New oil pump noisy?
Thread Starter
Drifting
Joined: Jun 2012
Posts: 1,990
Likes: 183
From: Port St. Lucie Fl
New oil pump noisy?
Had a problem with oil pressure dropping to 25 psi above 5k rpm. Replaced the melling m55 with a m155 to attempt to resolve the issue and now it sounds like a rod knocking. Anyone else have this issue?
Last edited by Kacyc3; Nov 7, 2021 at 07:16 PM.
Drifting
Joined: Nov 2013
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From: Scottsdale Arizona
I’ve heard oil pumps going bad make whirring or whining sounds, but not a sound like a rod knocking. Maybe you have problems elsewhere in your engine. I recall hearing one rattle a little, but a rod knocking is a pretty distinct sound. Post a video of your engine running.
Team Owner
Joined: Mar 2002
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From: Huntsville AL
If it sounds like a rod knocking than it could be rod knocking. The oil pump is a couple of gears turning , nothing to make a knocking sound. I have never seen a bad M55 oil pump in all my years of playing with small blocks, your low oil pressure is most likely bearing clearance related hence the rod knocking sound.
Further investigation required.
Further investigation required.
Last edited by Mr D.; Nov 8, 2021 at 08:56 AM.
Thread Starter
Drifting
Joined: Jun 2012
Posts: 1,990
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From: Port St. Lucie Fl
Last edited by Kacyc3; Nov 8, 2021 at 11:42 AM.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Corvette pan is 7” deep….the pickup needs to be 6 3/4 off the deck….is that what you are saying?
The only way you could drop pressure off above 5k is an inlet restriction then the pump will cavitate…..dropping pressure….the pump wants more than the pickup can deliver….
Is this a Corvette pan and pickup? The M155 is a 3/4” inlet and I do not know of a 3/4” inlet Corvette pan pickup….
Jebby
Last edited by Jebbysan; Nov 8, 2021 at 11:27 AM.
Thread Starter
Drifting
Joined: Jun 2012
Posts: 1,990
Likes: 183
From: Port St. Lucie Fl
Is the pickup at least 1/4 inch away from the bottom of the sump? I cannot tell from your text.
Corvette pan is 7” deep….the pickup needs to be 6 3/4 off the deck….is that what you are saying?
The only way you could drop pressure off above 5k is an inlet restriction then the pump will cavitate…..dropping pressure….the pump wants more than the pickup can deliver….
Is this a Corvette pan and pickup? The M155 is a 3/4” inlet and I do not know of a 3/4” inlet Corvette pan pickup….
Jebby
Corvette pan is 7” deep….the pickup needs to be 6 3/4 off the deck….is that what you are saying?
The only way you could drop pressure off above 5k is an inlet restriction then the pump will cavitate…..dropping pressure….the pump wants more than the pickup can deliver….
Is this a Corvette pan and pickup? The M155 is a 3/4” inlet and I do not know of a 3/4” inlet Corvette pan pickup….
Jebby
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Team Owner
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From: Southern Cal Ca
St. Jude Donor '22
i don't remember ever hearing about a knocking oil pump.
hydraulics may thump if a relief system is
malfunctioning?
cam and distributor gear mesh can be loud?
problem with shaft driving pump?
hydraulics may thump if a relief system is
malfunctioning?
cam and distributor gear mesh can be loud?
problem with shaft driving pump?
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Never seen a M55 cavitate at 5000rpm.......all of the original DZ302 and LT-1 pump were all 5/8" pickup.....plenty of oil to 6500 rpm.....so something else is wrong.
What exact pickup part # did you use?
Did you use a IS55 shaft with steel collar as well?
Jebby
What exact pickup part # did you use?
Did you use a IS55 shaft with steel collar as well?
Jebby
Thread Starter
Drifting
Joined: Jun 2012
Posts: 1,990
Likes: 183
From: Port St. Lucie Fl
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Usually to busy at 5k rpm to watch a gauge but the Holley EFI datalogged it.. not sure on the number of the drive shaft it was put in a while ago. Here is the video Melling oil pump noise
Jebby
Thread Starter
Drifting
Joined: Jun 2012
Posts: 1,990
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From: Port St. Lucie Fl
Pro
Joined: Jul 2021
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Never heard (or heard of) pump itself knock.
AFAIK, all OE sbc since about 1993 have OE M155 spec pump.
we Know your sump/pickup was also changed because the new M155 Requires larger 3/4" OD than the old 5/8" M55 pickup..
Is new pickup loose fit in new M155 pump ? ... banging into something and intermittently sucking air ?
Is new pickup brazed/welded to pump body ?
did you also replace oil pump intermediate shaft's plastic Retainer/Collar ? or R&R w/ all metal OPIS ?
Is windage tray not fully-tightened to studs or pan ?
Is dipstick contacting pickup or tray ?
Is there adequate clearance between top of OPIS and bottom of dist shaft ?
melling does sell a stronger chrome moly shaft (12550) that's a bit shorter.
Have ya tried a Different filter ? If filter has an anti-bypass valve ... perhaps valve is malfunctioning ?
AFAIK, all OE sbc since about 1993 have OE M155 spec pump.
we Know your sump/pickup was also changed because the new M155 Requires larger 3/4" OD than the old 5/8" M55 pickup..
Is new pickup loose fit in new M155 pump ? ... banging into something and intermittently sucking air ?
