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> Oil cap sticking
jmargush
post Apr 7 2025, 05:40 PM
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Has anyone had issues with the oil cap gaskets swelling and making it difficult to unscrew the oil cap?

Are there better sources for the gaskets and O-ring?

The O-ring was so expanded it wasn't really seated in the groove.

And the flat gasket was so swelled that after i got it out I can't get the cap to go back on.Attached Image
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jmargush
post Apr 8 2025, 05:33 AM
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I have seen some posts that there is a different size between 2.0 and 1.8 filler necks.
Does that affect the size of the gasket/seal?

Does anyone know if this is true? can anyone confirm dimensions?
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wonkipop
post Apr 8 2025, 11:19 AM
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QUOTE(jmargush @ Apr 8 2025, 05:33 AM) *

I have seen some posts that there is a different size between 2.0 and 1.8 filler necks.
Does that affect the size of the gasket/seal?

Does anyone know if this is true? can anyone confirm dimensions?


1.8s are L Jetronic. different EFI. the cap is also the PCV Valve/flame arrestor all-in-one for L Jet. quite a different beast to the regular cap on a d jet.

the sizes are not listed in the parts book (PET) - just that there are two, upper and lower.
i'd have to pull the cap off mine to get those sizes and measure with a caliper. which i don't really want to do.

the upper one is a normal kind of o-ring, circular cross section.
the lower one is a flattened cross section and i would call it a thick gasket rather than an o-ring. the cap compresses down on it. whereas the upper is a side sealing situation of cap to tube. the reason for the two seals is that the cap allows engine fumes to channel to the hose connected to inlet plenum via the space between the cap and the filler tube.

i made a sketch of it once when we were doing our L jet research. and it is a sketchy sketch. (IMG:style_emoticons/default/biggrin.gif)

Attached Image

however it does tell you there is one another place these caps can fail besides the two ring seals. there is a diaphram in the top of the cap that allows the fumes to channel or seals the passage off depending on engine vacuum. and if the diaphram fails then you have another source of air leak in an L Jet. given the age of these cars its on the cards these days.

so an l jet oil cap really has three seals.
the diaphram is the hard one to repair.
you would have to pull the upper cap apart to get at it.
and then try and find a hydrocarbon resistant diaphram to replace with.
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