5HP24 cooling: my personal experience

[jicaino]

Hey guys.

I know, I should be swapping out the slushbox, give a shift, 3 pedals rule, yadda yadda. Now, if you're actually interested in solving a potential issue, upgrading your auto driving experience, or got tired of wandering and wondering, I can offer here my 2 cents worth of experience with the 5HP24 cooling system.

My car is a post 9/98 prod date, with the coolant/ATF heat exchanger. Ever since I got the car, I felt intuitively that the transmission wasn't entirely "happy" all the time. I know, mechanics shouldn't be guided by "feel" or "intuition", but having driven a large number of different cars and transmissions (not only BMW ones) I could sense something I wasn't happy about.

When I first got the car and started to sort it out, the most stupid thing I read was the lifetime oil fill. Let's not get passionate about it. There's no way that leaving the ATF, a critical fluid in the drivetrain, for over 3 years without servicing made, make or will ever make any sense to me, except for a major automotive maker trying to avoid costly oil/filter services on parts they just started to guarantee for 10 years. I asked around and I finally decided that if the transmission was going to die, it wasn't going to be because a simple oil/filter service. Makes absolutely no sense for anybody that knows anything about mechanisms and mechanics.

After the fluid/filter refresh the transmission improved a lot.
Then I started to monitor the temperature and other parameters because of the known issue of the harsh downshift coming to a stop. Found out and learned about the exchanger "regulator valve" aka. tranny tstat. Replaced that part. Got slightly better. Made the mistake of replacing it and not replacing the exchanger, because I felt uneasy disturbing the quick connect hoses. Big mistake, as I learned later. The exchanger was partially clogged, and when I was replacing it, I cracked the recently replaced tstat, it was december, no replacement part available and upcoming holidays season meaning I wouldn't be able to meet with my family members that had already left town. Lonely, frustrated and angry at not getting the part, I got an external oil cooler, butchered the quick connect oil cooler lines, the cooling system connection fittings, put it all back together and left town with just enough time to spend new year with my people.

The operating temp dropped dramatically, improving the transmission behavior a lot. Firmer, crisper feel, better power to the ground, less "hesitation", I was very pleased. I drove the car for about a year like that, then grew the nuts to throw out the clutch fan, and the sight of a non OEM cooler with a botchered install started to tick me the wrong way. I could see it!

Long story short(er) I collected a bunch of parts planning to install all OEM components and pieces in the future. Got the pre 9/98 transmission cooler (fits below the radiator in the OEM location) a set of very good used transmission lines from a 528iA, expansion tank to WP hose (manual tranny version) and water cooled alternator cap (blind plug where the hose that connects with the coolant/ATF exchanger) but since the car was running fine never got to it.

A couple of months ago I went to a myriad of problems that ended in an alternator replace, and when I removed that I installed all the parts that had been sitting in the shelf.

Just performed some extensive test drives on the car. City, mixed, heavy stop and go, 15 mph strolling around town, unleashing the anguish of being a human being on the gas pedal, road in hot weather, you name it. I'm absolutely amazed by the way the car drives. And very angry that BMW engineers let them post 9/98 cars spend years with feverish tranny ATF temps just so they could get away with a single fill of oil and one filter by "burning the crap" in the ATF letting it operate between 110°C and 120°C.

Bottomline: 540iA - M60 intake - Alpina DME tune - Dinan Stg.3 EGS tune. 3.15 final drive.
On the stock tranny coolant/ATF exchanger it would always operate at engine temp, or even worse: if the DME activates MAP cooling, the exchanger t-stat leaves the tranny hanging, making it work at 105°C or above. Heavy stop and go in hot weather would raise ATF temp to around 120°C notoriously deteriorating shift quality. Very spirited driving (like continuous 1/8th passes) would make the tranny temp go around 125°C and cause the tranny to go into thermal protection program, shifting only 1st and 2nd gears (no BC message)
With the old air/ATF cooler, in the factory location (side to side with the PS cooler coil) the tranny never surpasses 90°C even with heavy abuse, long sustained top speed, you name it). Crips shifts, even if you do heavy stop/go in hot weather you don't feel like your tranny is going to faint like an old lady left in the sun ...

