TDV8 oil pressure concerns

New pump gear width 17.25mm and clearance to backplate 0.06mm (0.07 doesn't fit). I'll measure the old one for comparison and check its gears and backplate for scoring and that the relief valve seals, at least under gravity even if not under pressure.

Pump housing has 6H40-6600-DF in the casting. I'd like to know if this indicates a vehicle model as an indication as to when this version of the pump was introduced. I like that the pressure relief valve is retained by a roll-pin that is locked in by the backplate.

No dowels in either face so hopefully no need to lower the sump a little.

After nearly $1,000 in expenses and more than 2 solid days work and risking a motor out job to replace the sump gasket if the gasket repair wasn't successful, there's no improvement whatsoever with the new pump.

My only comparison is with the good pressures through to mid-warm-up for which I now have no explanation.

Well you've successfully scared the crap out of me, cannot wait to sell this van so the RRS's towing life is over...

There is a mob in the UK called MDRS Automotive.
They change over hundreds of late model LR engines,maybe the could give some feedback on the issue?

FWIW,the LC200 has an oil pressure guage,and I notice the oil pressure when hot at idle is not much lower than at 100 Km/hr,which is around 1450 RPM.First start it is much higher then it gradually drops back as the engine warms up.

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Originally Posted by Graeme

After nearly $1,000 in expenses and more than 2 solid days work and risking a motor out job to replace the sump gasket if the gasket repair wasn't successful, there's no improvement whatsoever with the new pump.

My only comparison is with the good pressures through to mid-warm-up for which I now have no explanation.

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You seem like a very skilled operator from the posts you make, so you will most likely be aware of this.... But anyway...

Whilst I also don't like the figures you posted up earlier re pressure, it may will be enough for the design of that engine, remembering more oil pressure doesn't necessarily mean better engine protection.

In fact if it is too high, that can damage things as well.

You obviously won't have a baseline pressure for when the engine was new, but that would be an interesting thing to know.

I see you remarked some of these engines have had bearing problems, which is why you were looking at the pump, is that correct?

It may be a chicken and egg scenario with this situation, as after the pump....the next obvious cause of low oil pressure is the main bearings.

The fact that a low oil pressure warning isn't triggered by the numbers you are getting is also of interest, although not cut and dried with LRs reliability/quality control with Vee engines.

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Originally Posted by scarry

FWIW,the LC200 has an oil pressure guage,and I notice the oil pressure when hot at idle is not much lower than at 100 Km/hr,which is around 1450 RPM.First start it is much higher then it gradually drops back as the engine warms up.

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Are there any numbers on the gauge?

Not that it would necessarily mean much.

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Originally Posted by shack

Are there any numbers on the gauge?

Not that it would necessarily mean much.

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Unfortunately,no.

The failures in the UK may be due to oil dilution from frequent incompleted then restarted DPF regens. LR changed the trigger for the computed oil dilution warning from something like 8% to around 18% because of some very short distances travelled since the last oil change. This combined with low hot pressures at the low revs at which the engine will happily operate may be the cause of the bearing failures.

Mine meets LR's pressure specs at idle and at 3500 at 85 degC even though specs are at 65 degC so I can only assume that the bearings are OK. Oil pressure at cold summer start-up is through the roof which makes me wonder if enough oil is getting through to all the bearings including the turbo's, but the engine is already up to temperature by the time I get to the tar road. I'll just ensure that I use a gear that keeps revs a few hundered rpm higher, always tow in sport mode and downshift to keep the revs up a little rather than my previous habit of upshifting all the time.

My temporary round oil pressure gauge will be replaced with a small 2-digit LED display located in the bottom right corner of the instrument cluster as a permanent reminder to drop a gear when pressure gets too low for my liking.

Quote:

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Originally Posted by scarry

FWIW,the LC200 has an oil pressure guage,and I notice the oil pressure when hot at idle is not much lower than at 100 Km/hr,which is around 1450 RPM.First start it is much higher then it gradually drops back as the engine warms up.

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Thanks - a similar story...

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Originally Posted by shack

Whilst I also don't like the figures you posted up earlier re pressure, it may will be enough for the design of that engine, remembering more oil pressure doesn't necessarily mean better engine protection.

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From my reading over the years, plain bearings in internal combustion engines rely on a "hydrodynamic wedge" of oil that keeps the surfaces separated. It's my understanding that this drag effectively pumps the oil through the bearing and that the oil supply pressure is there to ensure enough oil flow to continue to separate the surfaces. If that is the case, then as long as there's enough pressure to ensure replacement, flow and consequent cooling we're ok.

Remember these engines have piston squirters in them, so there's a considerable amount of oil required to keep the lifters pumped up and pistons cooled, let alone replenishing the plain bearings.

Do I like it? Hell no, but when fitting a higher flow (bigger impeller) pump and not seeing an increase in pressure it would indicate that maybe what's there is enough.