# Low Oil Pressure at Idle (Maybe)



## Ebartone (Aug 18, 2019)

So I have recently noticed that my oil pressure on my 68 GTO seems to me, to be very low at idle. By very low I mean when the engine is totally warm, and I sit at idle for a minute, oil pressure can drop to 10 or even nine psi. This only happens when warm, at initial startup idle pressure is at about 40 psi. Idle when warm is at about 600-700 rpm. On the other hand, as I start to accelerate it climbs steadily and when Im at about 15 or 1800 RPM, I’m back up to 55 or 60 PSI. I’m trying to figure out if this is normal, or not. I am running 10 W 40, Brad Pen oil, and recently change my oil filter just for good measure. What do you Guys think? Any idea what would cause this, or is it even normal? The engine actually runs perfectly, knock on wood. Even at idle at nine psi, I hear no sign whatsoever of a tappet tick, of any sort or any other unusual sound - it idles perfectly. In fact when I open up a oil cap, I see plenty of green oil on rockers moving all over the place! Also no sign of oil leaks, no oil in water, and the oil level is not decreasing. Like I say, if I didn’t have a gauge, I wouldn’t even know about this to worry about it, maybe I should remove my gauge! 

I should’ve mentioned, my counsel is a Dakota digital, that was installed when the car was rebuilt a year or so ago. Again, I don’t know if this is new or not, possibly it is the first time I’ve noticed.


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## RMTZ67 (Mar 12, 2011)

Ebartone said:


> So I have recently noticed that my oil pressure on my 68 GTO seems to me, to be very low at idle. By very low I mean when the engine is totally warm, and I sit at idle for a minute, oil pressure can drop to 10 or even nine psi. This only happens when warm, at initial startup idle pressure is at about 40 psi. Idle when warm is at about 600-700 rpm. On the other hand, as I start to accelerate it climbs steadily and when Im at about 15 or 1800 RPM, I’m back up to 55 or 60 PSI. I’m trying to figure out if this is normal, or not. I am running 10 W 40, Brad Pen oil, and recently change my oil filter just for good measure. What do you Guys think? Any idea what would cause this, or is it even normal? The engine actually runs perfectly, knock on wood. Even at idle at nine psi, I hear no sign whatsoever of a tappet tick, of any sort or any other unusual sound - it idles perfectly. In fact when I open up a oil cap, I see plenty of green oil on rockers moving all over the place! Also no sign of oil leaks, no oil in water, and the oil level is not decreasing. Like I say, if I didn’t have a gauge, I wouldn’t even know about this to worry about it, maybe I should remove my gauge!
> 
> I should’ve mentioned, my counsel is a Dakota digital, that was installed when the car was rebuilt a year or so ago. Again, I don’t know if this is new or not, possibly it is the first time I’ve noticed.


I recently finished with the break in on my 67, also with new dakota gauges. Mine was not reading so I purchased a cheap gauge from the parts store. Like you mine seem to be oiling good but was glad to verify with another gauge that all is well. Finally corrected my dakota gauge. Verify with another gauge and if all is well check your gauges to be sure they are set up correctly. If you need instructions, let me know or you may find it on the web.


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## Ebartone (Aug 18, 2019)

RMTZ67 said:


> I recently finished with the break in on my 67, also with new dakota gauges. Mine was not reading so I purchased a cheap gauge from the parts store. Like you mine seem to be oiling good but was glad to verify with another gauge that all is well. Finally corrected my dakota gauge. Verify with another gauge and if all is well check your gauges to be sure they are set up correctly. If you need instructions, let me know or you may find it on the web.


Thank you RMT, to make things a bit more complicated yet, I recall about a month ago sitting in a long, slow line for a cruise, when I was having definite engine overheating problems. I recall vaguely that I’ve noticed at that time my oil pressure was around the same low idle number. It seems though, that afterwards that was not happening, but now it seems like it’s happening again. I wonder if I cooked that sensor? I should mention that this car has Dougs headers, and these headers run fairly close to the sensor. I’m debating if I would be better off purchasing a new Dakota sensor and trying it, which would be an easy install, versus spending the money on a different gauge, and then coming back and buying a dakota sensor anyways? As I look at it, it’s probably indicating about 5 to 10 psi lower than I would expect across the spectrum. As I notice, it doesn’t look like it reads 60 anymore but maybe 55. When electronics fail, unfortunately they don’t always just die, I think it could be possible to get erroneous numbers. I think I’ll give it some thought. 

