Could you send me a copy too please mate?

 

Ok so you have done your oil change, most of the new oil is now in the sump so you dry crank the engine until the oil light goes out then you reconnect the sensor fire her up and away you go.

You Park your car up for a few days, the oil has returned to the sump or the vast majority of it. After a few days you decide to take the car for a spin. Do you disconnect the crank sensor before driving off? Maybe not, but why not, what is the difference as the oil is in the sump just like after an oil change?

Those that have stripped a Scoob engine will know how much oil is left in the gallerys etc after draining the sump.

Im no technican or mechanic but am i missing something here? I read on here to disconnect the crank sensor after an oil change. That was nearly 10years ago, never done it since and never will, i have changed the oil on numerous scoobs now without carrying out the Crank sensor bit and never had a problem with any of my engines or the other cars i have serviced.

Many will do it to be safe, personally i think its an Scoobynet myth and i will maintain that thought until the evidence is there either way.

 

WRONG !! Shaunyboyuk on two counts.

1/ A Subaru boxer engine is not the " same as all performance engines " It is a flat four and has a completely different set of dynamics working on the internals.

It is the fact that the pistons are going sideways that changes everything. Subaru engines are much more susceptible to det than just about any engine I have ever had to deal with.

I ran an EVo 4 for a while on 97 ron and it clanged like a fire engine in 3rd gear. But never suffered long term to the det. l did the same trick with a Skyline GTR and it also knocked its head off, but stayed together.

Get any amount of det in a flat four Subaru engine and failure is not very far away.

2. Don't just fill a Subaru filter and then start it. That is not a good idea, once filled with oil and with a primed filter, remove the cam or crank angle sensor wires and spin it over until pressure is established. Starting straight away wipes the bearings and over time will cause them harm, even if you just let it tick over.

For that reason, done clumsily, regular early oil changes can be harmful to the bearings. BUT done the ' safe way ' you could change to oil every day and not cause any harm....

David APi

 

There are very few engines upright or otherwise that have the crank dipping in the oil. Years ago when I was at Ford, we had problems with engines being overfilled with oil and the crank made a dull ringing sound as it constantly bounced off the oil.

I have even seen crank fail for dipping in the oil.

Splash from dripping down from the bores is nearly impossible, due to the high air speed in the crankcase created by the crank spinning. That makes all the oil fly away onto the crankcase walls.

The windage tray on a Subaru is there for the very same reason, but in reverse. It prevents the oil being flung off into the cylinders [ not very well I admit ] but that is the general idea.

David APi

 

You Park your car up for a few days, the oil has returned to the sump or the vast majority of it. After a few days you decide to take the car for a spin. Do you disconnect the crank sensor before driving off? Maybe not, but why not, what is the difference as the oil is in the sump just like after an oil change?

When you drain the oil out the pick up pipe empties. When you fill it again the oil will only go as far up the pick up as gravity will allow it So there is air above the oil in the pick up pipe. On a working, primed system, the oil will remain in the pick up pipe right up to the oil pump.

Try filling a glass of water with a straw in it. If you fill the glass and have 2 inches of straw sticking out the top, full of water? Of course not.

Drain the glass, does the water stay in the straw? Of course not.

David APi

 

I will..... if I remember!!

 

As David has already pretty comprehensively covered, wrong. There's a big difference between leaving your car parked up for a few days and changing the oil. The key difference is that one involves unscrewing the filter, the other doesn't.

Yes, and funnily enough, a bunch of people who have stripped these engines (a lot) are the ones suggesting removal of the crank sensor.

David has already drawn you the analogy of the straw full of fluid. There's an extra aspect to it though. Once the lubrication passages are fully primed, the anti-drainback valve in the oil filter will, as its name suggests, actively prevent the forces of gravity trying to return the latent oil to the sump when the engine is stopped. So, like a straw full of fluid with your finger held over the top.

The fluid lock on both sides of the filter will result in the oil system remaining almost completely primed, even if the car is left for months. However, removing the filter breaks the lock and will allow a significant quantity of oil that would otherwise be held in the system to drain out and be replaced by air.

