Musings on Oil Pressure - Oil Temperature and Ticking Lifters

[mcsquirt]

Musings on Oil Pressure, Oil Temperature, Heat Transfer, Oil Grades and Viscosity, Oil Change Frequency, Original & After Market Oil Pumps, Oil Coolers, Oil Filters, Bearing Lubrication, Engine Clearances, Engine Cooling, Bearing Wear and Tear and “Ticking Lifters” (It my experiences on the LS1 5.7L V8, at 10 years old as we get into the 250,000km + range).

Situation now is Original LS1 - 250,000 miles on the clock "Original Oil Pump" - Running Nulon 15W 50 Full Synthetic. Been doing the Oil Changes every 5,000km (New Oil + New Filter).

Using the Binnacle Gauge I currently get

Cold Idle - 39psi (270kpa) / 4000rpm 42psi (~300kpa) - Cold idle is around 800rpm at startup then it drops to around 650rpm as the coolant temp rises and engine goes into 'closed loop' operation)

Hot Idle (in Neutral) - 29psi / 4000rpm 42psi (~300kpa) - The idle in Neutral is about 650-670rpm)

Hot idle (in Drive) - The oil pressure can avalanche away to 10-12psi (~100kpa) The idle in Drive may go as low at 510-540rpm.

In my case if the Oil pressure drops below 29psi (200kpa) for more than about 5 min I get a lifter that starts to "tick" I had been using a 10W-40 like Castrol Magnatec from 1,500km all the way up to 150,000km No Problem . After 150,000km the "ticking Lifter" would come on in less than a minute during a Hot idle (particularly if idling in Drive).

As simply as I can, most of the important stuff in the engine needs Oil volume & Oil pressure.

That means having a capable Oil pump that puts Oil through an Engine faster than it can bleed away through all the clearances to create some reasonable value for Oil Pressure. The upper limit is set by RPM, Oil Viscosity and the Oil Pumps bypass spring setting. The Hot –Idle Pressure is set by Oil Viscosity – The Volume being pumped on each revolution & how fast the Oil bleeds away. As Oil gets hotter the Viscosity will become lower. Too low a Viscosity and you may have a problem when Hot / Too High a Viscosity and you may have a problem when Cold.

Getting the Oil type & grade and Lubrication right, and keeping it there over the life of an Engine, is a difficult balancing act between the needs of the engine, accumulating wear and tear, the variations in the characteristics of the Oil performance between Hot & Cold, the ability of the Oil Pump to supply the volume of Oil required, and the ability of the whole system to maintain the required pressure, despite the restrictions of the oil galleries and the bearing clearances that allows oil to drain away from bearing surfaces.

Then there is the variability in “how you drive” – Grandma taking the V8 to just above idling & tootling around at 50km/hr, and the WOT of a run down the quarter mile, then there’s the fully loaded family holiday towing the boat or caravan in bumper to bumper traffic on the annual Summer Holiday pilgrimage (the classic 0km/hr up to 110km/hr and back again) at an average 40km/hr, on a 40 degree day for 6 to10 hours.

Then there is accumulated Wear and Tear – as your mileage increases, the bearing clearances will open up (in the engine bearings and in the Oil pump) and the whole situation will change slowly over time.

A new or rebuilt Engine will perform differently to an old engine. Tight Clearances and a new pump mean you can generally run very low viscosity Oils. That position changes as time & mileage increases. If the Engine is flogged, worn out or damaged then this piece may be informative, but cannot undo the wear or “fix” the damage by simply changing the Oil to something approaching the Viscosity of Glue.

[mcsquirt]

Firstly – (Lubrication). To achieve optimum Lubrication and achieve engine reliability & longevity you want the lowest viscosity & highest quality Oil that will do the job under all the (normal & extreme) conditions in which the vehicle operates. You want the Oil maintained on the bearings at an adequate pressure, all the time. They say most of the wear will occur on start-up when the Oil residual on the bearing surfaces are at the minimum, consequently using a free flowing Low Viscosity Oil is a good thing. It’s a good idea at start up to give the engine a few seconds to build up the Oil pressure before you put the boot in. In Alpine conditions 0W & 5W Oils are a necessity or you may get a dry start! In temperate conditions a 5W, 10W, 15W will do the job..

If you are not getting to the normal cold idle pressure value in < 6 seconds there may be a problem. This may be due to using the wrong viscosity oil (too high or too low a viscosity), a failing oil pump / failed pump bypass spring-valve / sludge & or a blocked pickup, or the anti-drain back valve in the Oil filter not working. In a worst case it may indicate you may have done a main engine or camshaft bearing. These last two will be obvious to you in the unpleasant knocking noises that follow a start-up.

