View Full Version : Missing Oil

06-28-2005, 01:57 AM
After about a 225 mile drive this weekend, I found that I was about 1/2 qt. low in motor oil. I checked the normal leaking points, front seal, rear seal, oil filter adapter, pressure transmitter, etc. pressure guage, etc. There was a small amount on the oil pan, but it seemed to be leaking around the drain plug and not enoiugh to be missing 1/2 qt.

I checked beneath the car rear of the engine and found nothing to speak of, well, no indication that 1/2 qt had leaked out...well that missing oil has to go somewhere.

Since I do not have the crankcase breather valve and the hoses from the valve cover connect both carbs and the charcoal canister, I think that it may be passing the oil through the carbs. I would suspect that misting oil vapors could be drawn by vacuum into and through the carbs. I checked the plugs and they appear normal - no carbon build-up. I checked compression, 150-160 psi across all 6 cylinders (warm, but not hot).

Can you blow/burn 1/2 qt of oil and not foul plugs?

BTW: The car ran perfectly all day, did not overheat even though 90-93 degree day, no missing, no smoke (would think if oil is passing thorough carbs there would be some smoking)and the drive included small town stopping and Hwy speeds.

Anyone have a an idea?

06-28-2005, 07:52 AM
Hey Dugger,
These motors do use oil, although a 1/2 quart in 250 miles would be high. Even if the plugs show no sign , the tail pipe might.
Is it possible that your first reading was not accurate because not all the oil had time to drop to the pan , or you just did an oil change & the filter hadn't held (about a half qt) the fresh oil.
Before you make yourself nuts I would keep monitoring your readings & check for smoke on acceloration & startup, if you don't see any obvious signs, then enjoy!

06-28-2005, 09:54 AM
In addition to the small amount your car is using to mark it's territory (they really don't leak /ubbthreads/images/graemlins/wink.gif), the long drive may have allowed the motor to evaporate any moisture or other chemicals that had accumulated in the oil.

06-28-2005, 11:06 AM
Thanks for the info. I might be just a little over protective. I don't mind throwing a qt in her every once in a while, besides if something is amiss, it will eventually show its ugly head and then all the unknowns will evaporate along with the bank account.

Andy Blackley
06-28-2005, 02:36 PM
Dugger: I would concur with your conclusion. I had a 69 MGB with a similar PCV setup (through the carbs) and oil use would rise dramaticly when driven at freeway speeds for any length of time. At higher rpms, and with some blow by from a "well seasoned" engine, the crankcase pressures seemed to rise quite a bit. It never, ever smoked either, but would use 1 qt. per 600 miles in normal driving. It leaked from the front seal too.
There is some oil burning going on to be sure, but at a rate too small to see. Try having your wife drive the car and follow her. You may be able to smell it.

06-28-2005, 04:03 PM
My wife...drive the TR6 surely you jest????