Member Since: 21 Oct 2016
Location: kent
Posts: 13604
hi
may i ask a daft question please
why does the aircon have to be on whilst checking the atf level please
thks as always
9th Nov 2017 4:52 pm
Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10360
well it will increase the idle RPM slightly
and I guess that keeps the fluid pumping round more and oil level lower slightly
9th Nov 2017 6:31 pm
gstuart
Member Since: 21 Oct 2016
Location: kent
Posts: 13604
hi pete
many thks for the reply , always a learning curve for me,
9th Nov 2017 6:52 pm
CloudbaseJim
Member Since: 20 Dec 2017
Location: Cumbria
Posts: 79
Out of interest, why not disconnect the bottom hose from the radiator instead and flush the old oil out of the radiator at the same time?
3rd Jan 2018 6:23 pm
Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10360
access is very difficult
I think the rad oil gets drained anyway
3rd Jan 2018 7:29 pm
garrycol
Member Since: 06 Dec 2010
Location: Canberra
Posts: 1115
I have gone right through this a few times and an now happy with the procedure - even when changing the pan - but I am struggling with the logic of doing the change through the cooler pipes along the lines that Filio has outlined. I accept that if getting a professional megaflush where lots of fresh fluid is pumped through the gearbox then that is best through the cooler lines. However the method in this thread is not a megaflush.
Now the gearbox holds 9.5 litres and by just draining out the fluid by the sump plug you will get about 4 litres out - 42%. Now if the box was left a day or so before the drain you will get a little more (maybe 4.5l) and if not left very long maybe a little less (3.5lt).
Now reading the posts here, by connecting up to the cooler pipes and running the engine until fluid stops coming out some are only getting 4.5l, some 4l and some 3.5l so on average it is still only about 4 litres out - so about the same as just dropping the sump plug. Doing it again gets similar amounts but noting that on the second time the 4l out will comprise about 40% new fluid just put in and about 60% old oil - about the same if you dropped the oil direct from the sump twice.
So I am having trouble understanding the advantage of this system because after say 3 drains from the sump plug and 3 fills compared to 3 pump outs and 3 pump ins via the cooler pipes the composition of old oil and new oil remaining in the gearbox will be similar after both processes.
What am I missing here?
Thanks
Garry
14th Mar 2018 5:17 am
Tripe
Member Since: 28 Jun 2015
Location: Tasmania
Posts: 285
What I understand is,
A lot of the atf resides in the torque converter, if you drain via the cooler pipe you will get this dirty atf out of the TC.
With my method I did 3 flushes and the return oil on the third flush was new atf coming through.
If you drain via the pan, I reckon you will dirty your nice clean ATF before it passes through transmission.
14th Mar 2018 6:19 am
garrycol
Member Since: 06 Dec 2010
Location: Canberra
Posts: 1115
Thanks - the fluid in the TC is the same fluid as in the rest of the gearbox and as soon as the engine is running it circulates along and mixes with the rest of the fluid. So if 4 litres of fluid comes out of the TC via the cooler pipe and 4 litres of new fluid goes in, as soon as the engine is started and the car run a little then all the old and new fluid in the gearbox is mixed - exactly the same if you drained 4l of fluid from the sump and put in 4 litres in the filler hole - once the engine is run the mix through the entire gearbox, including the TC is the same - a mix of 42% new oil and 58% old oil - the same for both procedures. Now do both again and the % of new oil will go up but will be about the same using both procedures.
Now if the cooler pipe procedure pulled out much more fluid out of the box - say 6 or 7 litres compared to the drain method then yes the cooler pipe procedure would definitely be better. But as it is, it doesn't matter if the dirty oil is coming from the sump or the TC, once the engine has been running for a bit the oil throughout the entire gearbox is mixed and the oil in the TC is the same as in the sump as is in the valve blocks etc.
Thanks for your response because you have highlighted the except point that is made in this thread that I do not quite understand.
Cheers
Garry
14th Mar 2018 6:48 am
Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10360
I think the problems are with your quoted figures.
I don't think you get 4 litres out from just the sump plug
If you run the engine with cooler off and then drain the sump, you will get 5.5l out
This way is actually much better than a flush, because with a flush the clean and dirty oil just mixes in the sump, and it depends how much clean fluid you flush through (and waste) as you whether you replace 100% of the old fluid. Flushing machines claim 98% change. But all you are doing is paying a lot more money with little benefit to the car owner.
14th Mar 2018 1:14 pm
sputnixb51
Member Since: 23 Apr 2013
Location: Morayshire
Posts: 833
All I can say is if you read my earlier post on this including replacing filter it works and works better than a machine flush, one of the crucial parts of this is that the oil needs replacing much more often than Land Rovers view point, doing this means you are never dealing with oil that’s too dirty or burnt and your gearbox will thank you for it.
14th Mar 2018 1:54 pm
DiscoJeffster
Member Since: 27 Feb 2016
Location: Perth
Posts: 204
I got a smidge over 5L out last time I drained my box. I change it annually now doing the 5L each year to keep it humming along.
14th Mar 2018 3:23 pm
KostasA
Member Since: 23 Aug 2015
Location: nairobi
Posts: 286
the advice i got from a mechanic, and actually tried it, is to first drain from the sump plug, fill it in and then drain form the radiator (engine running). That way when you suck from the radiator (and also torque converter) eventually you get clean oil that you have filled in the sump.
14th Mar 2018 6:33 pm
trailhound
Member Since: 27 Aug 2015
Location: Colchester
Posts: 697
That makes sense. Looking forward to the counter argument
14th Mar 2018 8:16 pm
Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10360
No counter argument. Another perfectly reasonable and rational way to do it. And not a bad idea for the first change.
Although you could argue the 2 above posters and I would rather get some use out the oil and change it yearly, rather than use expensive oil as a flush.
14th Mar 2018 8:33 pm
garrycol
Member Since: 06 Dec 2010
Location: Canberra
Posts: 1115
Pete K wrote:
I think the problems are with your quoted figures.
I don't think you get 4 litres out from just the sump plug
If you run the engine with cooler off and then drain the sump, you will get 5.5l out
This way is actually much better than a flush, because with a flush the clean and dirty oil just mixes in the sump, and it depends how much clean fluid you flush through (and waste) as you whether you replace 100% of the old fluid. Flushing machines claim 98% change. But all you are doing is paying a lot more money with little benefit to the car owner.
Thanks for the input - in what way do you think my quoted figures are dodgy - I dont actually know just looked at the results on this thread. I agree with your comments on flushing machines.
Thanks
@DiscoJeffster - I am tending to lean to your way of thinking but just trying to understand the pros and cons of both methods and even a combined method. I agree that irrespective what method is used the follow on should then be a regular dump via the sump plug and refil to keep the fluid refreshed.
Thanks to everyone who has responded and if anyone else has a thought on what I have posed please provide input.
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