Oil Leak

[Sloan66]

I have 71 w/ 307 3OTT with a oile leak. Given the cold I have not had a chance to thoroughly inspect, but wanted to see if anyone had an idea.

I am getting a significant motor oil leak out of the inspection cover of trans. Left a good size puddle last night. The back of oil pan is wet, rear main? or pan gasket?

If it is rear main how hard to change?

[Tx Firefighter]

Sudden onset bad oil leaks are very often the oil pressure gauge fitting on the back top of the block. They run downwards and can mimic a rear main leak.

[scotts72heavyhalf]

give it a good engine degreasing then buy the oil additive that dyes the oil so you can see the leak with a black light, both very cheap and you will have an exact location of your leak and the dye does not hurt the oil or engine. NAPA or O`rileys and auto zone carry them.

[kcsa75]

Originally Posted by Tx Firefighter

Sudden onset bad oil leaks are very often the oil pressure gauge fitting on the back top of the block. They run downwards and can mimic a rear main leak.

Does it need to be replaced or just tightened?

[Tx Firefighter]

Originally Posted by kcsa75

Does it need to be replaced or just tightened?

If its an electric sending unit type like for the dash with oil pressure light rather than gauge, you replace it.

If the truck has oil pressure gauge, its a little copper line that goes from the engine to the back of the gauge. You'd want to look closely at it to see if its cracked or what.

We haven't heard back from the OP yet to see what he found.

[Grumpy old man]

The easiest way to find any type oil /trans leak is to wash the engine down with mineral spirits and once dry use baby powder and sprinkle engine /trans to locate leaks ,this procedure is used daily by aircraft mechanics to quickly find any leak in an engine ... try it ,I really works and is easy to clean off with clear water when done !

[GASoline71]

Lots of variable to oil leaks. Could be the pressure sending unit/line, rear intake manifold valley seal, valve cover gaskets, or the dreaded rear main seal.

However... the ones that come from the top (sending unit, intake, valve covers) can look like a rear main seal leak. Check up top first.

Gary

[Sloan66]

I replaced the oil sending unit, it was leaking. I am still getting a drip from the trans insp cover, but it may be residual oil from the leak. It was 10 degrees when I replaced so to cold for me to do a thorough cleaning. Today is warmer so I will degrease and see if I find anything else. Once again, thanks for all the good info!

[imjeff]

To answer your question about how hard it is to replace the rear main: you may have to lift the motor to get the pan off. After that you can usually roll the upper half of the seal out after removing the rear main cap. They used to sell a corkscrew tool to get ahold of the seal.

[burnin oil]

Originally Posted by imjeff

To answer your question about how hard it is to replace the rear main: you may have to lift the motor to get the pan off. After that you can usually roll the upper half of the seal out after removing the rear main cap. They used to sell a corkscrew tool to get ahold of the seal.

Alot of times this can be done by rotating the motor over until the counter wieght on the crank is out of the way. On the 4X4 the crossmember can be bolted out for easy pan access.

I to have a oil sender leak on the truck. I thought it was the valve cover. I have seen a sender go bad and pump oil out the wiring connector before. Had that happen on a grand am right after rebuilding the engine. Made for a fun WTF on the maiden voyage.