1998 Honda Accord 4-cyl Allen Head Bolt Under Oil Filter - what is it?

Thanks in advance for any answers on this.

I have a 1998 Honda Accord DX, and I accidentally removed the Allen Head
Bolt underneath the oil filter on the rear of the engine. The reason that I
did this is that I mistook it for the coolant drain (the Honda shop manual
shows an ordinary hex-head bolt at that location on page 10-10 under the
heading "Coolant Replacement"). A little reading of past posts on this
newsgroup shows that the coolant drain is higher on the block and next to
the oil filter.

Since this is a common confusion, a number of posts have been made on the
topic of find the coolant drain in the block, and one poster noted that this
is the oil pressure relief valve cover and has a spring and ball behind it.
Another poster stated that this is the rear balancer shaft alignment hole.
I did not see a spring come out of it, but I was on my back and the Allen
head bolt did seem to have some tension on it. A small amount (2 - 3
tablespoons) of oil drained out of the hole.

My concern is that I might have lost the spring if this is the oil pressure
relief valve.

The only thing that I found in the shop manual about an oil pressure relief
valve is one in the oil pump housing itself (shop manual page 8-7). As far
as the rear balancer shaft alignment hole goes, on page 7-19, the manual
shows a "maintenance hole" with an ordinary hex headed bolt on it, but it is
closer to the timing belt end of the engine. The engine lubrication diagram
on page 8-3 does not point out the hex headed bolt, although it appears in
the drawing (without the allen head on it).

Any replies to the group/and or directly are appreciated!

Thanks,

Allan


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