Oil pressure on the V8 has always been low, even our P6 used to drop to almost nothing on tick over when hot - I think theres even a note in the owners manual about the oil light flickering on idle. I'd change the rocker shafts and leave the rockers ( you could check them for wear but my understanding is the shafts wear not the arms). When you check the shafts you'll probably see the underside is worn badly. As they are indeed the last thing left in the oil run - no 'cap' here will loose you your oil pressure, if you pop the rocker covers off and its bone dry and crusty then it may be time to look elsewhere. Its a pity there's no Hi Volume pump available for the later engines as there was for the P6. Before you buy any parts look at the V8Forum as there's been some discussion on arms and shafts on there which you may find useful.

1 x Camshaft 4.0 ERR3720 £41.66
16 x Tappet V8 Lifter Cam Follower (OEM) ERC4949G £42.56
2 x Rocker Valve Cover Gasket V8 LVC100260 £3.00
1 x Front Cover Gasket V8 Petrol ERR7280 £2.33
2 x ROCKER SHAFT ASSY 611660 £130.78
4 x PUSH ROD X4 603378 £12.52
1 x Gasket Inlet (Valley) ERC3990 ERR7306 LKJ500020 £6.66
1 x Gasket Manifold Upper ERR6621 £6.66
2 x SEAL INLET MANIFOLD ERR7283G £1.90
1 x KEY-WOODRUFF ERR2609 £5.20

Totals £304 with the VAT

So that's my new year sorted!!

Stand by for the How To!!!

Hope it does what you want.
best wishes for 2015

Ant, Whip the rocker covers off and check the rockers/shafts by all means but the oil pressure is developed at the bottom end ie. oil pump through the main bearings that's why the o/p switch is down there. So perhaps you haven't got away with changing the shells and a regrind is called for. Save your money and change the o/p switch, the old one could be full of gunk or try to find a proper test gauge. Good luck.

tomcat59alan said:

Ant, Whip the rocker covers off and check the rockers/shafts by all means but the oil pressure is developed at the bottom end ie. oil pump through the main bearings that's why the o/p switch is down there. So perhaps you haven't got away with changing the shells and a regrind is called for. Save your money and change the o/p switch, the old one could be full of gunk or try to find a proper test gauge. Good luck.

Click to expand...

Cheers Alan...

OP switch is new....

The switch sits in the oil way leading to the block from there it through the block and diverts down to the crank and up to the rockers and the cam...

As we all know fluids like to take the path of least resistance, so now the bottom end is considered nice and tight, the next place pressure will escape from is the top end by the rocker shafts!

Pressure is not built solely on the bottom end, the system as a whole generates pressure, one weak point and the pressure will be lost there!

Really do appreciate everyones concerns regards doing the top end when it could be something else.

I measured the crank journals as best I could with a mic when I did the shells and they came up in tolerance according to RAVE.

As I said, when I got the car in June there was no oil pressure problem, just an oil leak from the front cover.

I replaced the front cover with another, this solved the leak but oil pressure was low.

So I replaced the Oil Pump gears, this lead to no pressure.

So I refitted the old front cover, and snapped the oil pump back plate, fitted the replacement back plate with new oil pump gears. Oil pressure was better but only if revs held around 2K.

Replaced Bottom End shells....Oil pressure returned, but now if idling for a minute or so, the light flickers on and off.

Sooooooo.....the thoughts are, the top end has been worn due to the period of low oil pressure before I changed the pump gears....

The shells were original and 18 years old....so were well worn before I changed them, even if the crank is a margin undersized, new shells will be considerably better than the old ones...so now the bottom end is relatively leak free, the next weakest point will be the top end!

Pressure will always find the next weakest point and leak out....it is now considered this weak point is the 18 year old rocker shafts and arms, cam and followers...

It has got to be worth a go....all this started when I changed the front cover....the car wasn't driven much after this due to the low oil pressure, and not left to allow the light to come on when it was driven.

If this top end refresh doesn't work, two things happen...you guys get a How To on changing the cam, followers, rods, rockers and shafts...and I then think about what to do next.

