Oil Pressure Question!

89FoxbodyLX

Member

Apr 20, 2012

5

1

13

Apr 21, 2012

#1

• Apr 21, 2012

• #1

So I recently bought a 90 LX Foxbody. Has a few issues here and there but over all is in good condition. What's weird is my oil pressure gauge reads normal when I'm driving. However when I stop at a red light or something of that sort.... My oil pressure gauge drop completely but as soon as I give it gas the oil gauge goes right back to normal. Not sure what the issue is or if this is normal for these cars. Please let me know!

 

stykthyn

I want to measure mine. It doesn't look that tall.

15 Year Member

Jul 6, 2006

5,232

2,652

223

gainesville

Apr 21, 2012

#2

• Apr 21, 2012

• #2

Replace the sending unit. If issues persist you have problems.

 

OonDeanisS

Founding Member

Jun 16, 2002

902

1

19

Danbury, CT

Apr 21, 2012

#3

• Apr 21, 2012

• #3

mine does that too, i have a mechanical gauge and it reads up to 60psi cold and 45 hot, but at idle it drops down to 20 when the oil is hot. Ive read that its ok as long as you have at least 10psi for each 1000 rpms. its been this way a long time, and i have no knock issues, so i wouldnt really call it a problem.

 

stykthyn

I want to measure mine. It doesn't look that tall.

15 Year Member

Jul 6, 2006

5,232

2,652

223

gainesville

Apr 21, 2012

#4

• Apr 21, 2012

• #4

the stock gauge is little more than an on/off switch saying there is pressure or there isnt. Before the rebuild I had the opposite problem. Pressure was ok until I gave it gas and then it would drop. Start with the sending unit. Its a fairly cheap part and you can get one for under 20 dollars. If you would rather go aftermarket your pressure should ideally be around 25psi hot and 50 cold, but I have seen engines run 10psi hot with no issues and last for years.

 

MFE92

10 Year Member

Aug 25, 2010

1,094

372

124

Phoenix

Apr 21, 2012

#5

• Apr 21, 2012

• #5

They didn't start the on/off switch pressure gauge until 94. If it drops to zero then you have less than 10-12 lbs at idle, and while the old rule of thumb says 10 psi per 1000 rpm so it must be good, that is NOT normal for a properly assembled, properly functioning 5.0. So as stated, put a new sender in it, or better yet hook up a diagnostic pressure gauge to it and get a real reading. If you're really reading that low at idle, the motor has problems, end of story.

 

stykthyn

I want to measure mine. It doesn't look that tall.

15 Year Member

Jul 6, 2006

5,232

2,652

223

gainesville

Apr 21, 2012

#6

• Apr 21, 2012

• #6

MFE92 said:

They didn't start the on/off switch pressure gauge **** until 94.

Click to expand...

I was not aware of that. good to know.

 

89FoxbodyLX

Member

Apr 20, 2012

5

1

13

Apr 22, 2012

#7

• Apr 22, 2012

• #7

Well I hope the motor has no problems and its something as small as a sending unit. Though I have AWFUL luck when it comes to car's it seems like.... So I wouldn't be shocked. Worse comes to worse.... 351 swap =)

 

Reactions: OonDeanisS

f8tlfiveo

My wife likes my spool and blow-off valve.

Aug 8, 2007

1,585

102

64

Lancaster, PA

Apr 22, 2012

#8

• Apr 22, 2012

• #8

I had the same issue.. Sender fixed it..

 

Reactions: OonDeanisS

ReefBlueHatch

Active Member

Jan 12, 2010

682

96

39

Central KY

Apr 22, 2012

#9

• Apr 22, 2012

• #9

I had the same issue and I could have had a few contributing factors. But I fixed all these problems and installed a new OEM oil pump.

1. I had a lot of sludge, maybe because I also had a clogged PCV screen.

2. Oil pick up tube was almost pinched shut.

3. Sending unit end was covered in sludge.

View attachment 151103

 

1987stangman

Member

Jul 12, 2006

684

24

19

Apr 23, 2012

#10

• Apr 23, 2012

• #10

Damn, I havent seen one that bad in a long time.