull the motor how and tear it down before you damage it any worse. If you pull the distributer and can't make 30-40 psi with a priming tool and a cordless drill on a mechanical gauge in place of your sending unit it's most likely hurt,Smitty

Thanks for the replies guys. Unfortunately, I can't use a primer with the engine in the boat due to clearance issues. Any ideas as to why I'm losing pressure so fast. It will have decent pressure and in an instant its gone. Its done this on both elec and mech gauges. Before I started having problems, I had 40psi at idle. Last night it had 30 with fresh, cold oil but dropped to just a couple psi after 2-3 minutes. The pressure would come up with a little rpm, so I wouldn't think it was sucking the pan dry. If its hurt its hurt, but I would like to figure out why I'm having this sudden drop before I pull it again. BTW, it does have an oil cooler that was flushed while the engine was out recently. Thanks.

Hate to say it but your mains are probably gone, i have been through this 7-8 times...Anything can cause this , dirty rebuild etc.....The reason your oil is loosing pressure after a coulpe of seconds is it is getting hot and thin.......I know this sucks but pull it and chech your mains.....

tj,
You are going to have to pull it to find out what is causing the problem. I would almost bet dinner on it that it is something internal. The more you run it, the more chance of hurting it bad enough that you will not be able to figure out what the real cause was.

Bill

Put a mechanical guage onit and make sure you have a problem in the first place. If your lifters are not clacking, you most likely have no problem.

He has tried a mech gauge.

Why was the oil cooler flushed? Did you happen to spin a bearing on the previous engine?

Did you lose a water pump impeller on the previous engine,pieces of rubber blocking flow through cooler?

Engine hasn't been run since the other night. I did go ahead and cut open the filter to find my bearings so its coming back out. The reason it was rebuilt in the first place was a milkshake this spring. Nothing major was found and water attributed to severe condensation (up and down winter this year). The cooler was flushed simply because it was out. I'm baffled as to why the bearings went in the first place. The bottom end is bone stock other than rings, bearings, etc - just a refresh while it was out. Clearances were checked, oil system primed, blah blah blah. I'm beginning to think I'll never know the initial cause. Its a gen v 7.4 if it matters. thanks guys!