Is new pickup brazed/welded to pump body ?
did you also replace oil pump intermediate shaft's plastic Retainer/Collar ? or R&R w/ all metal OPIS ?
Is windage tray not fully-tightened to studs or pan ?
Is dipstick contacting pickup or tray ?
Is there adequate clearance between top of OPIS and bottom of dist shaft ?
melling does sell a stronger chrome moly shaft (12550) that's a bit shorter.
Have ya tried a Different filter ? If filter has an anti-bypass valve ... perhaps valve is malfunctioning ?
Last edited by ebbnflow; Nov 8, 2021 at 08:34 PM.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Never heard (or heard of) pump itself knock.
we Know the sump/pickup was also changed because the new M155 Requires larger 3/4" OD than the old 5/8" M55 pickup..
Is new pickup loose fit in new M155 pump ? ... banging into something and intermittently sucking air ?
Is new pickup brazed/welded to pump body ?
did you also replace oil pump intermediate shaft's plastic Retainer/Collar ? or R&R w/ all metal OPIS ?
Is windage tray not fully-tightened to studs or pan ?
Is dipstick contacting pickup or tray ?
Is there adequate clearance between top of OPIS and bottom of dist shaft ?
melling does sell a stronger chrome moly shaft (12550) that's a bit shorter.
we Know the sump/pickup was also changed because the new M155 Requires larger 3/4" OD than the old 5/8" M55 pickup..
Is new pickup loose fit in new M155 pump ? ... banging into something and intermittently sucking air ?
Is new pickup brazed/welded to pump body ?
did you also replace oil pump intermediate shaft's plastic Retainer/Collar ? or R&R w/ all metal OPIS ?
Is windage tray not fully-tightened to studs or pan ?
Is dipstick contacting pickup or tray ?
Is there adequate clearance between top of OPIS and bottom of dist shaft ?
melling does sell a stronger chrome moly shaft (12550) that's a bit shorter.
The Corvette pickup is specific to the Corvette pan…..it picks up the oil much further forward….the two are not interchangeable so I would like to know what is on it and how it works.
I asked twice already and no answer on that…..
If the pass car style pickup was used on a Corvette pan and not brazed….when the pan is lowered on, the pickup would hit the sump and bend up….
Jebby
Last edited by Jebbysan; Nov 8, 2021 at 08:33 PM.
Pro
Joined: Jul 2021
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Yes….it requires a 3/4” pickup…..which there is no such animal for a Corvette pan…..so that means it has the passenger car pickup on it…..which I do not see how that would work….
The Corvette pickup is specific to the Corvette pan…..it picks up the oil much further forward….the two are not interchangeable so I would like to know what is on it and how it works.
I asked twice already and no answer on that…..
If the pass car style pickup was used on a Corvette pan and not brazed….when the pan is lowered on, the pickup would hit the sump and bend up….
Jebby
The Corvette pickup is specific to the Corvette pan…..it picks up the oil much further forward….the two are not interchangeable so I would like to know what is on it and how it works.
I asked twice already and no answer on that…..
If the pass car style pickup was used on a Corvette pan and not brazed….when the pan is lowered on, the pickup would hit the sump and bend up….
Jebby
fixed that for ya ... just looked it up using a little more than "that's the way I always did it" ... pickup is melling 254S
Thread Starter
Drifting
Joined: Jun 2012
Posts: 1,990
Likes: 183
From: Port St. Lucie Fl
Yes….it requires a 3/4” pickup…..which there is no such animal for a Corvette pan…..so that means it has the passenger car pickup on it…..which I do not see how that would work….
The Corvette pickup is specific to the Corvette pan…..it picks up the oil much further forward….the two are not interchangeable so I would like to know what is on it and how it works.
I asked twice already and no answer on that…..
If the pass car style pickup was used on a Corvette pan and not brazed….when the pan is lowered on, the pickup would hit the sump and bend up….
Jebby
The Corvette pickup is specific to the Corvette pan…..it picks up the oil much further forward….the two are not interchangeable so I would like to know what is on it and how it works.
I asked twice already and no answer on that…..
If the pass car style pickup was used on a Corvette pan and not brazed….when the pan is lowered on, the pickup would hit the sump and bend up….
Jebby
The drive shaft is a hardened one with the collar built into the shaft.
I have nothing…..but if it were mine….the pan would come back off…..
Here is another scenario I read on this forum 10 yrs ago.
I fella was laying on his back replacing the oil pump. He misplaced the pump mounting bolt and substituted one of equal diameter / threads.
Later it was found that the bolt was a tad longer than stock. It forced its way into the lower main bearing gouging the crank.
You can imagine the noise it made at start up.
I am not saying that's what happen to you. But my question is, does the Melling M155 use the same length bolt as the M55?
I fella was laying on his back replacing the oil pump. He misplaced the pump mounting bolt and substituted one of equal diameter / threads.
Later it was found that the bolt was a tad longer than stock. It forced its way into the lower main bearing gouging the crank.
You can imagine the noise it made at start up.
I am not saying that's what happen to you. But my question is, does the Melling M155 use the same length bolt as the M55?
I ordered the pump for a 93-97 Camaro with the LT1 thinking it would fit without issue and would be a pump to resolve the issue above 5k rpm. If you have a sump part number that is specific for a corvette id be interested in seeing it as Rockauto says they use the same as all other small blocks.
Last edited by Kacyc3; Nov 9, 2021 at 11:36 AM.
