Should Jabiru J170 oil level be checked hot or cold?

[Eric McCandless]

I cannot find reference anywhere to whether the the Jabiru J170 oil level should be checked hot or cold?

 

If one or the other, is there a procedure to compensate for checking when hot instead of cold or vice versa? e.g. oil level is 5mm higher when hot etc?

 

Also from what I have read, it seems that the best oil level strategy is not to fill to the full mark, but to the halfway mark, otherwise the engine will tend to just spit it out. Any comments or experience with that?

 

 

[old man emu]

Eric,

 

Check the oil level when the engine is cold, as part of your pre-flight. Fill your engine with oil to the full mark. There is precious little oil in a Jab engine, and all of it is needed to help cool the engine and maintain lubrication. If you overfill the engine, it will get rid of the oil (see your other post). Also in some cases, if you overfill the engine with oil, the oil can get whisked up like milk in a milkshake. It will be full of air bubbles, and since air is compressable, you could observe a drop in oil pressure.

 

If you have been flying, and the oil is warm, only add oil if you see that the oil level has dropped below "Full".

 

Just check your operator's manual to see if the dipstick should be screwed in or not when checking the oil. (I forget). Also check the part number of the dipstick to see that it is the correct one for your engine. There are different lengths of dipstick made by Jabiru.

 

Old Man Emu

 

 

[bushpilot]

Dipstick should be screwed in to check oil..

 

 

[turboplanner]

A manufacturer will usually expect you to dip the oil cold, when the oil has had time to run down into the sump.

 

Under that condition, the full line is the correct level to fill to.

 

Oil should consistently be dipped in this condition, because this method will show up actual oil depletion, and you can keep a record of oil burn.

 

Dipstick screwed in or dipstick touching is specified by the manufacturers who unhelpfully sometimes use one and not the other - you can do damage by using the wrong one.

 

If you dip hot, and fill to the full mark, the engine will be overfull at lower temperatures and suffer the problems referred to earlier, and froth can't be as good at lubricating/cooling as solid oil.

 

If you dip inconsistently, for example dip cold one day and fill to full line, then dip hot the next day, it will appear that the oil is down, but it's just sitting around the engine, yet to drain, and you'll finish up with an over-full engine.

 

That's why some of the comments about not filling to the full mark, but then in hottest operation you'll have less oil circulating than the designer tested with.

 

The problem with this is that oil also complements fuel flow and fins in cooling an engine, and the less oil circulating, the hotter the engine gets.

 

That then leads to a spiral because the hotter the oil gets, the closer it is to breaking down.

 

The volume of oil in an engine can be quite critical to long life. When comparing truck engines, I always look at oil volume, and as night follows day longer engine life always occurs on the ones with bigger sump capacity and oil cooling (there are many other factors, but this is an underlying one).

 

Having said all that I'm as guilty as the next person at shortening the life of an engine by dipping at any time and just keeping it between the lines.

 

 

[Compulsion]

Hi Eric,

 

I am looking at buying a 170 and would appreciate your advice. Sorry to post like this but I haven't worked out how to send a private post.

 

 

[Thirsty]

Eric ring Jabiru and get the answer to this from the manufacturer. You'll get 20 different answers here as we all have our own understanding of how things should work. I called jabiru when we bought our 160 and was told to keep the level fairly low on the dipstick which you'll find most jab owners on here will do also.

 

The jab manual isn't very helpful in this regard either but it does talk about levels.

 

 

[jetjr]

Yep the marks on the dipstick for me are a guide, If I fill to top mark it spits it out very quickly.

 

This can consume 100-200ml oil per hour if you keep putting filling to the top line.

 

Each engine seems to have a stable level, for mine its just above lower mark. If I top up to this level each time the oil use settles to 50-80ml/hr which is about right Im told. I still end up with ~ 200ml in the overflow at a service

 

An issue here could be the angle of the aircraft on the ground, some sit with tail down stance and dipstick is right at the front of the engine. The 2 engines Ive had in the same AC have both run similar levels.

 

If you overfill it can cause serious oil overheating in flight until its spat the extra out.

 

Checking a hot Jab engine doesnt seem to tell much as oil levels might be up or down depending how long its been sitting. I do add to hot engine sometimes but its based on the 50-80ml/hr not the dipstick.

 

 

[facthunter]

I've always felt that winding the dipstick in and out gives an inconsistent reading as when you move it around it can touch the side. The end should be sandblasted to make the oil level easier to see. I would rather not wind it but allow for the height difference of the thread length. You still end up with the same result.

