low oil pressure when accelerating
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On The Tree
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From: St. Petersburg, Fl
low oil pressure when accelerating brand new home built 500 hp 383 with 1500 miles over the last 8-10 months. haven drove it in a few months. went for a drive yesterday and when I accelerate my oil pressure wll go up for like 40 to maybe 45 and then start dropping to 35 and 30 and maybe more but i just coasted it home so the pressure stayed high. normally the pressure should increase until i shift but now it does this. what can the problem be?
Mine did the same ****, the cam bearings went bad due to the cam. Dont know if you were using a new cam or what. I used a cam i got off Ebay, used. So, it bit me in the ***.
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Verdad Gallardo The fact that I don't tell you to try it in park and you come back with "but I have a manual transmission"
Park= automatic only
Neutral= automatic or manual
But I don't just say neutral because I think if you have an automatic it's best to keep it in park for safty reasons.
My original intention was to not have to type all that out explaining something so obvious.
Park= automatic only
Neutral= automatic or manual
But I don't just say neutral because I think if you have an automatic it's best to keep it in park for safty reasons.
My original intention was to not have to type all that out explaining something so obvious. 
When it does this when you are accelerating, does it do it more when you accelerate under wide open throttle? If so, it is due to the oil pan. The oil is climbing the back of the pan and the oil pump pickup has no oil around it so it is picking up only air. To fix this, you need a larger capacity oil pan, 7 quarts, that has trap doors to keep the oil close to the oil pump pickup and an "anti climbing" wall welded onto the indside of the back wall of the oil pan. If the engine is doing this under a mild acceleration as well, two things come to mind.
1. The oil pump pickup depth is not correct in the oil pan. This should be 3/8" of an inch from the bottom of the pan.
2. There is a pressure relief valve spring and a plunger in the oil pump that disengages when a certain oil pressure is reached and it oscillates back and forth to maintain that pressure. However, sometimes the plunger sticks in this bore causing you to loose oil pressure. I know this because my 406 did the same thing with two different melling pumps. One was an m-select top of the line pump, and the other was a M55A pump. The plungers in both pumps were sticking in the bores.
1. The oil pump pickup depth is not correct in the oil pan. This should be 3/8" of an inch from the bottom of the pan.
2. There is a pressure relief valve spring and a plunger in the oil pump that disengages when a certain oil pressure is reached and it oscillates back and forth to maintain that pressure. However, sometimes the plunger sticks in this bore causing you to loose oil pressure. I know this because my 406 did the same thing with two different melling pumps. One was an m-select top of the line pump, and the other was a M55A pump. The plungers in both pumps were sticking in the bores.
I agree with 69ss but if you were loosing oil pressure due to the pump acting upp you should be able to see it in park/neutral. If its because of the pan which most likely I would assume it is you will only notice it on the road.
Loose bearings will cause low oil pressure at idle. I would only take the pan off at this time. What kind of pan is it?? If you want to be comfortable change the oil pump when you are down there but if it was a mechanical failure you would have seen it by now just my thoughts though.
Loose bearings will cause low oil pressure at idle. I would only take the pan off at this time. What kind of pan is it?? If you want to be comfortable change the oil pump when you are down there but if it was a mechanical failure you would have seen it by now just my thoughts though.
Thread Starter
On The Tree
iTrader: (1)
Joined: Mar 2006
Posts: 133
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From: St. Petersburg, Fl
The fact that I don't tell you to try it in park and you come back with "but I have a manual transmission"
Park= automatic only
Neutral= automatic or manual
But I don't just say neutral because I think if you have an automatic it's best to keep it in park for safty reasons.
My original intention was to not have to type all that out explaining something so obvious.
Park= automatic only
Neutral= automatic or manual
But I don't just say neutral because I think if you have an automatic it's best to keep it in park for safty reasons.
My original intention was to not have to type all that out explaining something so obvious. anyways it also does the same in park Thread Starter
On The Tree
iTrader: (1)
Joined: Mar 2006
Posts: 133
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From: St. Petersburg, Fl
thank you, it has a 7 qt oil pan and has a m-select hv55 oil pump. also the pan and pick up tube were bought to be correct, never measured it but they were bought to work together with each other. so if my plunger is sticking in the bore, what is the fix for that?? this is some information that is finally starting to make some logical sense.
Thread Starter
On The Tree
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Joined: Mar 2006
Posts: 133
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From: St. Petersburg, Fl
lol, yea thats eased up enough.. but i believe that the oil pickup is still attached because if it was not, then at start up it would not have proper pressure. if the pick up was on the bottom of the pan, then at start up it would be sucking air all the time.
thank you, it has a 7 qt oil pan and has a m-select hv55 oil pump. also the pan and pick up tube were bought to be correct, never measured it but they were bought to work together with each other. so if my plunger is sticking in the bore, what is the fix for that?? this is some information that is finally starting to make some logical sense.
Fixing the oil pump requires dropping the oil pan, pulling the pump off the motor, dissasembling the pump and honing out the hole that contains the spring/plunger assembly to be slightly larger, then putting it back together again.
My only guess is that it was funneling the oil, like draining a bath tub, you get that funnel of water that sucks air.
I just dropped the pan, replaced the pickup, and the problem was solved.
Actually Look at where the pickup is and look at the hole in the pump. Not much higher. I've pulled apart a stock engine that had good oil pressure with the whole pickup laying in the bottom of the pan.
Last edited by 9000th01ss; Mar 18, 2009 at 12:18 AM.