I would definitely recommend this upgrade to anybody driving a post 9/98 auto, even if they're not performance oriented (right, why get a 540i in the first place...?)

[dannyzabolotny]

Funny you post this, I had a very similar thought regarding my 04 Range Rover which has the same M62tu and 5HP24 that the 540i has. When I first got it, I drove it on a hot day, doing a lot of stop and go— it started holding gears longer and downshifting abruptly. I later learned this was the thermal protection operating mode. Later that night when I drove it on the highway with the outside temperatures about 30º cooler (in ºF of course) it shifted just fine, leading me to believe there was some overheating going on. While my initial thought was to just replace the heat exchanger and thermostat, I now want to look into a more proper solution with a larger external cooler, especially since I plan on towing with the Range Rover.

[gmak]

Now THAT would be an interesting DIY to read; an external cooler for the ATF on a 4.4L vehicle.

[Akash3230]

Pics please


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[philly98540]

Nice testing and analysis of the issue with real results at the end. DIY next?

[BMW540san]

Very good info.
It's another proof contrary to typical belief of people that BMW engineers are Gods and therefore it's sacrilege to contend any of their decisions.
People forget that BMW as any company have to consider the profit first and then quality or durability.
But of course there is the number of "experts" here who will boast that lifetime tranny fill is the way to go.
Even ZF changed their official standing in respect to Lifetime fairy tale.
So yes, it can only help to lower the running temp of fluid which will prolong the life of all components.

[jicaino]

I can take a few pictures of how I did it, that's for sure.

Parts list:
17221740798 ATF/Air cooler
583942_x800.jpg

Donor tranmission lines that needs to be chopped, any pre 9/98 car will have them, or any 6 cyls from the entire production span.
We need these:
s-l1600.jpg
But will only be using the "front" section of those lines, they're to be chopped after the pressure crimp before the first bend in the steel line.
This is the front part that will attach to the air/atf cooler
s-l1600.jpg

we also need the bolt that would secure the quick connect bracket to the cooler
07119915085_Bolt.jpg

blind plug for the back of the alternator (PN#11531436850)
manual transmission expansion tank to WP hose (PN#11531711377)
radiator plug (PN#17111712339)

Then you need to remove the radiator (upper and lower hose, expansion tank, full drain, good time to do any cooling system parts replacement you've been postponing) since we'll be fitting the cooler between the AC condenser and the radiator. Your holder has the mounting locations, all middle frames are the same so it would be plug and play. Good time to clean up all the road debris you don't see there but trust me, it is.

You now remove the coolant/ATF exchanger.

(Thanks to member 007008 for referencing those parts and for the following material)

UPDATE..
This is an unneeded step, but I wanted to loose the trans cooler and the extra plumbing. Only 3 parts are needed about $25 worth.
17111712339 radiator drain plug
11531436850 cap for the back of the Alternator housing
11531711377 hose from coolant bottle to waterpump



From this....

To this....


Bye, Bye cooler

make this "adjustments" to his procedure: first undo the frontmost quick coupling ATF line on the exchanger, and install a 10mm ID piece of hose over the fitting. Blow the ATF back to the tranny. Undo the other line and zip tie them together elevating them into the engine compartment so they won't spill while you're completeing the parts install.

Install your air/atf cooler (snaps into place) reinstall your radiator and hoses, Don't forget to cap the back of the alternator, and to add the radiator drain plug in lieu of the old coolant line at the bottom. Start filling your cooling system but don't start the car! Install the chopped donor lines (use new seals! PN#17211742635). The 90° bent steel elbows are to be placed ponting downwards. From here it would be pretty obvious where to chop the rubber on the tranny lines. Will get pictures of that as soon as I can remove the belly pan.

- - - Updated - - -

Funny you post this, I had a very similar thought regarding my 04 Range Rover which has the same M62tu and 5HP24 that the 540i has. When I first got it, I drove it on a hot day, doing a lot of stop and go— it started holding gears longer and downshifting abruptly. I later learned this was the thermal protection operating mode. Later that night when I drove it on the highway with the outside temperatures about 30º cooler (in ºF of course) it shifted just fine, leading me to believe there was some overheating going on. While my initial thought was to just replace the heat exchanger and thermostat, I now want to look into a more proper solution with a larger external cooler, especially since I plan on towing with the Range Rover.

