neilh68

i have been told that when i change the engine oil i need to take the crankshaft sensor off first is this right..thanks for any help

raw1879

Thats a big fat NO

neilh68

thanks.....

Luminous

iTrader: (3)

There is a great debate over this. There is one camp that thinks you should do all sorts of stuff, there is another that thinks you should change the oil like any other car.

Do a search for oil change and you will see that this has been talked about a lot before. I cannot add anything to what has been said before.

340BHP-WRX

iTrader: (6)

I'd say YES-better to be safe than sorry. Just crank it over for a few seconds with the sensor off then re-connect and fire it up

Shark Man

Subaru workshop manual doesn't say anything about cranking with the sensor removed.

Hence not needed to be done and dreamed up by someone with a little knowledge (yet not enough) who is paranoid about their engine blowing up. They probably took the spark plugs out too (which if it were really a problem - you should remove them )


Doesn't even mention prefilling the oil filter either.......but what the hey, if it makes you feel better, nobody is stopping you

340BHP-WRX

iTrader: (6)

It's better to do it than not to do it ! All it does is build-up abit of oil pressure and fill the filter etc before starting.

Who cares if it works or not,just do it to be on the safe side.

It's not just Subaru specific either-I use to do it on the cossie's years ago and on my M3 aswell

There's lots of things the manual doesn't tell you-doesn't mean it shouldn't be done !

Shark Man

Here we go again ....

Is it safe?: A slow spinning pump doesn't prime any quicker....anyway, that doesn't matter....

By design, bearings are hydrodynamically lubricated. All that is needed is an oil film, and that will always be present for the first 5 seconds (or even as long as 10 seconds or more under light load) of engine running, before any flow replenishes that oil film.

If that were not the case, removing spark plugs and cranking the engine would be required on every single mass production engine, after a service, as almost all of them use hydrodynamic bearings.

Now if the engine was bone dry (i.e rebuilt), it would be a different story, However, an oil change does not magically dry out all the oil still between the bearings and journals.


So its no safer to do it than not to do it.

340BHP-WRX

iTrader: (6)

Everyone has their own opinion-i've asked this same question myself many times and have never had a definitive answer. Some tuners say you should,some say you don't need to bother.

I only do it myself as it seemed to be better to build some oil pressure up before firing up the engine.

A well known tuner on here said they always do this after changing the oil-that's good enough for me.

I think this debate will go on and on

Shark Man

Yes, lol, the debate will go on and on...

One issue which doesn't help is many people are paranoid about oil pressure. Believe ir or not, an engine doesn't need oil pressure to be adequately lubricated. Well at least, not until the bearing is placed under substantial load. (revving, driving etc), where oil pressure is required to maintain oil flow. Oil flow is what is important; making sure oil squeazed out from between a bearing is replaced to maintain the film between the bearing and the journal (and to cool it).


Which brings us onto the other heated topic of debate...oil viscosity Thick oil; Great pressure, low flow. Or Thin oil; Low pressure, high flow.

Somehow I don't think we'll get people condoning 5w-30 anytime soon (even though it is in the listings for late model Impreza turbos ).

scooby,dlm.

oh no,look what you've started now!!!

JonMc

iTrader: (51)

The only thing missing from this thread is young Mr Lewis and the 'Oil Change Dance'

The Hoff

iTrader: (5)

I have always pre-filled the oil filter and cranked the engine over without firing with all the cars I have had, not just Subarus. For the few seconds its takes why not do it? Its just the routine I have got into over the years, not saying its the gospel way to do it tho.

andythejock01wrx

Excuse my dolly dimpleness, but when you say "crank it over", do you mean "turn the key without letting the engine fire up" ? And where's the sensor.

Just in case.

[Davey]

Just drain the old oil, remove the old filter, fit the new filter, fill it back up with oil to the full line, start the engine, run it for 60 seconds, turn it off and top up as neccessary.. I've done hundreds of engines and never once have I ever had to employ a Muslic Cleric or a Hindu high order monk to come and bless my sump plug and de-ionise my hoojamaflip..

Tidgy

shark, my question is, does the low oil pressure warning light come on when you fire up the car without cranking it first? o yes it does, so even the bleedin car says somethings wrong.

now you could argue, well its not gonna do any damage, but the engine is still reving at 1200rpm cos its cold so could the low oil pressure do damage for the short time its there? i don't know and theres no general consensus. but for the sake of pulling a plug, and cranking it for a few seconds, seems like a worth while thing to do to help protect your engine

[Davey]

a) Turning the engine over by hand does not produce enough oil pressure to give any extra lubrication to the crank other than what is already provided by the oil residue that is there...

b) You'd have to leave your engine dry with the sump plug out for about 2 months before the engine components are anywhere near oil free...

SUBARU's are NOT special cars, they do not need 10 virgins to hold hands and sing cambiare while you whisle the national anthem and spin your ratchet backwards..

trails

iTrader: (41)

fairly resilient things engines, fairly amusing things urban myths.

[Davey]

Have you seen how fast oil moves at 8bar +?

340BHP-WRX

iTrader: (6)

Turning the engine over by hand might not produce enough oil pressure to give extra lubrication etc but it's enough to make the oil pressure light go off and that'll do me

It's got nothing to do with SUBARU's being special cars-i've always done this on every car i've had-although I can't prove there's any benefit,why not just do it anyway for the few seconds extra that it takes ?