No oil pressure at startup after sitting overnight.

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LEGACY_GN

Active Member
Joined
Apr 16, 2007
Messages
772
Only a second or two but after first startup each after that day is instant pressure. Also, no pressure but no noise and when I change the filter it takes 3 or 4 seconds, definitely longer. Bad filter. Mobile 1 filter. Always run them and never noticed before but like I said no noise neither.
 
30 psi at hot idle but it has been dropping to 25 on occasion which is the first time in the 12k miles on the new motor. How do u check for functioning antidrainback before installing filter. I like mobile one because of the high filtration rating and in 8 years never had a problem till now. I bought 16 of them off eBay and have 7 left now
 
You can blow into the filter through the center to check anti drainback valve before install....should hold air pressure and make you feel a little crazy
 
Changed filter. New one didn't let any air through. We'll know tomorrow if that did the trick.
 
I just had a VERY bad experience with a K&N filter....someone I spoke with made the statement that the mobile and K&N filter were the same....I do not know if this is true or not. I posted my experience on this forum.....
 
[quote="LEGACY_GN, post: 3407178, member: 23491. I like mobile one because of the high filtration rating and in 8 years never had a problem till now. I bought 16 of them off eBay and have 7 left now[/quote]

My opinion is different than your's in wanting a "high filtration rating", I prefer NOT to have such a small level as 8-10 microns like Mobil I and K&N paper cartridge filters?

One reason is at higher oil pressure there is a much greater chance of a "blow-through" in the flimsy woven paper material so you can have oil passing through areas as much a 10 or 20 times the actual rating?

Many engines we build will idle at 25-35 psi and start up at 70-80 psi, so the very woven paper will usually show signs of "tracking" and also kill oil pressure when contaminated at low milage, at least we hove found this to be true many times when cutting filters open.

Many commercial and high performance use oil filters in the 40 micron range to protect multi-thousand $$$$ engines.

The 8 micron filters will restrict oil flow more than a 40 micron, but bearing and other parts are not damaged at the greater micron filtration level, and the additional flow is a big benefit in cooling as 30% of engine heat is dissipated and carried away by the oil.

Actually, after talking with a Wix tech rep, their performance filter is in the 40-60 micron range.

My personal preference is a stainless steel mesh 40 micron filter which can be used without a by-pass valve so ALL oil going to the engine or turbo is filtered.

Since we have been using SS mesh filters in various engines, street and strip, with thousands of runs and miles, we have not seen any bad effects on bearing on anything else in the engine.
 
Mobile one isn't paper like K&N although there probably is something to say about all the restriction. Didn't fix it anyways and it actually seems to drain down after a couple of hours. I did blow in the new one to make sure it sealed and it did. Strange thing is that I have no engine noise at startup, even when I changed the filter. I do fill the filter up as much as I can before installing it but still about 2 seconds of no pressure just like startup after a couple of hours. Any other ideas? Now I'm worried. Pump going bad? What else can cause this?
 
I know this might be a dump question, but did you try to replace the oil pressure switch and gauge to see if the result changes?
 
I know this might be a dump question, but did you try to replace the oil pressure switch and gauge to see if the result changes?
No, because if I shut it off and restart it I have instant pressure, therefore the gauge is working.
 
I read again your thread and you claimed 12k miles on the new motor
Was any changed or rebuilt on the timing cover and pump housing, gears?
 
I'm calling the machine shop monday. I'm 90% sure we went with new cover and pump, but now I'm second guessing myself as the last rebuild was only 10k miles before this one and may have done new then and not bothered on this rebuild but I find that highly unlikely with how much money I spent on this latest with the stroker and everything. (Alky pump failed and split a piston after 10k miles and before that wiped cam lobe)
 
What pre-lube oil system are you running. Maybe that's what I need to do. That would solve it, lol. I have ridiculously great oil pressure all the time. It just seems to be delayed after sitting a few hours.
 
Could worn pump or cover leak down? I don't know how the internals work.


No. If the cover is worn your efficiency will suffer. During cold start the end play will be a negligible amount tighter but not enough to matter. If you have a chinese cover your end play is out of spec no matter what. Their final machining errs on the side of caution so the pump can't be locked up during assembly. The gears are below flush compared to the housing. The side effect of that is very loose clearances no matter what.

It sounds like you've got a slight leak on the pump. Not enough to mess with your actual running but just enough were it takes several house to mess with the pumps prime. Bad drainbacks are a common culprit. I haven't ran a Mobil1 filter in years so I have no idea if they've went the path of AC Delco and outsourced to a cheaper bidder.


I will say that Wix and Purealotor Pure ONE filters don't do it right now. To keep from pulling your hair out try one of those. You won't lose much oil and it'll only take a second to swap them. (if you don't have a biggie filter kit, get a filter for a 94 S10 Blazer 4.3 VIN W)
 
I've tried 4 different oil filters from 3 different manufacturers and still no pressure at startup. Only thing I can think of is the ridiculously huge oil cooler I am running maybe losing pressure or taking time to pressurize? But when I remove the filters there doesn't seem to be much oil in them either, so I don't know what to do. May just have to get prelube system.
 
I almost wonder if you just have a gauge that sticks after it sits overnight. If you truly have low oil pressure at start up, you would normally hear lifter rattle until they pump back up. Does your 'oil' idiot light work and if so, does it back up your gauge reading?


except.. When you said there doesn't seem to be much oil in the filter when you remove it.... are you saying there's air in there? If so you have an air leak letting that air in, and your theory is correct.
 
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