Mmo--no!
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Junior User
Joined: Jun 2006
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Mmo--no!
finally changed oil in my truck(71 f-250, 360fe). had pressure on guage well past half way. put 30wt hd in it with a quart of mmo to try to quiet noisy lifter. now lifter is louder than ever, and intermittantly ticking instead of all the time. main problem now is oil pressure stays on the L on the guage, or lower. wont even get to halfway when engine is cold. put new sending unit on at change. dont understand! what is up? Now definately wont be able to sell for a good price. will almost have to give it away now!
Elder User
Joined: Feb 2004
Posts: 909
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From: San Luis Obispo, CA
I agree that a mechanical gage is a good idea - you can just screw one on at the engine end if you do not want to install one permanently. (On the other hand, I doubt that the gage would suddenly change at the same time you put in the MMO (Marvel Mystery Oil?).
If the MMO loosened up some sludge and it got through to moving around, it could be causing your problem. The two things that come to my mind are that enough sludge may have been "liberated" to partially clog your oil pump pickup screen. If you have the time, you could drop the pan and replace the pickup for the reasonable cost of the pickup and a pan gasket.
Another possibility is that your oil pump pressure relief valve plunger is stuck open. First, I would recommend a few oil changes with a middle-priced oil to see if things get better. Then dropping the pan will be necessary to replace the pump. It still should not cost too much other than your time. The one-piece oil pan gasket on the FE engine makes this job a little easier to deal with.
If the MMO loosened up some sludge and it got through to moving around, it could be causing your problem. The two things that come to my mind are that enough sludge may have been "liberated" to partially clog your oil pump pickup screen. If you have the time, you could drop the pan and replace the pickup for the reasonable cost of the pickup and a pan gasket.
Another possibility is that your oil pump pressure relief valve plunger is stuck open. First, I would recommend a few oil changes with a middle-priced oil to see if things get better. Then dropping the pan will be necessary to replace the pump. It still should not cost too much other than your time. The one-piece oil pan gasket on the FE engine makes this job a little easier to deal with.
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
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From: Simi Valley, CA
You replaced the oil sending unit, and now the gauge reads low. That new sender (prolly made in China) could be defective...regardless they aren't too reliable when they do work. Do what jsutton & acheda suggest, put a direct reading oil pressure gauge on.
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Junior User
Joined: Jun 2006
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oil pressure did great for a couple of days after changing, then went belly-up. so screen or pickup tube could definately be a problem, as could the sending unit.(it may have plugged also since they have such a small hole). next question is, what all will have to be done to remove pan? will i have to loosen motor mounts and raise motor, or will it weasel out like it is? will try good mechanical guage first. i always did like one that actually reads pounds instead of just a scale. is there any other place on an fe to plumb guage from, or does it HAVE to come from fitting by filter. Thanks fellas for all the fast responses!
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