With this atf/air cooler you won't need additional cooling. No pre 9/98 car with the old style tranny cooler ever had temp issues, because tranny temp doesn't get past 100°C even if you're doing continuous "drag" passes. Towing ins't as severe as "going full throttle from red light to red light" driving conditions. I'm running on the aux fan alone, we're approaching the summer and I've done almost everything I can to see if I could get the ATF temp to get over 100°C and I couldn't. Same driving style and conditions would have resulted in ATF temps of 125°C and above with the coolant/ATF exchanger. And it never dropped below 105° which made the car feel like crap when you wanted to drive between 5/15 MPH (think urban tour, traffic jam, or checking nice butt girls strutting down the sidewalk )

Be aware that the harsh downshift can also be due to other reasons:
*maf fading out
*idle speed dropping too low when coming to a stop when engine is hot
*sudden throttle pressure changes (bad TB, bad pedal poti, funky vac lines allowing idle to hunt down and up)

If the tranny stays in 1st over 3500rpm, then harshly shifts into 2nd and stays into 2nd no matter what, then it's in thermal protection mode (BC won't show any message and it won't throw codes!)

Now THAT would be an interesting DIY to read; an external cooler for the ATF on a 4.4L vehicle.

It's external but it's also OEM locations and parts. The best of retrofitting is when you can use OEM parts and locations to improve function with neat undetectable mods and still being able to use available replacement parts and bits.

Pics please

Will take more pictures as soon as I can get under the car. For the time being I just put together a visual reference for you to start getting a general visual idea of the retrofit.

Very good info.
It's another proof contrary to typical belief of people that BMW engineers are Gods and therefore it's sacrilege to contend any of their decisions.
People forget that BMW as any company have to consider the profit first and then quality or durability.
But of course there is the number of "experts" here who will boast that lifetime tranny fill is the way to go.
Even ZF changed their official standing in respect to Lifetime fairy tale.
So yes, it can only help to lower the running temp of fluid which will prolong the life of all components.

+ (times a zillion)

[vinyldude]

Thank you for this information.

[geargrinder]

Just saw link to this thread in other one... very groovy. Im not slushed anymore needless to say but this seems like a huge Must-Do at the LEAST for anybody who runs into the tranny-tstat/clogged-exchanger issues that crop up! Don't mess w that stuff, go straight to the mod... And indeed seems like a good mod for anybody committed to the autobox.

[jicaino]

Just saw link to this thread in other one... very groovy. Im not slushed anymore needless to say but this seems like a huge Must-Do at the LEAST for anybody who runs into the tranny-tstat/clogged-exchanger issues that crop up! Don't mess w that stuff, go straight to the mod... And indeed seems like a good mod for anybody committed to the autobox.

I'm not committed, but resigned to the slushtronic. It does make a helluva better experience (this mod). If anybody has doubts just check on how many funny tranny behavior post from older cars you see reported: none!

GG is right, don't even try to replace the coolant/ATF exchanger. You could end up stranded on the side of the road if the silly engineered plastic tranny tstat takes a dump on you, crippling your transmission's oiling system and your engine's cooling system all together at once.

[AK_5eries]

Very interesting. I'm not sure what the exact differences are between the pre/post 9/98 tranny cooling system, but J how sure are you that your tranny was running that hot? Were you using INPA to measure temps? I know on the pre 9/98 there is an inline 82C stat for the tranny before fluid starts to flow through the cooler. Can the post 9/98 be that much hotter? I also remember reading on some ZF tranny expert website, that the 5hp24 starts to experience some heat related damage above 100C operating temp.

[jicaino]

Very interesting. I'm not sure what the exact differences are between the pre/post 9/98 tranny cooling system, but J how sure are you that your tranny was running that hot? Were you using INPA to measure temps? I know on the pre 9/98 there is an inline 82C stat for the tranny before fluid starts to flow through the cooler. Can the post 9/98 be that much hotter? I also remember reading on some ZF tranny expert website, that the 5hp24 starts to experience some heat related damage above 100C operating temp.

