So, over the last couple weeks I was noticing that my upper timing chain tensioner (new model):

https://www.jaguarforums.com/forum/x...so-fail-61698/


..... was making quite a bit of racket upon startup, which it has done here and there since I've owned the car. But over the last couple weeks it seemed to rattle quite a bit more raucously and reliably every time after sitting for several hours. Like prior tensioner rattles, it went away in a 'second' once the engine started.

This in itself is not so odd again because it always had the tensioner rattle every so often, but for some reason I can't really explain I had also let my oil change interval run over by about 2k miles, so about 7k total miles. And I hadn't thought to check the oil level in weeks as it had never burned/lost any significant amount of oil between changes before.

But while verifying that I had the new upper tensioner since I thought I may just need to swap out the old version to address the now "every time it starts after sitting overnight" rattle, I thought to check the oil level since the tensioner relies upon oil pressure.... only to find that the dipstick was dry. It had a little oil just barely on the tip which may have just been from the sump splashing, but essentially showed no oil on the stick.

Now, at no time did my oil pressure gauge read anything other than "normal" right on center, and at no time did my oil pressure warning light even flicker when the car was running.

And the gauge does work, as it reliably shows "zero" pressure before started, and the oil "idiot" lamp does light when the key is on but engine is off.

And when the engine ran I never noticed any untoward noises that one normally associates with low oil, etc other than the aforementioned tensioner rattle upon initial crank, which again went away in about a true second.


I was right next door to a "Jiffy Lube" when I noticed this, so I had the oil changed immediately, which didn't provide me a chance to take individual quarts and pour in to see just how much lower than a full 8.5 quarts I was at. So I don't know how low I really was.


Now some two days later following the oil change, good news... I've not been able to get it to reproduce the tensioner rattle and the car still seems to run fine, no smoke, no other odd noises or vibration.

So, this leads me to wonder a few things.

First, even if one doesn't have low enough oil to trip the gauge or light, being a quart or two under apparently is enough to let the upper tensioner drain down more easily than not and rattle more frequently. I only have two days of results so far, but if the tensioner stays quiet for a few more days, I'm convinced the low oil was a major contributor to the upper tensioner rattle issue even with the new model tensioner. So issues with tensioner rattling may be due to a high sensitivity to oil level, perhaps more than thought.

Second, although I was clearly much lower than spec for oil capacity, it seems I must not have been quite low enough to lose oil pressure as there never was any indication while running that oil pressure was low and the car also never got hot. So that leaves me to wonder just how low the oil (in capacity) can get below the full 8.5 quarts in an AJ16 without trouble?

Finally, since I never saw oil pressure drop in the gauge or warning lamp, and I didn't and don't hear any odd noises nor smoke and engine is running smooth.... am I safe to assume/hope that no significant damage was done with the oil level as low as it seemed to be?


...really stressed me out, but here's hoping that if I didn't see pressure loss and immediately notice crazy noises, etc that the "bulletproof" AJ16 can run a bit low with no ill effects

Thoughts?

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Bugga,

Oil pressure is oil pressure, and as long as the pump can pick up something, the rest is elimentary.

Oil flow is oil flow, and again a close relation to pressure.

I reckon the fact that the oil inside that engine was sooooooo far past its use by date, was more of an issue than the actual level in the sump.

The oil light is designed to come on at ABOUT 7psi from memory.

Most engines in my time can safely operate at about a Litre (Quart approx) down. NOT recommended of course, but do-able.

The Jags with the larger than normal sump capacity have a greater tolerence, again, MY opinion.

From my V12 days, as the oil got to end of its useful life, the engines did sound a little different to me. New oil, sweet as ever.

 

Yep, I agree, I meant to also add that along with a potential sensitivity to volume, perhaps another component was the "age" (condition) of the oil in playing a role in the tensioner rattling more frequently toward the end of an oil change duration.

BTW, the oil was 10W-30 Pennzoil Platinum synthetic, so it in theory has a longer change interval.

So I wonder:

1) If oil is just touching the tip of the dipstick, how many quart(s) low is it than the full 8.5?
2) How low the oil can go in the AJ16 and still maintain flow/pressure?



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OK.

Botttom of the dipstick I reckon is about 2 - 2.5 ltrs (quarts close).

The 10W30 is MAYBE a tad light for that older style engine design/clearences. My 3.2 runs 10W40, or 15W40, and thats about as low as I would go.

How low can the level go before damage?, no idea, I am simply not that brave.

As the oil level drops the heat builds up SERIOUSLY, so the oil breaks down even quicker. The engine oil dissipates a LOT of engine heat.

 

Thanks Grant. I'm hoping my level may have actually been a bit higher. I checked the level after having started the car, and I know that the manual states that the car must sit for at least 2 minutes or longer before the oil level on the dip stick reads reliably. I didn't wait around much longer than that before literally going around the corner to get the oil changed.

