Oil pressure problem??
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Freshman User
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From: Alexandria, VA
Oil pressure problem??
I just finished replacing my oil pump in my 92 5.0 EFI F150. After bumping the engine over until I got 20 psi, I started it up and the pressure went to about 80 psi at 1,500 rpm, then after I drove it around a while and got it hot the pressure dropped to about 6 psi at idle (700 rpm) and about 1 psi per 100 rpm on up.
Chiltons says the pressure should be 40-60 psi at 2,000 rpm. ??
There are no leaks, and it seems to run o.k. I used a melling high volume pump.
Is this pressure too low?? Any Ideas???
Chiltons says the pressure should be 40-60 psi at 2,000 rpm. ??
There are no leaks, and it seems to run o.k. I used a melling high volume pump.
Is this pressure too low?? Any Ideas???
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Joined: Mar 2004
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From: Spokane
Why did you replace the oil pump in the first place? What are you measuring the pressure with? Does the pressure go back up again after the engine cools down? If the pressure is really that low you will destroy the engine shortly.
Last edited by fordberg; Apr 20, 2004 at 10:17 PM.
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From: Alexandria, VA
When the truck was hot the oil pressure guage needle in the dash was going past the L up out of sight, so I bypassed it with a Sunpro guage. That showed about 30 psi at idle cold then it dropped to 0 at idle when hot and about 15 at 2500 rpm.
So, I replaced the pump, I actually found four large pieces of gasket material clogged up in the pick up screen from a previous timing chain gasket job that an idiot mechanic did.
I checked the pressure this morning and it was up to about 70 psi at 1500 rpm cold, I didn't have time to let it warm up.
While I was priming the pump with oil I put some wheel bearing grease in the hole to help keep the oil in. Would this clog up the oil filter??
Thanks for your responce
So, I replaced the pump, I actually found four large pieces of gasket material clogged up in the pick up screen from a previous timing chain gasket job that an idiot mechanic did.
I checked the pressure this morning and it was up to about 70 psi at 1500 rpm cold, I didn't have time to let it warm up.
While I was priming the pump with oil I put some wheel bearing grease in the hole to help keep the oil in. Would this clog up the oil filter??
Thanks for your responce
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Joined: Jun 2002
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From: CT
By passed what oil pressure gauge?
Its just an on off switch (idiot light) is'nt it -- I don't recall the 5.0l having a real gauge in it stock -- they should of made it say yes/no instead of mimicing an analog gauge.
I'd start with a mechanical gauge -- pull the oil sending unit out and attach there. See what your pressure really is and go from there. The swinging gauge was/is probably from loss of ground at the sending unit.
For the heck of it pull the wire off the back of the sending unit and touch it to engine ground (the block) and see what it does at the gauge -- key needs to be in run position. If its bouncing the problem may be in the dash.
If you have an after markert oil sending unit already I'd still start try an analog gauge.
Its just an on off switch (idiot light) is'nt it -- I don't recall the 5.0l having a real gauge in it stock -- they should of made it say yes/no instead of mimicing an analog gauge.
I'd start with a mechanical gauge -- pull the oil sending unit out and attach there. See what your pressure really is and go from there. The swinging gauge was/is probably from loss of ground at the sending unit.
For the heck of it pull the wire off the back of the sending unit and touch it to engine ground (the block) and see what it does at the gauge -- key needs to be in run position. If its bouncing the problem may be in the dash.
If you have an after markert oil sending unit already I'd still start try an analog gauge.
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From: Alexandria, VA
Yes, I bypassed the stock idiot light guage with a mechanical guage hooked straight into the block and got the readings I posted. I've done the test where you ground the lead to the idiot light guage to the block and the needle went to dead center between the L and H.
I really dont know why Ford put a BS oil guage in their trucks but....
The problem is definatley not the stock guage, thats been disconnected for a while, its the low oil pressure when the engine gets hot, and with a new oil pump!
I just don't get it
I really dont know why Ford put a BS oil guage in their trucks but....
The problem is definatley not the stock guage, thats been disconnected for a while, its the low oil pressure when the engine gets hot, and with a new oil pump!
I just don't get it
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From: Spokane
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From: Alexandria, VA
-The pressure is a little better than before - 6 psi at hot idle vs. 0 psi.
-Where is the bypass valve located?
-138,000 on the odometer and 10w 40 Valvoline Max Life oil w/ a Purolator oil filter.
-Where is the bypass valve located?
-138,000 on the odometer and 10w 40 Valvoline Max Life oil w/ a Purolator oil filter.
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Senior User
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From: Spokane
Since this seems to be related to the temp of the oil I would have to say that the engine is worn out. Presuming that it didn't happen all of a sudden. You might try running straight 30 wt. to get the pressure up.
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From: Spokane
Multi-viscosity oil might not be the right viscosity for a worn engine. 30 wt. is always the same viscosity and can help identify oil pressure problems. 30 wt. is fine to run spring-summer-fall.
Last edited by fordberg; Apr 22, 2004 at 01:50 AM.
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From: Spokane
I'll try and remember what a mechanic told me. I think they posed a question.
What weight of oil is 10-40 after it is used or starts to breakdown? Who knows.
Same question for 30 wt. Answer 30 wt.
That was one opinion. Good mechanic. Might make some since for higher mile engines.
What weight of oil is 10-40 after it is used or starts to breakdown? Who knows.
Same question for 30 wt. Answer 30 wt.
That was one opinion. Good mechanic. Might make some since for higher mile engines.
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From: Spokane
Back to the oil pressure problem. You said there were some pieces of gasket in the oil strainer. I'm guessing you would have done like me and replaced the oil pump and put the original strainer on the new oil pump. Well, what if there is some junk in the strainer? That would starve the oil pump of oil and you would lose pressure. Not sure why the temp would change the starving.
A friend did a complete rebuid on a 401 and everything was great until he had to pull the intake for something. When he was puting it back together a small blob of gasket goop fell under the intake and made it's way down to the oil pump screen and then got inside in some way. His pressure was good until he stepped on the gas and the pressure dropped to 0 for 1/2 second and then shot up. If he wouldn't have had an electronic oil pressure gauge on it he wouldn't have seen it because the mechanical gauge wasn't fast enough. Tore the engine down twice to find the problem.
A friend did a complete rebuid on a 401 and everything was great until he had to pull the intake for something. When he was puting it back together a small blob of gasket goop fell under the intake and made it's way down to the oil pump screen and then got inside in some way. His pressure was good until he stepped on the gas and the pressure dropped to 0 for 1/2 second and then shot up. If he wouldn't have had an electronic oil pressure gauge on it he wouldn't have seen it because the mechanical gauge wasn't fast enough. Tore the engine down twice to find the problem.