Hey GT.
After BMW updated their warranty to include oil and filter services, they launched the "Lifetime Oil" BS. They removed the ATF/Air cooler that sits between the A/C condenser and the radiator, and replaced it with a coolant/ATF heat exchanger that bolts below the water cooler alternator case. They spec'd the tstat in that system to run at 105°C like the engine tstat. By means of elevating the tempetarure of the ATF to always above 105°, the ATF "lasts longer" burning the crap out like condensation and other contaminants. But as you figured out, it reduces the life of the transmission. BMW spec'd their own tranny operating temperature and service intervals above those of ZF, the manufacturer.

As you mention, there's thermal protection on the earlier (and better) system too. You wouldn't want to be driving around in cool climates with your ATF below 15/20°, and optimal clutch engagement vs. slippage occurs at around 50°C so they made sure the operating temp doesn't drops below ~70°C (not sure about the 82°C figure you mention, I don't recall reading that number and IIRC my ZF official tranny shop guy told me that it was something around mid 70°C). The earlier system is so effective that even doing drag passes or spirited driving it cools back to around 75°C with a hot engine operating temp of 105°C/110°C and no viscofan, while the coolant/ATF exchanger struggled to keep it around 110°C/115°C, and that is working properly. As soon as any of the components in that ill conceived system deteriorates, the temp raises and you're likely to end up with a fried tranny.

As for real time data monitoring, I have a pocket C110 scanner that's the best $20 I've ever spent. It does live datastream, specific codes reading and erasing. All of the systems/components, not only drive components.

[geargrinder]

I"m picturing the internal engineering 'optimization' graph charting "fluid service life" and "tranny service life" vs operating temp.

It definitely looked something like this (made up numbers of course) with a band for "optimizing transmission life vs optimizing fluid life" and involved a starting conversation agreeing that "we do not give 2 F's in a bucket of dead rats about cars that are over XXX miles and XX years old".

[jicaino]

Or as they eloquently put it: RATTEHINTERNGEBEN_ALTESAUTO : > nicht_aktiv

[theshadow92]

As for real time data monitoring, I have a pocket C110 scanner that's the best $20 I've ever spent. It does live datastream, specific codes reading and erasing. All of the systems/components, not only drive components.

Would I also need to use the 20 pin connector underneath the hood or just the OBD port under the dash? First time hearing of this C110 scanner but seems cool. Anything else like it?



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[geargrinder]

If your car has full OBD access (transition cars need a jumper to bridge the 2 networks that are available at the Pac-Man connector to the OBD...) then there's a lot of things that should work, many generic OBD scanners can pull a lot of standard info.

Carly for BMW is pretty cool from what I've seen and is BMW-customized/proprietary. They are bit costly as you need their interface AND pay for the app but in the end it looks like a good setup. I've often been tempted as it would be 100x easier than lugging my dedicated auto-diag laptop out to the car and wiring it up and waiting for it to boot & load...

[Mannyf540]

If your car has full OBD access (transition cars need a jumper to bridge the 2 networks that are available at the Pac-Man connector to the OBD...) then there's a lot of things that should work, many generic OBD scanners can pull a lot of standard info.

Carly for BMW is pretty cool from what I've seen and is BMW-customized/proprietary. They are bit costly as you need their interface AND pay for the app but in the end it looks like a good setup. I've often been tempted as it would be 100x easier than lugging my dedicated auto-diag laptop out to the car and wiring it up and waiting for it to boot & load...

Estas chingon mi Cano. I love this mod, a will perform soon. Subscribed !!

[jicaino]

Would I also need to use the 20 pin connector underneath the hood or just the OBD port under the dash? First time hearing of this C110 scanner but seems cool. Anything else like it?

the "drive" modules can be accessed thru the OBD under the dash (I'm guessing your car has both of them, as mine, post 9/98 but pre facelift) Those are DME, EGS, EWS. Almost all of the parameters you may need to monitor are on the EGS live datastream (Engine coolant, RPM, ATF temp, turbine speed, solenoids, you name it)

If you want to access all the modules/components from the uderdash OBDII port you need to mod your 20-pin cap or open it and bridge the K and I lines together.