Also googling around, I keep hearing about a 10psi per 1000 rpm rule, in general. So does that mean at a 700 rpm idle, 10 psi is fine? Like I said though, I'm not positive I believe the number is actually 10.

Thanks for your response.


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## cij911 (Oct 25, 2017)

Just install a manual pressure gauge (I believe you can even borrow from the parts stores) and test . My guess is it is either the gauge or the sending unit.


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## Ebartone (Aug 18, 2019)

cij911 said:


> Just install a manual pressure gauge (I believe you can even borrow from the parts stores) and test . My guess is it is either the gauge or the sending unit.


Thanks CIJ - I hate to show my ignorance, but can you tell me / link me to what you mean? As simple as an 1/8" NPT tube with a mechanical gauge on the end? Maybe just rout that up to the drivers compartment to watch it?

Ed


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## cij911 (Oct 25, 2017)

Ebartone said:


> Thanks CIJ - I hate to show my ignorance, but can you tell me / link me to what you mean? As simple as an 1/8" NPT tube with a mechanical gauge on the end? Maybe just rout that up to the drivers compartment to watch it?
> 
> Ed


Ed - Here is a link to a mechanical tester https://www.autozone.com/shop-and-garage-tools/oil-pressure-tester

You can find them anywhere auto related....

There are several ports you can use you read oil pressure depending on the motor and heads. Basically connect, run the motor and see what you are getting. (Obviously this is meant to be used while the car is stationary.)


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## Ebartone (Aug 18, 2019)

cij911 said:


> Ed - Here is a link to a mechanical tester https://www.autozone.com/shop-and-garage-tools/oil-pressure-tester
> 
> You can find them anywhere auto related....
> 
> There are several ports you can use you read oil pressure depending on the motor and heads. Basically connect, run the motor and see what you are getting. (Obviously this is meant to be used while the car is stationary.)


Awesome CIJ, thank you - I'll find one and report back.....


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## Ebartone (Aug 18, 2019)

cij911 said:


> Ed - Here is a link to a mechanical tester https://www.autozone.com/shop-and-garage-tools/oil-pressure-tester
> 
> You can find them anywhere auto related....
> 
> There are several ports you can use you read oil pressure depending on the motor and heads. Basically connect, run the motor and see what you are getting. (Obviously this is meant to be used while the car is stationary.)


This guy seem legit? 

https://www.amazon.com/Shankly-4350...,p_72:2661618011&rnid=2661617011&rps=1&sr=8-2


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## cij911 (Oct 25, 2017)

Or this https://www.harborfreight.com/engine-oil-pressure-test-kit-62621.html


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## Ebartone (Aug 18, 2019)

cij911 said:


> Or this https://www.harborfreight.com/engine-oil-pressure-test-kit-62621.html


Better yet, thanks!


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## RMTZ67 (Mar 12, 2011)

Ebartone said:


> This guy seem legit?
> 
> https://www.amazon.com/Shankly-4350...,p_72:2661618011&rnid=2661617011&rps=1&sr=8-2


 This one looks like it has quick release fittings.


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## 1968gto421 (Mar 28, 2014)

RMTZ67 said:


> This one looks like it has quick release fittings.


True, but the gauge only reads to 10 PSI. AutoZone also has the Shankley and their's is only 10 PSI also. :surprise:


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## cij911 (Oct 25, 2017)

Guys the kits you are referring to are 10 bar or 140 psi - not 10 psi....look at the gauge more closely...

https://www.amazon.com/Shankly-4350...ngine+oil+pressure+test&qid=1570625011&sr=8-5


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## Ebartone (Aug 18, 2019)

cij911 said:


> Guys the kits you are referring to are 10 bar or 140 psi - not 10 psi....look at the gauge more closely...
> 
> https://www.amazon.com/Shankly-4350...ngine+oil+pressure+test&qid=1570625011&sr=8-5


Yea, I saw that. I ordered the Shankly one - hopefully the resolution is ok - I would have preferred 0-100 psi, but suspect this will do...


