1973 T Rebuild - Burning Oil

[pcivalero]

Hi-
I had my engine rebuilt a few years back - and have a few questions. I have an oil leak that drips onto the garage floor. Bothersome, but not too much of a concern. I have asked several times to fix (long story)

My main concern is the following - it SMELLS like it is burning oil. When I get to stop lights I can see a puff of white smoke pass by me. When I park it in the garage after driving it, the whole house will smell like it. I went to a few shops to talk about repainting it and they both said, you are burning oil just from the smell.

QUESTION- does this mean that some seal inside is not set and burning oil? Do I need to ask my mechanic to take it apart again? At first my mechanic says that oil is dripping onto exhaust causing the burn, but I am not so sure... I am NOT mechanically inclined so any advice would be helpful.

Thanks,

[tharbert]

If it were mine, I'd eliminate the easy stuff first. It could be as simple as an oil overfill or a valve cover or thermostat leak: all easy fixes. It sounds like you're dealing with fumes. Unless you see this smoke coming from the exhaust, suspect a leak.

[earossi]

First off, what is your oil consumption for the engine? If recently rebuilt, you should expect well in excess of 1000 miles per quart of oil? If the engine was properly broken in, then you could see consumption as low as a quart every 3000-4000 miles.

Second, 911 engines are known to be "leakers", but usually on an engine that is high mileage. So, if your engine is a recent rebuild and is leaking oil, you should have your mechanic determine the source of the leak. If the leak is due to an improper reseal of the engine case halves, then there is little to be done without a rebuild of the motor. However, if the leak is from any other seals,most of them can be replaced with the engine in the car.

The design of the 911 engine has the exhaust on the very bottom of the motor; so, any oil leak that travels by gravity will more than likely leak onto the hot exhaust system. Vaporization of the oil as it runs over a hot exhaust is producing the smell of which you refer. To eliminate the smell you must fix the oil leaks.

You mentioned "white" smoke in your posting. White smoke is usually due to condensed water vapor boiling off from within your exhaust system. And, white smoke is usually seen on a cold engine start. Once the engine is at temperature, there should not be any evidence of white smoke. If you are burning oil, the characteristic color is "blue", not "white".

Hope that helps.

[pcivalero]

Than you Ernie! When you say If the leak is due to an improper reseal of the engine case halves, then there is little to be done without a rebuild of the motor.

What do you mean by rebuild? Is it not simply taking the halves off and revealing them? I can't imagine it would require a full rebuild?

[earossi]

Splitting the engine case into its two halves is ONLY done during a total engine rebuild. To get down to the point of being able to split the engine case requires that the engine be fully disassembled including removing the induction system, all accessories, the cam carriers, heads, and pistons and cylinders. Once you are down to that point, it is relatively easy to separate the engine case into its two halves.

When you split the case, you are now down to the crankshaft, its bearings, and the intermediate shaft and its bearings, and the oil pump. That is where you go when you are doing a total engine rebuild

The seam that exists between the two case halves is NOT sealed with a gasket. Instead, a thin bead of case sealant is spread over one of the case half seams. Then the cases are "joined" together and bolted up. This sealing of the case halves is a tricky process that can be problematic. The sealant usually has a finite "cure" time. From the time that the sealant is spread on one of the case halves, you have less than an hour to mate the two case halves and to torque up all the mating bolts. Sounds easy, but the process needs to be expedited. In total there are in excess of 20 perimeter bolts and an additional 13 through bolts that need to be assembled and torqued properly and in sequence. The jointing of the case halves is usually best done with two people so that the process can be completed before the sealant "cure " time. Consequently, there is a high probability of experiencing a leak from an improperly sealed case. And, if you do experience a leak along that split line, there is no way to repair it short of tearing the engine down and splitting the case once more.

Please understand that sealing the case is not complicated.....but rather a lot of work that needs to be completed in a very short time window.

Hope that helps.

[pcivalero]

Fantastic reply! Thank you Ernie!