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The cooler line trans flush #4441083
06/25/17 12:44 PM
06/25/17 12:44 PM
Joined: Jul 2012
Posts: 663
Perth, Western Australia
Brad_C Offline OP
Brad_C  Offline OP
Joined: Jul 2012
Posts: 663
Perth, Western Australia
So I've seen it recommended frequently. I've done it a few times and the results have been universally good. I'm not questioning the validity, but I wonder about the absolute efficiency.

I can understand replacing the fluid in the pan. I can also understand replacing most of the fluid in the valve body, pump and cooler lines. That is directly fed from the pump, which is directly fed from the sump which is all clean and new. Over half my trans capacity is in the torque converter, which to me looks like a dirty great pudding basin. The fluid gets pumped in there, and the stuff that comes out goes out to the cooler. So I have a 8L capacity in the trans (~3 in the pan, ~1 around in general and), 4 of which is in the torque converter (which rotates and mixes like a washing machine).

So here's the question. When I pump 4L into that converter, how much of what comes out is old fluid? I'd *assume* that as the new fluid gets pumped in, it's constantly mixed with the existing fluid and it's that mix that comes out to the cooler, so short of pulling the converter and draining it there is no way to replace *all* the old fluid. Just a good proportion of it (in theory). The old proportional dilution conundrum, somewhat like the repeated drain and fill theory.

Am I missing something?

Re: The cooler line trans flush [Re: Brad_C] #4441090
06/25/17 12:51 PM
06/25/17 12:51 PM
Joined: Jun 2003
Posts: 33,100
ME
eljefino Online content
eljefino  Online Content
Joined: Jun 2003
Posts: 33,100
ME
IMO what you get the most of is convenience and not constantly retorquing pan bolts which could dent the lips of the pan.

A dozen quarts of ATF is 90% new either way you do it, and 100% is unachievable.

I take it the TC drain plug is not present or easily reached.

If you do a pan drop and the shifting improves this might say, hey, do it again. If nothing changes it says, hey, you're right on schedule, good job.

Re: The cooler line trans flush [Re: Brad_C] #4441113
06/25/17 01:10 PM
06/25/17 01:10 PM
Joined: Feb 2009
Posts: 3,653
down in the park
Jetronic Offline
Jetronic  Offline
Joined: Feb 2009
Posts: 3,653
down in the park
Yes, it's usually a convenient way to flush the fluid. Go by colour, if the colour looks new after changing the amount the trans holds, it's time to quit. if it bothers you that you didn't get the last drop out, reduce the OCI slightly.


AR Giulietta 2.0 JTDM-2 -- Total Quartz 9000 Energy 0w30
Hankook Ventus Prime 2 215/50R17 (front)
Pirelli P7 Cinturato 225/45R17 (rear)
Re: The cooler line trans flush [Re: eljefino] #4441116
06/25/17 01:12 PM
06/25/17 01:12 PM
Joined: Aug 2010
Posts: 5,677
Champlain/Hudson Valley
Kira Offline
Kira  Offline
Joined: Aug 2010
Posts: 5,677
Champlain/Hudson Valley
Hello Western Australia, Here's what's been missing all the while. Nobody will address the exit flow rate of a torque converter. I believe they do not empty that fast at all. I believe the pressure comes up when you start the car and the transmission's pump starts turning. Maybe an ounce or two fills any void in the TC.

I've seen TCs taken from operating trannies and handed about the room. Never is there fluid dripping out of them.
I liken them to a full-to-the-brim milk bottle. If you gently pour water from a shot glass onto the milk's meniscus-how long will it take to displace the milk so you end up with a bottle of clear water?

I do remember hearing something about older VW autos having TCs which empty down to the low point of the input shaft and upon startup they refill.

Also, I've seen TC drain plugs on my friend's Ford truck. That tells me that's "the only way out" for dirty fluid.

ERGO the best way to go about things is to displace dirt all the while. Do drain & fills from youth.
Ideally, don't let it get dirty in the first place. With drain & fills starting early on you'll always have clean fluid.

People will scream and shout at each other over this but no one seems to know about the TC.

Re: The cooler line trans flush [Re: Brad_C] #4441151
06/25/17 01:54 PM
06/25/17 01:54 PM
Joined: Dec 2016
Posts: 6,241
Waco, TX
Linctex Offline
Linctex  Offline
Joined: Dec 2016
Posts: 6,241
Waco, TX
I honestly (FWIW) think your obsessing about a few ounces of oil left behind - - in the "the real world", will not affect transmission life at all.

I only ever do "pan drops" (essentially, since I actually run out through the cooler line)... and 4 qts/liters every 30-40,000 miles (50,000-65,000 km) is all that's really needed for the life of the vehicle as you own it.

I also have an auxiliary cooler (I do a lot of towing) and a spin-on WIX filter in the cooler lines.

The transmission filter in the pan is typically very COARSE - some say no finer than 100 Microns.


"The evidence demands a verdict".
(Re:VOA)"it's nearly impossible to actually know the particular additives that are in there at what concentrations."
Re: The cooler line trans flush [Re: Brad_C] #4441168
06/25/17 02:12 PM
06/25/17 02:12 PM
Joined: Oct 2015
Posts: 475
MN
WillsYoda Offline
WillsYoda  Offline
Joined: Oct 2015
Posts: 475
MN
I just to the trans cooler line flush and then add a magnefine. No pan drop.

Re: The cooler line trans flush [Re: WillsYoda] #4441170
06/25/17 02:15 PM
06/25/17 02:15 PM
Joined: Sep 2010
Posts: 7,000
Texas
4WD Online confused
4WD  Online Confused
Joined: Sep 2010
Posts: 7,000
Texas
... and your pan filter just became a rock catcher (catastrophic failure screen) when the inline filter went in ...

