What happened to your D3/D4 today?

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Originally Posted by Graeme

I check pressure for hot idle before switching-off and when in hot weather I feel the engine starting work at low revs in top gear ascending rises to decide whether or not to drop a gear, as pressure approaching 100kph can vary quite a lot depending on temperature.

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Ambient temperature or oil temperature?

I tend to watch the oil temp. The biggest thing I've learned is no 6th gear for towing (100kph max in WA) and I tend to tow between 90 & 95. I target ~2k rpm and it tends to keep the temps at their minimums for the speed. More than that and the coolant temp comes down but oil temp comes up a bit, and lower than that both rise.

Motor memory ensures I'm in the right gear for the speed so I don't tend to think about it. At 2k the road noise still masks the engine noise.

Normal hot engine temperature being after at least a 20km drive at 100 kph.

I tow my van at 95-100 kph, previously in 7th on inclines or 8th at just under 1200 rpm elsewhere, but since becoming aware of the low pressures I now tow 1 gear lower, with 7th at around 1400 rpm. I haven't monitored oil temperature other than a couple of times looking to see how it gets up to temperature compared with coolant getting up to temperature when the oil pressure display was first installed, but will do some spot checks the next time the van's out. My yardstick is 9 psi idle after a slow climb up a range with the van in early winter, manually shifting keeping revs under 2000 rpm because the engine was pulling so well with no indication that it was getting hot.

I think your V8 might have a *slighly* different torque curve to the 2.7 V6. At 1200RPM I couldn't pull the skin off a rice pudding, let alone a van.

Oil pressure deep dive

Interesting comments on the squirters.

https://youtu.be/6XHV0DrOjXE'si=Q6FylZZL8ZD_BSQx

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Originally Posted by PerthDisco

Oil pressure deep dive

Interesting comments on the squirters.

https://youtu.be/6XHV0DrOjXE'si=Q6FylZZL8ZD_BSQx

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I don't have a D4, I like simple things.

My 74 RRC came with a 350 in it with about 400 thousand kms already on it.

Fitted with stock Smiths gauges. There are wiring issues to the oil temp and pressure circuits atm.

When they were working oil pressure was around 20 psi at idle (hot) and 30 to 35 at cruising speed. I learnt that if it was under 20 at idle it meant the oil would be below the bottom mark the dipstick, so it got topped up before that.

The oil temp sender is in a stupid place..........it had been brazed into the side of the sump and the sender wire keeps getting snapped off.

However when it works (hot) the oil temp is around 100 to 120 depending on ambient. Before fitting thermo fans it was 120 or a little more. The gauge red upper limit is 140.

It had a tick in the top end of one bank in recent times so I got hold of a tin rocker cover and cut the top off it and installed it so I could see what was going on with the motor running. Couldn't see anything wrong, but what was really surprising was the oil flow across the top of the head.........like a river.

This motor has around 700 thousand on it now. I keep thinking I should get it recoed but it runs fine.

Oil of choice used to be really high tech........... Valvoline XLD premium on special. $15 for 5 litres pre -covid

I'm just posting this info to complement the info in the video.

'Progress' is an interesting thing.

David L

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Originally Posted by PerthDisco

Oil pressure deep dive

Interesting comments on the squirters.

https://youtu.be/6XHV0DrOjXE'si=Q6FylZZL8ZD_BSQx

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Pretty devoid of actual fact other than "oil pressure at the crank and head is less than at the pump", and that is obvious to anyone really.

About 10 years ago I had a great conversation with an engineer who worked on static bearings. His were generally found fitted to steam turbines in power stations, but as he said "same theory, different diameter". His comment was in the process of operation where it is floating on the hydrodynamic wedge it will, given the opportunity, actually suck oil through the feed hole. Supply oil pressure had to be sufficient for 2 things. 1) keep the bearing fed, and 2) keep the bearing cool.