You can see this for yourself next time you do an oil change. Put a receptacle under the filter, undo it carefully so none of its own contents can spill out, and then see how much oil drains out from "above" it both immediately and over the course of a few hours. You'll be surprised.

Even if you fit a new pre-filled filter, there will probably be a significant quantity - maybe over a hundred cubic centimetres - of air in the system that needs to be purged out. Until *all* of it has been removed, the pressure of the oil throughout the system will be a little inconsistent due to the compressibility of the air - which will, in any case, be making its way "out" through the bearings.

If the engine is running at the time you will have the oil pump forcing air under pressure through the oil system. If it's simply being cranked on the starter, it'll be pumped through at a fraction of the speed and pressure - and whatever oil remains in the bearings won't have to deal with full combustion loads.

That's a pretty bold statement, especially given you've already exhibited a fundamental misunderstanding of the way the oil system works, and appear to be putting other owner's cars where your mouth is.

Indeed. It's an insurance policy that doesn't do any harm. So, you think that "being safe" is such a bad thing you don't bother with it?

When you service cars belonging to other people, do you tell them that you think "being safe" in this area is unnecessary, but offer them the option of doing it if they want you to? How would you go forward if one of these people suffers a bearing failure just after you've serviced their car, searches SN, and ends up reading this thread?

 

Of course. Said that in the "other" thread I put the theory into. Until someone puts some money into testing it exhaustively, it's all surmise.

The principle problem with that line of logic is the assumption that the manufacturer's published tolerances are themselves optimal. I don't have any manuals in front of me at the mo but from what I recall some of the numbers have changed over the years - so this is Subaru themselves changing their definition of what's acceptable and what's not.

Agreed. As said elsewhere, any damage in the engine, no matter what its root cause, has to be fairly well advanced for the typical driver to notice something wrong.

That's very much a theoretical example as, in practice, a leaky seal would be unlikely to fail in a manner that it performed acceptably before the change, but not immediately during/after it. In this scenario it'd probably be allowing the pickup to drain (and air to be introduced) almost constantly. However, taking the example as you wrote it, the o-ring is clearly the primary causal factor.

Although, in practice, cranking the engine to establish oil pressure prior to starting should ameliorate the consequences of such a problem - flow would be established prior to the pump being driven at high speed, and therefore less opportunity for cavitation.

The engine's probably still living on borrowed time, but cranking prior to start removes a potential crunch-point.

It'd make for an interesting exercise to compare an engine like that with a Subaru. Just looking at the relative area of the main bearings would, I suspect, say a lot. The BM, being a straight six, not only has two extra main bearings, each one of them is likely to be wider, and possibly larger in diameter, than the shells of an EJ2x.

The smaller the overall bearing area, the greater the relative load, and the easier it'll be for the lubrication to be undermined and direct contact to occur. Then you consider that it's a much longer crank than an EJ's and should therefore be able to deal with a loss of oil supply to one or more of its bearings in a more stable manner by spreading the load across its neighbours.

The fact that the EJ is a flat four introduces changes on so many levels, comparisons with other designs - especially inlines - largely become meaningless.

Every cloud, etc.

 

I cant pre-fill my oil filter as its sits with the seal pointing to the floor (relocated behind headlight)

done 4 oil changes and havent had any issues yet (rabbits foot in pocket mind)

Might do the cam sensor this time round tho,now ive jinxed myself

 

That would be great if you could do that Joz

 

hi guys

i know its been done to death im changing oil on my motor, and i cant get the crank senor off and i dont want to damage it. cant i disconnect a coil pack or fuse of the fuel pump?

thank you in advance

mus

 

What can't you get off Mus? Do you have a very early car with a sensor with a captive wire, or can't you get the plug off a newer one? If the latter just wiggle it with the detent held down and it'll eventually work free.

If you're absolutely sure it won't come off, disabling the fuel pump and the coils will get you more or less to the same place - but it'll still inject fuel until the rail empties, so this is still not as good as removing the crank sensor.

Inciidentally, if the crank sensor plug won't come adrift, have you tried the camshaft one?

 

will give it a try its a classic. if that doesnt work just getting rid of one coil pack would that do the trick and i will only be cranking for around 20 seconds.

