High Oil Pressure Upon Starting

boomkat · Sep 10, 2016

Hello everyone!

New to stangnet.com, but have been browsing around for a while.

Just traded for my first mustang - a 1998 Cobra clone with a 4.6L. Absolutely love the mustang. It's the most enjoyable vehicle I've ever owned. I'm hooked for sure.

I'm currently working on fixing a few things (IAC, finding the mysterious 'antifreeze' leak and overheating issue, and the AC Clutch), but what has me most puzzled is the high oil pressure when I first start it up.

I have a mechanical gauge on the pillar and it reads right around 80psi. It tends to go down as the car warms up. Is that normal? What would be a dangerous range that I need to keep an eye out for?

Thanks in advance for your help!

- Boomkat

Adieu · Sep 10, 2016

80psi on startup is a little high, but not unheard of. I see 3.6 Chryslers hit 100psi+ with a fresh oil change before they warm up.

My 302 will hit 70psi, but I'm running 20w50 in it.

My old GMC would see 80 immediately after every oil change, and then not see it again until the next one.

Really not that unusual.

boomkat · Sep 11, 2016

Thanks for the quick reply. Learning more every day. Glad to know it's not unusual. now to focus on the bigger items!

Have a great day!

- Boomkat

mogs01gt · Sep 12, 2016

I'd drain the oil and put a 5w30 or 10w30 in, the previous owner could be attempting to cover up spun bearings with super thick oil. 80psi is pretty ing high.

boomkat · Sep 14, 2016

mogs01gt said:
I'd drain the oil and put a 5w30 or 10w30 in, the previous owner could be attempting to cover up spun bearings with super thick oil. 80psi is pretty ****ing high.

Thanks for the advice! I've got it parked for the moment until I can get the coolant leak issue fixed. Once I start working on that I'll try the oil weight you recommended.

Sent from my SM-G935R4 using Tapatalk

boomkat · Sep 18, 2016

So good news - I stopped off the coolant and picked up a new thermostat. I noticed that once I replaced the thermostat that it was still running 230-240 degrees on idle. I went back to the parts store and found out that I had a V6 thermostat rather than the 4.6l thermostat. Call me crazy, but I think that may have contributed to the high temps. I replaced the thermostat and its running at a cool 205 degrees under load. Very, very happy. Oil pressure runs about 80 psi around startup, but even it's dropping down to 40-60 psi while going down the road. Seems like all good news!

Thanks for the help in getting all this figured out!
- Boomkat

High Oil Pressure Upon Starting

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Adieu

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mogs01gt

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