Oil pressure light coming on at idle

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new oil pump when you can, for now heavier oil. i agree with dan except that 20-50 is fine is you run the car at temp for long highway cruises and/or you live in a very hot area. lots of stop and go traffic where the engine is idling a lot, you are stuck in traffic and it's 90 to 100 degrees out, the 20w50 is fine.

cooler temps, short trips, engine rarely gets to max temp then 20w50 would be a bad idea.
 
moparlover said:
new oil pump when you can, for now heavier oil. i agree with dan except that 20-50 is fine is you run the car at temp for long highway cruises and/or you live in a very hot area. lots of stop and go traffic where the engine is idling a lot, you are stuck in traffic and it's 90 to 100 degrees out, the 20w50 is fine.

cooler temps, short trips, engine rarely gets to max temp then 20w50 would be a bad idea.
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Totally agree with you on this.
Castrol GTX 20-50
I do lots of stop and go, and live where it gets pretty hot sometimes.
I also go on 200 mile runs at 75 mph down to Phoenix where it is 90 degrees at 8am and over 100 by 11am.:violent1:
 
I have a high mileage 67 engine in my Valiant. It runs great but when warm, the oil light flickers at idle with the AC on. It had a manual gauge in the car I took if from and the idle pressure does drop below 9 psi when hot. I have another engine ready to go in if it ever dies, but for now I've been adding motor honey (STP) to up the oil viscosity whenever it happens. It's a Band-Aid approach, but it will make the pressure go up and the light go off.
 
gregpurcell said:
I have a high mileage 67 engine in my Valiant. It runs great but when warm, the oil light flickers at idle with the AC on. It had a manual gauge in the car I took if from and the idle pressure does drop below 9 psi when hot. I have another engine ready to go in if it ever dies, but for now I've been adding motor honey (STP) to up the oil viscosity whenever it happens. It's a Band-Aid approach, but it will make the pressure go up and the light go off.
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Get the MP big block high pressure spring Greg. It's like 5 bucks from Summit. The slant uses the same one. It even installs without removing the pump.
 
RustyRatRod said:
Get the MP big block high pressure spring Greg. It's like 5 bucks from Summit. The slant uses the same one. It even installs without removing the pump.
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The higher pressure spring won't help the oil pressure at low idle on an older motor with lots of clearances though, right?
 
TylerW said:
In my experience the oil light at idle is the beginning of the end. Had a 198 start doing that after the Po had "extended" the oil change intervals out to about every 12000 miles...

New pump turned the light back off at idle but didn't save the engine later on...knock knock knock.
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I'll bite----- "Who's there?":finga:
 
TrailBeast said:
The higher pressure spring won't help the oil pressure at low idle on an older motor with lots of clearances though, right?
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That's correct, and it won't fix worn bearings either. Assuming the pressure relief valve isn't stuck, a heavier duty spring will just raise the PSI point where the oil is dumped back into the pan. A stiffer spring might bring the cold or high RPM pressure from 65psi to 80psi but it won't effect the hot idle pressure as the valve should be closed at that point, assuming the spring is good. If the spring is bad or broken, you should see a drop in the high RPM reading as well. If the bearings are badly worn, raising the high RPM pressure limit might actually cause the bearing to spin easier. If keeping the original block is important to you, I'd replace the bearings before you have a failure. Slant 6's have a bad habit of slinging a rod through the block when they fail. I've seen many lose #6 rod bearing where it slung the rod through the block so violently that it hit the starter and broke it off too, ruining the transmission in the process.
 
cudamark said:
That's correct, and it won't fix worn bearings either. Assuming the pressure relief valve isn't stuck, a heavier duty spring will just raise the PSI point where the oil is dumped back into the pan. A stiffer spring might bring the cold or high RPM pressure from 65psi to 80psi but it won't effect the hot idle pressure as the valve should be closed at that point, assuming the spring is good. If the spring is bad or broken, you should see a drop in the high RPM reading as well. If the bearings are badly worn, raising the high RPM pressure limit might actually cause the bearing to spin easier. If keeping the original block is important to you, I'd replace the bearings before you have a failure. Slant 6's have a bad habit of slinging a rod through the block when they fail. I've seen many lose #6 rod bearing where it slung the rod through the block so violently that it hit the starter and broke it off too, ruining the transmission in the process.
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While it will not "fix" any physical wear, it most certainly will turn the oil light off at idle.
 