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## geeteeohguy (Feb 2, 2008)

You're doing the right thing verifying the accuracy of your gauge and getting a true pressure reading. My experience: the 10 psi per 1000 rpm is a valid value, that's all that's needed in these engines. Saying that, and having owned a few GTO's over the past 40 years, if your oil pressure really is 10 psi at idle and only goes up to 40-ish going down the road, that is on the low side. Normal pressures for these cars in stock condition are 20-30 psi at idle and 50-70 psi going down the road. The usual culprit for low oil pressure is increased bearing clearances due to normal wear. If it were me, and my car, and it wasn't making any strange noises, I would change the oil to a thicker viscosity and run it.


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## Ebartone (Aug 18, 2019)

geeteeohguy said:


> You're doing the right thing verifying the accuracy of your gauge and getting a true pressure reading. My experience: the 10 psi per 1000 rpm is a valid value, that's all that's needed in these engines. Saying that, and having owned a few GTO's over the past 40 years, if your oil pressure really is 10 psi at idle and only goes up to 40-ish going down the road, that is on the low side. Normal pressures for these cars in stock condition are 20-30 psi at idle and 50-70 psi going down the road. The usual culprit for low oil pressure is increased bearing clearances due to normal wear. If it were me, and my car, and it wasn't making any strange noises, I would change the oil to a thicker viscosity and run it.


Thanks GTOG - Yea, this engine has been rebuilt within the last few years buy a previous owner (professionally), and as I mentioned, I've had no sign of any problems at all. From a number standpoint, per the current (Dakota Digital) gauge, when cold it will idle at about 40, then go up to 60 PSI no problem with very little additional rpm. When hot, I see this 9 psi thing when idling (at 700 or so), but it does go to 55-60 by about 2000 rpm or so when hot. 

My concern was at idle being 9 or I saw 8 once, and it really makes no sense - I've heard engines with very low oil pressure before - the tappets talk to you! But no ticking whatsoever, or anything odd! Like mentioned before, about a month ago it did this low idle pressure thing, but then stopped and idle went back to 20 or so hot - but here I am again. Just seems odd.... With a little luck I'll try this tonight and see what happens.

Thanks!


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## Ebartone (Aug 18, 2019)

Well I have an update. I received my pressure gauge from Amazon today, and was excited to do this easy test. After all, my car has no air conditioning, and access to the oil filter and sender was pretty straightforward, except for dealing with the headers. My first challenge though was the sender that was already installed was incredibly tight. After a great deal of wrestling with it, I finally got the sender off, then installed the Male part of my gauge. After connecting at the gauge, happy as a lark, I went up, started the engine, and quickly ran around to take a look at what kind of pressure I was getting. What I got to see instead, was not what I expected! Oil was not just dripping from the area, but was squirting out at an incredible rate! It was unbelievable to me that I could have not tightened my adapter properly, or possibly the quick connect wasn’t working properly, but let me tell you that, you can drain the better part of 5 quarts of Brad pens finest within about five seconds at 60 PSI! After playing around, adjusting fittings, with the continued same problem, I eventually stole my wife’s mirror, looked around the back of the oil bracket, and, well you take a look at the picture - apparently my wrestling with the tight sender caused this. So now My simple Wednesday night project has turned into a catastrophe! I spent the next hour managing to get the bracket off, and will now shop for a new one! Not sure I remember what the original problem was anymore!  I think I remember a post where someone was asking the question, why do I work on classic cars anyways!