The scanner I have is this:
http://www.ebay.com/itm/General-Crea...-/272308222214

- - - Updated - - -

Also have a ELM-327 for using Torque on the mobile, a real-deal GT1, and a laptop with INPA, NCS, KFP and BVMW Scanner. I end up using the C110 on the go and the GT1 for more advanced stuff, and perhaps the ELM327 with the tq app for using my phone as a second set of "eyes" on the data while driving on long trips, to monitor voltage, coolant temp, O2 sensors voltage, those things.

[theshadow92]

the "drive" modules can be accessed thru the OBD under the dash (I'm guessing your car has both of them, as mine, post 9/98 but pre facelift) Those are DME, EGS, EWS. Almost all of the parameters you may need to monitor are on the EGS live datastream (Engine coolant, RPM, ATF temp, turbine speed, solenoids, you name it)

If you want to access all the modules/components from the uderdash OBDII port you need to mod your 20-pin cap or open it and bridge the K and I lines together.

The scanner I have is this:
http://www.ebay.com/itm/General-Crea...-/272308222214

- - - Updated - - -

Also have a ELM-327 for using Torque on the mobile, a real-deal GT1, and a laptop with INPA, NCS, KFP and BVMW Scanner. I end up using the C110 on the go and the GT1 for more advanced stuff, and perhaps the ELM327 with the tq app for using my phone as a second set of "eyes" on the data while driving on long trips, to monitor voltage, coolant temp, O2 sensors voltage, those things.

I would LOVE to use the ELM327 with the Torque app on long trips. Best place to buy?

[jicaino]

I would LOVE to use the ELM327 with the Torque app on long trips. Best place to buy?

I guess I lucked out on eBay buying a chinese unit for 15 bucks shipped to my concierge address in the states.
If I had to pick one ELM based BT device, I'd be pointing at a better device, like Launch Easy Diag or Kiwi which now has its own app besides being compatible with torque pro.

[Mannyf540]

I guess I lucked out on eBay buying a chinese unit for 15 bucks shipped to my concierge address in the states.
If I had to pick one ELM based BT device, I'd be pointing at a better device, like Launch Easy Diag or Kiwi which now has its own app besides being compatible with torque pro.

Try amazon

[AK_5eries]

You're correct J. The pre 9/98 does not seem to have a thermostat.

But the post 9/98 does. It's actually an 86C thermo. Part number: 17211437772

[vinyldude]

I guess the confusing part to me is, why you needed to cut the pre-9/98 cooler lines. Do you have pictures of your setup? Is there some reason why one couldn't just use the pre-9/98 cooler lines "as is", essentially replicating the transmission cooling setup of a pre-1999 year model 540. Apologies if I'm missing something here.

[jicaino]

I guess the confusing part to me is, why you needed to cut the pre-9/98 cooler lines. Do you have pictures of your setup? Is there some reason why one couldn't just use the pre-9/98 cooler lines "as is", essentially replicating the transmission cooling setup of a pre-1999 year model 540. Apologies if I'm missing something here.

Because the oil ports location in my transmission didn't match any pre 9/98 lines. Mine has 2 banjo bolt fittings on the transmission end, and they aren't one next to another.

As soon as I have to change oil I will drop the belly pan tray and snap some pictures.

Essentially I don't think there's readily available lines for this project, you have to mix and match.

[geargrinder]

why i am curious about this I dunno but I was so i looked it up - indeed the facelift break specs a slightly different 5HP24 / A5S-440Z tranny. the early cars have suffix TB & SH, and the later cars have TE & TF (depending on normal or short final drive torque converters...)

that difference must be about the housing and the cooler ports.

seeing that, i'm sure somebody has bumped into that problem before from another direction - i.e. trying to fit a later model used tranny into an early car... presumably theoretically a case-swap would be possible but of course a totally huge hassle and not practical in 98.7% of situations.