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Joined: Jul 12 2016
Posts: 922

I've just been watching a video on YouTube discussing the front cover. I think it was Atlantic British.

The guy described each part of it and listed a few common issues that arise in that area. One of the parts that he mentioned was the oil pressure relief valve. I figure that its job is to release oil pressure when it gets too high. Is that right? Does it release the pressure by squirting the oil out of the engine or back in to the sump?

If so, if/when it fails could it possible lead to low oil pressure at idle but when the engine revs it produces enough pressure that the sensor reads OK again?

I'm wondering if I've gone a bit overboard with my low oil pressure at idle issue (I've ordered a set of new pump gears and a timing chain kit) and perhaps my relief valve has failed.

There's no procedure for replacing it in RAVE under the Engine > Repair section but it is mentioned in the Engine > Description section. I also can't find a part number for it on the LRCat, Bearmach or Turner Engineering websites.

Is this a serviceable part or is a case of replacing the whole front cover?

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Joined: Dec 30 2015
Posts: 3527

You're right, it doesn't seem to exist but on LRCat the oil pump gears aren't listed either, just a complete front cover. The oil pressure relief valve is removable and has an O ring which has a tendancy to leak, so people have removed it to replace the O ring. You are quite correct in how it works, it's simply a spring loaded plunger that lifts off a seat and allows oil to dribble back to the sump if the pressure is too high. If the O ring is leaking, it also allows oil to dribble down the side of the block, usually dripping off the oil filter. Too much oil pressure can do just as much damage as too little. A trick on old Ford engines when the pump started to wear bringing the light on at idle, was to fill with thicker oil and put a washer behind the spring (then flog it quick....) so it took much more pressure to lift it off the seat.

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Joined: Jul 12 2016
Posts: 922

Hmm, sounds like the pump being worn is still more likely then.

Any idea what size the o-ring for the pressure relief valve is? Might as well replace it while in there.

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Joined: Dec 30 2015
Posts: 1080

I believe it's 19mm x 1.5mm, from memory.... I will have a look in my parts sheet from when I did my engine a few years ago to see if I made a note of it...

If not, then I might still have a spare or old one in a bag kicking around in the garage that I can measure... but I do recall it being a slightly strange size

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Joined: Jul 12 2016
Posts: 922

Might have to skip it and just hope it's ok.

My pressure issue seems to be getting worse and will need sorting ASAP. I was managing stop-start traffic by shifting to neutral so the revs rise but today that wasn't enough. I'm having to shift to neutral and press the accelerator a little to make enough pressure :(

Not sure how or when though! My parts are in the neighbours house as I was out when they came. I've tried a few times since Thursday but they never seem to be there! I'm looking after a toddler on Monday and back to work Tuesday and Wednesday!

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Joined: Sep 13 2016
Posts: 473

The releif valve is in use all the time, and bypasses oil back to the sump.

The oil pump is fixed displacement, but pressure varies with viscosity as well as flow. So for instance at high rpm, the releif valve opens and bypasses the excess oil back to the sump. Or when the engines cold and oil is thick, it could well be operating from idle.

Every engine differs, and i dont know the exact figures for the rover V8, but on my Audi A4 for instance, a healthy engine will reach maximum oil pressure at around 3000rpm when fully warmed up, and when cold maximum pressure occurs at not much more than idle.

The valve can stick partially open, giving symptoms like you describe.