X5 4.6is 5HP24 External Transmission Cooler - My Solution
 

Bit of background information to start with.

X5 4.6is done 104k. First time I drove it home from buying it I found it had the harsh 2-1 downshift issue and also came up with a transmission code 'too much slip'.

Car went in to have the torque convertor replaced under warranty and have the transmission fluid and filter changed.

Got it back....and unfortunately the harsh downshift was still there. Checked the transmission fluid which was red (incorrect) and the sump had never been removed so filter had obviously never been done.

After complaining the car went back in to have the transmission fluid changed and filter done properly this time and I insisted they use the proper fluid which they ended up getting direct from BMW (more fool them!).

Got the car back....harsh downshifts were still there although they did seem to not be as bad - might have just been my imagination!

Anyway....I decided to investigate further myself and found that as soon as the transmission temperature rose to above 95degrees the harshdown shifts started.

First port of call was to replace the transmission thermostat which I did but unfortunately it made absolutely no difference.

I then decided that if I was going to make any signficant reduction in the transmission temperature then I was going to have to fit an external oil cooler. So this is what I did.

Parts used...

2 x -8AN Push on fittings (1x straight, 1x 90 deg)
4 x -8AN Fittings (2 x 90deg, 2 x 45deg)
4m -8AN Braided Hose
1x 19 Row Oil Cooler (-8AN Fittings)
1x Mocal 80deg -8AN Oil Thermostat
2x Rubber Bobbin Mounts

I basically cut into the return line of the standard piping system and used the push on fittings to attach to the thermostat then fed the cooler off the other side of the thermostat.

I'll let the pics do the talking...

http://img.photobucket.com/albums/v1...psxbagl5qa.jpg
http://img.photobucket.com/albums/v1...psqjz7munq.jpg
http://img.photobucket.com/albums/v1...psstddzrtp.jpg
http://img.photobucket.com/albums/v1...ps1r0wocgh.jpg
http://img.photobucket.com/albums/v1...psdayti9ds.jpg
http://img.photobucket.com/albums/v1...ps4flvu1hi.jpg
http://img.photobucket.com/albums/v1...psyqcvkjht.jpg
http://img.photobucket.com/albums/v1...psxb8e6lsu.jpg
http://img.photobucket.com/albums/v1...psueidra2m.jpg

...and the real test.

This was before the cooler was fitted - a typical 45 minute, 20 mile journey into work where the last 5 miles is stop/start urban type driving.

http://img.photobucket.com/albums/v1...psgk7d0w4n.jpg

That's the transmission fluid sat at 107 degrees.

....and now after the cooler has been fitted..

http://img.photobucket.com/albums/v1...psimdp8hgp.jpg

That's the transmission fluid at 80 degrees - a differences of 27 degrees!

It usually sits around 76/77 degrees whilst cruising and only rises slightly in traffic - basically sat more or less on the opening temperature of the thermostat.

Has it made a difference to the shifts? Yes, yes it definitely has. Harsh 2-1 downshift has completely been eliminated. All gearchanges are totally smooth and seemless throughout. Massive improvement all round.

Would I recommend this mod to others? Yes I most certainly would. Anything to extends the life of these gearboxes. Even if it means I only get an extra 10k out of it it's definitely money well spent. It's even a good mod to do on a car with no transmission issues - cooler transmission fluid definitely makes for a happier gearbox all round - which is probably why nearly every automatic vehicle since the E53 X5s runs a separate transmission cooler.

wow... I have the same problem ''Lurch'' as we call it.

Very interesting solution... fantastic post! :)

Since mine is being replaced as we speak, I'm thinking about doing this. You're not the only one that has done this and reported good results. Not sure why BMW would think those temps are OK for a transmission, but, nobody's perfect I guess?

Seems relatively cheap compared to a new transmission.

I did not expect such a crazy temp drop with a cooler. Simply amazing. But don't we have a transmission cooler already. I know my face lift 4.8is does.

Yes we do....a losely called transmission cooler when in actual fact it's more of a fluid to fluid heat exchanger.