RustyRatRod said:
While it will not "fix" any physical wear, it most certainly will turn the oil light off at idle.
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Huh, I was under the impression that it wouldn't change the idle oil pressure also.
Only the point where it allows too much oil pressure to bypass it.
(higher RPM's)
 
No. The high pressure spring holds the release valve more and allows more pressure to build up. It's an old trick to pull the oil spring out, stretch it and put it back.
 
RustyRatRod said:
No. The high pressure spring holds the release valve more and allows more pressure to build up. It's an old trick to pull the oil spring out, stretch it and put it back.
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This is my reasoning on it.
Lets say the oil pump puts out 5 gallons a min max.
But worn bearings allow a 6 gallon per min flow.
I don't understand how a tighter spring is going to make the oil pressure compensate for a 6 gallon loss through the bearings if the oil pump can only do 5 gal a min anyway.
I always thought the spring was to relieve to high of a pressure and had zero effect at Idle RPM's unless cold oil was just to thick to pump through the bearings at 5 gallons per min.

See why it doesn't make sense to me?
 
the spring is actually a bypass. it let's much more through than the engine can use.

the pressure comes out another place and up to the engine. what is left over goes thru the spring back to the oil pan
 
TrailBeast said:
This is my reasoning on it.
Lets say the oil pump puts out 5 gallons a min max.
But worn bearings allow a 6 gallon per min flow.
I don't understand how a tighter spring is going to make the oil pressure compensate for a 6 gallon loss through the bearings if the oil pump can only do 5 gal a min anyway.
I always thought the spring was to relieve to high of a pressure and had zero effect at Idle RPM's unless cold oil was just to thick to pump through the bearings at 5 gallons per min.

See why it doesn't make sense to me?
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What you and I think is correct. The pressure relief valve only governs the high end of the pressure, not the low end. This assumes that the valve is not stuck open and the return spring is present and not broken. The pressure relief valve doesn't even move until the RPM's are about 1500 when the enging is at operating temp. Naturally, when the oil is cold or if it's a real thick oil that figure will be a lot lower. With a stiffer spring, it just holds the valve closed until a higher RPM is reached.
 
Well if that's the case, why is it you have more oil pressure all the way across the spectrum with a high pressure pump?
 
RustyRatRod said:
Well if that's the case, why is it you have more oil pressure all the way across the spectrum with a high pressure pump?
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I would think that the high pressure pump has a larger pumping volume and also a higher pressure regulator spring.

I could see a tighter spring making an oil pressure light go off at hot idle if the regulator valve was regulating pressure from idle to full rev, but I have always been under the impression that the regulator valve really only moved when the RPM's got high enough or the oil cold and thick enough where the bearings couldn't bleed off the full pump volume.
 
The only difference between a stock and high pressure pump is the regulator spring. The rotors are the same. I have used high pressure pumps for years on worn engines as a band aid for customers who didn't want to rebuild engines but wanted the oil light out. It works. I'm not basing my opinion on a bunch of who shot John online theories. I know what I'm talking about, because I've done it. A lot. Now, the high volume pumps are a different animal. They do have deeper rotors to move more oil.
 
RustyRatRod said:
The only difference between a stock and high pressure pump is the regulator spring. The rotors are the same. I have used high pressure pumps for years on worn engines as a band aid for customers who didn't want to rebuild engines but wanted the oil light out. It works. I'm not basing my opinion on a bunch of who shot John online theories. I know what I'm talking about, because I've done it. A lot. Now, the high volume pumps are a different animal. They do have deeper rotors to move more oil.
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Hm, ok.
I guess that's that then.
I always thought the reg valve only moved after the oil that was pumped became too high of a volume or pressure.

BTW, I shot John just in case you needed to know. :D
 
As I said...a new stock pump turned the light off for me at idle but it did NOT save the worn-out bearings. It's just a Band-aid...you will have to pay the piper eventually.
 
TylerW said:
As I said...a new stock pump turned the light off for me at idle but it did NOT save the worn-out bearings. It's just a Band-aid...you will have to pay the piper eventually.
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No arguments on that.
 
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