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550iFreak 05-21-2017 12:29 PM

F10 550I Thermostat R&R (Upgrade to 90C)
Hello, here is my first DIY for the F10 550i:)

Nothing kills the engine ( or anything really) more than unnecessary heat. These engines run very hot from the factory, hotter than the typical car from other manufactures was allowed to.
The operating temp for the N63 is 105C (221F) and may run towards to 107 or so depending on how hard you run so imagine running the engine close to its maximum temp allowed before declaring an overheat condition. The engine oil runs close to 250F which again, VERY HOT!!

Seals goes bad, along with other associated issues which gave the poor N63 such a bad rep thanks to BMW to comply with emission standards to run such a temp....

Now, I found an old thread in the 7 series section about swapping out the thermostat for a cooler variant which receives mostly good reviews. Some swapped the element from the 90C to the original 105C housing since the 90C housing were known for exploding.....Seems like they got alot better since the newer reviews are positive. So here we go, let's get it started.

I am not held responsible for any issues or damage caused by this DIY. This should be conducted at your own risk. This DIY is a guide but always refer to the appropriate manuals and technical updates for a thorough procedure and proper removal/installation. If the procedure cannot be conducted, go to your indy or dealership for consultation and replacement. This may void the warranty due to tampering with "normal" operation (even though this will improve the engine as a whole). Remember murphy's law applies and associated parts can potentially break depending on their age. ALWAYS USE CAUTION when removing plastic parts or damage may occur. O-rings not needed for replacement but they are recommended. Use your best judgement and good luck!******

Here is what you need, this list will be subjected to change if needed:
7/16 socket
1/4 ratchet and extensions
1/4 wobbly
90 degree dental pick
flathead screwdriver
inverted torx set (E8 will be used)
torx set (T25 or T30 used)
8mm socket
pliers or needlenose
BMW Genuine coolant
distilled water
90C thermostat( will provide link of purchase)
clean bucket
jack and jackstands( ramps are better if available)
battery charger(for venting procedure)
1/4 adapter from drill or 8mm drill adapter

Step one: GET EVERYTHING! make sure you are prepared, and have a second car at hand just in case. Don't put yourself in a stranded situation.
Allow the car to cool for no less than 4 hours or safe to touch to avoid burns and damage from high internal pressures. Open the coolant cap to allow further decompression. I parked the car for the whole night prior working on it.

Real step 1:
Jack the car up or briefly run the car up the ramps( allow an hour to cool down if running ramps) and locate all 8mm bolts holding the engine cover plate. Remove all bolts holding the cover plate and remove the cover plate. I believe there's around 12 bolts or so (there's alot). A drill with the 1/4 attachment and a 8mm socket works wonders here.

You will be able to see the thermostat from the bottom quite well, and access the difficult torx bolt holding the thermostat towards the block. But dont get excited, you'll want to remove the assembly from the top if you don't want to be douched with coolant lol.

Now go the top of the engine compartment, remove the engine cover.

GET THAT BUCKET READY, you'll start leaking here shortly.

That intercooler reservoir will need to be removed. Two 7/16 plastic bolts hold the reservoir. All hose connections are clipped on. Remove all hose connections from the intercooler sides. DO NOT REMOVE THE PERMANENT CLAMPS ON THE RESERVOIR SIDE.
Driver side intercooler elbow comes off, the little hose from the reservoir comes off, and the passenger intercooler tee comes off. Then remove the large hose connection from the reservoir( this is tough, be patient.) the 90 degree dental pick is useful here to lift all the clips holding the connections to allow removal.

Now the reservoir out, remove the aux pump. Two torx T25 or 30 are used here. Remove them and undo the clamp with a flathead. The other clamp can be removed using a pair of pliers or needlenose. The electrical connector, be careful. remove it carefully.

Now you can see your precious thermostat :) Remove the hose connecting the thermo ( this will begin draining your coolant so beware).

Let the coolant drain out the hose to the bucket. There's a drain **** on the driver side of the radiator but you'll need a special large torx driver. Also, the drain is plastic and i'm scared that I'll damage it so no need for me to tamper with it. After drainage, remove the two accesible inverted torx bolts holding the thermo to the water pump. The last hard to reach one will have to be accessed through the bottom utilized with extensions and a wobbly. After removing all three bolts, remove the electrical connector and tap the housing using a soft drift and a hammer. The seal is tight on it so it will take abit to be successfully removed.

Now here's the comparison between the two thermostats. Both are made by WAHLE, one will have the P/N shaved off since it is modified for 90C operation.