Owning an aging vehicle is a test of will and patience, I am learning a lot about the engine that I can pass on to others....by doing is how we learn...by giving up and moving on is how we fail.

be very carefull,check the aftermarket rockers to see how deep the oil grooves are verses the genuine ones, some are very deep and they will drop the oil pressure faster than a tarts knickers on wall street.

Saint.V8 said:

Cheers Alan...

OP switch is new....

The switch sits in the oil way leading to the block from there it through the block and diverts down to the crank and up to the rockers and the cam...

As we all know fluids like to take the path of least resistance, so now the bottom end is considered nice and tight, the next place pressure will escape from is the top end by the rocker shafts!

Pressure is not built solely on the bottom end, the system as a whole generates pressure, one weak point and the pressure will be lost there!

Really do appreciate everyones concerns regards doing the top end when it could be something else.

I measured the crank journals as best I could with a mic when I did the shells and they came up in tolerance according to RAVE.

As I said, when I got the car in June there was no oil pressure problem, just an oil leak from the front cover.

I replaced the front cover with another, this solved the leak but oil pressure was low.

So I replaced the Oil Pump gears, this lead to no pressure.

So I refitted the old front cover, and snapped the oil pump back plate, fitted the replacement back plate with new oil pump gears. Oil pressure was better but only if revs held around 2K.

Replaced Bottom End shells....Oil pressure returned, but now if idling for a minute or so, the light flickers on and off.

Sooooooo.....the thoughts are, the top end has been worn due to the period of low oil pressure before I changed the pump gears....

The shells were original and 18 years old....so were well worn before I changed them, even if the crank is a margin undersized, new shells will be considerably better than the old ones...so now the bottom end is relatively leak free, the next weakest point will be the top end!

Pressure will always find the next weakest point and leak out....it is now considered this weak point is the 18 year old rocker shafts and arms, cam and followers...

It has got to be worth a go....all this started when I changed the front cover....the car wasn't driven much after this due to the low oil pressure, and not left to allow the light to come on when it was driven.

If this top end refresh doesn't work, two things happen...you guys get a How To on changing the cam, followers, rods, rockers and shafts...and I then think about what to do next.

Owning an aging vehicle is a test of will and patience, I am learning a lot about the engine that I can pass on to others....by doing is how we learn...by giving up and moving on is how we fail.

Click to expand...

Go for it mate, don't want to **** on your chips but the o/p switch measures pressure in the main oil gallery.

Where are those parts from just out of interest? All OEM, or just those where stated?

You need to get to the bottom of the oil pressure issue instead of throwing money into a pit..... Or get rid

I'm looking forward to your 'how to..'. Hope the work solves the oil pressure problem. I agree with you that the system is seen generally as a 'whole' by the O/P gauge and the worn rocker shafts can cause L/P. I take it those are two genuine Rocker shafts and you're re-using the arms. As posted the new ones seem to have very large oil ways. You may find the used arms pick up a little on refitting to the new shafts, as can the pillars.
What make are the Lifters? I know there are some cheap ones out there so hopefully yours are from the US. Same goes for the Cam. While you're at it I'd think about swapping out the timing chain and chain cog. You'll be amazed at how these can be worn.
It'll sound like a manic typewriter when you first fire it, but make sure the cam gets bedded in at whatever RPM is stated ( I think from memory its about 2000 ish? for about 20 mins?) otherwise you could wear out a lobe. There are some good cam lubes on the market - a quick call to Real Steel in Middlesex or RPI might give you some pointers. Good Luck with it.

tomcat59alan said:

Go for it mate, don't want to **** on your chips but the o/p switch measures pressure in the main oil gallery.

Click to expand...

The system is a 'closed' system, pressure in the main gallery will be the same as it is at the rocker shafts, the cam and at the pump. The Pressure Switch sits at the entrance to the block in the feed line from the filter....regardless of where in the system the pressure would be taken from, in a working system, the pressure will be uniform throughout (minor variances where the venturi effect is made at restrictions aside...

That is the way I see it....but I do understand what you are saying, trust me!

kooky_guy said:

Where are those parts from just out of interest? All OEM, or just those where stated?

Click to expand...