I fail to see how the standard transmission cooler can work at all well given that fluid that's supposed to be using to cool the transmission fluid with runs at temperatures of 105 degrees and over in normal running conditions.

On the 4.8is the coolant systems runs significantly lower and thus I imagine so will the transmission fluid - another possible reason why you hear of less problems with the 6HP24 boxes than you do with the 5HP24 boxes as they run cooler.

When ambient air temps get hot like the state of Texas liquid cooled heat exchangers are far more effective than the liquid to air heat exchanger.

By the way what is the temperature where you are and while you were taking these temp measurements?

We aren't so lucky to enjoy temperatures such as those you are referring to over here in the UK.

Ambient temperature at the time was around 13 degC.

Also, if anything the hotter ambient temperature would have a slight knock on effect with transmission fluid temps anyway - it won't run any cooler thats for sure if you're 10-20degs hotter over there no matter how effective the heat exchangers are.

Excellent post! Link to where you bought all the supplies, and maybe better pics of where you mounted everything up?

I deal with a lot of European vehicles and VW had a BIG problem with the valve bodies prematurely wearing the spool valve bores. Many of the problems started at early as 60k miles.

The problem was very harsh downshifting once the trans fluid temperature got pretty warm. The warmer the harsher downshifting.

I do not have a lot of first hand experience with the transmissions in the X5, but I also wonder if a trans control module update could help.

Also noticed your engine coolant temp is 226F/108C. My 4.8l E70 ran at the same temp. I was not so happy with this "excessive" temp situation.

I installed a Hamburg Technic 90C thermostat and have been very happy with the current engine temp. Would prefer a 95C stat, but 90C is far better than 108C.

Might want to consider the 90C thermostat.

I am curious as to where the temperature sending units are that are being measured. Most of the time, sending units are located where the highest temperatures will be found, prior to the radiator/heat exchanger. I understand your concern and we always tend to think "cooler is better", but as long as the fluids in question are adequately cooled before going back into the engine or transmission, their performance shouldn't be compromised.

2002 X5 3.0 289,700 miles
2004 325i 123,000 miles

Very interesting post. Any idea at what temperatures issues started to occur?

Also with regards to the high coolant temperatures.....I was concerned when I first saw how hot it ran and I thought I had some kind of issue until I researched it further and found it to be normal and was like that due to try and aid economy and emissions. I'll definitely look out for one of the lower stats though. Interestingly enough when out cruising on the motorway it sits at 100degrees. I believe they are electronically controlled too?

I sourced everything from UK eBay. I'll get some better pics for you no problem.

The temperature sendor is I believe located in the valve body loom. Basically just slightly above the sump line. So it's in a pretty accurate location. I wouldn't like to see my engine oil consistently sat over 100degrees.....same applies for gearbox oil.

Little update.....currently on a 250 mile trip towing a 21ft twin axle caravan. Been monitoring temps whilst on the motorway sat at a constant 60mph and transmission fluid is sat at a stable 75degrees.

Correct the engine coolant thermostat in the N62 V8 engine is electrically heated to drop the engine coolant temperature under certain driving conditions. This is considered a MAP or controlled thermostat.

As for transmission fluid temperature when the VW harsh down shift started to occur, I am not sure, but when I did finally have the ability to monitor the transmission fluid temperature, it would typically run close to engine coolant temperature, but I recall the downshift problem started after idling and crawling in stop and go traffic. I would have to guess that the transmission fluid temperature was over 96C, probably getting close to 100C??

With regard to srmmmm's question. I am not usually one to jump on the cooler thermostat band wagon. I CLEARLY understand what a proper ending coolant temperature is and I am the only on other forums that have pointed out that probably over 30% of the vehicles on the road had "soft" thermostats and are running too cool.

Most engines have the engine coolant temperature sensor in the return coolant path, typically in the rear of the cylinder head just before the coolant returned to the radiator. This location allows for accurately monitoring the combustion chamber temperature changes in case the engine runs lean or starts to overheat for other reasons. This typically throws people because they may have say a 185F thermostat listed for the engine and then they are confused or worried why the engine may be running at 205F. This is very typical where most engines will run 15-20F higher than the the thermostat rated temperature.