Limiting the wear at a “Cold Start”, and the ‘long time between start-ups’ issues are why some high performance cars & large scale industrial engines are equipped with pre-start Lubricators to pump up the Oil pressure and pre lube the bearings before each Engine start-up. This is the same reason why you should thoroughly prime an engine with Oil after a major rebuild, and check you have good Oil Pressure before you fire it up.

There is always a delay between increasing the RPM’s and the Oil Pressure coming up. That delay should not be more than about 3 seconds. If the Oil pressure climbs too slowly it may be due to restrictions in the Oil delivery system (Blocked Pickup or damaged “O” Ring / Sloppy Pump / Blocked Galleries) or the volume being pumped is just not sufficient to cover the oil flowing out.

[mcsquirt]

Secondly – (Normal Oil Pressure / Low Oil Pressure / High Oil Pressure / Oil Pressure Warning signs).

What’s a good Oil Pressure?
The general rule of thumb is > 30psi (200kpa) at Hot idle, with the upper limit at high RPM’s of ~ 65psi (425kpa). Put differently 10psi (70kpa) for every 1000rpm.

Now you can increase the Oil pressure (at idle) by increasing the Oil Viscosity – on the downside the Oil being more viscous is harder to pump around and may take longer to get it to the bearings where it needs to be. In winter (very cold weather) the High Viscosity is undesirable. Using a lower Viscosity and keeping the Oil Cool when Engine is at normal or higher temperatures, will give you tighter control of Oil Viscosity and better control of Oil Pressures.

If you read the overhaul specs the minimum spec for a Hot idle pressure may be given as ~6 psi (40kpa) – If everything else is in good condition you may be able to float the journals without damage. Things like Lifters may not like the Low Oil Pressures. Low Oil pressures like this increase the risk you may damage a bearing. ~30-40psi at a Hot idle is a better position.

Some builders of high performance engines like the Oil pressures at WOT above 65psi (up to 90psi+) – In a specially built engine with larger clearances and in race cars, this higher pressure – or higher volume pump will be appropriate.

The upper limit of Oil Pressure is set by the bypass spring in the Oil pump. That spring sets the upper limit, above that point increasing the RPM’s has no effect on increasing Oil Pressure as the bypass opens up and Oil is being recirculated inside the Oil Pump. Putting in a heavier spring will raise the upper Oil Pressure limit (assuming your pump & oil filter can handle it). Some people pack the stok spring with a 1-2mm spacer – that will lift the bypass pressure by about 10-12 psi.

Changing to a longer or stiffer spring or adding a spacer is not going to help you if the problem is Low Oil Pressure at idle (that’s Low Oil Pressure at a Hot idle).

The pressure you get at (Hot and Cold) idle is determined by a combination of: The overall condition of the Engine, Oil & Pump, that’s the Oil Volume moved by the pump at each revolution of the pump (Volume) + Oil Condition and Viscosity (Age & Thickness of the Oil) + condition of the Oil Galleries (Restricted or not) and Bearing Clearances (and their Resistance to Oil Flow inflows & outflows). The majority of these things (except for increasing the Viscosity or Lowering the Oil temperature) have the effect of LOWERING idle Oil Pressures. You should expect to see a drop between a Cold Idle & Hot idle of around 20-30psi (~200kpa). Some people compensate or low hot idle pressures by bumping up the base idle value. (The difference in pressures at a hot idle between 550-700rpm may be 100kpa or more)

If you are getting engine warning lights “Check Engine Oil” (the Oil Can Symbol flashes up or worse still stays on) at either Cold or Hot idle it generally means your Oil pressure has dropped below 5psi (<40kpa)- you definitely have a problem. The best thing here is a quick shutdown till you find out what is happening & why!

The ambiguous “Service Vehicle Soon” warning often means the Oil Pressure Sensor has failed. This can be a bit unnerving – especially if you don’t know what that warning means.

[mcsquirt]

Thirdly - (Oil Temperature) As the Oil warms up normally, or your driving style loads things up, or you are enduring the commute to work bumper to bumper low speed stop-start or it is a really Hot day, all these things may pump more heat into your Engine than the radiator can shift, this can trigger Oil Pressure problems.. If your engine temperature gauge is regularly going above what is normal, the whole situation with Oil Pressure and Lubrication changes. The bottom line is the hotter the Oil – the lower the Viscosity. If the viscosity drops low enough (due to Hot Oil, big bearing clearances, fair wear & tear in the pump), the Oil may bleed away from the bearings faster than the pump can deliver it. This will eventually set the low idle pressure and that value may become too low over time.

Oil performs two important roles. The Oil lubricates the engine, and also it carries away excess heat.

