1987 R10 oil pressure switch location/leaking

[rcotner]

I have a 1987 R10 Chevy with a 305 ci. Just noticed an oil leak on what appears to be some type of oil sending unit or switch near the oil filter. Does anyone know what the exact terminology is of this part so that I can get the proper part to fix it? I see other threads state there are 2 of these switches/sensors. I understand the other one to be behind the manifold near the distributor.

 

[Jgonick]

Just throwing this out there. Possibly it's the knock sensor.

 

[Rusty Nail]

The knock sensor is on the passenger side on the block.

Yea that is the oil pressure safety switch -it runs the light... it may be called??
The pressure reading comes from the part next to the distributor.

It splits at the seam.. no biggie. Good eye. Might consider changing them both at the same time. Buy from a parts store - not online.

 

[Redfish]

Sorry, wrong answers all around. Except for the knock sensor. It is indeed on the block on the passenger's side.

The sending unit near the oil filter is for the oil pressure gauge. It will have a single wire attached.

The switch under the distributor is a backup to the fuel pump relay circuit. It has a plug with two wires. If the fuel pump relay circuit does not work for some reason, that switch will still allow current to pass to the electric fuel pump.

 

[rcotner]

Redfish, I think you have answered my question. It is near the oil filter and does have 1 wire attached to it. Mine is threaded into a tube looking part maybe 2-3 inches long. Off topic, but is the sending unit standard right hand thread or left handed? I put a 9/16” wrench on it this evening and could get it to turn. Got scared as I didn’t want to risk breaking that tube sticking out from the side of the block. Any thoughts?

 

[Redfish]

Redfish, I think you have answered my question. It is near the oil filter and does have 1 wire attached to it. Mine is threaded into a tube looking part maybe 2-3 inches long. Off topic, but is the sending unit standard right hand thread or left handed? I put a 9/16” wrench on it this evening and could get it to turn. Got scared as I didn’t want to risk breaking that tube sticking out from the side of the block. Any thoughts?

Regular right hand threads. I know for a fact because I have replaced the switch, the sending unit, and the knock sensor on my '87.

The switch, located under the distributor is on a rather delicate brass piping assembly that can easily be broken off leaving the threaded part inside the motor. I know this because I made that stupid move too.


The Oil Pressure Sending Unit (for the gauge):

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This is the switch, below and behind the distributor. It is on a piece of pipe I had to piece together from the hardware store...

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[rcotner]

Yes sir thats it. Maybe try again tomorrow with a longer wrench for better leverage.

 

[Ricko1966]

Well there seems to be some confusion,I've always seen the O.P. sender located behind the distributor,and just yesterday or so somebody wrote about how they relocated theirs from behind the distributor to the port above the oil filter,and what fittings they used. So if redfish truck came that way from the factory,then we all need to take note that they are not always behind the distributor.

 

[Maknwine]

While this discussion is going on, should the two pipes that thread into the block have thread sealant on them? I dont recall seeing a torque spec on them either but my thinking is that they should be tightened to really snug but not crazy snug.

 

[Rusty Nail]

I shy away from thread tape and opt for something called Permatex brush on gasket sealer.

But I may be wrong.

 

[Maknwine]

That's what I was thinking...I have permatex thread sealant in a tube.

 

[Ricko1966]

While this discussion is going on, should the two pipes that thread into the block have thread sealant on them? I dont recall seeing a torque spec on them either but my thinking is that they should be tightened to really snug but not crazy snug.

There isn't a torque spec, it's tapered that's what makes the seal. If you over tighten it that's bad, it can cause cracks. Threads should be dry, that switch has to ground through the threads. Look up national pipe thread on Google. I forget what the taper is I think it's 1 /16 inch taper per inch of thread anyway it acts like a wedge,too tight damages things. There is a spec but it's not torque,it is x number of turns past hand tight I go snug plus barely any it's a judgement call.

 

[Redfish]

I second @Ricko1966 on the tapered threads. The new sending unit will have a small amount of dry sealant painted on the threads. It's usually a dull red color. The sending unit has to ground through the engine, it is a single wire system.

I did apply teflon tape to the threads on the switch...but that carries risks. If some of that tape were to get washed into the oil system...

 

[Ricko1966]

I found a rule of thumb spec for you better than my snug plus barely any description I gave you 2 posts back.