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## RMTZ67 (Mar 12, 2011)

Ebartone said:


> Well I have an update. I received my pressure gauge from Amazon today, and was excited to do this easy test. After all, my car has no air conditioning, and access to the oil filter and sender was pretty straightforward, except for dealing with the headers. My first challenge though was the sender that was already installed was incredibly tight. After a great deal of wrestling with it, I finally got the sender off, then installed the Male part of my gauge. After connecting at the gauge, happy as a lark, I went up, started the engine, and quickly ran around to take a look at what kind of pressure I was getting. What I got to see instead, was not what I expected! Oil was not just dripping from the area, but was squirting out at an incredible rate! It was unbelievable to me that I could have not tightened my adapter properly, or possibly the quick connect wasn’t working properly, but let me tell you that, you can drain the better part of 5 quarts of Brad pens finest within about five seconds at 60 PSI! After playing around, adjusting fittings, with the continued same problem, I eventually stole my wife’s mirror, looked around the back of the oil bracket, and, well you take a look at the picture - apparently my wrestling with the tight sender caused this. So now My simple Wednesday night project has turned into a catastrophe! I spent the next hour managing to get the bracket off, and will now shop for a new one! Not sure I remember what the original problem was anymore!  I think I remember a post where someone was asking the question, why do I work on classic cars anyways!


Sounds like a quote I put up in april. "someone remind me why I am still working on old cars" lol:crazy: So far I am still at it. My new post "Timings off what gives" Well, when you get it back together, there is a plug near the distributor that you can tap into instead.I'm hoping your pressure (oil that is) will be ok and soon you will be past it all. Then it will be winter and unable to drive it ha ha.


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## Hjudge49 (Feb 25, 2015)

I am still in the breakin period with my rebuilt 400, Dakota digital gauges and dougs headers. My oil pressure is also about 60 at start up and when running, but also drops to about 20 at idle when a temperature. I have a 180 degree thermostat in the car and in Florida, in 90 degree temps, it runs about 185-190 degrees on the guage and on the het gun. I'm running Valvoline 10-40 racing oil. I wasn't too surprised the oil pressure dropped down when hot and idleing. Hope I'm not wrong to not worry.


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## cij911 (Oct 25, 2017)

Ebartone said:


> Well I have an update. I received my pressure gauge from Amazon today, and was excited to do this easy test. After all, my car has no air conditioning, and access to the oil filter and sender was pretty straightforward, except for dealing with the headers. My first challenge though was the sender that was already installed was incredibly tight. After a great deal of wrestling with it, I finally got the sender off, then installed the Male part of my gauge. After connecting at the gauge, happy as a lark, I went up, started the engine, and quickly ran around to take a look at what kind of pressure I was getting. What I got to see instead, was not what I expected! Oil was not just dripping from the area, but was squirting out at an incredible rate! It was unbelievable to me that I could have not tightened my adapter properly, or possibly the quick connect wasn’t working properly, but let me tell you that, you can drain the better part of 5 quarts of Brad pens finest within about five seconds at 60 PSI! After playing around, adjusting fittings, with the continued same problem, I eventually stole my wife’s mirror, looked around the back of the oil bracket, and, well you take a look at the picture - apparently my wrestling with the tight sender caused this. So now My simple Wednesday night project has turned into a catastrophe! I spent the next hour managing to get the bracket off, and will now shop for a new one! Not sure I remember what the original problem was anymore!  I think I remember a post where someone was asking the question, why do I work on classic cars anyways!


Sorry .....You can find the filter housing easily (especially since you are in MI). Also the fitting near the distributor could be on very very tight, but I always like to test in both places.


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## Ebartone (Aug 18, 2019)

RMTZ67 said:


> Sounds like a quote I put up in april. "someone remind me why I am still working on old cars" lol:crazy: So far I am still at it. My new post "Timings off what gives" Well, when you get it back together, there is a plug near the distributor that you can tap into instead.I'm hoping your pressure (oil that is) will be ok and soon you will be past it all. Then it will be winter and unable to drive it ha ha.


Thanks RMT - As much as I'd like to blame this on a previous owner for torquing a 1/8" npt brass fitting so tight that I had to jump on the wrench, the more probable explanation is that the wrench I used was jammed between the sensor and one of the housing bolt heads, so most of my force was really just yanking the housing away from the housing bolt - the result? Well, you see it. Really its pretty easy to get to, at least two of the three bolts anyway, the third is hidden behind a header but with about 7 universals on a 3/8" drive I can kinda get to it. 

So licking my wounds, ordering from Ames the housing a couple gaskets, new bolts with actual lock washers, AND a 45 deg brass fitting that apparently is popular, so the sensor is a little easier to get to.

I'll clean the crap off of the block surface - really not too bad already - try to torque to about 30 or so - not sure to use permetx (?)