Re: The cooler line trans flush [Re: Brad_C] #4441226
06/25/17 03:30 PM
06/25/17 03:30 PM
Joined: Mar 2004
Posts: 20,758
Upstate NY
Donald Offline
Donald  Offline
Joined: Mar 2004
Posts: 20,758
Upstate NY
Your not in a sterile operating room. So exchanging "pretty much all" is the best you can do. When the ATF coming out looks like new, you are done.


2015 Subaru Forester 2.5 engine/CVT
2015 Ford F250 w/Powerstroke
2016 Subaru Crosstrek CVT (wife's)
Re: The cooler line trans flush [Re: Brad_C] #4441404
06/25/17 07:02 PM
06/25/17 07:02 PM
Joined: Jun 2002
Posts: 12,521
The Motor City
Kestas Offline
Kestas  Offline
Joined: Jun 2002
Posts: 12,521
The Motor City
To put things in perspective, even an engine oil change doesn't get 100% of the fluid out. There's still old oil in the oil galleys and lifters.

Re: The cooler line trans flush [Re: Brad_C] #4441700
06/26/17 07:14 AM
06/26/17 07:14 AM
Joined: Jul 2012
Posts: 663
Perth, Western Australia
Brad_C Offline OP
Brad_C  Offline OP
Joined: Jul 2012
Posts: 663
Perth, Western Australia
Yeah, not disputing anything you all said. It was just something I've never seen raised. Everyone seems to imply that a cooler line flush completely replaces the fluid and I couldn't see how that could actually be true.

My trans is a Volvo AW70, which is basically a Toyota A43D. No drain on the converter and at rest the converter very slowly drains down to the bottom of the input shaft (so just over half). I've pulled the converter a number of times now, and it's only ever half full. That explains how the level on the dipstick is *so* much higher at rest.

I added a magnefine last time I did some work on it after I changed the internal screen and cleaned the pan. I must replace and inspect that, it has about 40,000km on the filter now. I don't bother with drain and fills, just do a cooler line flush every couple of years.

Re: The cooler line trans flush [Re: Brad_C] #4441709
06/26/17 07:28 AM
06/26/17 07:28 AM
Joined: May 2012
Posts: 453
Connecticut
Sam_Julier Offline
Sam_Julier  Offline
Joined: May 2012
Posts: 453
Connecticut
I have two AW70 transmissions both with inline filters. I do a cooler line exchange and filter change every 20,000 miles. It takes 10-12 quarts to get clean fluid.


2005 Highlander 3.3L PC Duron 0W30, 47k
1993 Volvo 245 Delo 10W30, 140k
1993 Volvo 244 Delo 10W30, 152k

Re: The cooler line trans flush [Re: Brad_C] #4441815
06/26/17 09:58 AM
06/26/17 09:58 AM
Joined: Dec 2006
Posts: 7,654
Toronto, Canada
KrisZ Offline
KrisZ  Offline
Joined: Dec 2006
Posts: 7,654
Toronto, Canada
When I do a cooler line exchange, I use clear vinyl tubing and I can see the dirty fluid coming out of the cooler line all the way until the last pan fill up, when the fluid starts to clear up. That tells me that there is minimal fluid mixing. And there shouldn't be a lot of mixing happening, because the majority of mixing happens in the pan itself, as the fluid that is already in the circulation can only be pumped one way, so naturally as the new fluid enters the system, it will push out the old fluid.

Pan drops or D&Fs require emptying the pan, refilling it and then running the tranny and going through the gear selector. This mixes the fluid 100%.


2015 Dodge Grand Caravan-27k miles.
2006 Mazda 3-163k miles
Re: The cooler line trans flush [Re: Brad_C] #4441874
06/26/17 11:07 AM
06/26/17 11:07 AM
Joined: Oct 2008
Posts: 19,091
Sunny Florida
SteveSRT8 Offline
SteveSRT8  Offline
Joined: Oct 2008
Posts: 19,091
Sunny Florida
^^^Likewise. The fluid becomes clear quite suddenly. As close to 100% as is possible without disassembly. Nothing is perfect.

IMO you must start with a pan drop so you can change the filter or you're not doing it in the correct order. After some serious miles many slushboxes practically quit generating debris. But a driveway fluid exchange is a primary player in keeping a slushbox on the road...


"In a democracy, dissent is an act of faith."
J. William Fulbright
Best ET-12.79 @ 111 mph
4340 pounds, Street tires
Just like we go to Publix
Re: The cooler line trans flush [Re: Brad_C] #4443437
06/28/17 05:58 AM
06/28/17 05:58 AM
Joined: Jun 2002
Posts: 12,521
The Motor City
Kestas Offline
Kestas  Offline
Joined: Jun 2002
Posts: 12,521
The Motor City
When doing a cooler line flush, I'll shift through the gears during the flush. Sometimes I'll see a pulse of dirty fluid go through.

Re: The cooler line trans flush [Re: Brad_C] #4444270
06/28/17 08:23 PM
06/28/17 08:23 PM
Joined: Jul 2011
Posts: 1,224
Houston, TX
Coprolite Offline
Coprolite  Offline
Joined: Jul 2011
Posts: 1,224
Houston, TX
So this tranny holds 8 and takes 10-12 for it to come clean ? Is 125-150% a good ballpark for purchasing purposes? I am assuming it might take more if interval is extended or done for the first time on a used car with 80 instead of 40k miles.

Are these generalizations close enough? Thx

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