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Oil pressure sending switch


Okiegirl

Question

We have a 2004 Chevy Silverado with the 5.3 Vortec engine. We are not the original owners.

 

We are on the 5th or 6th...really I lost count...oil pressure sending switch. All replacements have been aluminum bases. Last few have been torqued to 15 ft-lbs. We are replacing it yet again, this time we are getting a brass base and torquing it to 15 ft-lbs. They all work great for a few weeks and then they fail or blow up sending oil all over the engine and engine compartment and the pressure to zero. It has never completely run out of oil, the tip of the dip stick still has oil on it when this happens. We limp it back home, making sure to stop and check the oil often.

 

Please advise on why they keep failing and/or what to look at for other issues that may be contributing to their failure.

 

Thank you

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Are you applying Teflon tape to the threads prior to installing?  Teflon tape is not to prevent leaks, it is to lubricate the tapered threads.  

You may want to put a mechanical oil pressure gauge on it to see what the oil pressure actually is.  

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1 hour ago, starman8tdc said:

I keep hearing about a clogged oil screen, that can be removed and cleaned. It is accessed by removing the sender, and pulling the screen out with a hook?

Not on an '04. Starts with the 900 series AFM.

 

I would wonder if OP is damaging it while installing. Crack that plastic and you're done. 22 ft lbs is spec so at 15 you're not overdoing it

Edited by txab
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9 hours ago, starman8tdc said:

Ya might take a look at the electrical connector, and wiring. You could also test the "bad" sensors in another truck. 

It would be far easier to simply test the oil pressure with a mechanical gauge.  That being said, OP has said he has replaced the sensor multiple times already.  He is also changing them due to leaking oil to the point that the pressure sensing portion inside the sending unit is on the wrong side of the leak and is reporting very low or zero oil pressure. 

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After re-reading, yep - its not a wiring issue if the senders are blowing up. 

 

I agree that a mechanical gauge is a great place to start.

 

I would also make sure that the oil does not smell like fuel, that it is the correct weight, and that its at the proper level. 

 

I wonder if his oil pressure is too high, fuel in the oil, over tightening them, cheap knock off sensors?

 

 

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My guess would be all the sensors have been purchased at the location.  He should get one from the dealers parts department. And if he has been getting them from the same dealer, go to a different dealer.  This sounds more like counterfeit parts.  In the last 40 years I can count the number of oil pressure sensors that leaked bad enough to impact pressure readings on the in dash gauge on one hand, and everyone one of them were the OP's. 

If it's oil pressure causing this, then it is for sure counterfeit sensors.  If the oil pressure is high enough to blow an authentic sensor you would see an enlarged oil filter as well.  It also would have pegged the in dash gauge. 

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21 hours ago, Doug_Scott said:

Are you applying Teflon tape to the threads prior to installing?  Teflon tape is not to prevent leaks, it is to lubricate the tapered threads.  

You may want to put a mechanical oil pressure gauge on it to see what the oil pressure actually is.  

No my son has not used teflon tape on the threads. The first one, that came in the truck, did not have it so I don't think he thought to use it.

21 hours ago, tbarn said:

What is the oil pressure before failure?

Hangs around 40 when driving. He actually left his truck with me today as he was taking a trip and didn't want to worry about breaking down. So when I drove it I watched the gauge.

 

7 hours ago, starman8tdc said:

After re-reading, yep - its not a wiring issue if the senders are blowing up. 

 

I agree that a mechanical gauge is a great place to start.

 

I would also make sure that the oil does not smell like fuel, that it is the correct weight, and that its at the proper level. 

 

I wonder if his oil pressure is too high, fuel in the oil, over tightening them, cheap knock off sensors?

 

 

My son went to a tech college for auto technician and is working is way up to technician at a local repair shop. I will have him check the pressure with a mechanical gauge at work, along with checking for fuel smell. He keeps it at the proper level and weight.

