Oil Leak - I Screwed Something Up.

[dklawson]

My son borrowed the GT6 today to go out with his girlfriend. When he got home he told me that for the last part of the drive the car was smoking. I expected to find blue or white smoke coming out the exhaust but it came from under the car. It looks like a catastrophic failure of the rear main seal. Probably 1/2 cup of oil in a minute or two of idling.

This is the engine I rebuilt a year ago and there are hardly any miles on it. I know I have done something wrong. I got as far as slipping the gearbox off the engine before the sun went down. I hope to get the flywheel and blackplate off tomorrow to see what is wrong. I'll post back with my findings.

Sympathy and advice is welcome.

Doug

 

[philstr6]

Doug
there is also the cam plug or the oil galley allen screw in the back of the block and the top bolt that needs a cooper washer in the oil seal housing
Philstr6
Phil

 

[DNK]

Might not be your fault Doug.
Maybe it was a bad seal to start with

 

[dklawson]

Obviously I was thinking about this last night after quitting for the day. The early 6-cylinders before the GT6 used a scroll seal instead of a lip type shaft seal and they did not have bad oil leaks when blow-by was "normal". Therefore, I am thinking along the lines of what Phil was suggesting that I did not get a galley plug in correctly. The volume of the oil on the driveway is much larger than can be explained by a shaft seal... it's more like the oil was being pumped out.

It is supposed to be warm this afternoon so my plans are to finish removing some rear engine parts, degrease them, and maybe put the flywheel and starter back so I can turn the engine over to better identify where the leak is. I'll post more as I figure it out.

Thanks for the comments and suggestions.

 

[DNK]

We like videos ,Doug

 

[dklawson]

There was no point in taking a video of what I found and even the pictures I took are not worth posting. All they would show is an oil soaked back plate.

When I got the back plate off the engine it was bone dry on the engine side. However, there was one spot that was soaked with oil, the 1/2-20 threaded galley plug. For some reason the back plate has a clearance hole right over the galley plug that was leaking so all the oil just pumped through that hole to the gearbox side. I pulled the distributor and ran the oil pump on a drill to confirm that the galley plug was the problem.

When I rebuilt the engine I gooped the plug up with Permatex but it looks like I forgot to run it all the way down until its thread really seated. The gasket compound had been washed out and the oil was coming around the threads.

I went overkill putting this back together today. I made a 1/2-20 socket plug, wrapped it with Teflon tape and ran it all the way in until it bottomed out. That left about 1/2" up to to the back of the block. So... I made a second plug, this one with a flange and a gland for an o-ring. I countersunk the back of the block just enough to create a seat for the o-ring and place the plug's flange below flush. I know I shouldn't need to do this but I really don't want to pull the gearbox again if I don't have to.

 

[philstr6]

Doug
did you run your drill to ck to see if it was still leaking,after you put the plug in,I just did a motor and the machine shop said it was 1/4-18 pipe thread,Im going to go look to confirm,you might want to ck that out also
Phil

 

[dklawson]

The plug I took out was straight, not tapered so I assumed it was not a pipe thread and the pitch I measured was 20 TPI. This is not the original block that was in the car so maybe someone "altered" it at some point. A pipe plug would have been much easier to deal with than the plugs I made.

I will run the oil pump again before putting the transmission back in place. It will be a while before this car is back on the road. I tore a gearbox mount pulling the transmission and had to order replacements so I have plenty of time to check for leaks using the drill.

 

[dklawson]

Phil,

I went ahead and pulled my homemade plugs out and chased the threads with the NPT tap loaded with grease. It went in VERY easily and didn't seem to cut at all, confirming your observation that it was a pipe tap.


When I went looking for my stash of parts I remember now why I thought the threads were straight. What came out during the rebuild was destroyed. The replacement I ordered was not a properly formed/complete plug. It did not have a screwdriver slot or internal hex to drive it and the threads were not formed right.


This time I put in a hex socket 1/4" pipe plug. I ran the oil pump on a drill for about 2 minutes and no oil came out of the galley plug so I continued to re-assemble the bits that came off.


Thanks for letting me know about the pipe thread.


Doug L.