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Old 06-09-2017, 05:49 PM
pmac pmac is offline
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Oil pressure relief valve.

Over time the spring pressure can decrease on the ball bearing.
Tim and me were not happy with the function of the one in the L28 we are currently building.
Direct replacement is one option
A quick phone call to Mr F soon produced a replacement item.
I was a little concerned about ease/difficulty of removing the old unit.
Fortunately my trusty Snap On hook set levered the old one out without drama and more importantly without leaving any swarf in the gallery.
Happy days.
One more "job done"
Pics to assist any "newbies" to this process
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Old 06-09-2017, 08:51 PM
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Farmer42 Farmer42 is offline
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Never even thought to look at or replace that when I was rebuilding my L26 last year. Didn't even realise there was a pressure release valve & the 'How to rebuild your....' book or the Haynes manual doesn't mention it as far as I remember.

Might take a look at that when I do the next oil & filter change, thanks for the heads-up. It is a common problem & what is the impact of a faulty or worn valve?

1975 Fairlady Z 2+2
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Old 07-09-2017, 10:32 AM
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Mr.F Mr.F is offline
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It has been known for the action of the ball bearing against the retaining flange to cause sufficient wear to release the bearing and spring from it's housing. Fortunately there is no path into the engine for the part(s) and they end up in the oil filter (or in the 280ZX in the upper tray of the oil filter angled adapter).
If you can't see the ball in the end of the valve, it popped out long ago...
280ZX owners will have to remove the adapter to check.
Mike Feeney at MJP (Eastern Auto)
Battlesbridge, Essex 07785 932086

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Old 07-09-2017, 11:00 AM
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jonbills jonbills is offline
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The oil relief valve is discussed in the 'How to Modify Your Nissan & Datsun OHC' book. It says you can remove it and blank it, which I've done. That puts the onus on me to remember to change the oil filter regularly.
1974 260z
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Old 07-09-2017, 11:37 AM
SKiddell SKiddell is offline
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With brass blanking plug

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Old 09-09-2017, 09:48 PM
stuart barrie stuart barrie is offline
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I think the wording of pressure relief valve is incorrect should it not be referred to as bypass valve the object of the valve is to keep the engine fed by oil even if the filter has never been changed and blocked.
The engine will keep running with unfiltered oil better than no oil.
Many modern filters have the valve built into them this can be something not in cheep will fit filters.
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