The churning of oil in the bearing heats it significantly, so it thins out. The supply pressure had to be sufficient to "push" cool oil through the bearing to replace the stuff that was heating up. That process was more than sufficient to keep the bearing fed. Obviously as things wear and clearances open up, flow will increase resulting in a drop in pressure for a given supply rate. Heavier oil would compensate for that by reducing the escape volume through the bearings.

Where the gentlemen in the youtube video came up with "minimum bearing pressure of 20psi or they fail" is anyones guess. The pressure has to be sufficient to create adequate flow.

Interesting point on the squirters. Absolutely a failed squirter is going to spell disaster. That's one failure an oil pressure gauge would pick up pretty smartly.

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Originally Posted by BradC

Pretty devoid of actual fact other than "oil pressure at the crank and head is less than at the pump", and that is obvious to anyone really.

About 10 years ago I had a great conversation with an engineer who worked on static bearings. His were generally found fitted to steam turbines in power stations, but as he said "same theory, different diameter". His comment was in the process of operation where it is floating on the hydrodynamic wedge it will, given the opportunity, actually suck oil through the feed hole. Supply oil pressure had to be sufficient for 2 things. 1) keep the bearing fed, and 2) keep the bearing cool.

The churning of oil in the bearing heats it significantly, so it thins out. The supply pressure had to be sufficient to "push" cool oil through the bearing to replace the stuff that was heating up. That process was more than sufficient to keep the bearing fed. Obviously as things wear and clearances open up, flow will increase resulting in a drop in pressure for a given supply rate. Heavier oil would compensate for that by reducing the escape volume through the bearings.

Where the gentlemen in the youtube video came up with "minimum bearing pressure of 20psi or they fail" is anyones guess. The pressure has to be sufficient to create adequate flow.

Interesting point on the squirters. Absolutely a failed squirter is going to spell disaster. That's one failure an oil pressure gauge would pick up pretty smartly.

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I think we are are all starting to feel is the gist of what he was saying is a trend in the wrong direction for longevity.

Thinner oils and reduced friction designs vs what worked perfectly in engines for years prior.

Anything we speak about here in terms of oil pump upgrades and 5W40 are the right steps.

No oil wedge no lubrication.

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Originally Posted by PerthDisco

I think we are are all starting to feel is the gist of what he was saying is a trend in the wrong direction for longevity.

Thinner oils and reduced friction designs vs what worked perfectly in engines for years prior.

Anything we speak about here in terms of oil pump upgrades and 5W40 are the right steps.

No oil wedge no lubrication.

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I don't think there's any argument there. I do sometimes wonder. I had a new oil pump fitted of the latest design back in 2017. I've checked with the borescope and the casting numbers appear to be the same as the stuff I've seen recently but I suppose without removing it there's no way to measure the actual impeller thickness.

I'm due a timing belt this year, but wondering whether its worth looking at the pump given it was done last time. It's not like they wear and become less efficient significantly, and it's already the latest casting design so it's not going to snap on me.

My gut says either spend the money on a new oil cooler while I'm in there, or perhaps drivers side cam pulley instead.

Decisions decisions.... Of course I'd rather put the money towards a roof re-spray, but then if I do that and lunch the donk it's all down the pipe anyway.

See when I drove Volvos, I never minded spending money on the upkeep of the vehicle because I knew if I looked after it, it'd last forever. The D3 feels like so much more of a gamble every time I open my wallet.

Frankly if they kept making reliable Volvos I'd still be driving those, but they migrated away from solid and reliable and seemed keen to market to hairdressers instead. Shame.

After consideration, my son Justin's D4 replacement engine isn't getting a new pump but I'm still happy that both camshaft sprockets are now the later version. Oil is 5W40 A3/B4.

I suspect the cam shaft sprocket failures are mechanic error in either over cranking the tensioner or relying too much on the cam timing pins to hold the position. It’s always the RH side cam from what I’ve heard