 

Does the cam sensor removal prevent firing and fuelling a la the crank sensor, then?

 

John, The crank angle sensor is there to trigger the spark for the plugs. The cam angle sensor is mostly there to tell the ECU that the cams are rotating during start up.

It drops out at about 1500 rpm and has no further purpose.

So if the ecu doesn't see the cams rotating it doesn't spark and it doesn't fuel.

David

 

I'm with yer.

So, in some ways the crank sensor is subordinate (a kind of "slave") to the cam one... as if there's no cam rotation, then the crank sensor can't even begin to do its fuelling/sparking thang, right?

 

[quote=APIDavid;9245712]There are very few engines upright or otherwise that have the crank dipping in the oil. Years ago when I was at Ford, we had problems with engines being overfilled with oil and the crank made a dull ringing sound as it constantly bounced off the oil.

I have even seen crank fail for dipping in the oil.

Splash from dripping down from the bores is nearly impossible, due to the high air speed in the crankcase created by the crank spinning. That makes all the oil fly away onto the crankcase walls.

The windage tray on a Subaru is there for the very same reason, but in reverse. It prevents the oil being flung off into the cylinders [ not very well I admit ] but that is the general idea.

ok here we go given up reading this thread some going one way others the other so i contacted subaru uk and spoke to there chief tech officer in depth ,
he has heard these problems floating around and has even looked into it , but the only problems he has come across in oil changes is as above. Subarus have a very low tolerence to over fill , taking just a small amount over, to cause problems because the crank splashes in the oil causing it to be whipped up eventually foaming ,as it foams and goes into the pick up obviously there is more air than oil and hey presto your problems hit home,thats why it can take a while after an oil change befor any thing goes wrong ,
he recomends to take your time filling up , if you wish and can pre fill your filter do so as it helps once your full to the mark , start the engine dont rev and leave it on tick over for ten min, turn off rest the engine and check your levels again and adjust either way but do not leave it over the full mark even if its just a smidging . removeing the crank sensor if it makes you feel more secure will not do any harm....

 

I still find it amazing that people can't even get the very simple task of getting oil level correct when refilling an engine with oil:

This is the sole reason why one should NEVER dump 4.5 litres of oil straight into the engine. Despite technical data saying it has a 4.5 litre capacity for the sump, that data may assume a dry fill of a newly assembled engine, not one thats just had its oil drained out. The amount of DIYers and garages alike that do this bad practice of dumping in the full capacity in one go is unbeliveable; Too many times I've had a car serviced at a main dealer (not just Subaru) and found it has been overfilled to some extent (My Monaro had a litre too much oil, yes a whole litre! ). The level should be BETWEEN max and min, the max hole is there for good reason, as described in the above post.

It really is simple; Stick about 4.2 litres in, start it up, let it run for a few seconds, turn off, wait half a minute and recheck and add as required. Its about a pint between max and min, so use that as a guide of how much extra is needed. This can be tricky to the uninitiated with the way the Subaru dipstick wicks oil up the tube, giving a false high reading. Look closer at the dipstick; The actual level is where the oil completly covers the whole width of the dipstick, not the edges.

 

Hoyty, I would be interesed to know whether the procedure set out verbally by the Subaru technician is actually recommended to their dealers and carried out by them in that manner.
Has anyone got a copy of the schedule as set out to them by Subaru UK?
The reason I ask is that my car suffered big-end and crankshaft failure after being serviced exclusively by main dealers from new and had covered just 36k miles.
The big ends went about 200 miles after a full service and when I suggested to the same man you quote that they should review their recommended procedures I was told by him and the Customer Relations manager (by letter) that "We do not feel that the service procedure regarding oil and filter changes is in need of revision"
They were not able to suggest any reason why my engine should fail, and when pushed on the point would only say that "Crankshaft or bearing failure can be caused by many factors beyond our control"
Presumably those factors are beyond anyone's control then, since I trusted my oil changes to their trained technicians and regularly checked the levels between services.
Please let me know, anyone, who has sight of the actual procedures recommended to their mechanics and we will see how they compare to what you were advised.