Now on to the the BMW V8's that I am familiar with the S62 and N62, the engine coolant temperature sensor is not located in the cylinder head, it is actually located direct on the the water pump (N62) directly on top or near the thermostat. The S62 has the engine coolant temperature sensor directly on top of the thermostat, mounted in the thermostat housing.

The S62 actually runs too cool in my opinion, there is VERY little margin for the engine temperature to drop too low before the engine starts to run way too rich and looses performance. On the opposite end of the spectrum, I believe the N62 runs too warm. With all the problems with valve seals and coolant O-ring seals on the N62, I feel the engine operating temperature can be a contributing factor to the early rubber seal failures. Also the elevated temperature can stress the cooling system components more than lower engine coolant temperatures.

Although I have found the Hamburg Technic 90C thermostat for the N62, I would prefer to have a 95C thermostat if on was available. I ran the thermostat for almost 9 months without a problem during the Spring and Summer months, but like all thermostats, the main spring started to get weak and the temp started to drop slightly and it was enough to finally trigger the P0128 MAP thermostat too cool error code.

I just replace the Hamburg Technic thermostat with a warranty replacement because the unit was still within its 1 year warranty period. I would say the thermostat was starting to run between 5-8F lower then when it was originally installed. So this thermostat is very close to the threshold for the P0128 trigger.

I will wait and see what happens over the Winter, I may end up reinstalling the OE thermostat or modifying the OE thermostat to try and get closer to what I feel is the magic 205F/96C operating temp that I like to see.

Is this the guy you got? Are you saying this could work in my 2006 4.8is N62? If so, thank you very much.

I wouldn't mind swapping this bad boy in for the summer.

https://www.ecstuning.com/ES2807159/

[QUOTE=V8 00USH;1055768]


I wouldn't like to see my engine oil consistently sat over 100degrees.....same applies for gearbox oil.

QUOTE]

Engine oil is one fluid I do want to see at 100C or 212F and maybe a few degrees higher so I know unburned fuel and moisture has been released and evacuated effectively through the CCV and I know synthetics easily handle that kind of heat.

I'm not sure what the desired operating range is for the transmission fluid, but I know I've had other vehicles that altered shift characteristics and would not lock up the torque converter until fluid temps were in the neighborhood of 77C to 82C or 170F to 180F.

2002 X5 3.0 289,800 miles
2004 325i 123,000 miles

Yes, verify fitment to make sure if will fit for sure, but I am running this in my 2008 4.8l N62 at the moment and plan on running mine through the Winter.

[QUOTE=srmmmm;1055789]Even if the engine oil temp does not register 100C/212F, chances are it is much warmer in other areas in the crankcase. This being said the 7-9 quart sumps that these engines have means there is a lot of oil to actually warm up.

I have no problem running my engine as long as I monitor the underside of the oil fill cap. If any Mayo builds up, I will usually remove the oil fill cap over night to allow the crankcase to breath.

I made a piggyback circuit and control my engine temp using the electric thermostat. I have been running 93C~94C for a couple of years now.

A quick search will bring up my write up including the theory, and how and why the DME does what it does. The original 228 degrees was a bandaid. Downside of course is the cooling system pressure that goes along with that heat, and we know how our systems can tend to crack and fail. On top of that is the fact they use 4 knock sensors, as warmer cylinder walk temps increase susceptibility to detonation. BTW, gas mileage was not on my list of concerns here; for others it may be. Read the write up I did I think in 2012 (?) on that.......

I put an external cooler on my trans in 2010 (?). There's a write up in here on that too.

The trans heat exchanger has a small thermostatic valve, and 2 water inlets (and one outlet return to the water pump). The inlets are from the engine and the lower part of the radiator. The little thermostatic valve simply balances the flow between the 2 inlets. It starts at 100% from direct engine-heated coolant, and as the coolant heats up begins to balance between the 2 sources. It is easily removed/modified if you want a lower net water temp passing through that heat exchanger (yes, I did that too).

