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Username Post: Replaced oil pressure switch now reading near zero at idle        (Topic#352293)
96hoe 
Member
Posts: 70

Loc: jax fla
Reg: 12-11-04
08-01-18 04:51 PM - Post#2741719    

My oil pressure gauge has been bouncing around for a couple of years. I had a lifetime warranty on the switch so I decided to swap it out.
Prior to the swap the lowest it would read was 20 then max at 60 settle around 40 but would bounce all over the place.
Now with the new one max 40 settle around 20 then drop to near zero at hot idle. No engine noise oil just changed and full on the stick.
Bad new pressure switch? clogged brass elbow?
Any one have this happen. Also there was a plastic nipple in the end of the threaded tube on the new on and no nipple on the old one.
Also new fram extended guard filter. could that be bad?




Edited by 96hoe on 08-01-18 04:53 PM. Reason for edit: No reason given.

 
rockfangd 
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rockfangd
Age: 32
Loc: Utica ny
Reg: 04-13-10
08-01-18 06:03 PM - Post#2741726    
    In response to 96hoe

I dont use Fram. Had bad luck with them
Did you put anything on the threads of the sensor?
If you did that could be your issue

Old School GM fan FOREVER


 
thx1138v2 
Contributor
Posts: 159

Reg: 05-01-14
08-02-18 07:35 AM - Post#2741764    
    In response to 96hoe

How many miles on it and which engine?

Mine was doing the same thing and I changed the oil to 20W50 high mileage since it's getting up to 225K miles on my '94 4.3L C1500. Now it's ~15-20 PSI at idle when hot.

I've been running it that way for a couple of years now.



 
454cid 
Valued Contributor
Posts: 2975

Age: 45
Loc: West Michigan
Reg: 02-18-12
08-02-18 10:43 AM - Post#2741777    
    In response to thx1138v2

Heavier oil isn't the solution.

99 K3500 RCLB


 
454cid 
Valued Contributor
Posts: 2975

Age: 45
Loc: West Michigan
Reg: 02-18-12
08-02-18 10:48 AM - Post#2741779    
    In response to 96hoe

  • 96hoe Said:
My oil pressure gauge has been bouncing around for a couple of years. I had a lifetime warranty on the switch so I decided to swap it out.
Prior to the swap the lowest it would read was 20 then max at 60 settle around 40 but would bounce all over the place.
Now with the new one max 40 settle around 20 then drop to near zero at hot idle. No engine noise oil just changed and full on the stick.
Bad new pressure switch? clogged brass elbow?
Any one have this happen. Also there was a plastic nipple in the end of the threaded tube on the new on and no nipple on the old one.
Also new fram extended guard filter. could that be bad?




My oil pressure bouncing around a little too. I've wondered if it was a grounding issue in the dash. I have not bothered to check into it. You might clean all your grounds under the hood.

I have no idea on the plastic piece. I've never changed the oil pressure sensor before.

How long had it been since you changed your oil? Did you do anything different.... different type/viscosity/additive? Did the old oil look really bad?

No strange sounds is good. If you have a manual oil pressure gauge, or can get one, check the pressure that way.


99 K3500 RCLB


 
runamukker 
Poster
Posts: 57

Reg: 01-01-18
08-03-18 05:49 AM - Post#2741842    
    In response to 96hoe

Could be just a difference in ohms from the new sensor, especially if you used a non-GM replacement.


'92 K1500 Blazer Z71 350TBI 700R4 , 253,000 miles
'94 C1500 Cheyenne WT 350TBI 4L60e , 565,000 miles


 
96hoe 
Member
Posts: 70

Loc: jax fla
Reg: 12-11-04
08-03-18 11:13 AM - Post#2741867    
    In response to runamukker

new oil 10-30. non gm part. auto zone duralast.
went from carquest pro<wix> to Fram.
Although i have used fram on various cars for years with no problem. I am now starting to move away form them, except in this instance. Im not sure how a oil filter would effect oil presure.
Motor has 221K. 5.7 Vortec

Please keep opinions coming. I will be swapping out the pressure switch tomorrow and posting results.