In any case, since I didn't hear any untoward noises and never saw low pressure, I'm hoping no damage of any significance was done. Keeping fingers crossed.

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I'm sure it's fine. I also got a bit worried when I checked the oil level right after a short drive, since it was just above min. But then I left the car parked overnight, and surprise, it was just below max in the morning!

Apparently it takes much longer for oil to settle in this engines.

 

Yep, checked my oil today after running the car barely 15 seconds, and although completely full the dipstick barely showed probably an 1/4 inch of oil on the tip.

So the direction in the manual is definitely correct that checking the oil after running the engine will show an abnormally low reading on the dip stick until it drains back down.

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Al,
A couple of thoughts;
- Do you have an oil leak? The reason I ask is that if the sump was full after the previous oil change, a dipstick of oil is a lot to burn in 7000 miles. Or might the oil not have had a chance to drain fully back into the sump when you took the reading?
- You mentioned that there were no signs of oil starvation, and that the only issue was timing chain rattle on cold startup. The issue with the top tensioner allowing rattling on startup is, as far as I know, pressure leaking back out of the tensioner piston as the engine cools. When the oil pressure reaches the top of the engine on startup, the pressure is replenished, the chain tensioned, and silence restored. Unless it was taking markedly longer for the rattle to subside, I would not take it as evidence of oil starvation.
- You are using oil which has a 10w rating. That may be what is specified for your location, but in the UK, 5w is specified. As it has been explained to me, the lower the W number, the better cold start performance, so that might be worth looking into that, although in truth I suspect the difference is marginal unless you live in the Arctic! You are also using synthetic rather than the specified semi synthetic oil, although I don't feel qualified to comment on whether that makes a difference (other than to your wallet, especially as you change oil every 5000 miles!)
Al, from what you have described, I doubt that you have damaged your engine by running the oil too low, and I certainly don't think that low sump oil level is the cause of the startup timing chain rattle. Having replaced the tensioner, the chains, and tried every viscosity of oil known to man, I am now resigned to the occasional momentary startup chain rattle after a cold night. (That said, I am wondering whether a stronger/ longer spring behind the piston might work....)

 

Thanks, yes this has been an interesting 'learning experience' with regard to perhaps another idiosyncrasy of the AJ16 where the dipstick has special requirements to read correctly

At this point I'm not convinced I really was all that low on oil, although definitely some. I haven't owned the car long enough to know if it is a chronic oil burner (I have no smoke or odor BTW) and it doesn't leak oil at this time. So maybe its nothing to worry about.

As you mention, I'll probably do two things going forward (along with a shorter oil change interval) is to maybe switch to 5 or 10W-40 since I'm in a warmer climate and stay with semi-synth.


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I had a slow oil leak a year ago, and I neglected it, not realising how much I was losing.
I thought after a while there was a bit of a rumble. It took 3.5 to 4 litres to top up to the top of the dipstick.
I don't know why I let it get so low - I am usually an **** oil and water checker, even in new cars. I know oil is a major coolant as well as lubricant.

The leak was sorted - a broken O-ring on a grub screw that blocks off an oil gallery in the block. It was not the rear crankshaft seal.
It took gearbox and torque convertor removal to sort a 10 cent O-ring,but put in a new crank seal at the same time.
Dry as a whistle now

 

Al,
My recollection is that it takes about two quarts to move it from the min to max mark on the dipstick. In the interest of not over-filling, I'll normally just add 7 qts at an oil change, then after running, little-by-little to get it in the cross-hatched range. As you noted, the 2-min guidance in the manual is important in getting an accurate level. My own 2-cents would say give it 2-hours! But that is not always practical.


I don't think you've done any damage. I would encourage you to give the Rotella T-6 5W-40 diesel oil (Well, it truly is dual-spec) a look for an affordable synthetic option. When I first acquired mine, it had a recent oil change and reportedly contained 15w-40. I ran that to interval then executed an oil-change to Valvoline 10W-30 Synthetic and it went through my engine like (food) thru a goose! Then I switched to Valvoline's 20w-50 Racing oil which was great until a couple of rare teen-20's F N. Texas morning starts where I was treated to the tensioner clattering you mention for several seconds. Then I got the "gouge" from both Motorcarman and Brutal that these engines just seem to love the heavy-duty truck oils, and shazaam!!! I already had the dual-spec item I needed in stock for the Excursion! I'm not "shillin'-for-Shell;" any 15w-40 or 5w-40 oil of the proper spec will do fine, it is just that I can find it reliably $4-$5 less per gallon (~$20/gal and readily available at any NTX Walmart, don't know about your NC locations, most everyone here has at least one diesel pickup, so demand is firm) than any other synthetic. I've recently converted both S-Types and both F-150's to it as well.


For perspective, the turbo-diesel Excursion is even more demanding on oil than most engines, not only a turbo-charger, but it also uses oil-pressure to fire the fuel injectors, and the dipstick is stamped with "Min mark indicates 2 qts low" but then it sports a total capacity of 15 qts.