Again, when I started the car yesterday (obviously before I destroyed the housing) cold idle was right at 60. I suspect I don't have a serious problem, or at least not yet - the more I try to fix, the more problems my engine seems to have. So:

1) New housing - $90
2) Gaskets - $10
3) Bolts - $6
4) Overpriced 45deg brass fitting that Home Depot of course does not have - $12
5) 6 new quarts of Brad Penn 10-W40 to replace the oil now on my driveway - $50
6) A new oil filter, just because - $10
6.1) Shipping for all of the above - $20

7) Pressure gauge set $30
8) Years taken off my life due to stress - $Who knows....
9) Embarrassment in front of wife - well, I'll never hear the end of it....

You know, I'm not even going to add this up, or then I'd have to add in the cost of paper towels to clean up my tears.

All for a problem I probably don't have - I'll call it now - the root cause is an intermittent Dakota Sensor....

Arggggg....


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## Ebartone (Aug 18, 2019)

Should I use permetex on this gasket?

Ed


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## geeteeohguy (Feb 2, 2008)

Yes....sparingly. Permatex number 2 is the best for this. 30 foot pounds is too tight. I would go more like 20. The new oil filter adapter should come with a new bypass spring and valve.....potentially eliminating your original problem, which sounds like it could have been a relief valve hanging up with junk in it. As to the gent who is using racing oil in his street engine: bad idea. Racing oils lack the additive package needed to protect a street-driven engine. They are not meant to sit in the crankcase for any length of time, and they do not neutralize acids that cause corrosion to bearings and moving parts.


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## Ebartone (Aug 18, 2019)

geeteeohguy said:


> Yes....sparingly. Permatex number 2 is the best for this. 30 foot pounds is too tight. I would go more like 20. The new oil filter adapter should come with a new bypass spring and valve.....potentially eliminating your original problem, which sounds like it could have been a relief valve hanging up with junk in it. As to the gent who is using racing oil in his street engine: bad idea. Racing oils lack the additive package needed to protect a street-driven engine. They are not meant to sit in the crankcase for any length of time, and they do not neutralize acids that cause corrosion to bearings and moving parts.


Cool GTOG, thanks, I'll be light on the wrench. So at lunch I picked up a small tube of this - we good with this?

https://www.permatex.com/products/g...m-oil-resistance-rtv-silicone-gasket-maker-4/

On second thought I think I have some Gray laying around - this black stuff is "fast curing" and I suspect I'll take at least a good hour to get that third behind the header bolt snugged in! Gray it is....


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## PontiacJim (Dec 29, 2012)

geeteeohguy said:


> Yes....sparingly. Permatex number 2 is the best for this. 30 foot pounds is too tight. I would go more like 20. The new oil filter adapter should come with a new bypass spring and valve.....potentially eliminating your original problem, which sounds like it could have been a relief valve hanging up with junk in it. As to the gent who is using racing oil in his street engine: bad idea. Racing oils lack the additive package needed to protect a street-driven engine. They are not meant to sit in the crankcase for any length of time, and they do not neutralize acids that cause corrosion to bearings and moving parts.


Pulled out Cliff Ruggles Pontiac book for rebuilding. He states 30 ft lbs on the 3 oil filter housing bolts. :yesnod:

X2 on using racing oil for the street, not a good idea for the reasons stated. :nonod:


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## Ebartone (Aug 18, 2019)

PontiacJim said:


> Pulled out Cliff Ruggles Pontiac book for rebuilding. He states 30 ft lbs on the 3 oil filter housing bolts. :yesnod:
> 
> X2 on using racing oil for the street, not a good idea for the reasons stated. :nonod:


I'll stick with Brads 10W40 green stuff - this major oil release I must say was at least partially my fault.... :rolleyes2:


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## 1968gto421 (Mar 28, 2014)

Ebartone said:


> Thanks RMT - As much as I'd like to blame this on a previous owner for torquing a 1/8" npt brass fitting so tight that I had to jump on the wrench, the more probable explanation is that the wrench I used was jammed between the sensor and one of the housing bolt heads, so most of my force was really just yanking the housing away from the housing bolt - the result? Well, you see it. Really its pretty easy to get to, at least two of the three bolts anyway, the third is hidden behind a header but with about 7 universals on a 3/8" drive I can kinda get to it.
> 
> So licking my wounds, ordering from Ames the housing a couple gaskets, new bolts with actual lock washers, AND a 45 deg brass fitting that apparently is popular, so the sensor is a little easier to get to.
> 
> ...


