After 23 years of changing oil filters on this engine, three or four times in
the last few years there has been a problem in that the filter doesn't seem to
have sealed properly, and chucked out about a cup-full of oil at first start.
Oiled the new seal as usual, and the filter head was oily anyway. This time
it didn't seal at all. Started up twice and it gushed out. Removed the
filter, everything looked OK. Refitted tighter, tried again, gushed out
again. Tried a new filter and this time it didn't leak, but oil pressure
didn't rise as it should. Checked the dipstick and it was off the bottom,
having been up to Max before, i.e. chucked out a couple of litres or more
previously. Refilled and this time it was OK. These are Mann filters, with a
bypass valve as well as an anti-drainback valve.
What's the direction? I thought it came from the pump out of the back of the
block past the oil gauge tapping, through the cooler, into the filter head
(inverted replaceable cartridge type in my case), up the outside of the
filter, then down through the middle and into the block for the bearings.
This is what Haynes and the Workshop Manual appear to show.
The curious thing is that immediately before oil started gushing out there was
a sort of squeal from the direction of the filter, as if there was high
pressure somewhere, but almost nothing was shown on the gauge. If there was
something wrong with the filter such that it wasn't passing oil i.e. both the
filter was blocked and the bypass failed, surely that should have shown on the
gauge if that's between the pump and the filter? And if the filter was
flowing oil (the middle had plenty in as normal when I took the first
replacement off, and the anti-drainback tube on the filter head) why was so
much pressure apparently developing to blow the seal?
PaulH.
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