 

Having different lengths of dipstick out there, is crazy. ( Murphy's law). Do it with engine cold or sitting for as long as possible for a consistent result. The set-up is a poor design anyhow. Nev

 

 

[turboplanner]

What I would do as a manufacturer, if I'd let production engines out of the plant semi developed and found the natural level was down the dipstick is amend the drawing to extend the dipstick by the 5 mm or so to get industry consistency, and FH I'd also extend it by the thread length and specify dipping without thread engagement.

 

 

[Thirsty]

I agree TP, it's crazy to have different dipsticks out there and we shouldn't have to wind the thing in to check the level. Having said that Jab are not alone, my CBR1100 needs to have it's dipstick wound in to check the level so Honda do that too for some reason.

 

 

[turboplanner]

I've got a mixture and can never remember them so I thought about an acronym but the only one which came up was CRAFT.

 

 

[Vev]

G'day Eric

 

Jab produced the attached doc ..... This should help you work out the oil levels for each engines and the levels associated with each dip sticks in production.

 

http://www.jabiru.net.au/Service%20Bulletins/Engine%20files/Dip%20Sticks%208A035A0D-1.pdf

 

Cheers

 

Vev

 

 

[facthunter]

I'll bite Turbo. what's it mean. CRAFT.

 

I hate acronyms. I've really never used them .It's nearly as easy to remember the items. With an acronym you have to remember "IT" and what the hell each one is supposed to mean. IF the thing has been "tailored" too much, it gets a bit stupid. It removes the sense of appropriateness to actions performed at certain stages of the flight. What you are doing should directly relate to your management of the plane at where you are at. Do you need a checklist to remind you to watch the airspeed on final somewhere? Should you need a checklist to remind you to have a look before you turn?

 

Even wheels "down& locked". It should be done long before you check it. The check is just that. Not a prompter .That only happens when you have forgotten, which should be rare. ( usually happens when you are doing something non standard) Nev

 

 

[turboplanner]

You've obviously forgotten it FH, Can't Remember A F*$?*#^ Thing!

 

 

[Eric McCandless]

G'day EricJab produced the attached doc ..... This should help you work out the oil levels for each engines and the levels associated with each dip sticks in production.

 

http://www.jabiru.net.au/Service Bulletins/Engine files/Dip Sticks 8A035A0D-1.pdf

 

Cheers

 

Vev

Well that is an interesting bulletin. That is the first reference I have seen from Jabiru to whether to check the oil hot of cold. It is not presented in my POH which I think it should be. It seems that if you have the old engine, then you do it cold, but if you have the newer engine then you do it hot. I just now need to find out if my engine is the old type (unfinned) or the new type (finned). Thanks.

 

 

[Vev]

G'day Eric,

 

My only additional comment is in relation to the lube oil level ... I would lean towards the very bottom end of the of the oil level marks, particularly on the finned 4 cylinder engines. (The non finned sumps have a deeper sump and don't have same issues.)

 

There is a number of reasons to do this:

 

• It helps with oil drain back from the rocker chest in older 4 cylinder (finned) ... an extended dwell period in terms of lubricant retention in the rocker chest can cause the base oil to thermally crack from too much heat. If the base oil cracks it will quickly die and chemically fall apart and not do the job it was intended to do. Having a lower sump increase the sump/crankcase voids and reduces the crankcase pulse which affects the rocker chest drain back via the push rod tubes. More void = better drain back, thats why Jab went to the non finned sump.
   
   
  
• If you fill to the top of the oil level mark on the older finned engines you will find most of the lube oil ends up in the oil breather bottle.
   
   
  

 

 

Seeing that you have a J170 I would suspect you will have one of the latest engine sumps, therefore things wont be so critical ... never the less, low end (of a dip stick) is better for your top end in a jab.

 

Hope this helps?

 

Cheers

 

Vev

 

 

[facthunter]

Turbo, Not sure that I can" Obviously forget" something that must have been so important that I feel I was never taught it. We relied on a memorised list of actions that were used prior to carrying out airwork, aerobatics etc. I don't like the use of acronyms particularly. I have mentioned that a few times.