Lots of reasons to want your oil temp sufficient to burn off moisture. I change my oil twice a year regardless as it's cheap and fast to do. Since rebuilding my trans in the garage 5 years ago, I don't subscribe to the lifetime fill idea, so I most certainly don't need my trans running over 212F to keep moisture at bay. Those of you who are or intend to subscribe to the mfr recommended extended/lifetime trans fills may wish to consider that moisture and condensation will not be effectively burned off at 80C operating temps. Wasn't a tough call for me, though.

civdiv99

Oh, and hey Slick, how's it been treating ya? :D

I had been thinking about this myself using the thermostat heater and the OEM stat to actually run the engine cooler.

But I am also thinking about unplugging my 90C stat heater for the Winter and putting a resistor in place to keep the DME from triggering a any codes for an "open" stat heater. I may just plug my original stat housing in and wire tie it out of the way in the engine bay somewhere??

I will try to search out your threads. It was CRYSTAL clear to me when I purchased the X5 with the N62 just over 6 months ago that 226-228F AT THE THERMOSTAT housing was BAD. So this is why I quickly put the 90C stat in because it was the quickest and easiest thing for me to do in early Spring to get ready for the Summer temps.

BTW, I made a straight 1100 mile trip averaging 70 MPH for the entire 1100 miles and was able to get 23 MPG in my 4.8l.

where can i get the Mocal 80deg -8AN Oil Thermostat... lmk thanks

Been good. It's a BMW, what can I say. I knew this thread would bring you out. Lol.

Excited about this lower temp tstat. Will report after more research.

Why do you class 100C as the 'magic' number that everything 'bad' will be released and disappear from your engine oil?

Fluids dont need to boil to release vapour either (bear in mind engine oil will boil at around 300C). Also if the engine is running as it should and there's no issues with combustion then there should be very little with regards to fuel contamination anyway.

Moisture will be evaporated at much lower temperatures than 100C. Also it's more about the length of time the oil is at a higher temperature than the actual temperature itself.

For example - 30mins at 80C will mean alot more moisture will be burnt off than 100C for 1 min! I bet moisture will even start to get burnt off as low as 65C.

Ask yourself the question - why is the oil thermostat used an 80C one and not a 100C one for example - answer is because it doesn't need to be. If the oil is kept at at least around 80C operating temperature then everything that needs to happen will happen.

^this. I can almost guarantee that if you had 2 X5s that had done the same mileage under the same driving conditions yet the transmission fluid in one had been kept at least 20 degrees cooler than the other over say a 5 year period - the quality of the oil of the cooler running one would be higher.

I too also tend to change my engine oil every 6k - probably not required but I like to do it for peace of mind and knowing that the quality of the oil is as high as it can be - I like to drive my cars rather than just dawdling around in them too.

Gearbox oil I would quite happily do a flush every 2/3 years also especially if it means increasing the lifespan of the ridiculously expensive gearbox - after all - prevention is better than cure.

Spoke to a few people over the weekend that also told me that if you had the towing pack option fitted from factory when you bought the X5 then they fitted an external gearbox cooler as part of this pack which is interesting! This being the case BMW obviously didnt see any issue in running the X5 transmission fluid at a cooler temperature - I also doubt they altered their 'lifetime gearbox fill' policy either if you had one fitted.

I got mine from here...

Mocal Oilstat Oil Thermostat -8 AN male - 574-OT2F - Speedflow

Interesting bit of reading here - Everything about your ZF 6HP26 transmission issues | BMW Logic7 site

Granted it's for the 6HP26 gearbox but I can't imagine the 5HP24 characteristics would be much different if at all when it comes to heat/behaviour issues!

This immediately caught my eye.

Everyone also needs to keep in mind that in addition to oil/oil sump temperature being important for fuel and moisture cook off, remember the crankcase is also under a vacuum the majority of the time. Liquids boil/outgas at lower temperatures when under a vacuum or at less than atmospheric pressure.

So at the end of the day, the length or duration of the engine operation is more important than the absolute highest oil/oil sump temperature.

