Subject: [Mgs] MGB oil filters and flow direction

From: "PaulHunt73" <[email-masked]>
Date: Sat, 13 Apr 2013 15:39:57 +0100

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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From: <[email-masked]>
Date: Sat, 13 Apr 2013 11:24:13 -0400

----- Original Message ----- 
From: <[email-masked]>
To: "PaulHunt73" <[email-masked]>
Sent: Saturday, April 13, 2013 11:19 AM
Subject: Re: [Mgs] MGB oil filters and flow direction

> Paul: I recently lost an entire crankcase of oil similar to what you 
> describe. Then I proceeded to lose another 5 quarts when I discovered that 
> the O ring from the  old filter had ahdered itself to the filter housing 
> and when I screwed the new filter on I had two O rings where there should 
> only have been one thus crating the oil leak. It was a costly lesson but 
> one I will never repeat. Check to make certain the old filter O ring  came 
> off with the old filter.
> Frank Krajewski
> ----- Original Message ----- 
> From: "PaulHunt73" <[email-masked]>
> To: <[email-masked]>; <[email-masked]>
> Sent: Saturday, April 13, 2013 10:39 AM
> Subject: [Mgs] MGB oil filters and flow direction
>
>

[email-masked]

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From: Barney Gaylord <[email-masked]>
Date: Sat, 13 Apr 2013 19:06:54 -0500

Paul, -- You have the flow path right, but the gauge pressure tap is 
wrong.  The gauge port is not directly connected to the large 
outletport at the RR corner of the block.  The outlet fitting at this 
point has an extended tube inside the block that isolates the outlet 
port from the gauge port.  The gauge port is at the back end of the 
main oil gallery in the block, downstreanm from the filter.  The 
gauge will register oil pressure as presented to the crankshaft main 
bearings.  If the oil filter is clogged or leaking badly, it is 
possible to have god oil pressure before the filter, and poor 
pressure shoeing on the gauge (insufficient oil to the crankshaft).

See notes and picture 3/4 down the page here:
http://mgaguru.com/mgtech/engine/of101.htm

A few pages to follow have more information on oil flow path, oil 
gallery drillings, port plugs, and either excess or deficient oil 
pressure issues.

It sounds like you have run across some faulty oil filters blocking 
the flow.  Since the pressure relief valve comes before the filter, I 
have no idea why they leak.  Could be a bad filter base seal ,or 
perhaps a faulty female thread teh prevents the filter from screwing 
on all the way.  I recently ran across an incomplete thread like that 
in a NAPA Gold (WIX) oil filter (just one in a lifetime).

Barney Gaylord
1958 MGA with an attitude
http://MGAguru.com

At 03:39 PM 4/13/2013 +0100, PaulHunt73 wrote:
>.... 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. .... This time 
>it didn't seal at all.  .... 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 .... up the outside of the filter, then down 
>through the middle and into the block for the bearings.
>....
>
>.... 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?  ....
>....

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