 

Checklists, I have do difficulty with, the emergency ones being committed to memory, the others NOT being used to initiate an action but to check that an essential action has been done . I use the CDMVT thing with compasses but many of the other uses seem so varied and non standard that they may be for local consumption and may vary from instructor to instructor and not be desireable from that viewpoint..Nev

 

 

[turboplanner]

Turbo, Not sure that I can" Obviously forget" something that must have been so important that I feel I was never taught it. We relied on a memorised list of actions that were used prior to carrying out airwork, aerobatics etc. I don't like the use of acronyms particularly. I have mentioned that a few times.Checklists, I have do difficulty with, the emergency ones being committed to memory, the others NOT being used to initiate an action but to check that an essential action has been done . I use the CDMVT thing with compasses but many of the other uses seem so varied and non standard that they may be for local consumption and may vary from instructor to instructor and not be desireable from that viewpoint..Nev

Can't Remember A F$$$ing Thing

 

I agree with you on Acronyms - they weren't too bad before the CAA days but are out of control now.

 

You're right about the acronyms varying from instructor to instructor, which makes it very hard you remember ANYTHING at a big school

 

It's also hard not to forget the odd check when the acronym includes some letters repeated three or four times.

 

The one going at the moment - HASSELL is a good example, sounds the same as my HEL except it seems to have developed enough S additions to confuse Einstein.

 

Accident records over the years indicate that a lot of acronyms were forgotten in the panic of a sudden change in aircraft status.

 

I did some hours using checklists but found they had their shortcomings too, mainly in a crowded circuit where you could rip through acronym checks without having to look down and read a bouncing card. I also found I was concentrating on the card and not actually doing the check on a couple of occasions.

 

But there's one lot of acronyms that drives me berserk and that's the ICAO location protocol.

 

Before it we had a clue; it wasn't hard to remember that EN was Essendon, ADL was Adelaide etc, but why on earth would you adopt a domestic system where you related over and over Y, for Australia, then B for Queensland, or M for Victoria (but not all the time) then ran out of space for the three letters which identified the airfield so well.

 

And why on earth do people, talk about a trip from YBSD to YSRF dropping in for a coffee at YSBG and doing a touch and go at YBKL?

 

Do they really think we're going to look for the ERSA and decode the location?. I'm sure many a good travel story is dropped because of this little habit.

 

 

[facthunter]

Exhausting isn't it so... YFKN do it? Don't have difficulty with remembering what BS stands for..Plain language for planes... Nev

 

 

[nong]

I reckon check oil level before aircraft is moved from its overnight position. Unscrew the stick and read it. No wiping required.

 

Horizontally opposed aero engines with wet sumps generally react poorly to high oil levels by spitting out the excess oil or overheating the oil.

 

Although a 2.2 lit. Jabby only carries 2 litres or so of oil, I once discovered this to be well in excess of requirements when a structural failure resulted in all but 500 mls being lost overboard. Despite this, temps and pressure remained stable. A lower oil level during colder months will allow the oil to reach a reasonable operating temp and to get there faster.

 

 

[turboplanner]

Those of us with farm machinery may have experience running and engine without any oil at all, and I can dimly remember this subject coming up in a magazine, and virtually a competition to see who could run their car engine the longest with just the residual oil minus the sump - they got some surprising times.

 

One of the secondary functions of oil is an upper cylinder coolant, helping fins/water jacket and fuel flow to keep the temperature at a safe level.

 

Oil gets in close to the combustion chamber which is where the heat is generated, it is pumped onto the rockers and cools them, keeping the diameters nicely tight to maintain even valve clearances and it flow onto the valve stems, reducing the peak temperatures and keeping them well lubricated in their thousands of kilometres of travel.

 

Nong raised the issue of overheating oil - which makes it virtually ineffective as a lubricant and pressure separator.

 

Sump capacity has a lot to do with this.

 

In comparing heavy trucks, where engines are so expensive that maintenance is often recorded cylinder by cylinder, a bigger sump capacity can usually be found on the engine with a longer life cycle, because more oil circulating means more oils spends time away from the upper cylinders and so gets cooler, and so takes longer to break down.

 

 

[jetjr]

While concepts are similar its pretty hard to compare light AC engines with large diesels.

 

If these heavy engines had 2500km services, major top end work scheduled @ 100,000km and 200,000km rebuild no one could afford to own them.

 

In order to make them run 100hrs or more between oil changes volumes etc need to be larger and filtration better. Regularly Turboed too which loads up oil temps.

 

 

[turboplanner]

I was only talking about the simple principle that more sump oil = more cooling, cooler oil and longer time before the oil breaks down.

 

The heavy diesel engine market is a lucrative one so manufacturers spend billions of dollars on development. They've been focusing on lowering emissions in the last 20 years so they've been sidetracked off increased power for decreased fuel consumption.

 

However they regularly achieve 20,000 km to 50,000 km oil changes, and one truck became the worlds first throw away truck, not requiring any oil changes during the life cycle.