Oil Leak at rear of Engine & Top of tranny

[DaleG]

I have a 1998 Silverado 2500 with a 7.4L with 158K miles. Original engine and tranny.
I have developed a bad oil leak that comes from the back of the engine and TOP of the transmission.
I can't see back there to see where it comes from... BUT
With everything clean, and viewing from underneath, I start the engine. Everything looks fine for approx. 1 minute and the the oils starts to leak down the drivers side of the tranny where the trans bolts to the engine. It is not a slow drip, drip... but a steady flow. It seems to come from high on the tranny, above the rear main. But that's just my uneducated guess. The leak comes down the tranny and off the bell housing cover at about a drip/sec.
BUT then, if I take it out and drive for roughly 10 miles and then check it while still running. It appears as if the leak has stopped????
Any help or ideas would be greatly appreciated.

 

[stutaeng]

Engine oil pressure sender? Is that back there also on the BBC Vortec?

 

[someotherguy]

Engine oil pressure sender? Is that back there also on the BBC Vortec?

That is indeed where it sits. At least on my (former) '96 Vortec 7.4, it is aimed straight up out of the rear of the block on the driver side, just ahead and above the transmission bellhousing. Good place to start looking for the leak source.

Richard

 

[DaleG]

Wow... I can ALMOST see where you mean. I can see the back side of it from underneath the truck. And yes, it is oily. Do you know if it can be replace from the top side if the Distributor and Intake Manifold is pulled?

 

[Matt98]

Wow... I can ALMOST see where you mean. I can see the back side of it from underneath the truck. And yes, it is oily. Do you know if it can be replace from the top side if the Distributor and Intake Manifold is pulled?

You don't have to pull anything, you just need an oil pressure socket. I swapped mine last week it was slightly tight of an area but the only thing I took off was the air intake. It's threaded into an elbow. I used a flex head ratchet with the socket and it took me maybe 5 minutes to change.

EDIT: I didn't notice you said 7.4 it may be slightly different.

 

[stutaeng]

I happen to have a 4.3 Vortec block in my garage, but you can see that right adapter. The sender was removed after I had removed the intake manifold.

With the engine in the vehicle it's kinda tight back there though. You need a special socket to remove the sender. When I changed the sender while engine was on the truck I also used a flex head ratchet. 1/4" ratchet with a 1/4x3/8 adapter worked for me. Just removed the distributor cap.

 

[DaleG]

I just wanted to follow up on this, and give thanks to you guys.
Matt98, Stataeng & Someotherguy... Thanks for your help. It was the Oil Pressure Sensor, Replaced and no leaks... Yay. Although Matt98, on a 7.4L... it took longer than 5 minutes. At least for me.
Thanks again guys.

 

[someotherguy]

I just wanted to follow up on this, and give thanks to you guys.
Matt98, Stataeng & Someotherguy... Thanks for your help. It was the Oil Pressure Sensor, Replaced and no leaks... Yay. Although Matt98, on a 7.4L... it took longer than 5 minutes. At least for me.
Thanks again guys.

Since my site is no longer, it took me a minute to dig up the files, so now that you've done the job already here's a clear view of the oil pressure sender on the Vortec 7.4 ... possibly help others searcing in the future, anyway:

You must be registered for see images attach

Richard