Now you got the new one, the installation is reversed. The O-ring needs to be lubricated with coolant prior installation, no other lubricant can be used due to possible cross contamination or improper seal operation. I didn't use the torque spec on the bolts installing the thermostat since the bolts are small and I couldn't find the specs. I used the general torquing procedure which is tighten until snug and a 1/16- 1/8 of a turn past that. Reinstall all electrical connections and all associated hoses. Do not reinstall the bottom engine cover yet. After all connections are made, go ahead and fill coolant mix with distilled water in the intercooler reservoir first, then the main engine coolant reservoir.

Then activate the engine cooling venting procedure, car must be level and highly recommend using a battery charger since this takes around 20 mins or so.

I bought this awesome BMW OEM battery charger from the dealer for 70ish dollars. Will come in handy for things like this or to keep your battery maintained. Awesome investment in my opinion.

So after everything is hooked up and filled with coolant, press the start button once activating the ignition. DO NOT START THE CAR. Immediately depress the accelerator to the floor and turn both HVAC to 84 degrees( highest heat setting) with blower manually set at lowest setting. You should hear the aux electric pumps to run. Let go the accelerator and leave it alone. Go to the engine bay and with both reservoir opened, keep filling coolant/distilled water mix as you can see them gurgling down and consuming the fluid. If it stays in the max marks and will not change within 5 mins, close the caps and allow it to pressurize. Go inside the car, you should hear water gurgling through the heater cores. You'll know when it is ready when the gurgling slows and barely hear any activity. Should hear like a steady stream with barely any gurgles knowingly it may have worked through the air pockets. It should shut down on its own within 20 mins. If it still going, and you are sure that the air pockets are worked through, you can stop the procedure simply by turning the HVAC system off completely. Turn the car off, and inspect any leaks. Disconnect the charger and open the caps. They should still be full. If not, top it off. Then close the caps.

Reinstall the engine cover, but not the bottom engine cover yet.

Now go to your car and start it up, and allow it to reach operating temperature.

To access this special hidden info, here's a youtube clip of it

Basically turn the car on, hold the trip button and don't let go of it until the menu shows up. Then go to UNLOCK, put the code in which is the addition of numbers of your VIN. Then go to temperature and monitor from there.

Once it reaches 93C, then it should fluctuate between 92-93C. Then it will stabilize and go up to your true new setting at 96C. You'll know it is working since it won't spike suddenly after that. If it goes past 101C, something is wrong or you still have air.

Shut the car off, and inspect leaks again. If there is no leaks, install the bottom cover.

Clean everything up, go take a shower, eat, poop or whatever then go to your car and start it up.

Start driving the car, with the temp screen still active. If it isnt, go to the hidden menu again using the youtube link.

Mines run at 96C now, planted. When I give more gas, it goes down to 95C and then Back up to 96C. When Idling, it went up to around 98 to 99C. This is okay since once I start moving, it goes back down to 95-96C. Also, being 90 degrees outside in sunny florida, this is a great improvement.

The car runs ALOT better, more power demand when warm and it feels more alive. Your car will thank you for this. Your Oil temps will be lower than usual and if you opt with badblack550ix oil plug bypass to allow full cooling with the oil cooler, then you'll be set.

Congrats on your new mod, and ENJOY!!

_des_ 06-04-2017 01:25 PM

Thank you for taking the time to write a well detailed DIY.
It sounds very promising, but are their any negative side effects to having this mod? I know the oem operating temperature is usually higher to pass emissions.
Do you know if this effects the AFR's any?

550iFreak 06-04-2017 05:59 PM

:thumbup:Thanks bud

Well, the ONLY negative side effect ( and if you even consider this a negative effect but you should be expected if you own such a beast) is a very slight decrease of MPG. And I mean 0.1 of a mpg lost on your average. Since it is running cooler, the car will tend to run a tad richer than usual. But the positive effects outweigh this such as:

Longer overall engine life

Less stress on critical/sensitive components such as coolant lines/plastic connections, turbos,etc

More consistent and powerful performance at operating temps( timing and other parameters able to give full potential)

Excellent in areas that ambient temps are usually on the high side(Floriduhhh) so no more heatsoak or reduced power output due to higher temps.

Coolant/oil consumption reduced( I noticed before I had to add coolant. Even though it was a small amount, I do need to top it off here and there. Now to this date, it is still at MAX level. My oil consumption also improved as well. I still dont need to fill oil yet and I put almost 2k miles on it already).

Also, still to this date, It did NOT trigger a check engine light nor a malfunction light. I was spirited driving with a Fiat Abarth lol....and we were having fun until boof my malfunction light came up and my oil temp reading at 250. I was running hard though. After putting the 90C, I NEVER got one and I do drive it hard time to time. Even now with your former precious JB4 file, it still doesn't trigger it. Just hauls ASS hahaha.