OEM where possible, the parts are from Island 4x4, whilst the cam is Eurospares I think, and some parts just aren't listed by island as from OEM but Aftermarket OEM Quality. Trie to avoid Britpart where possible, but some parts are still BP!

cooltide said:

You need to get to the bottom of the oil pressure issue instead of throwing money into a pit..... Or get rid

Click to expand...

See next post by me in this thread....we did a vid of the pressure gauge and etc...might offer more light on the subject!

forthbridge said:

I'm looking forward to your 'how to..'. Hope the work solves the oil pressure problem. I agree with you that the system is seen generally as a 'whole' by the O/P gauge and the worn rocker shafts can cause L/P. I take it those are two genuine Rocker shafts and you're re-using the arms. As posted the new ones seem to have very large oil ways. You may find the used arms pick up a little on refitting to the new shafts, as can the pillars.
What make are the Lifters? I know there are some cheap ones out there so hopefully yours are from the US. Same goes for the Cam. While you're at it I'd think about swapping out the timing chain and chain cog. You'll be amazed at how these can be worn.
It'll sound like a manic typewriter when you first fire it, but make sure the cam gets bedded in at whatever RPM is stated ( I think from memory its about 2000 ish? for about 20 mins?) otherwise you could wear out a lobe. There are some good cam lubes on the market - a quick call to Real Steel in Middlesex or RPI might give you some pointers. Good Luck with it.

Click to expand...

Followers are OEM, the rocker assemblies are bought pre-assembled.

Timing chain and gears were replaced when I swapped the front cover a couple of months ago.

Will take one of the rockers off the new shaft and compare with one of the originals and take a view...interesting the oil groove is deeper on the new arms....will check, thanks for the heads up....

Fitment of new parts will be subject to further investigation, see next post by me in this thread for details!

UPDATE AFTER PRESSURE CHECK - WITH VIDS

So after reading the comments on this thread regards throwing money at an old rope and wasting my time, I have taken the opportunity to do a check using a pressure gauge.

I post the vid here....

http://www.youtube.com/watch?v=shPlWb5G4pw

I took advice from one of our Lead Hydraulic Engineers, he knows pumps and their behaviour inside out and backwards.

What would appear to be happening is, when started from cold, the pump has to re-prime itself which is wrong! the pressure then builds, but then is lost. Jason (LHE) reckons that the the fast idle part of the start process is enough for the pump to suck the oil up into the pump body, but when the idle settles back down, there is wear in the front cover and the back cover plate despite being new gears and the oil pressure starts to bleed out. The pump then starts to cavitate hence why the pressure fluctuates as the pump tries to expel the air pocket and picks ups oil again....

When sitting at idle for a period, it can no longer expel enough air and the pressure drops to almost zero. Speeding up the pump by either revving up or just bring the revs to above idle is enough for the pump to suck harder and draw oil in to itself and the pressure builds again.

The pulsing at around 1800 to 2000rpm is the pump cavitating and getting the air out.

When revved higher, the pressure holds reasonably steady and the odd bounce could be down to the relief valves opening and closing as it reaches around 50psi, then it fluctuates around 40psi...which according to RAVE is around the right figure (30-40psi @ 2400rpm according to the specifications apparently).

Jason seems to be 99% sure it is the pump losing its prime, which would seem to fit with the fact that when the car has stood for a short while and then gets started, the light takes 5-10 seconds to go out and the followers to stop tapping. it would appear the oil is draining back to the tank and the oil pump is starting dry in effect and it has to re-prime itself!

Here is a vid of the oil light at the start of my journey home... the light flashes on then off, then on again then off etc.....

https://www.youtube.com/watch?v=SQskUDK1KyY

And a vid of the end of the journey....

https://www.youtube.com/watch?v=2o9cu6RokRE

Soooooooooooo........

What I will do as the parts for the refresh have been ordered, I spoke with the other half and she has agreed to getting a brand new front cover which will come fitted already with the pump and relief valves etc. She also said, you may as well do the refresh as I intend to keep the car!.....

I will then speak to Island 4x4 and explain my problem and ask them that if I hold off on doing the refresh and fit the new front cover and see if the oil pressure returns to normal, if this solves the issue I will then fit the refresh parts.

If it doesn't fix the issue I will then consider if the refresh will help or return the refresh parts as there would be little point in bunging £300 worth of parts on the engine as long as Island will accept the unused items back!