 

just pmd you lol

 

[QUOTE=hoyty;9260051]
We've just measured an oil level and a crank position relative to the correct oil level and overfilled level.

In normal circumstances, the oil at correct level is best part of 18 mm below the height of the sump, where it bolts to the crankcase. The crank is nearly another 25mm above that, at it's lowest point.

That is one hell of an overfill if the crank could dip in the oil. Like about 2 litres too much......................

David

 

up for a quality thread

 

[quote=APIDavid;9261453] just saying what the man told me , but as suggested before perhaps subaru are aware of the problem and cover it up ,there again being around garages i ve noticed that the simple jobs like oil and filters are sometimes left to the apprentices , no offence to any one who is , but if theyve not been shown ... well who knows , mistakes happen , we all make em , i remember arching a spanner to the body more than once when playing with batts ,,,
Perhaps the site should run an online petition to subaru asking them to investigate , and review practices acorddinly, and to make accessable as requested earlier what those servicing practices are , after all they charge enough for them

 

[quote=hoyty;9262696]good idea that online petition whos gettin the ball rolling i think api david he is a top engine builder

 

[QUOTE=hoyty;9262696]Hoyty, No sweat mate, not having a dig at you, but clearly the 'experts' at IM can sometimes be off the pace.

As you say; it is often the simple job,s that get left to the simple people.....

In the case of a flat four Subaru it is probably the most important job of any. AND I doubt any proper Subaru tuner or specialist would ever do a slack oil change, the risk is way too high.

David

 

[QUOTE=nick schofield;9262708]
No way man, I'm already in enough trouble at IM.

D

 

Indeed. As explained by David, the overfill/crank and rods in oil suggestion is bizarre, to say the least. It just doesn't fit the facts as they are known, even allowing for a bit of leeway for the oil to misbehave as the car is being driven.

I doubt any garage would routinely overfill the sump to that extent as, aside from anything else, it's a waste of oil. If IM's technical people are saying that, it, well, possibly explains a thing or two. Worrying.

Mind you it'd be interesting to see what would happen if you phoned him back up and asked him to put the same comments in writing. I've got a quid says he won't.

There's not a cat in hell's chance of IM taking any notice of anything like that. If they were that responsive to what the online owner community wants we'd never have had to wait two years for the bugeye to be killed, and we wouldn't be stuck with the hatch now.

Aside from anything else nothing could be okayed by Subaru UK without approval from FHI in Japan, and the last thing they, or their major shareholder Toyota would want right now, is to admit a fault or shortcoming in their engine designs.

 

FYi, I tripped across a data table today and found out:

BMW M52/M54 engines have smaller big end bearing diameters (45mm). EJ20 has 48mm or 52mm depending on year/model. Sadly I don't have the widths at hand to compare.

It is possible they may not be too different in width either as to maintain good fuel ecomony and get into lower EU emissions bands etc that bearings are not made excessively large, which aids to reduces drag (same theory with them using 0w-30 oils on later engines).

There are two extra main bearings (60mm - same as Impreza) - but then they have to support the weight and load of another two big ends, extra counterweights, pistons and rods flying up and down. So horses for courses.

Either way going on the basis that 5 seconds of idling without oil flow or pressure is enough to cause cumulative wear/damage. And seeing there is an extra four bearings to supply oil to, then this engine should be dead. It'll probably put a rod through the block tomorrow now I said it.

 

So basically the gist of this whole thread, is that disconnecting the crank sensor is NOT needed?

The above, explanation, admittedly I have never met you, but that explains why you are apparently one of the best tuners in the UK

You have a brain (i mean the glass and water explanation)

I agree totally, how is filling your car with oil "the normal way" any different from leaving your car for a day, and starting up It isn't (only difference is, that you have newer oil)

Either way, unless the system is in motion, the oil will go down to the sump... it won't stay all primed like it is when moving

 

No, no. After you have drained the sump and refilled it with a primed filter YOU MUST disconnect the crank [ or cam ] angle sensor to prime the whole engine before it starts. Just pulling off plug leads [ if you have that type of engine ] will just stop the spark, it will not stop the fuel pump running and washing the bores.

Cam or crank angle sensor stops spark and fuel.

David