I did notice one thing though that is funny, and must be related to the JB4 stg 2 tune. Before, I consistently pull 95-97C at any engine load applied to it. Now when I go WOT, it drops considerably to as low as 79C O.o . Give it a minute and it will gradually go back up to 96C. When I am cruising and not go stupid, it will stay at stock 96C until I hit the gas, Then it will go back down depending how long I WOT. I am sure that the JB4 is doing this and thought it was an issue but then again those running the JB4 for many miles and still have no issues meaning it must be fine. Then again...they were running stock 105C thermos. Hmmm...something to look into once I get my cable.

daders 06-04-2017 06:29 PM

Thanks for a superb write-up, just curious...what was your typical mileage until oil consumption alert?

I'm going to have to check out that hidden menu temperature next time the missus lets me drive her car...we're due for fluid flushes so this might be a perfect time to get this installed.

550iFreak 06-04-2017 06:41 PM

My oil consumption ranges 1500-2000 miles per quart depending. After a fresh oil change, it can go 2K before the 1 quart low warning comes on. Then thereafter, it will go to 1500 but depending how I drive overall can yield back up to 2K. This is all on the stock thermostat.

When it is time for my next oil change, I will re document the new oil consumption to accurately answer the question as if it truly improves the consumption while utilizing the 90C thermo.

Even if it stays the same......this is still a great upgrade if you want to experience more consistent performance when your engine is at operating temps. That I can accurately tell you that there is a difference in overall operation of this engine. It's more "Alive" if you will.

Especially if you live in hotter climate, this is it.

I remember going to Sears one day and my Fiance wanted to wait in the car. It was around 85 degrees outside with AC set at 73. Around 10 mins I come back and saw my oil temp is at 250 degrees straight up. I'm like WOW, she runs hot.....

Now, I did a similar scenario but I was waiting in the car for about 15mins and outside was around 90-91 degrees ( IIRC, it was hot as balls.) The oil temp needle never reach past over the number "2" on the gauge. Check the coolant and it rest at 100-101C. After a minute of driving, it goes back down to 96-97C. And it runs well too.

daders 06-05-2017 05:04 AM

Thanks for the reply, I'm mostly interested in reducing stress on the system due to high running temperatures, especially as our running joke is that we live on the surface of the sun :rofl: most of the summer after we set a record a few years back with something like 114 straight days that breached 100F. We thought we knew heat from living in NE FL and spending much time in your neck of the woods of central FL, but we were cured of that silly notion by TX. I'll be interested in the oil consumption as well. Our N63 (knock on wood) has never indicated needing oil between oil changes (I've only remembered to check once before an oil change and the indicator was still at max, but our oil intervals usually are due to time rather than mileage).

vien727 07-06-2017 12:55 PM

very interesting.

our car programmed to continue to cool the turbo with the electric water pump after the car is shut off. with the lower operating temperature, does the electric pump and the fan still operating ofter the engine is off? or it wont run because it sense that the engine temp is lower and not neccessary to continue cooling the turbo after a hot run?

im very interested getting this mod done. would you please help?

550iFreak 07-06-2017 08:25 PM

It will operate as normal but I did notice a shorter time for cooldown due to lower temps. Especially now in Florida where highs are subpar 90 degrees, this really shines.

So far, no issues. About to do an oil change possibly next week which I'll start the new oil consumption report.

daders 07-14-2017 12:06 PM

Spoke to Indy mechanic about this and his response was mostly quizzical as to effectivess and possibility of fault codes being thrown if operating outside temperature range. Then he quoted me the price for doing the job (5hr labor, btw) which has me rethinking whether a 10, maybe, 15C temperature drop will make a significant change in mean time to failure...particularly considering this isn't a vehicle that typical sees daily driving. I figure I'll save paying the labor for an actual failure and perhaps I will try to tackle this on my own further in the future (or be cursing myself for not having done it earlier when the coolant and turbo lines need replacing, lol!). I look forward to hearing your long term experience 550iFreak.

vien727 07-14-2017 03:04 PM

i just got my 750 f01 changed to the 90c tstat.

im in tampa, florida.

before my operating temp was 105c to 108c. now with the 90c tstat, the temp is normally around 98-102c. goes down to 93c under "sport mode" and crusing on the freeway.

my first concern is that my oil temp is around 99c most of the time. i like the oil to be a bit hotter to burn off any moisture in the oil or the engine.

i ordered the tstat on the link above and had an indepedant shop put it in. about 500 USD altogether.

den550 09-08-2018 06:39 AM

Was this part changed in the n63tu update?

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