Mystery Low Oil Pressure
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turbo nasty
Turbo Dojo / MNTR
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Have you tried another gauge?
TT/Ameasap
The White Blur
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No. Cold idle
That makes more sense. The only way it can be lower that norm is if the pump is less efficient, a clearance(s) opened up, or your have a flow restriction in the form of a filter or such.
just for grins, have you changed the filter with another high quality unit just to make sure you didn't get a bad one?
just for grins, have you changed the filter with another high quality unit just to make sure you didn't get a bad one?
TT/Ameasap
The White Blur
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Ya, I changed to a new filter with same results.
Only thing I noticed on the pump gear, was a small ding on all the gears in the middle on the tips. Maybe .010 - .015 thou deep. and same in width.
Only thing I noticed on the pump gear, was a small ding on all the gears in the middle on the tips. Maybe .010 - .015 thou deep. and same in width.
Now you have my attention. An actual .010" to .015 ding is HUGE!...... BUT in my personal experience what feels deep as hell really isn't in real life...
That being said, these gears aren't hardened like a lot of people think they are. They can be cut, dinged, scraped, etc... Looking at your dings, what to you think caused it?
That being said, these gears aren't hardened like a lot of people think they are. They can be cut, dinged, scraped, etc... Looking at your dings, what to you think caused it?
TT/Ameasap
The White Blur
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We'll I examined the other oil gear( the one without the rod) and it didn't have any dings at all. Are both gears the same size? I can't remember. I know their close. If one is smaller, then all it would take is a small piece of anything to get rung through it. But if they are the same size ( as in synchronized) the debris would have had to been very long.
Maybe I over estimated the ding, but it is still a ding on the tip of each gear in the middle. Wonder if that could be it?
Maybe I over estimated the ding, but it is still a ding on the tip of each gear in the middle. Wonder if that could be it?
They are the same size.
Why I mentioned about the ding..., We have a game at the machine shop..... Any time we (the shop owner and I) see a ding, we feel it and guess how deep it is. (keep in mind I can look at stuff and guess within less than 10 thou)... we both consistently guess about 400% deeper than actual.
Moral of the story, it's probably not as deep as you think... BUT if there's a divot, it was caused by something.
On the upside, if that something was big, the oil filter should have caught it.
Why I mentioned about the ding..., We have a game at the machine shop..... Any time we (the shop owner and I) see a ding, we feel it and guess how deep it is. (keep in mind I can look at stuff and guess within less than 10 thou)... we both consistently guess about 400% deeper than actual.
Moral of the story, it's probably not as deep as you think... BUT if there's a divot, it was caused by something.
On the upside, if that something was big, the oil filter should have caught it.
TT/Ameasap
The White Blur
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What are the chances of a small external leak causing this? I noticed a coffee cup saucer sized oil spot where I initially reved the car up after I noticed the drop in pressure next to my trailer to hear for any ticking.... Only in that spot for maybe 30 seconds or so. I Just noticed it outside a few minutes ago. The last time I boosted it, I saw smoke in the rear view mirror and thats when it started.
a small leak on the low pressure side can probably cause it. If you're drawing a stream of air bubbles with your oil I can see how that can lower your pressure but not enough to kill it. Plus, that theory lends itself to how you lost prime.
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We have seen similar oil pressure issues over the years, and recently a couple of 109 blocks have had a sudden drop in oil pressure.
One that I have dealt with for years had great oil pressure, but after a trip to the track it went to 5-10 psi from 30-35 psi at idle hot. After lots of external checking and filter/oil changes we pulled the engine and found the block split from the main bearing saddle to the cam bearing.
We suspected it was bleeding oil at the cam, and it was doing just than.
Last week we received a 109 short block for a freshen, and found it has a crack in the same place?
I hope you find it is not the block, but some other issue, as I just wanted to present this as a a possibility.
One that I have dealt with for years had great oil pressure, but after a trip to the track it went to 5-10 psi from 30-35 psi at idle hot. After lots of external checking and filter/oil changes we pulled the engine and found the block split from the main bearing saddle to the cam bearing.
We suspected it was bleeding oil at the cam, and it was doing just than.
Last week we received a 109 short block for a freshen, and found it has a crack in the same place?
I hope you find it is not the block, but some other issue, as I just wanted to present this as a a possibility.
TT/Ameasap
The White Blur
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Thanks for the info. Nick. Do you think this could happen to a girdled block?
turbo nasty
Turbo Dojo / MNTR
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Second block Nick is speaking of is yours truly. While it didn't have a girdle it was filled with HardBlok to the bottom of water pump. The bottom end had studs, forged crank/rods/pistons and two billet center caps.
Mine had a hard uhh ohh on the dyno at almost 30 PSI so that didn't help. But, with that said the spot he is mentioning is obviously weak.
Mine had a hard uhh ohh on the dyno at almost 30 PSI so that didn't help. But, with that said the spot he is mentioning is obviously weak.
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We have seen this more in girdled block, but they are usually run much harder.
It happens with girdled engines. Usually there is a lot of evidence of cap walk and oil pressure will drop as Nick stated. I've never been worried about oil pressure at idle because it hardly needs any. If it normally had 25psi at hot idle then all the sudden had 6psi I'd be concerned and depending how it was used would probably pull the engine
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TT/Ameasap
The White Blur
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Is there any way to get a borescope in there to check this? maybe through the plate on the front cover?
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If there is a crack, it is very hard to see even with the naked eye.
The symptom of oil pressure going away as the engine gets to operating temp is what usually accompanies a crack in the web.
You could try some heavy oil like straight 50W to see if oil pressure increases to help determine the ultimate cause?
The symptom of oil pressure going away as the engine gets to operating temp is what usually accompanies a crack in the web.
You could try some heavy oil like straight 50W to see if oil pressure increases to help determine the ultimate cause?
I sounds to me like you aren't going to be truly convinced unless you do pull the motor and go through it with a fine tooth comb. I know if I had a sudden drop in pressure like that and didn't spot the issue on the suction side of the pump right away I would be pulling it out and going through it rather than risk damaging it.
ek02
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X2 on the cracked main webs. Very hard to see until the cracks really open up. My # 3 cam bearing slid back 3/4" and caused the oil pressure to drop on my 4.1, or maybe the crack caused the drop. Pull the pan and look at the cam bearings to make sure they have not moved. Look at the casting lines on the bulkheads from the mains to the cam, and the struts next to the main saddles. If the block is cracked the line bore will eventually be off and you may have a vibration or some noise on acceleration.
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