 

28 minutes ago, Doug_Scott said:

My guess would be all the sensors have been purchased at the location.  He should get one from the dealers parts department. And if he has been getting them from the same dealer, go to a different dealer.  This sounds more like counterfeit parts.  In the last 40 years I can count the number of oil pressure sensors that leaked bad enough to impact pressure readings on the in dash gauge on one hand, and everyone one of them were the OP's. 

If it's oil pressure causing this, then it is for sure counterfeit sensors.  If the oil pressure is high enough to blow an authentic sensor you would see an enlarged oil filter as well.  It also would have pegged the in dash gauge. 

2 sensors were purchased at O'Reilly, 2 at Napa and this last one at Advance. He did not say it pegged on the dash gauge. I know he watches it for obvious reasons. 

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Since he is not the first owner...could the previous owner made mods to the truck to change the oil pressure?

 

We know it's a good motor, we're just baffled as to why the oil pressure sensor keeps blowing.

 

I found a Corvette forum (same motor) where they were talking about the same issue. It was suggested to the lady on there to get a brass base sensor and tighten it to 15 ft-lbs. Do any of you think that a brass base would be better than the aluminum ones?

Edited by Okiegirl
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With the old sensor in place:

 

1)  Soak the whole area in brake cleaner. Scrub the block around the sensor with wire brush. Rinse with brake cleaner. 

2)  Repeat step 1. 

3)  Allow to dry for 1 hour. 

4)  Install new sensor while wearing gloves (to keep skin oil off of parts and block). 

5)  Put "gasket maker" in a circle all the way around the sensor on the block, extending out 2 inches, and 1/4"  thick. 

6)  Completely coat the entire sensor in 1/4" of gasket maker, extending up 1" of the wire. 

7)  Allow to dry for 24 hours. 

 

 

It will NEVER leak again. If the part fails to report proper readings, you can cut around it with a razor knife for easy removal. 

 

You must use ONLY this specific gasket maker. It is extremely strong, and adheres to clean surfaces better than any other product: 

 

 

 

 

 

 

permatex-right-stuff-brochure-320125_1b.jpg

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44 minutes ago, starman8tdc said:

With the old sensor in place:

 

1)  Soak the whole area in brake cleaner. Scrub the block around the sensor with wire brush. Rinse with brake cleaner. 

2)  Repeat step 1. 

3)  Allow to dry for 1 hour. 

4)  Install new sensor while wearing gloves (to keep skin oil off of parts and block). 

5)  Put "gasket maker" in a circle all the way around the sensor on the block, extending out 2 inches, and 1/4"  thick. 

6)  Completely coat the entire sensor in 1/4" of gasket maker, extending up 1" of the wire. 

7)  Allow to dry for 24 hours. 

 

 

It will NEVER leak again. If the part fails to report proper readings, you can cut around it with a razor knife for easy removal. 

 

You must use ONLY this specific gasket maker. It is extremely strong, and adheres to clean surfaces better than any other product: 

 

 

 

 

 

 

permatex-right-stuff-brochure-320125_1b.jpg

That's a good idea, if it were leaking. It is blowing...every time it has gone out or blows it sprays oil all over the engine and engine compartment. :-(

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34 minutes ago, Okiegirl said:

That's a good idea, if it were leaking. It is blowing...every time it has gone out or blows it sprays oil all over the engine and engine compartment. :-(

I have a hard time believing his post was even serious.  

Get a new sender from the dealer.  Use Teflon tape on the threads, your son should have been taught how to apply it correctly. You want to wrap the tape around the threads in a clockwise direction when the threaded end is facing you. Wrap 3 complete turns, pulling the tape tight as you wrap it. It needs to start at the first thread and wrap up the threads.  Teflon paste is another option. Ignore the post suggesting permatex, or any other of his suggestions. 

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2 hours ago, Okiegirl said:

Since he is not the first owner...could the previous owner made mods to the truck to change the oil pressure?

Not to the point of breaking a oil pressure sensor. Take a look at the oil filter, if it appears to be bulging then you likely have an oil pressure issue. It is still same shape as a new one then you do not have an oil pressure issue. 

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