Edited by 96hoe on 08-03-18 11:16 AM. Reason for edit: No reason given.

 
rockfangd 
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rockfangd
Age: 32
Loc: Utica ny
Reg: 04-13-10
08-03-18 05:03 PM - Post#2741891    
    In response to 96hoe

stick with wix. Excellent brand for filters

Old School GM fan FOREVER


 
96hoe 
Member
Posts: 70

Loc: jax fla
Reg: 12-11-04
08-03-18 05:31 PM - Post#2741892    
    In response to rockfangd

I forgot to mention I did use teflon tape on the switch end. wrapped two times.



 
rockfangd 
"5th Year" Gold Supporting Member
Posts: 2482
rockfangd
Age: 32
Loc: Utica ny
Reg: 04-13-10
08-03-18 06:36 PM - Post#2741900    
    In response to 96hoe

there you go.
There is not supposed to be anything on those threads.

Old School GM fan FOREVER


 
CowboyTrukr 
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CowboyTrukr
Loc: Salt Lake City
Reg: 06-20-09
08-03-18 06:54 PM - Post#2741901    
    In response to 96hoe

You might just pull the switch and remove the Teflon.

Greg

'95 K1500 Z71 EC Short Step 5.7L+0.040/NV3500
'00 Explorer XLT 4.0 V6 Auto
'94 K2500 5.7 NV4500 ECLB - SOLD
‘87 GMC S15 SCLB 4.3 Auto - SOLD

"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke


 
96hoe 
Member
Posts: 70

Loc: jax fla
Reg: 12-11-04
08-04-18 06:19 AM - Post#2741925    
    In response to CowboyTrukr

Teflon removed same results. waiting for it to cool down and pull it to swap out for a new one.



 
96hoe 
Member
Posts: 70

Loc: jax fla
Reg: 12-11-04
08-04-18 11:25 AM - Post#2741946    
    In response to 96hoe

Same result. going to pick and pull in the morning. I did spray carb cleaner in the hole to try to free up any debris before putting new switch in.
If that one doesn't do it I'll change oil filter and add some 20-50 to get pressure up and light off.



 
454cid 
Valued Contributor
Posts: 2975

Age: 45
Loc: West Michigan
Reg: 02-18-12
08-04-18 11:35 AM - Post#2741948    
    In response to 96hoe

  • 96hoe Said:
Same result. going to pick and pull in the morning. I did spray carb cleaner in the hole to try to free up any debris before putting new switch in.
If that one doesn't do it I'll change oil filter and add some 20-50 to get pressure up and light off.



You don't need heavy oil. Your engine wasn't built for it, and any extra pressure you get out of it will be feel good oil pressure, not helping your engine oil pressure.

Have you checked your grounds yet? How about a manual gauge?


99 K3500 RCLB


 
96hoe 
Member
Posts: 70

Loc: jax fla
Reg: 12-11-04
08-04-18 05:10 PM - Post#2741965    
    In response to 454cid

lol I know but it will feel good not to see that gauge at 0.
i wish i never changed out the switch to begin with but, i was tired to watching the needle bounce all over the place. But never below 20.
now I am paranoid.



Edited by 96hoe on 08-04-18 05:10 PM. Reason for edit: No reason given.

 
Mercedes 
Contributor
Posts: 189

Reg: 07-09-18
08-04-18 05:20 PM - Post#2741966    
    In response to 96hoe

At this point, I would put a mechanical oil pressure gauge in the port and see what the pressure really is. You can keep changing those switches but that is just a way of guessing.

If you had a switch that showed 40 lbs at idle would you believe it?



 
rockfangd 
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rockfangd
Age: 32
Loc: Utica ny
Reg: 04-13-10
08-04-18 05:44 PM - Post#2741969    
    In response to Mercedes

agreed. I would only use a oem pressure sender also.
Been there done that, with the CTS also

Old School GM fan FOREVER


 
someotherguy 
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Posts: 28754
someotherguy
Age: 48
Loc: Texas
Reg: 08-01-03
08-04-18 11:31 PM - Post#2741979    
    In response to rockfangd

As others have mentioned since you have a questionable situation test it with a mechanical gauge. You can tap in dow ln near the filter. If the mechanical gauge shows good pressure and multiple senders don't fix the gauge, pull the dash lens and adjust the needle to match the mechanical gauge.

Richard

06 Silverado ISS / 06 Silverado SS / 06 300C SRT8


 
96hoe 
Member
Posts: 70

Loc: jax fla
Reg: 12-11-04
08-05-18 01:41 PM - Post#2742030    
    In response to someotherguy

Solved. Although I did not put a mechanical gauge on it. Don't have one. I know, only like $20 at Harbor Freight.
I did get a switch from the pick a part yard that seemed to agree with values the original switch read before I pulled it out. It bottoms out at 20 now.
Thanks for all the input.

Now on to find that exhaust leak from the header install on the RT.