Too much heat will destroy the lubricating properties of the Engine oils. Repeated Engine Over Temperature conditions are not good for the engine block & heads either. The really good quality Oils may give you an upper Temperature limit of >200C before they start degrade. This is why people who want performance & reliability will run Engine Oil / Transmission Fluid & Differential Oil Coolers. If the engine can’t shift the heat away the Oils will cause varnish & carbon to be formed inside the engine. If left long enough the engine will produce deposits or the Oil will turn to sludge and have all the lubricating properties of porridge.

It is important that the Radiator / Cooling Fans & Water Pump are all doing their job properly. If you have an Engine overheating condition the Oil or Engine will eventually get toasted. The Engine will create varnish & sludge from the overheated Oil which will come back to haunt you later by blocking up galleries and closing up bearing clearances. – assuming you avoid the immediate & catastrophic failures that come from a failed cooling system. If you have accumulated deposits cleaning them away at higher mileages (with Engine Oil Flushing additives / Lifter Free up treatments) may fix one problem and create a new one. Accumulated sludge is bad – so are opened up bearing clearances and an Oil pump that can no longer deliver a big enough Oil Volume to maintain the pressures.

If you fit an engine Oil Cooler (of the right size and in the right place) it may allow you to run a lower Viscosity Oil (or keep the current Viscosity & run it in an engine with high mileage). In any case it will act as a supplementary engine cooling radiator. The Oil cooler cannot be either too big or too small.

Too big and the Oil gets too Cold, or you cut down the airflow over the engine radiators and the overall cooling benefit can be lost (Oil is cooler but Engine coolant is Hotter). Too small and you don’t bring the Oil temperatures under control in the extremes.

You may want to consider things like the length & size of the Oil Cooler lines (AN10). Small diameter and long hose runs will restrict the Oil flow and cause a pressure drop.

[mcsquirt]

Fourthly - - How Frequently should you change the Oil, and what brand / grade should you use?

Most Cars have recommended Oil change interval of 10,000km (or 6 months whichever comes first).
In severe operating conditions like very Hot days, dusty environments, prolonged high speed, towing you may want to do that sooner and make the change every 5,000km (New Oil plus a new filter).

As to Oil Brand and Grade – pick either the builders recommendation or something that works for your particular circumstances (That is matching the oil to the Car model – driving conditions – Engine age – options fitted eg Exhaust / Turbo / Blower etc) . Just because someone else uses brand “X” or the manufacturer markets a particular oil very strongly is not a guarantee that a particular Oil setup will work the same for you.

There is a heap of material around about the bases and values of various additives in Oil (Mineral / Semi-Synthetic / Full Synthetic).

Just a warning –if you do change from a Mineral Oil to a Synthetic or go the other way make sure you thoroughly get all the old Oil out of the system You may have to use a flushing Oil or do two oil changes in quick succession. Mixing Oil grades and additives can be really bad news. The different Oil additives can react together and change the Viscosity or create a serious problem like aeration (Foaming Oil). Foaming Oil does Lubricate well – Air Bubbles in the Oil acts like a heat insulator rather than a heat transfer fluid. Even using two different grades from the same manufacturer can have the same effect. You can destroy an engine this way and never know why it went bang!

If you have to “top up” the Oil because its low on the Dipstick and you put something in that is different from the base Oil – change the Oil out as soon as you can. (The smart solution is to carry about 1 litre of whatever Oil you do use - that way you don’t create a new problem).

I started off with Castrol Magnatec 10W-40 at 1,500km and got good results with it all the way up to about 150,000 km. My Car was smooth – bags of power – low oil consumption – and did not sound like a bucket of bolts)... After 150,000km I got the intermittent “ticking” lifter at Hot idle problem.

The ticking would come on about 2,000km after an Oil change and when the engine was hot and doing long duration low RPM idling (Read the Lifter would “tick” when in bumper to bumper traffic – on a Hot Day – while Sitting in Drive).

Best case “ticking” scenario for a Hot idle immediately after an Oil change was it would start to “tick” after about 15min. After the oil had been in the Car for 2-3,000km, a Hot idle could bring on the “tick” in under 2 minutes. After 5,000kmafter an Oil change it would tick when Hot after < 1min of idling in Drive

For me the problem “Ticking Lifter” is the one on the Front RHS - that is the one furthest away from the Oil Pump! Lifters need Oil Pressure to function correctly.

To stop the ticking you had to keep the Oil pressure up by raising the RPM (Dropping it into Neutral and giving it a gentle nudge to bring RPM’s up to 2,000) – the alternate was to turn the Engine off if really stuck in traffic. On a restart the ticking would go away and as long as we held normal road speed at above 2,000 rpm – No Problem!

