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Question Oil Flush Do Or Don't?

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#1 R32Egor

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Posted 11 May 2022 - 01:09 PM

Hi all,

 

Going to be removing my engine and wondered what people thought about flushing the engine with an Oil flush cleaner?

 

I am thinking this is not a good idea because of the gearbox -

 

Comments .......

 

It is an SPI with 61000 KM, suspected worn diff and I am not intending to split the gearbox and motor while changing diff to X pin.

 



#2 weef

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Posted 11 May 2022 - 02:50 PM

The use of a good quality flushing detergent will enhance the capabilities of the engine oil to do its job, by removing sludge and combustion deposits. There are a few misconceptions about the use of flushing detergents, some say it led to oil leaks after its use, but it maybe that by removing the old sludge from around seals and gasket  faces it has shown up the poor condition the engine was in, whilst others fear that the released sludge will block small oil galleries and lead to trouble. Modern oils do contain a percentage of detergent to help with harmful deposits, but a good quality flushing agent is purely a detergent and only performs this task. 

If going down the line of using a flushing detergent follow the instruction, usually adding the flush to a warm engine, let the engine idle for 10 to15 minutes then drain the sump in the normal way and replace the oil filter. If an engine flush was needed the drained oil will look "dirtier" showing the detergent has done the job. Preferably next you refill with fresh oil and a new oil filter and give the engine another warm up cycle them drain the oil and change the filter again. This removes any residual deposits and any remaining detergent, remember the flush has few lubricating properties. Refill with a quality oil and filter and the job is done.

The choice of using an engine oil flush is up to the individual but remember the pros and cons, if the engine is an older high mileage unit it may be that it is the sludge that is keeping it oil tight 

I do not know if this will help you decide, I hope so. 



#3 cal844

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Posted 11 May 2022 - 02:51 PM

You will need the engine and box out the car to split the diff, it's worth removing the motor from the box to check the internals, especially 2nd gear.

I wouldnt use an engine flush due to the gearbox bearings, personally I buy the cheapest nastiest 20w50 I can buy and do a few miles with that, then use a top quality oil (valvoline VR1 is my recommended choice).

Edited by cal844, 11 May 2022 - 02:52 PM.


#4 slidehammer

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Posted 11 May 2022 - 03:54 PM

my feeling is if you are pulling the engine out for work on the diff, you will have the engine far enough apart to clean it all manually. I would also take the opportunity to renew oil seals and maybe the clutch (dependant on age) as these are simple jobs with the engine out and a pain with the engine in.



#5 cal844

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Posted 11 May 2022 - 04:09 PM

my feeling is if you are pulling the engine out for work on the diff, you will have the engine far enough apart to clean it all manually. I would also take the opportunity to renew oil seals and maybe the clutch (dependant on age) as these are simple jobs with the engine out and a pain with the engine in.


I agree, in addition to seals, check clutch wear and contamination too

Edited by cal844, 11 May 2022 - 04:09 PM.


#6 sonscar

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Posted 11 May 2022 - 04:42 PM

Alternatively you could just change the oil and filter.My view which may not be shared by others is...if the rocker cover is caked with burned on carbon it is probably dirty enough to need dismantling and cleaning,if it is oily and clean then it does not need flushing.
If you have several thousands of pounds and months of free time then have the engine and gearbox rebuilt.If it was OK before then renew the broken bits.Just my view as mentioned.
In my experience the bit that needs the most cleaning is the oil drain holes behind the oil rings in the pistons,I cannot see flushing oil doing anything here.Steve..

#7 R32Egor

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Posted 12 May 2022 - 11:14 AM

Well it has taken me over 1 year to be able to drive the mini, then on 'shakedown' drives I found these problems that I really did not want to do.

So as i have got to take the engine out for the diff - then I will do alot of suspension work etc while it is out (planned mods but was planned for later) and i really do not want to split the engine and gearbox as -

 

1 - Gearbox seems ok no faults while driving or changing gears

2 - Budget - have enough for my planned mods but not another 300 odd pounds for a refurb of gearbox (basically thats the cost of the minimum refurb kit if you split the box and engine).

 

So i will change diff and do my mods - get it on the road and drive it for summer then we can see later on about enginegearbox mods/refurb etc.

 

Hopefully after dropping the engine and subframe out goes ok and then I will be an expert

 

So I could just takeoff rocker cover and see what it looks like and then decide about flushing.



#8 Ethel

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Posted 12 May 2022 - 11:23 AM

I thought the concern with flushing oil was flushing the lube out of gearbox components that don't have a pressure feed - layshaft needle rollers.



#9 nicklouse

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Posted 12 May 2022 - 11:54 AM

I thought the concern with flushing oil was flushing the lube out of gearbox components that don't have a pressure feed - layshaft needle rollers.

Me too. I would not use a flush. But an oil change to “flush” is no bad idea.



#10 weef

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Posted 12 May 2022 - 11:58 AM

You add the flushing detergent to the existing engine oil and the ratio of flush to oil is about 15 to 1. The engine only idles over the period the flush is present, no driving, so gearbox bearing loads an minimal. Once the flush has been drained , followed by another immediate straight oil and filter change then refilled with fresh oil and filter the gearbox bearings are once again fully loaded with oil. If lubrication of bearings is your worry then I think engine main, big ends and camshaft would trump any gearbox bearings.



#11 Ethel

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Posted 12 May 2022 - 01:20 PM

Forced (and filtered) circulation would give me more confidence. If flushing is worthwhile the gunk it removes will end up in the same place as your gearbox bearings. Not saying it's black 'n white though, it's a judgement call to consider against other factors.







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