Richard I see you over at the LX forums too.
~SlickAWD





Edited by 96hoe on 08-05-18 01:43 PM. Reason for edit: No reason given.

 
runamukker 
Poster
Posts: 57

Reg: 01-01-18
08-05-18 03:29 PM - Post#2742038    
    In response to 96hoe

Is your gauge still bouncing around?

'92 K1500 Blazer Z71 350TBI 700R4 , 253,000 miles
'94 C1500 Cheyenne WT 350TBI 4L60e , 565,000 miles


 
96hoe 
Member
Posts: 70

Loc: jax fla
Reg: 12-11-04
08-05-18 06:24 PM - Post#2742051    
    In response to runamukker

Nope, nice and steady.



 
rockfangd 
"5th Year" Gold Supporting Member
Posts: 2482
rockfangd
Age: 32
Loc: Utica ny
Reg: 04-13-10
08-05-18 07:23 PM - Post#2742061    
    In response to 96hoe

See, they are picky with these aftermarket sensors.
I cant even get into what I went through with the coolant temp sensor. The only way I could fix it was to go to my local yard and pull a used oem one.
All the others readings were like 25-30*off

Old School GM fan FOREVER


 
Mercedes 
Contributor
Posts: 189

Reg: 07-09-18
08-07-18 05:38 PM - Post#2742260    
    In response to 96hoe

I don't know that it is "solved" or you kept looking until you found the answer that you wanted.



 
bowtie44s 
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bowtie44s
Age: 35
Loc: wv
Reg: 08-29-12
08-07-18 05:45 PM - Post#2742264    
    In response to Mercedes

  • Mercedes Said:
I don't know that it is "solved" or you kept looking until you found the answer that you wanted.



I agree. He wanted someone to agree with him from the beginning. I'd be putting a mechanical gauge on it to see what the oil pressure is.

Jeff

'88 Chevy K3500, aluminum head roller cam 511in³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap


 
rockfangd 
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rockfangd
Age: 32
Loc: Utica ny
Reg: 04-13-10
08-07-18 06:37 PM - Post#2742274    
    In response to bowtie44s

Member installed a oem used one from a pick and pull and it now works properly.


Old School GM fan FOREVER


 
GreatNorthWoods 
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GreatNorthWoods
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Reg: 03-31-02
08-08-18 07:39 AM - Post#2742325    
    In response to 96hoe

IMHO, 10 pounds of oil pressure sounds about right for a relatively stock hot high mileage engine at idle. Don't know if it is true or not but I've always heard that 10 pounds is enough to turn off a GM idiot light.

Vern

1953 Chevy Belair Sport Coupe - 355 Blueprint Engine, 700-R4, Vintage Air, EZ Wire, Ididit column, Cruise/Tilt, 59 Vette Steering Wheel, 4-Wheel Disc Brakes, Posies Springs, Coker Radials, Nova 10-bolt, Mustang II front, Continental Kit


 
Mercedes 
Contributor
Posts: 189

Reg: 07-09-18
08-08-18 03:14 PM - Post#2742372    
    In response to bowtie44s

Swapping over switches until you get the reading that you want is a little like turning over cards until you get the car that you want.

If there is a question about the viability of the switch, then swapping in another switch is not the answer. The switch is supposedly warning of low oil pressure and taking a mechanical reading will verify a faulty switch versus a faulty oil pressure condition.

He didn't want to know about low oil pressure so he kept swapping switches until the problem went away, or so he believes.



 
rockfangd 
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rockfangd
Age: 32
Loc: Utica ny
Reg: 04-13-10
08-08-18 06:02 PM - Post#2742388    
    In response to Mercedes

not sure here.
Only way to know would be to put a mechanical gauge in and compare them

Old School GM fan FOREVER


 
454cid 
Valued Contributor
Posts: 2975

Age: 45
Loc: West Michigan
Reg: 02-18-12
08-08-18 06:26 PM - Post#2742389    
    In response to rockfangd

I don't think it's that big a deal. The issue started when he changed something electrical, and there was no change in sound. The electrical change can not cause damage to the engine. It would be highly unlikely that an electrical change coincided with a silent mechanical event.

I wouldn't not have been switching sensors that much, However. I would have either lived with the change in oil pressure reading, or I would have gotten a mechanical gauge. When my engine was reading oddly (high) I didn't put a gauge on it. I added Seafoam, and drove it. The pressure eventually went back to normal and the noise went away after startup like normal. Oh, I also changed the filter again. I did have the knowledge that my oil had been changed recently, but had been way too long before that.


99 K3500 RCLB


 
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