Is the oil filter before or after the oil pressure sensor? 1995 Tahoo 5.7L

[ecomike]

Simple question on the plumbing . Is the oil filter before or after the oil pressure sensor? on a 1995 Tahoo 5.7L engine

[Blue Bowtie]

That depends upon where your oil pressure switch is connected:

[ecomike]

LOL, the answer to my question, depends on the answer to my question? I love it.

I will ask again, on the 5.7 L engine of the 1995 Tahoe, did they put the Oil pressure sensor

(1) between the pump outlet, and the oil filter inlet, or

(2) on the filtered oil, outlet side of the oil filter ?

Originally Posted by Blue Bowtie

That depends upon where your oil pressure switch is connected:

[Tech II]

OK, I'll bite, why the question?

[Blue Bowtie]

Typically, the oil pressure sensor is located at the test port above the filter boss on the left side of the engine, or is located at the top of the cross-drilled passages between the filter gallery and horizontal feed to the camshaft gallery, accessible behind the intake. Either of those would sense pressure after the filter.

However, many SBCs in this age range had oil filter adapters to permit connection of external oil cooler lines. In those installations the location is not as certain. I have a '94 SBC and '96 SBC, both with external oil coolers, and both have the oil pressure sensor in the test port on the left side of the engine, along with a second oil pressure switch in the upper position, rearward of the intake. The sensor is used for the instrument and switch is used for the fuel injection system. Both are LT1s, similar to the Vortec truck engines but not identical.

I also have three 2000-up SBC-based 262 inch Vortec V6s, all of which have the sensor located at the top passage, behind the intake. These are also similar to the Vortec V8, but not identical.

Not to be too difficult, but I'm not certain which configuration was installed as the '95 "Tahoo" version.

There's a pretty good bet it is sensing pressure after the filter, however.

As Tech II asked, this begs the question, "Why?"

[ecomike]

Thanks for the detailed feedback of what you do know.

Why?

Because I need to know?

LOL

I changed the oil and filter, prior oil was believed to by 10W30. I used 15W40 NAPA universal fleet (gas and diesel) SN API spec, and a premium high efficiency 99% rate filter (STP IIRC).

Now the oil pressure is running 40-70 psi. I think the filter is after the sensor, and the tight filter (with a thicker oil) is causing the the sensor to see high pressure at the pump, with out telling me what the real oil pressure is in the engine. As the pressure should be lower, if the filter is restricting flow. Thinking the filter I used may have been meant for the new thinner synthetic oils 0-20 stuff.

But I need to know which side of the filter the sensor is on for this one, to complete a proper diagnosis.

Originally Posted by Blue Bowtie

Typically, the oil pressure sensor is located at the test port above the filter boss on the left side of the engine, or is located at the top of the cross-drilled passages between the filter gallery and horizontal feed to the camshaft gallery, accessible behind the intake. Either of those would sense pressure after the filter.

However, many SBCs in this age range had oil filter adapters to permit connection of external oil cooler lines. In those installations the location is not as certain. I have a '94 SBC and '96 SBC, both with external oil coolers, and both have the oil pressure sensor in the test port on the left side of the engine, along with a second oil pressure switch in the upper position, rearward of the intake. The sensor is used for the instrument and switch is used for the fuel injection system. Both are LT1s, similar to the Vortec truck engines but not identical.

I also have three 2000-up SBC-based 262 inch Vortec V6s, all of which have the sensor located at the top passage, behind the intake. These are also similar to the Vortec V8, but not identical.

Not to be too difficult, but I'm not certain which configuration was installed as the '95 "Tahoo" version.

There's a pretty good bet it is sensing pressure after the filter, however.

As Tech II asked, this begs the question, "Why?"

[aleekat]

So is 15w-40 what the manual recommends? Or just what you decided to run in it?

[ecomike]

Originally Posted by aleekat

So is 15w-40 what the manual recommends? Or just what you decided to run in it?

Multiple choice:
Option
(1) Why? Is that relevant to location of the pressure sensor? LOL

(2) You tell me?

(3) This is a 1995 with almost 300,000 miles, last time I checked manuals did not cover 22 year old 300,000 mile rigs?

(4) It is what I recommended based on 45 years of experience with rigs almost as old as me LOL

(5) What manual, LOL

(6) I don't need no stinkin manual

OK, back to MY QUESTION, so are there any old school engine rebuilder gurus here at all that know how this beast in 1995 was plumbed that can answer MY question PLEASE!!