I have since moved to using Nulon 15W-50 Full Synthetic (Did that at about 200,000km) and the ticking lifter issue has largely subsided – but it is still not “fixed”. The Engine will still tick, in the most extreme conditions (Oil approaching 4-5,000km, Very Hot Weather – Stuck in traffic at idle – very low engine RPM’s) it will tick slightly but a few cycles of revving and idling sort it out in a few seconds.

[mcsquirt]

Fifthly –The inevitable – Should I just keep fixing things, Is it time to sell the vehicle, should I rebuild it, or should I go nuts and work it up into a VZ Supercar?

I know eventually I will have to replace the lifters – they do wear out. It’s just a bugger of a job to change them (you have to takes the heads off to get the Lifters out) and right now I am not enthusiastic about that task. Note: Some folks suggest changing out the lifters after 100,000km.

A lot of folks who cam their Cars get this outcome (new Lifters) by doing the Cam upgrade.

There are aftermarket Oil pumps like the Melling 295 / 1029 / 10296. That can get you back to stock Oil Pressures or better. The New Oil pump may give you the option of going back to a lower Viscosity Oil. Again a somewhat painful job but on the evidence you can get a new Oil pump fitted in 5-6 hours without having to take the Engine out. See lots of reports of 60-70psi Oil pressures at WOT, and a respectable 40psi at a Hot idle - with these pressures the Lifters may go back to behaving normally.

If you have do get to the stage where have to pull the Engine out – then why not put on a new exhaust, chip it up – do the Over the Radiator (OTR) MAFLESS Tune, or go the whole nine yards and put on a SuperCharger / Turbocharger. Good time for a new radiator – new belts – new hoses.

Stuff it – if we are going that far, might as well do the transmission up as well. Could be $20,000 in that lot.

Now if you add that up in time and money- it’s a lot of dough poured into a high mileage Car – maybe a brand new of second hand R8 Clubby, GTS or a new LSA powered beast is the better option.

It’s all about the choices and the Budget really!.

[mcsquirt]

Interesting graph of a Standard Melling pump in a VZ GTO (Temperature / Oil Pressure & RPM)

https://www.google.com.au/search?q=o...q57jiygnWbM%3A

[Micks]

They are a decent pump! My L76 converted to L98 has the L76 dod oem hi volume pump gives me 80psi @ full noise. Not bad on a 90K+ engine.
That also includes blocking off the secondary dod redundant oil feed.

[mcsquirt]

This time some links to the issues of Oil Temperature on Oil Life - Various Oil Grades 0 through 50 weight & the changes in Temperature / Viscosity

http://www.elephantracing.com/techto...emperature.htm

[Wonky]

The VE L76 in the ute which had DOD delete used to cruise at 100kmh at around 4.3 bar (63psi) but being VE didn't have the redundant oil feed blocked (I don't believe).

[Micks]

The VE L76 in the ute which had DOD delete used to cruise at 100kmh at around 4.3 bar (63psi) but being VE didn't have the redundant oil feed blocked (I don't believe).

Yes Gaz unfortunately the VE L76 didn't have the external bung that you could easily undo & insert a blanking plug! It can be done in the VE but it's a sump off job only.

[Wonky]

Yes Gaz unfortunately the VE L76 didn't have the external bung that you could easily undo & insert a blanking plug! It can be done in the VE but it's a sump off job only.

Yep, I remember reading Swingtan's thread on it and thinking that should be easy ..........

[Micks]

The DOD specific oil pressure relief valve inside the oil pan. When main oil pressure exceeds 55psi this relief valve exhausts excess oil to the sump.
L76 oil pump displaces 1.24"/rev compared to non-DOD 6.0 engines (LS2 and L98) which have 0.95"/rev oil pumps.

[mcsquirt]

Diagnosed that the Ticking Lifters is primarily and Oil Pressure Problem (Oil Pressure going Too Low).
Found that with the Car on a steep Nose Down Attitude the pressure would stay around 200kps.
Nose Up on a hot idle it would avalanche away to Nothing (I mean The Low Oil Warning - Chimes & the Oil Can Symbol).

Any nose up attitude with Hot Oil (15W - 50) and the Liftrs will tick after 10-20 seconds

Found the "O" Ring hand gone rock hard and had a small crack in it.

Just finished fitting the Melling 10296 (High Volume / High Pressure) Oil Pump - Note: I fitted the Blue Standard Pressure Spring


Dropped back to Mobil 1 5W-30

38-40 PSI Hot Idle - up to 55psi (Hot at 4,000rpm).

Up to 50 PSI on a Cold Oil (Idle) and WOT up to 70Psi.

Woo Hoo

Fitted a Setrab 625 Oil Cooler as well using AN10 Fittings (No drop in OIl Pressure)


NO TICKING LIFTERS AT ALL

In fact the start ups are dead quiet!!!

[Micks]

Glad you got it sorted & those numbers are sounding good too.