It's finally gone bang!

Well I've had 40,000 miles (now on 150K) of very enjoyable and reliable motoring out of a £2K car! As the law of sod would have it - just as I entered a contraflow on the M6 the oil pressure light came on, the contraflow was 6 miles long and I didn't want to stop and block it - by the time I exited the contraflow the engine was sounding pretty tappy so I thought **** it - 22 miles to go to the hotel - see if it'll make it - it did.

I did an oil and filter change two weeks ago and the levels were fine.

This morning I started the car and the oil pressure light went off and the tapping greatly reduced. I wonder if there's wear in the rocker shafts and it's bleeding oil pressure when hot? The bottom end sounds fine - no knocking. I'll get relayed back to home tomorrow - I guess I'll have to purchase an emergency auction car until I find time to investigate my oil pressure failure.

It was a good innings - I'm not complaining. What went wrong? Oil pump? rocker wear? Oil pressure release valve sticking?

I replaced the rockers on mine with brand new ones and a supplier sent me the wrong parts which meant oil was ****ing out between the post and shaft.

That caused my oil light to come on but only on idle, anything above and it would go off. So I would think you would need a pretty big amount of wear between the rockers to loose a lot of oil pressure. Only my 2 cents though, I could be wrong.

Hopefully your going to fix it and not get rid of it?

It's strange, from cold it drives fine for about 40 miles then you get the occasional flicker of the oil pressure light, press on and the light comes on more regularly and it starts to get tappy as the lifters start to bleed down. Turn it off for half an hour and it'll cool down enough to drive another 20 miles - repeat. I find it hard to believe general wear and tear will suddenly cause this problem - something must have failed!

I'll whip the sump off when I get time, if the crank has survived unscathed and the tolerances are okay then I'll replace the, cam, rockers, lifters and front cover/oil pump assembly. Finding the time is the issue!

What grade of oil do you use? Can you get an oil pressure guage on it?

stopover said:

What grade of oil do you use? Can you get an oil pressure guage on it?

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10w60. I reckon the oil pressure relief valve must be stuck partially open. As the oil gets hot the loss through the valve must become too great.

Don't Panic Mr Mannering!!!

You could put a guage between the oil pressure switch and front cover - about 4 bar - 30/40psi?

Check out: http://www.rangerovers.net/forum/7-...oil-pressure-relief-valve-not-pass-valve.html they seen to be able to remove both in situ ?? And: http://www.rangerovers.net/forum/7-range-rover-mark-ii-p38/16511-oil-pressure-relief-valve.html which is interesting reading.

If you have to remove the front cover its fairly easy to remove. Remove radiator if extra access needed, Viscouse fan etc. The oil pump / pressure relief valve and front engine cover is one integrated unit but I have seen oil pumps as separate items on eBay for £80 or so??? You will need to drop the sump too.

With the front cover off I would also consider replacing the water pump, hoses and 'serpentine' belt at the same time. At 150,000 new timing chain (stiff) and sprockets would be a good idea too. If after all that and you still have the problem then its a look at the top of the engine.

Range Rover 4.0 & 4.6 (from XA426594) - Part # LJR105040G see the video on the Atlantic British site its very informative http://www.roverparts.com/Parts/LJR105040

Range Rover 4.0 & 4.6 and Discovery Series II (to XA426593) - Part # ERR6438G

Have a look at this possibility too:

Range Rover P38 4.0 V8 Oil Pump Broken - YouTube

Thanks for the info. I drove home (200 miles) keeping it down to 50mph, the engine sounded sweet and the oil light didn't come on, so this would again tally with the oil pressure relief valve being partially stuck open or a weak spring. Driving gently mean oil pressure was kept low (so as not to disturb the valve) and dumped less heat into the oil keeping it relatively thick.

I haven't decided what to do yet - I'm just too busy!

StuckAgainSteve said:

10w60.

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I've never seen 10/60 are you mixing ep90 with 10/40???


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zzr1200 said:

I've never seen 10/60 are you mixing ep90 with 10/40???


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Bought loads when it was on offer: TRIPLE QX SynPlus Fully Syn 10w60 Engine Oil - 1ltr

Have you tried putting in the correct 10/40 oil in and running the car since the issue first occurred?

I'd hazard a guess that the current oil is an issue.

10w60 is listed in the owners manual as acceptable oil.

chomerly said:

Have you tried putting in the correct 10/40 oil in and running the car since the issue first occurred?

I'd hazard a guess that the current oil is an issue.

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How would thicker oil lower oil pressure? It's been running on that for about 25K miles. There's no "correct" grade as outlined in the owner's manual where it specifies 10W/60 as one of the valid grades in the -10 to 50C ambient temperature ranges.

Wow - both posted exactly the same answer in exactly the same minute - spooky!

StuckAgainSteve said:

How would thicker oil lower oil pressure? It's been running on that for about 25K miles. There's no "correct" grade as outlined in the owner's manual where it specifies 10W/60 as one of the valid grades in the -10 to 50C ambient temperature ranges.

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desert temps

But wouldn't it expose, or eliminate depending on your perspective, the possibility of it being part of the problem?

chomerly said:

But wouldn't it expose, or eliminate depending on your perspective, the possibility of it being part of the problem?

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I doubt it.

10/60 means viscosity 10 when cold and 60 hot, so unless it is running hot it shouldn't make too much difference, although I guess the diesel runs hotter? Interestingly RAVE says 10/60 is OK for petrol but NOT diesel. Diesel only goes up to 10/50 which would fit with oil being too gloopy.

Is it an oil burner?

Grrrrrr said:

10/60 means viscosity 10 when cold and 60 hot, so unless it is running hot it shouldn't make too much difference, although I guess the diesel runs hotter? Interestingly RAVE says 10/60 is OK for petrol but NOT diesel. Diesel only goes up to 10/50 which would fit with oil being too gloopy.

Is it an oil burner?

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Diesel runs cooler, Steves is a V8. Thicker oil would tend to keep the pressure when hot rather than lose it.

Even if his pressure relief valve is sticky? On my Mk II cavalier I had to clean the pressure relief valve once a year or the pressure dropped 50%!

You'll be surprised how quickly multigrade oil loses the ability to thicken appreciably when hot. Within a couple of thousand miles 10W60 will soon effectively become 8W/40.

The "cold" figure drops slowly as the oil ages, the hot quickly as the long-chain viscosity enhancers literally get chopped up. I used to work for an oil company and read several classified multi-million pound research documents including the detailed analysis of competitors' oil. In a nutshell - change your oil between services unless you run Mobil 1 - but then the cost of that means it's cheaper to just change the oil more often. I didn't work for Mobil, we came to the conclusion there's no way we could match it and make a cost-effective product - but claimed like everyone else that our oil is the best.

My car is with a trusted mechanic for a new oil pump. I just haven't got time. I'm driving an emergency auction buy - a Honda CR-V - a hateful boring piece of crap - drives like new admittedly - but I'm seriously in danger of crashing from falling asleep every time I get behind the wheel. I guess it's time to relegate the p38 to a weekend plaything and start looking for a newer car. I drive a lot to client sites all over the country as part of my living and I can't expect a 15 year old car carry on racking up 15K+ miles a year. I've had a good four years of reliability (luck!) and am not going to push it any further - I'll probably use the p38 for 1 in 4 weeks for work to keep the moisture out the drive-train and interior.