We all do stuff like this, ticking off our wives and ourselves. Appreciate your courage in putting this all on the forum:crying:


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## Ebartone (Aug 18, 2019)

1968gto421 said:


> We all do stuff like this, ticking off our wives and ourselves. Appreciate your courage in putting this all on the forum:crying:


Ah, I really don't mind. I've loved everything GTO since I was a kid - first car was a '73 Lemans - I recall the day I decided that a 2 bbl would never do, so bought a quadra-junk (in those days we all hated the Rochester, but used them anyway) - then realized it wasn't going to fit on my intake manifold without drilling two more very large holes for the secondary's, or replacing it, which I did. I then learned about bolt torquing - and why torquing intake bolts to about 3000 ft lbs. each doesn't provide the best seal! I learned a lot about Pontiac in those days....

Anyway, this forum is a huge source of information, and I'm constantly blown away by the knowledge of so many people, like GTOG, and Pontiac Jim and so many others - although I still can't get past the pork chop post! 

It's a great community, from the forum to the shows to me sneaking on a nearby road to see how fast I can get to 60 mph without getting caught - the wife tells me its just a matter of time. I suspect she' right.....


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## Ebartone (Aug 18, 2019)

Well, Mission accomplished. It looks a bit messy, on account of the black permatex all over my fingers, and then all over the bracket, which I will touch up, but even overcoming the bottom right bolt access due to the headers, all seems to be OK. Strangely enough, after reconnecting the same old sensor, the oil pressure is perfect, 60 PSI generally, only as low as 30 at hot idle. Odd that a mechanical failure would come and go like this! If it starts up again, I’ll probably just bite the bullet and purchase a new sensor. Also, Take a look at the 45° fitting I put in. Maybe everybody already knew about this, but it sure made things more convenient. Sidenote, I thought number two permatex was gray! The white foam you see all over the place is the permatex gasket remover. It worked OK, nothing to brag about. Thanks everyone for your help.


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## PontiacJim (Dec 29, 2012)

Ebartone said:


> Well, Mission accomplished. It looks a bit messy, on account of the black permatex all over my fingers, and then all over the bracket, which I will touch up, but even overcoming the bottom right bolt access due to the headers, all seems to be OK. Strangely enough, after reconnecting the same old sensor, the oil pressure is perfect, 60 PSI generally, only as low as 30 at hot idle. Odd that a mechanical failure would come and go like this! If it starts up again, I’ll probably just bite the bullet and purchase a new sensor. Also, Take a look at the 45° fitting I put in. Maybe everybody already knew about this, but it sure made things more convenient. Sidenote, I thought number two permatex was gray! The white foam you see all over the place is the permatex gasket remover. It worked OK, nothing to brag about. Thanks everyone for your help.




Success! It is possible that you were not getting a good enough ground or even the pressure relief valve was not functioning as it should. Redoing everything may have corrected it. Things happen for a reason, you had to bust the filter adapter to fix the low reading problem. :yesnod:

Just wait until you grenade the 10-bolt to fix a weak rear-end problem. Yep, _things happen for a reason_. You can use that line with your wife, and you don't have to tell her where you got the line from - it'll be our forum secret. :wink2:


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## Ebartone (Aug 18, 2019)

PontiacJim said:


> Success! It is possible that you were not getting a good enough ground or even the pressure relief valve was not functioning as it should. Redoing everything may have corrected it. Things happen for a reason, you had to bust the filter adapter to fix the low reading problem. :yesnod:
> 
> Just wait until you grenade the 10-bolt to fix a weak rear-end problem. Yep, _things happen for a reason_. You can use that line with your wife, and you don't have to tell her where you got the line from - it'll be our forum secret. :wink2:


Well, it’s a bit too late! I already read her the post about the Porkchop and the cookies, so Pontiac Jim has become a bit legendary around our house already!


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