[Vid]

Towards the end of this summer I kept having a minor oil leak somewhere around the oil filter area that dripped right down onto the headers causing annoying smoke and stink. I didn’t really have time to properly investigate the cause so I did a couple of quickie attempts to the primary suspects, making sure the mechanical oil sending line and the warning light sending unit was tight and also the oil filter. All three seemed fine.

Now that I had some time for a closer look, it was the warning light sending unit but not at the threads. It was seeping a bit from the seal where the metal meets the plastic. I’m running an 80 psi pump and apparently it’s too much pressure for what I recall to be an old OE sending unit that I used because it was kicking around in a parts drawer for decades and I thought “Aha! Finally I can use that thing!” I guess I’m lucky it didn’t completely blow apart and cause a real problem.

My question is, who makes a good idiot light type sending unit that can take the pressure? I’m looking at an Auto Meter #3241 that activates the light at 18psi but not sure if it can tolerate the 80psi pump. My gauge usually reads no higher than 75lbs when cold fwiw. What are you using that works?


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[steve25]

It’s not the added oil pressure of the 80 psi pump ( that you likely don’t need any away!) your leak is purely age related .
Expansion and contraction from accumulated heating and cooling cycles will do that.

Folks also tend to tighten them too much which distorts there structure..

Such takes place even with vacuum switches use for example in the water crossover in the front of the motor and they never see more than 20 psi or so.

The factory sender idiot light sender case is made the same way as the 60 psi one.

[Formulajones]

That's just an old sender that needs replaced. Not an oil pressure issue. Every car we own has oil pressure like that with factory senders, they all work fine. Sometimes you just get a dud. Simple fix, just a correct sender for the make and model is all you need.

[george kujanski]

Change that before it blows! I had one that blew while driving uphill in the Black Hills in S. Dakota years ago...oil everywhere. Was able to coast downhill to a small convenience store for oil, and then further to a small garage to get a pipe plug. Replaced the switch later in Rapid City.

George

[Vid]

Thanks everyone. I picked up the new sender today and will drop it in this weekend.
That ought to do the trick.


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[steve25]

Put some Teflon tape on the threads so you do not need to really crank it down to the point of possibility distorting it’s case.

[Dragncar]

Teflon tape does not belong in a engine. Asking for trouble.
Now Permatex pipe dope with Teflon in it, sure.
I piece of Terlon tape could get stuck in your check ball, restricted pushrod hole ect. Not good.

[Bill Hanlon]

Plus the tape (and anything else you might put on the threads) COULD interfere with the sending unit's connection to ground.

[Dragncar]

Originally Posted by Bill Hanlon

Plus the tape (and anything else you might put on the threads) COULD interfere with the sending unit's connection to ground.

Thing is, its tapered pipe threads. You "must" put some sort of sealant on the threads or it will leak. Don't care if its brass into steel you need something on the threads.
Even if its just neverseize the threads can not be dry. And neverseize can seal NPT threads if the pressures you are dealing with is not too high.
Heck, a lot of guys use it to seal head bolts-water jacket on sbc engines.

[mgarblik]

I am using an Echlin {NAPA} oil sending unit in the stock location for the idiot light without an issue. No leaks in 2 years so far. I also have a copper line tied into the same location for my mechanical gage in the car. I have about 105-110 PSI oil pressure on cold start-up. 10W-30 VR1 full synthetic oil. Once up to operating temperature, oil pressure is 25-30 PSI at idle. 40-50 PSI cruising, around 65 PSI@ 5000 RPM. Stock Melling 80 lb. pump.

[Formulajones]

Electric sending units do need a ground to work and that is done by the threads, grounding to the engine.

I have heard of tape sometimes stopping the ground. I have always used a liquid Teflon sealer however and have never had an issue with the ground using that stuff.

[Cardo]

This. https://www.amazon.com/Permatex-5652...2f3bf507c41637

[Sirrotica]

Or go to HD and get more for less money:

https://www.homedepot.com/p/Blue-Mon...6009/306136418

[b-man]

Just replaced my pressure switch yesterday, old one leaking between the plastic and steel parts.

Thin layer of good ol’ teflon tape sealed it right up fine and it still grounds the sender.

Trick is to use thin tape (stretch it thinner if needed) and only wrap it maybe one and a half times around, most importantly wrapping it at least a thread or so away from the end of the fitting so no tape remnants end up inside.

[pont3]

Leaks are a part of the experience of owning an old Pontiac, or any other old vehicle. Get used to it because as soon as you solve one leak another will appear. This is from a fifty year Pontiac owner, and I have ten thousand dollars waiting for anyone who can build me a Pontiac engine that doesn't leak when used as a daily driver.

[Dragncar]

Originally Posted by pont3

Leaks are a part of the experience of owning an old Pontiac, or any other old vehicle. Get used to it because as soon as you solve one leak another will appear. This is from a fifty year Pontiac owner, and I have ten thousand dollars waiting for anyone who can build me a Pontiac engine that doesn't leak when used as a daily driver.

FJ ? Bet he might have one.

[Formulajones]

You would be right dragncar

Someone owes me $10k

I daily my formula and it doesn't leak a drop of anything.

[steve25]

I was not in any way shape or form inferring to putting 4 rap’s of tape on the sender threads, just one is insurance enough to seal yet make the needed ground connection for a electric sender.

[mgarblik]

Originally Posted by Formulajones

You would be right dragncar

Someone owes me $10k

I daily my formula and it doesn't leak a drop of anything.

That is very impressive indeed. You are very skilled with a little luck thrown in for good measure. Pontiac V-8 engines, by design are very difficult to seal up 100%, zero leaks. They have many things working against them vs say a SBC. Many fewer fasteners on the oil pan with much wider spacing. The weird angles of the timing case to block and oil pan with three different metals, aluminum, iron, and sheet metal. A piece of rope for a rear main seal. A giant metal pan with 2 tiny fasteners to hold it in place against a thin flange to an iron head and a weird formed shape at the front and rear. Giant, paper thin valve covers bolted to iron heads with 8" between fasteners. Just to name a few. I love my Pontiacs just like Harley owners love their leaky bikes. But when you do build a leak free Pontiac engine, you have really accomplished something!

BTW, when I worked at the Pontiac dealer as a tech, I was in charge of all the leaks. Drivetrain and passenger compartment intrusion. In one week, I had 13 oil pan and rear main seal R+R's to do for oil leaks. Most of them were under warranty. We had to do them all with the engine in the car. No fun. I had a bunch of 4X4 wood blocks cut to different lengths for A, B,G, and F bodies. Could do a rear main seal and pan in 3-4 hours, 2 a day. Olds 403 was no picnic either.

[PontiacHO]

Originally Posted by b-man

Just replaced my pressure switch yesterday, old one leaking between the plastic and steel parts.

Thin layer of good ol’ teflon tape sealed it right up fine and it still grounds the sender.

Trick is to use thin tape (stretch it thinner if needed) and only wrap it maybe one and a half times around, most importantly wrapping it at least a thread or so away from the end of the fitting so no tape remnants end up inside.

Agree. Ensuring that the tape doesn’t overlap the end. Just on the threads….. Replacement Delco senders used to come with a pre-applied sealer on the threads. I reckon they knew these senders were always going to be a source for a leak. Every oil leak repair that rolled the Chevy dealership were I worked always got a new oil pressure sensor regardless of the source of the leak.