I will be doing this too. Never heard of it before this thread.

Think it will probably be the one out the 750iL/850ci

Part number - 11531704704

You'll just change the actual element so that you can retain the housing with the heating element in it.

Very tempted to do this myself to be honest.

As long as the element has the hole in the center for the heated post, it should work. Seems from the pictures I have seen the 750/850 stat may not be a heated stat?

One thing to keep in mind, with the 90C stat, you may trigger a P0128 code from time to time. I finally did, but my thermostat actually got soft and the operational temp had dropped about 8-10F from time to time due to the main spring getting weak. I just replaced the stat and will see what happens over the Winter as I have not run this stat through a full Winter season yet.

If someone can find a 95C stat, I think this wold be a big more ideal overall, but the 90C is fine until it goes soft.

ok so the part number 11537586885, it the same as your car. As a matter of fact, this thermostat is used across most V8 engines in BMW lineup.

The hamburg tstat looks like a direct swap to ours, even part number is same, other then the 90C at the end. 11537586885-90C

The 750 Tstat is also 90c, we are looking for a 95C one. The 750 tstat is also not heated. I don't think this will work, or worth while.

So far, the hamburg one is in the lead.

As you say....completely different type of gearbox coupled to a completely different type of engine which also should be worth noting runs substantially cooler. So really bears zero relevance to this post.

In fact the only similarity between the 2 gearboxes is that they are both automatic!

You'd struggle to find an original 5HP24 box in an X5 4.6is with 290,000 miles on it that's for sure!

Out of interest......what makes you think the 90deg one wouldnt be worthwhile (if it worked)?

Only downside I can see is that it might trigger a fault code from time to time.

Wonder if you could delete this from the map on the ECU so it either didnt check the temperature at all or perhaps if the temperature/conditions could be altered so it didn't register the fault in the first place!

Because time is money. Coding out a function is a little bit worrisome. Sticking in a tstat into our housing, and then having to figure out how to code, or make the heater work. Pass.

Hamburg one would be $50 more than the factory 750 one. $50 is not worth it for me to fiddle with for half a day. That is why I say not worth it. If someone can figure this out and make it work, then sure, I might try it.

I'm still looking for a 95C one, but not looking good.

Valid points.:iagree:

2002 X5 3.0 290,000 miles
2004 325i 123,000 miles

But that's the whole point behind it - it wouldnt matter if the heater didnt work - it just needs to be still plugged in so it didn't trigger a code - or you could resistor across the plug if you used a housing without the heater port so it thought it was still there!

Remember the heater is only there to prematurely open the thermostat before it was designed to - if you ran a 90C stat it wouldnt need to be prematurely opened as it would already be open!

The 90C will work, it may occasionally trigger a P0128 MAP thermostat code, mine did recently. But I had been closely monitoring the engine coolant temperature with my UltraGauge and saw that the temp had drifted down slightly since the installation about 8 months ago. The main spring was getting weak. The engine was running about 8-10F lower in temp once the outside temps started to drop off.

I went ahead and got a warranty replacement and so far no more P0128 yet and the temps have been holding right at or very close to 90C with the cooler outside temps that have recently arrived.

With the 90C stat, it works, personally I would really like a 95C stat. I find that 205F/96C seems to be a very happy operating temperature for most modern vehicles. What I find is ALL thermostats get soft over time as the main spring looses its strength. With a 95C stat, there is more buffer room before the stat gets weak enough to trigger a P0128, the 90C stat has little wiggle room before the P0128 pops up.

Now I am the primary driver the vehicle and I watch the temps closely and I can quickly and easily read the DTC's with the UltraGauge so I am not worried. If my wife drove this daily, it would be a very different issue. She HATES lights and buzzers, they put her into a funk and she thinks the world is going to end. This is fine for a oil pressure light or a high temp alert, but I cannot get her to understand the yellow lights are usually less of a problem and not so catastrophic.

