 6.0 Diesel engine oil filler cap perforation
I was checking the oil when I happened to notice that the plastic cap that closes the engine oil filler/top up tube was perforated with about 8 holes right through the plastic. The holes are irregular in shape and size with the appearance that they have been eaten through by acid or a squirrel. However, there is no sign of acid burn or any other residue anywhere else, abd the filler cap sits against the hood sound proofing liner when the hood is closed. The rest of the cap is like new; even the "Engine Oi" decal is good. I changed the oil about 1000 miles ago, using recommended oil from NAPA. The cap was fine then.
I have never seen anything like this before in 30 years of home car maintenance. A couple of days ago, the "check engine" light came on. The car had been sitting in the baking sun for several hours. This is when I checked the oil and notined the cap. On finding no other problem, I drove home (few miles) without a problem. After sitting in the garage over night (and cooling), the light did not come on the next morning, but did later in the afternoon. I patched the holes in the cap with aluminum tape. The light has not come on since. I am guessing that a pressure sensor in the emmissions control system that feeds oil/exhaust vapors back round for a second 'burn' had been triggered by a 'low' reading when the cap had holes.
Has anyone seen anything like this before? I will get a new cap as soon as convenient. Can the oil become this acidic after 1000 miles? Is the cap made of a material that degrades after too many hour of high temperature?
The long shot answer could be that it is just a faulty cap and that the temperature out there in the sun (which must have been well ove 100°F under the hood) finally killed it.
I would be intereted to hear from anyone with experience on this.
Clive | 
Hybrid Mode
