Buick v6 oil leak advice

So I drove my even fired Buick :v6: powered 49 CJ3A to Glamis, CA round trip from Peoria (northern Phoenix), an it did pretty well. One issue that popped up is making me wonder and I hope someone with more Buick :v6: experience could help.


Somewhere along the way it developed an oil leak that is strange to me. It seems to be mostly leaking from the back of the motor (but there was some oil puddled next to the distributor). It lost maybe a quart or a quart and a half of oil one way on the trip (~ 180 miles? I think)

The thing is is only seems to leak a lot when driven i.e. when the engine is revving and warm. When its parked there is very little oil leaking, just the oil that has splattered around the engine compartment/drive train that drips off. It also did not leak nearly as much when I drove it around town before leaving on this trip.

I parked it over night at glamis both nights, and there was almost no additional oil under the jeep either morning.

Any ways I think the suspects are:

1)Rear main seal (but why doesn't it leak when sitting)?

2)The dipstick? there seems to be a small amount of oil leaking from the block where the dip stick tube fits in when the jeep is sitting (can someone tell me about how to seal this up). Also the dipstick does not have any kind of gasket or o-ring where the dipstick goes in the dipstick tubecan I get a factory seal for this area, or new dipstick?). I have used some inner tube rubber to seal this up, and I think its pretty tight, but It was probably related to the initial leaking because first I tried to seal it up with a piece of hose (it did not work very well and there was lots of blow-by because the hose fell out).

3)maybe some oil leaks from the valve cover gaskets, but it does not look like much?

Any ways if any of you have any ideas of an oil leak that could occur during driving (~2500 rpm (60-65mph) on the high way, and occasional higher revving in the dunes) I would greatly appreciate it.

 

Check and make sure the PCV valve is working correctly. They are on the back passenger corner on the intake manifold pushed into a rubber grommet on a 231. If this is plugged with carbon (common) it can cause crank case pressure to build up and force oil out the breathers, dipstick tube, various seals and gaskets.
The rear main seal normally will not leak at rest as the oil level is below the crank and when not running the system is not pressurized forcing the oil against the seal.

 

Awesome will do! So I should change the PCV and if it still leaks prepare myself for the rear main seal replacement?

 

I'd change the pcv valve, they're cheap and it's good piece of mind. Before diving into the rear main I'd double check that the leak isn't coming from above somewhere and running down and making it look like the main seal. Intake manifold, valve covers leaking, etc. can give the illusion of the rear main leaking. If everything above is dry and not leaking and engine oil, not transmission oil is coming from the bellhousing area then I would suspect the rear main. The stock rear main is a rope type seal. There is a neoprene seal upgrade that I highly recommend doing if you're diving in this far. Got mine from Napa years ago, but don't remember the part #'s.

 

Thanks again. Any advice on the dip stick situation.

 

as mentioned, sounds like a crankcase breathing problem to me as well.
make sure the pcv system is functioning.
then clean and try it out again.
new gaskets and seals won't stop a crankcase breathing problem.
if the problem persists, then a cylinder leakdown test may be in order.
anyway, what Nick said; good advice.
the dipstick problem will cease once the breathing problem is solved.
path of least resistance......

 

Awesome flatty. Glamis is my back yard, gimme a holler next time.

I have a similar issue. If/when I figure mine out I'll try to remember to post up here.

 

Congrats on the trip and nice flatty for sure. Conquering 360 miles on the road in a flatty is an accomplishment to say the least.

Sounds like PCV to me also. I wouldn't worry about the rear main seal at all.

 

thanks guys! well I pulled the PCV and while it is not a thing of beauty it does rattle, and some air will move through it. I am sure that that is not a scientific test of its function, and I will replace it today for sure.

I guess the idea is that if there is some leaking around the pistons then it could be forcing the oil out?

thanks

 

Oooh, your engine is toast. We'll have to put your L-head back in!


Put a baggie over the carb and distributor and spray it down with some oil eater (whatever kind you like) and rinse it off so you can better tell where the oil is coming from.

I'd think upper end of the engine like the rear of the intake manifold gasket or rear corners of the valve cover. Around town you're hitting higher rpms, then backing down. It gives the oil a chance to drain back to the bottom end. At highway speeds, more oil stays up top in the rocker/lifter/camshaft galleys. That's one of the reasons racers will port/smooth the oil drain return passages on the top end and install oil restrictors on the bottom end - keep that oil downstairs.

The rear main seal isn't impossible to replace, but the intake manifold removal/reseal is a little easier for me. My money is on the intake or valve cover gaskets. Rear main seal would be a distant "third" for my guess. If it's the rear valley gasket on the intake, toss the rubber replacement gasket that'll come with the kit and use a 1/4-inch bead of silicone. There's a thread about it already somewhere here recently.

Bummed I couldn't make it out there, but a day-trip was my only option and all I had rolling was the 4-cyl YJ. Would've been a long day of driving/wheeling for the 2 older boys.

 

Christian,
you were missed but I understand.

Will do. I am not afraid to replace any and all gaskets....but I am lazy.

I think its prolly the rear main seal, but I know oil is coming out the dipstick unless I seal it of a bit.

 

If it's coming all the way out the dipstick tube, then Nickmil nailed the diagnosis. More'n likely it's the PCV.

 

yea John said the same thing and I hope thats it!

 

Love your flattie! Not sure what you mean by full breather? Can you show me a picture or elaborate a little. Thanks!

 

Full Breather: Pop out the PCV and grommet and nab a cheapie open breather with a foam, gauze, etc filter. These aren't cheap, but you get the idea:



Engine for my M-715.

 

Oh! Oopse!
I already have one of these on the PS valve cover ( I think its a Mr Gasket?)...I just ran a connector hose from it to the bottom of the air filter.

The PCV is stuck in the intake manifold behind the carburetor flange and slightly to the PS.

I got a new PCV valve and some new valve cover gaskets. The guy at the parts store told me to make sure the oil return holes at the front and rear of each head were not blocked with gunk. I tried, but these return holes only seem to be a couple inches deep before a right angle turn or something. I looked with a light and it looks like the holes in the head don't match the holes in the block so well...??? (he said he had a 65 CJ5 with a 225 (Cool!))

Either-way I have to wait for some header gaskets from summit to arrive. I was running exhaust manifold gaskets. (I did not realize that there was a difference)

 

Yea, I was running around 30psi on the highway at 60-65 mph.

 

Just food for thought.
I had a shiny new breather but didnt notice it had a plug in it that had to be punched out.
Had the exact symptoms you have until I found it.