Lost Oil Filler Cap
10-03-2013, 09:45 AM
#11
Join Date: Nov 2012
Location: Kitchener, ON
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10-03-2013, 09:56 AM
#12
With the oem oil caps there is a thin rubber gasket/ring under the cap with an elevated center rib to help provide grip to the valvecover. Over time the elevated part of the gasket wears smooth and it doesn't give any resistance to the valvecover. So if the cap isn't real tight it will back off due to vibrations. Given the age of our cars I imagine many oem oil caps are like that now, mine was like that when I bought my car, so I ended up putting on a new cap . It is a very subtle part of the oem oil cap, you don't really notice unless you sit there and give it a close look. They show that rubber gasket/ring as a replaceable part on some of the on-line parts dealers.
10-03-2013, 10:02 AM
#13
Originally Posted by myflys2k' timestamp='1380822068' post='22809390
Yeah threads look good. That was my first thought. Maybe crank pressure from the boost popped it off but there are plenty of other hoses that would have come off before hand.
10-03-2013, 10:16 AM
#14
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When I went out to the track a couple years back, I went with a neighbour who owned an S2000 and this happened to him as well. He said his mechanic always reefs on the oil fill cap so he has no idea how it came loose. Maybe the engine runs so hot that the degree of thermal expansion between the plastic and the head is large enough to untighten a tightened oil cap?
Time to invest in some aluminum oil fil caps me thinks.
Time to invest in some aluminum oil fil caps me thinks.
10-03-2013, 02:27 PM
#18
With a good condition oem oil cap you will feel resistance as the cap screws down. The rubber gasket is kind of like a locking washer design, it keeps constant pressure on the cap. With a worn oem oil cap rubber seal it just bottoms out without any resistance on the cap, and then it backs off with vibrations of the motor. The rubber seal part of the oil cap is key to keeping it tight.
10-03-2013, 02:32 PM
#19
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With the oem oil caps there is a thin rubber gasket/ring under the cap with an elevated center to help provide grip to the valvecover, over time the elevated part of the gasket wears smooth and it doesn't give any resistance to the valvecover. So if the cap isn't real tight it will back off due to vibrations. Given the age of our cars I imagine many oem oil caps are like that now, mine was like that when I bought my car, so I ended up putting on a new cap though they show that rubber gasket/ring as a replaceable part on some of the on-line parts dealers.