All is not lost, but I concur with Jason, it does seem pump related as all this has happened since I changed the front cover and the oil pump....

St.

I totally agree with your man Jason.

video is great info.

I reckon you a have it...best of luck.

please enjoy a family Christmas...

regards..

Island were pretty good when I ordered a new coli plugs and leads after the plugs and leads the issue was fixed so they accepted the coil pack back

Been an interesting thread on diagnosing this issue. Thanks for all the good info chaps.

Have a happy and trouble free Christmas!

donp38 said:

St.

I totally agree with your man Jason.

video is great info.

I reckon you a have it...best of luck.

please enjoy a family Christmas...

regards..

Click to expand...

Yep, I have to agree it does seem as though the pump body is worn to a point that it can't contain its own oil and flow is lost resulting in low pressure. the leaking inside the pump due to wear in the front cover and the back plate is enough for the pump to drain itself and start cavitating hence why the needle bounces...as the pump expels the air it can suck the oil from the sump, this is then lost and the needle drops...bring the engine speed up and it can then overcome the gravity draining the pump and can generate flow and hence pressure!

I'll certainly try and enjoy crimbo with our baby girl, but she is refusing to sleep recently which is tiring for my partner and frustrating for me!

Hope yours is full of joy and fun!

So as I said ,it is nothing to do with it being a "closed circuit" system and is down to low oil pressure in the main oil gallery, what ever the cause. The fact that you put the old front cover back on was lost on me, probably because of my absence.

tomcat59alan said:

So as I said ,it is nothing to do with it being a "closed circuit" system and is down to low oil pressure in the main oil gallery, what ever the cause. The fact that you put the old front cover back on was lost on me, probably because of my absence.

Click to expand...

Old Front cover went back on becasue S/H replacement cover was worse for pressure, no matter what revs I gave it the light never went out!...

Old cover was always fine just leaked...I fixed the leak and refitted the old cover, but I broke the oil pump back plate on refitment due to misalignment (read my threads on this subject!) so I fitted the S/H front covers back plate and oil pressure was only moderate and was quite bad...so I changed the Main Bearings and Big Ends and we are now were we are....oil pressure is OK when running above idle

Hence why I put the old front cover back on...as Oil Pressure is better with the old one, but I believe the oil pump back plate is worn excessively causing pressure and flow loss!

I will now get a brand new front cover and see if that restores oil pressure fully!

Think that's the best way forward. See if you can get decent oil pressure first then have a look at the amount of oil being delivered at the rockers before you spend more money. Hope you put it together last time with wing nut's . All the best for Xmas and the New Year

Saint.V8 said:

I will now get a brand new front cover and see if that restores oil pressure fully!

Click to expand...

If you are not already, maybe change to a quality 20w50 like valvoline vr1 or millers and check oil strainer is not holed and still torqued correctly?

Just looked at the You tube links, weird, you have low oil pressure with a cold engine and according to your light oil pressure when its hot - I knew P38's were quirky but that takes the biscuit. I think the pulsing may be the relief valve ?
Thinking on the start up noise - and what your Tech said, do you have a filter with pressure valve fitted? You engine sounded like the old P5 and P6's before the oil pressured filters become available so they had no oil in the circuit on start up - rattled like hell for the first couple of seconds until oil got going.
The lifters drain down as well - but your's was loud enough to suspect something else is happening - like the oil pump draining down.
With that mileage if that's the original engine the cam and lifters will probably be due for a refit so I reckon you'll probably end up doing that too.
Also I didn't know you had a GEMs - why not just pop the valve cover off and making sure you don't displace the push rods into the engine (they'll be 'stuck' onto the arm sockets), take a shaft off, and without dismantling it just push an arm across so you can see the wear on the underside of the shaft. That way you can still put it back together temporarily if they are worn and you'll know better the extent of the work you've got in front of you.
With the new fully built shafts, if your arms have the three or the larger oil way cut into them , you may want to look into re using the arms that come off. As you're putting new push rods on keeping the arms in order may not be as critical but on the off chance you do re use it'll do no harm to log and keep the arm to valve relationship.
Hope this helps