I am a bit shocked the answer has not been posted yet.

[j cAT]

The oil to use is 10-30wt not 40wt .. that was banned by GM 1980's LOL!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

45 years working on lawn mowers .

70PSI too high .. 40-60 psi normal range ... pressure output is after the oil pump .. can be mounted anywhere who cares ...certainly not before oil pump..

my 1967 olds V8 had 10-30wt oil that was the spec 400CU 400 tranny .

you put the wrong oil in it .

[ecomike]

I did not ask what oil to put in it. I asked where the bleep-in oil pressure sensor is plumbed, on the inlet or outlet side of the oil filter. An I do not know is valid answer.

This thread is not about oil type or oil specs, it is a simple question that no one here seems to know. I guess I will need to find it out the hard way.

I have run 20W50 for 10 years in my 2001 Saturn for the last 100,000 miles with no issues. I run 15W40 in my custom 1981 Nissan SD-22 diesel engine with nearly 1/2 million miles that I custom installed in my 1985 FrankenJeep. I run 20-W50 in all my 1987-89 Cherokee that all have nearly 300,000 miles now and are all DD because I know the fork I am doing. I do not give a rats ass what spec GM says to use.

I did not ask if 70 psi was too high!!!!

Originally Posted by j cAT

The oil to use is 10-30wt not 40wt .. that was banned by GM 1980's LOL!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

45 years working on lawn mowers .

70PSI too high .. 40-60 psi normal range ... pressure output is after the oil pump .. can be mounted anywhere who cares ...certainly not before oil pump..

my 1967 olds V8 had 10-30wt oil that was the spec 400CU 400 tranny .

you put the wrong oil in it .

[ecomike]

Originally Posted by Blue Bowtie

Typically, the oil pressure sensor is located at the test port above the filter boss on the left side of the engine, or is located at the top of the cross-drilled passages between the filter gallery and horizontal feed to the camshaft gallery, accessible behind the intake. Either of those would sense pressure after the filter.

However, many SBCs in this age range had oil filter adapters to permit connection of external oil cooler lines. In those installations the location is not as certain.

There's a pretty good bet it is sensing pressure after the filter, however.

"

In my case, if the pressure sensor is after the filter, I already know the possibly thicker oil (prior fill may have been 10-40, high mileage GTX) and the tighter filter media, should have lowered the oil pressure, not raised it, on the oil filter outlet side.

So if your bet is correct, then there is a new restriction after the oil pressure sensor or the pressure sensor decided to add 20 lbs to the gauge pressure and lie at the dash gauge right after the oil and filter change, which I find unlikely since it does zero out, and ramps up smoothly with higher rpms. But sensors do go bad, thus the reason for the location question.

[j cAT]

Originally Posted by ecomike

I did not ask what oil to put in it. I asked where the bleep-in oil pressure sensor is plumbed, on the inlet or outlet side of the oil filter. An I do not know is valid answer.

This thread is not about oil type or oil specs, it is a simple question that no one here seems to know. I guess I will need to find it out the hard way.
I did not ask if 70 psi was too high!!!!

your question was answered !

[brcidd]

Why not test it yourself?-- that's what I would do - regardless of the answer I got-- Simply plug the oil port(s) needed and blow air through with ignition on and see what the sensor does when pressurizing different locations- Obviously you have to be a little creative and remove the oil filter and find or make or improvise port taps. Like using rubber inserts or tire valve stems or the like. I would not trust anyone's answer but my own, after I experiment. That way you can prove it to yourself.....

[j cAT]

Originally Posted by brcidd

Why not test it yourself?-- that's what I would do - regardless of the answer I got-- Simply plug the oil port(s) needed and blow air through with ignition on and see what the sensor does when pressurizing different locations- Obviously you have to be a little creative and remove the oil filter and find or make or improvise port taps. Like using rubber inserts or tire valve stems or the like. I would not trust anyone's answer but my own, after I experiment. That way you can prove it to yourself.....

many test oil pressure because it is reading too low.. or no pressure.. simply remove the sensor and put a mechanical pressure gauge ............or if enough room put a T on the port and have both set up now compare both pressures to each other ..

[Tech II]

Wow, this started to get pretty rowdy....guess free info is not appreciated...