High Oil Presure?
Thread Starter
Instructor
Joined: Apr 2005
Posts: 141
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From: Downers Grove IL
High Oil Presure?
My 91' L98 has had oil preasure at idle (1,000 rpm on stock tach, engine has a modified cam) that varies but is around 30 psi. At 1,200 rpm the oil preasure pegs the needle at 100 psi, and stays there. the good news as this has been occuring since I purchased the vett 37,000 miles ago and I have seen no noticable issues.
I replaced the oil presure sending unit from the silver one to the good black replacement. Now I get a more accurate reading (the gauge responds quicker) of the oil preasure, but it reads the same.
The oil pan is colapsed at the oil pick up about 1/4 inch. (like someone dropped the motor on the oil pan).
I am thinking that the high oil presure may come from the oil pump presure relief spring being bad, or the pickup being crushed, or both.
I have a new/used oil pan to replace oil pan, but should I replace the oil pump? What is the stock deapth of the oil pump pick up on an L98? Are the high volume oil pumps beter or worse than stock?
I am trying to do this in one repare rather than burning through gasket sets and time.
Thanks in advance.
I replaced the oil presure sending unit from the silver one to the good black replacement. Now I get a more accurate reading (the gauge responds quicker) of the oil preasure, but it reads the same.
The oil pan is colapsed at the oil pick up about 1/4 inch. (like someone dropped the motor on the oil pan).
I am thinking that the high oil presure may come from the oil pump presure relief spring being bad, or the pickup being crushed, or both.
I have a new/used oil pan to replace oil pan, but should I replace the oil pump? What is the stock deapth of the oil pump pick up on an L98? Are the high volume oil pumps beter or worse than stock?
I am trying to do this in one repare rather than burning through gasket sets and time.
Thanks in advance.
Thread Starter
Instructor
Joined: Apr 2005
Posts: 141
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From: Downers Grove IL
Sorry PatsFan, while I have taken the great route 100 many times (when it was dirt, ice, snow and asphalt ), and partaken in the sport of falling off of the snowy fields of the white and green mountains, I am not a woodchuck. Born in the south (around Milbury MA) a flat lander I remain. And presently residing in the great and flatter than a pool table state of Illinios. It's so flat out here that when it rains water gets lost and confused.
Keep it green, Polo.
Keep it green, Polo.
Team Owner
Joined: May 2002
Posts: 24,337
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
But if all is well, the relief shouldn't be needed right? If that's bypassing oil, you're getting less oil through the bearings.
Mine idles hot at 60psi, but most of the time it's 80+. Sending unit is fine. I'm gonna check the ohms at it while running, just haven't gotten around to it since it's buried under the dist.
Mine idles hot at 60psi, but most of the time it's 80+. Sending unit is fine. I'm gonna check the ohms at it while running, just haven't gotten around to it since it's buried under the dist.
Team Owner
Joined: Sep 2001
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From: Athens AL
C7 of the Year - Unmodified Finalist 2021
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The connector on the sending unit is likely bad, I had to splice a new one in when a new sender didnt fix it.
Your pressure should not be over ~65psi
HV pumps are not necessary or particularly useful unless you were racing and have a larger pan.
Your pressure should not be over ~65psi
HV pumps are not necessary or particularly useful unless you were racing and have a larger pan.
Thread Starter
Instructor
Joined: Apr 2005
Posts: 141
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From: Downers Grove IL
Thanks for the presures.
But any idea of what may be wrong? I will replace the sending unit clip, however, if I am going through the trouble of pulling the pan I would like to fix something while I am in there. If there is something to fix.
Thanks Polo
But any idea of what may be wrong? I will replace the sending unit clip, however, if I am going through the trouble of pulling the pan I would like to fix something while I am in there. If there is something to fix.
Thanks Polo
Pro
Joined: Jul 2005
Posts: 741
Likes: 37
From: Athens, GA
Polo -
If you had a problem on the pickup side, then you wouldn't see higher than expected pressure - you'd see lower pressure.
The biggest problem with high oil pressure is the chance you'll blow the gasket on the oil filter. Since you've been operating this way for 37k miles, it doesn't sound like much of a problem.
The most likely cause is a stuck pressure relief spring. When you drop the pan, you could remove the pump and check it.
Another cause of high oil pressure would be a clogged oil passage. However, since you haven't experienced any engine damage, then I wouldn't expect that to be the cause.
What viscosity oil are you using, and do you use any oil additives? Higher viscosity oil will increase pressure, but I wouldn't expect it to increase it this much.
Good Luck,
Steven
If you had a problem on the pickup side, then you wouldn't see higher than expected pressure - you'd see lower pressure.
The biggest problem with high oil pressure is the chance you'll blow the gasket on the oil filter. Since you've been operating this way for 37k miles, it doesn't sound like much of a problem.
The most likely cause is a stuck pressure relief spring. When you drop the pan, you could remove the pump and check it.
Another cause of high oil pressure would be a clogged oil passage. However, since you haven't experienced any engine damage, then I wouldn't expect that to be the cause.
What viscosity oil are you using, and do you use any oil additives? Higher viscosity oil will increase pressure, but I wouldn't expect it to increase it this much.
Good Luck,
Steven
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Thread Starter
Instructor
Joined: Apr 2005
Posts: 141
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From: Downers Grove IL
Steven,
Thanks for the advice. I am using Mobil 1 10w30. This oil runs quiet and the engine just sounds better. Yes I have been a Mobil 1 fan before I got the vett. Other oils that I have used in the vett, 10w40 and 10w30 regular blends sounded like they slowed the car down and ran ruff.
As the cost of a stock replacement oil pump is cheap I may just replace the whole pump while I replace the oil pan.
But this fix will have to wait a while as I have to replace the y-pipe and cat, and complete the weather strips on the top, align the windows etc, so I can take the vett to Indy next week.
Thanks again, Polo
Thanks for the advice. I am using Mobil 1 10w30. This oil runs quiet and the engine just sounds better. Yes I have been a Mobil 1 fan before I got the vett. Other oils that I have used in the vett, 10w40 and 10w30 regular blends sounded like they slowed the car down and ran ruff.
As the cost of a stock replacement oil pump is cheap I may just replace the whole pump while I replace the oil pan.
But this fix will have to wait a while as I have to replace the y-pipe and cat, and complete the weather strips on the top, align the windows etc, so I can take the vett to Indy next week.
Thanks again, Polo