Rear Bumper Oil Spray

I recently rebuilt the engine in my 1955 Century. The car runs great. However after the drive to the National Meet in Portland (about 800 miles round trip), and a recent tour with our local Buick Club chapter (about 720 miles round trip) I have noticed, after each trip, a light film of oil on the rear bumper and the vertical portion of the trunk lid. It seems to be mostly on the passenger side but it does cover the entire bumper.

One member in our local club has a ‘53 Special and says he gets the same thing after a trip and determined it is the oil breather tube that’s causing it. As a kid, I don’t ever remember my father complaining about oil spray on the rear bumper after a trip in our ‘55 Special.

I will add that after each trip I used no oil as measured on the dip stick. I am running Valvoline VR1 Racing 10W-30 motor oil, and have put about 3,000 miles on the engine since the rebuild. I have also noticed a fair amount of oil on the undercarriage of the car. The spray is not red-colored so I have ruled out the transmission.

So, what could be causing this oil spray? Is it the oil breather and that is normal? Is it the rear main seal which still dribbles a bit after I park the car? Am I running too light weight oil? I give up.

Rear main seal.

My wagon sprayed the oil so badly, that I thought it was permanently changing the color of the car.

When I pulled the seal, I noticed that there was actually a quarter inch gap in one of the ropes. Duh, maybe that was it.

I have not had the problem since I installed a new (rope) seal.

Joe

The draft tube can leak oil if the aluminum mesh in the valley cover was dissolved during the cleaning at the machine shop. Or if stopped up, can lead to pressure buildup in the crankcase leading to leaks elsewhere.

Like Mike noted, it is probably the rear main seal. Servicing the valley cover and rear main rope seal is detailed on my website under Low Tech tips. Hopefully a rope seal was installed...if a neoprene lip seal was installed, not so easy.

Driving with it a little low on oil (one and a half quarts low on the dip stick) will lessen the leak on the road. With only 3,000 miles on the engine, I would drive it a little more to be sure no other issues show up.

Also check for leaks further up on the engine: valve covers, oil filter mount, valley cover, distributor, head gasket...

Willie

Willie and Mike, thanks for the information. The more I read your information on possible causes the more I suspect the valley cover. I never tore it apart nor cleaned the inside of it when I rebuilt the engine; I only painted it. One question though, Willie. I read your re-servicing the valley cover on your web site and was wondering if brass Brillo pads would work for the new mesh I would install? Are they too fine or not fine enough? Good idea, bad idea. Just curious.

Thanks again.

Well, I started in 1959 and seen lots of people come to the junkyard looking for used Ford oil pans to replace their rusted ones. That's the story; Ford's are dry and rust, GM cars leak oil from day one and don't rust so bad.

Yesterday I was puttering around with my brand X Packard. I sprayed WD-40 on a paper towel and put a light coat on the metal inside the engine compartment. I do the same thing on my Buicks. Being a GM guy all my life I just figure everything should have a light coat of oil to stop rusting. It is GM's natural protection.

Bernie