I would never even worry about attempting to code out the MAP thermostat issue. I may plug an older stat housing into the heater connection and see what happens over the Winter. With the engine running at 90C, not sure the stat heater is really needed, but when looking at the I6 engines, I recall the 96C stat will drop to around 81C when the stat heater is commanded on assuming the ambient is cool enough to drop the temp this low. I may need to verify this number, I may have some graphs/data for the I6 somewhere around here.

After doing some more research I've found an 88 deg one that I will probably look to fit.

BMW Part Numbers 11 53 2 248 542 or 11 53 1 715 254

They come from the 740d and 745d.

Housings appear identical the only difference being the hole for the heater part is blanked. I'm either going to leave the heater part unplugged, resistor it or try and remove the old heater element from the old housing and leave it plugged in.

http://img.photobucket.com/albums/v1...322/stat01.jpg

X5 4.6is 5HP24 External Transmission Cooler - My Solution
 

Sorry for the old bump.
In your pics. Where exactly is your thermostat mounted?
Is the 4.6 like the 4.8iS with the stock pos heat exchanger at the bottom of the passenger side of the radiator?

I like the idea of a thermostat, I just can't make out where you have it mounted.

You also said you cut the return run line. So the stock heat exchanger is still there, you just ran a detour from the return line to your 80c thermostat then to your cooler, then back to your return line?




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It's sat literally right next to the standard heat exchanger.

Up until a couple of weeks ago I had the standard heat exchanger still plumbed in but one of the OE couplings failed and spat 6 litres of transmission fluid out so I've completely bypassed it now so it's no longer in the equation.

Do you have some new pics of your revised setup?
Have you left the factory trans heat exchanger in place and just blanked off the openings or ports for the hoses?

I don't have some pics but I'll try and get some next time I'm under there. Yes left factory heat exchanger in place so I didnt need to do anything coolant wise - I haven't actually blanked off ports as the exchanger was empty anyway due to what happened but could blank them or loop together with pipe if there was still fluid inside to stop it dripping out.

X5 4.6is 5HP24 External Transmission Cooler - My Solution
 

My plan is to fit these...
https://vadersolution.com/products/6...itting-adapter

Then run AN8 lines to a cooler placed in front of the others. (Radiator/ps cooler/condenser)
Bypassing the factory thermostat and cooler.
I've got my eye on a a CXracing 19row cooler. Just have to see what length lines I need.


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Love those fittings - I never even knew they existed. They would certainly make installation a breeze. If I had to do it again I would use a 16 row cooler rather than a 19 row - would make installing it where I did alot easier indeed and would still be enough to cool the transmission.

Oh yeah. 16 is adequate? Well poop. I may do that too.
Yeah a buddy that suggested I run the external cooler showed me these. He's done a few on DCT cars, apparently they run too how in track conditions too.

I'm probably gonna order the cooler and these line adapters today.
Then get an8 lines made locally once I figure out what length and angles I need.


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You can make the lines up yourself - piece of cake. Just work out what you need. If it's going in a similar place to where mine is I reckon you'll need 2x 90 deg for the top of the cooler and then you'll probably get away with either 2x 45deg or perhaps 2x 90deg coming off the original lines to get them heading in a decent direction. Beauty of the old fittings is that they are already on rubber hoses which will help you direction wise.

Forgot to add....I'd still look at running a thermostat too.

You think so, i was thinking to go without. It's never really cool down here in south Texas.


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Have you got any way of monitoring the transmission temperature?

X5 4.6is 5HP24 External Transmission Cooler - My Solution
 

Only INPA. And I haven't driven around with it.
It was at 83 about an hour after driving yesterday. I had INPA plugged in.

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I read your post and thought.....86 degrees is fine for normal running....and then I read it again and realised you'd said it was at 86 degrees an hour AFTER driving. As in it had been stopped for an hour and then you hooked up INPA? Am I reading it right?

Yep. Said TC was slipping too. Never seen that error before.
My shit is fucked.


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I think I will be doing this too!

Been researching on AT coolers for Subarus and been thinking about putting them on the BMW's. Looks like they do good in this application also.

It looks amazing is it still working ok? I'm thinking of doing the same. Do you have links to the exact parts you used you could post please. Thanks in advance.