Oil Pressure Problem
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Oil Pressure Problem
Hello everyone, I have a ’90 bronco, 302, AOD, and about 222000 miles on what I guess is the original engine. My problem is as follows during start up my oil pressure gauge on the instrument cluster reads in the middle of the normal band of the gauge. However, when the engine warms up to normal operating temp. the oil pressure gauge on the instrument cluster reads below the zero mark or the red band signifying that there is less than zero p.s.i. of oil pressure, also the redundant engine light comes on . This also happens when I take my foot off of the gas peddle and allow the bronco to coast. But when I apply a little pressure to the gas peddle the oil pressure gauge starts to go back into the normal area and the redundant engine light goes out. Also when I apply enough pressure to the gas peddle to keep a steady speed the oil pressure reads in the normal area. There is not a noticeable knocking or pinging sound coming from the engine.
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Any thoughts on what it could be, the oil pressure sending unit or maybe the oil pump??? If it is the oil pressure sending unit where is it located and how do I get to it. Thanks in advance for the ideas and help. I'm not too mechanically inclined so any help would be greatly appreciated. Thanks again!!!!
<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com
fficeffice" /><o></o>Any thoughts on what it could be, the oil pressure sending unit or maybe the oil pump??? If it is the oil pressure sending unit where is it located and how do I get to it. Thanks in advance for the ideas and help. I'm not too mechanically inclined so any help would be greatly appreciated. Thanks again!!!!
Post Fiend
Joined: Mar 2002
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From: Bonita Springs FL
First thing to realize is that the Ford oil pressure gauge is nothing more than an idiot light. If there is 7psi of pressure at the sending unit, then the gauge will read about halfway up. Second thing is that Ford's gauges are known to be less than accurate.
Since engine rebuilds are pretty expensive, it would be worth it, IMO, to at least temporarily install a mechanical oil pressure gauge. If your oil pressure really is falling to less than 7psi at warm idle, then you have to start saving your pennies for a rebuild.
220k is a respectable life for any gas motor. It looks like yours might be raising the white flag.
Since engine rebuilds are pretty expensive, it would be worth it, IMO, to at least temporarily install a mechanical oil pressure gauge. If your oil pressure really is falling to less than 7psi at warm idle, then you have to start saving your pennies for a rebuild.
220k is a respectable life for any gas motor. It looks like yours might be raising the white flag.
Junior User
Joined: Aug 2006
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From: Wood Ridge NJ
Lets not forget the oil pressure switch located by the oil filter. its like a $9 item and may solve the problem..... Would be easier and cheaper to try this than to just give up and say that the motor is shot. Also sounds like you are unsure of the miles.... maybe a rebuilt motor or a low mile motor from a doner truck (that what mine is).
hope this may help.
Al
hope this may help.
Al
Tuned
Joined: Sep 2005
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If you install a mechanical gauge then you don't have to worry about the sending unit being bad. Spen the $40 to eliminate those stock gauges. The gauge sets are easy to install and much more accurate. Once you do this if the oil pressure sender is right then your main bearings are probably going and you're looking at a rebuild. I think a rebuilt motor from where I work is about 1,000-1200.
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One of my buddies has an oil pressure sending unit that he is willing to allow me to install for the moment to see if it's the sending unit. Money is tight right now. Does any one know where the sending unit is located???? I took a look tonight and there is something that kinda looks like the sending unit under the oil filter on the driver side of the block could this be it???? Thanks for all of your help. As soon as I have the money I'll put a mechanical gauge in it for the peace of mind. Once again thanks for all of your quick replies.
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Sorry rods4life I didn't see that part of your reply, I'll try my buddies sending unit 2morrow. Once again thanks for helping.
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Well my friends sending unit didn't fair much better. However the gauge looked like it didn't want to go to zero but after a while it did. Could it be something with the distributor or cap, since correct me if I’m wrong but the distributor and oil pump are connected by a rod, just a thought. I popped the distributor cap off and it looked bad, carbon tracks and other such abuse. Or could it be a warn oil pump??? I’ve been trying to get this truck to run ever since I bought it, about 10 months ago. Any thoughts would be greatly appreciated, thanks to everyone.
Last edited by new2bronco; Oct 31, 2006 at 04:17 PM. Reason: Another thought
Senior User
Joined: Jan 2004
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From: NW Ohio
Its unlikely the problem is with the distributor. Yes, the oil pump is driven off the bottom of the distributor by a hex shaped shaft, but if it falls out you have no oil pressure at any time (no drive to the pump), and I don't know of any way one could slip only part of the time. However, if you have noticeable carbon tracks inside the distributor cap it will really make it run bad, especially in wet weather since you won't be getting good spark to the right plug at the right time. You could have a worn out oil pump, but since you'll have to drop the oil pan to change the pump you may as well at least check the main and rod bearing clearances with some plastigage (pretty sure the procedure is in the Haynes/Chilton manuals, only takes a few minutes once the pan is off). I'm betting that you'll find that the bearings are at the end of their life, and a rebuild or replacement of the motor is due.
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Try this. When you idle and have low pressure, shut it off, wait a min. or so and restart it. Does some pressure come back for a short time and fall off again? If so then it may be a clogged pickup in the pan. Had this happen to a 351 after changing valve cover gaskets when I used a bit too much silicone, oops! I had to drop the pan to clean the pickup and if you do drop the pan you might as well change the pump while the pan is off. Good luck.
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Thanks for the idea Netfly, quick question. I did as you advised today warmed up the engine and then killed it as the oil pressure dropped waited about a minute or two and then restarted. I had normal oil pressure for about thirty seconds to a minute and then it started to dance down to zero. Is this the same thing that your truck did? Also instead of dropping the oil pan could I try some oil flush or comparable product, since I don’t have the time, any ideas? I know that an oil pump is around $20 but what I’m short on is time, all I need is something that might work for a month or so until I can tackle the oil pump. Or would it be better to just wait and replace teh pump. Thanks once again one and all.
Last edited by new2bronco; Nov 2, 2006 at 05:12 PM. Reason: Just another thought
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Same thing mine did. I was told the pickup clogs easily on these and the pumps aren’t that strong. Try the flush, i did. I gave it a while and it never got better. Finally I had it done. It's not that easy to get to. Shop replaced it with a melling high volume, stock pressure. Said he had to lift it as much as possible off the mounts to get the pan out and reach it. Make sure you prime the pump before install if you do it yourself.
Post Fiend
Joined: Mar 2002
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From: Bonita Springs FL
With 220k on the clock, I'm going to venture a guess that your motor is worn out. A new oil pump is not likely to fix the problem. It might band-aid it for a little while, but you're just throwing money at the side effects of the real problem.
For $20, you could buy a mechanical oil pressure gauge like I suggested and narrow down the problem to a bad gauge, a wiring problem, or the engine itself.
For $20, you could buy a mechanical oil pressure gauge like I suggested and narrow down the problem to a bad gauge, a wiring problem, or the engine itself.
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Well it look as if the stock gauge was telling the truth. At first the new gauge read about 50psi and slowly dropped off to zero when the engine was warm at idle.
So where should I go from here? Should I start by replacing the oil pump or calling around for prices on a rebuild? Anyway, does anybody know of a good cheap machine shop for a rebuild in the Springfield, MO area? Or of a shop that will replace the oil pump cheaply; once again thank you all that replied.
So where should I go from here? Should I start by replacing the oil pump or calling around for prices on a rebuild? Anyway, does anybody know of a good cheap machine shop for a rebuild in the Springfield, MO area? Or of a shop that will replace the oil pump cheaply; once again thank you all that replied.