Thread: 300tdi oil pressure relief valve

Isn't the aim of an oil pressure relief valve to by-pass oil around the filter in case it gets blocked ? Usually a spring pressing on a ball bearing. If the filters blocked the pressure on the ball bearing overcomes the spring pressure and allows oil to 'bypass' the blocked filter therefore not starving the engine of lubrication.
All very well and good, but after 17 of inaction and residue build up I would be surprised if it still worked which I guess is why you're changing it.
As far as I know modern filters have a bypass valve built into them for the same purpose.
The Z9 definitely does the Z1159 does and I think the Z79A does as well. So why not just run a Z9 and let sleeping dogs (oil pressure relief valves) lie ?

Deano

Excellent!
thats what I was hoping to hear.
I am running a Z79A if I'm not mistaken, but have absolutely no idea whether the valve is buggered or not.... just one of those "while I'm at it" modifications.
Tho only down side I see here is that if the valve is or will ever get stuck in the open position, the oil won't run through the filter anymore.... however... the engine is pretty pristine inside and I keep on top of oil changes etc, so the oil is not really dirty. and in the end, better run "dirty" oil through the engine rather than no oil at all!

Thanks again

The oil pressure relief valve and spring in the engine block, beside the oil pump controls oil pressure from the oil pump.
Quote from 300TDi Overhaul manual:

Oil pressure is controlled by a pressure relief valve
(12) incorporated in the timing case housing
together with the oil pump. The valve allows excess

oil to be recirculated back into the oil feed gallery.

The By-Pass valve in the oil filter is just that a by-pass which allows the oil pump to work around a blocked oil filter, you should be able to get a six sided socket and breaker bar onto the plug and replace the old valve (piston/plunger) and spring, Regards Frank.

Originally Posted by DeanoH

Isn't the aim of an oil pressure relief valve to by-pass oil around the filter in case it gets blocked ? Usually a spring pressing on a ball bearing. If the filters blocked the pressure on the ball bearing overcomes the spring pressure and allows oil to 'bypass' the blocked filter therefore not starving the engine of lubrication.
All very well and good, but after 17 of inaction and residue build up I would be surprised if it still worked which I guess is why you're changing it.
As far as I know modern filters have a bypass valve built into them for the same purpose.
The Z9 definitely does the Z1159 does and I think the Z79A does as well. So why not just run a Z9 and let sleeping dogs (oil pressure relief valves) lie ?

Deano

DO NOT USE A Z9 on a Disco 300 Tdi, the oil filter is too long and WILL hit the front differential on full compression of front suspension. Ryco also used to have I think the Z139 as a filter option, after several engine failures early on from this happening they ammended it to the Z89a.

The 300Tdi oil pressure relief valve plug is just a giant flat screwdriver type of slot in the fitting, and sometimes very tight. I have used a large flat blade screwdriver in the past and tapped it around to loosen it first, then undo it as normal.

JC

JC

Originally Posted by Tank

you should be able to get a six sided socket and breaker bar onto the plug and replace the old valve

I WISH it was a normal socket

Originally Posted by justinc

The 300Tdi oil pressure relief valve plug is just a giant flat screwdriver type of slot in the fitting, and sometimes very tight.

yep, mine is VERY tight. I think I will try to find something to fit the giant screwdriver slot to get an impact drill on it this afternoon - I'm just not strong enough

Thanks for your replies guys!!

After a slight modification of an old chisel with a grinder to make it fit the giant screwdriver slot and attaching an impact drill to it I have to lay my tools in defeat, I don't think there is a way to get it off!!

So I guess it has to stay there with all fingers and toes crossed that the valve doesnt fail........

Sorry, I thought it would be a six sided nut, like anyone but Land Rover would use, Regards Frank.

You may be able to get it off by either using a shifter on the blade of the chisel after tapping the chisel a few times on the end keep inmind the torque you can achive with a shifter like that so you have to be pushing the chisel into the plug quite hard. This is assuming you dont have a traditional impact driver with screw driver bits that you belt with a hammer they can be very useful tools and should be pretty cheap. Hope this helps. Will have a bash at doing mine in a few weeks time i had a quick try before but was in a rush so left it for next time