BMW 90C Thermostat For N62, N63, N73 Engines - Page 16 - Bimmerfest - BMW Forums



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7 Series - E65 / E66 (2002 - 2008)
Discussion of BMW's 4th generation E65/E66 7 Series flagship. The E65 generated much controversy, due to its radical styling and iDrive user difficulties. Nonetheless, the E65 broke records to become the best-selling 7-series iteration ever, especially after its 2005 facelift.

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  #376  
Old 12-19-2018, 05:35 AM
pelensky pelensky is offline
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I installed a 90 degree C thermostat. My temperatures are running 83 to 87 degrees C on the highway. has been very responsive but I'm now on a second unit with the same results. My 645 only has 49,000 miles on it. It has been immaculately maintained and I am running 40% coolant and 60% distilled water. I know my cooling system is doing a super great job cooling but it still seems like it's running too cool. The first unit I got was throwing a code 0 1 2 8. I just installed the second unit and do not know if it's throwing a code yet. I only drove it 10 miles and it did not throw a code even though I was expecting it to with temperatures that low. Anybody else have a 90-degree C thermostat that's running that cool?

Last edited by PAPER; 12-19-2018 at 10:49 AM.
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  #377  
Old 12-31-2018, 12:23 PM
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Jaystyles Jaystyles is offline
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Iím running a 90 tstat on my 545i with a 1.4bar expansion tank cap and I was getting a check engine light for tstat stuck open. I read that changing the map sensor fixes this for some members. I changed my map sensor and cleared the fault and a couple month back and my 90c thermostat runs fine with no check engine light.


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  #378  
Old 01-01-2019, 10:09 AM
David.W David.W is offline
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How do you re-calibrate a thermostat? I don't see how it is possible to disassemble the wax motor... Sure it can be removed from the thermostat housing and possibly replaced with another but I don't see how it could be modified other than possibly to squeeze in the sides of the copper body and reduce the internal volume of the wax motor which might make it open sooner. It is riveted together and this is one time assembly at the factory.
Our thermostat has a heater element that runs up the inside of the wax motor. My understanding is this turns on under engine control and raises the temp of the wax motor and so opening it sooner. I doubt the heater would last long if it were energized continuously.

Last edited by David.W; 01-01-2019 at 10:12 AM.
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  #379  
Old 01-30-2019, 07:20 PM
amandash amandash is offline
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just mod my thermostat. Put a spacer. at ambient temp 20c it runs about 87c - 93c. Short distance test only. Down side is the thermo starts off slightly open and take a it of time to warm up. Any advice on this? Its quite a simple mod without the $$$
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  #380  
Old 01-30-2019, 08:00 PM
rbryantaz rbryantaz is offline
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Originally Posted by amandash View Post
just mod my thermostat. Put a spacer. at ambient temp 20c it runs about 87c - 93c. Short distance test only. Down side is the thermo starts off slightly open and take a it of time to warm up. Any advice on this? Its quite a simple mod without the $$$
If the car takes too long to warm up you risk damaging the rings.

Damage the rings and your "without $$$=200" easily becomes about 30 * $$$ if you pay for labor....

I just changed an N62 in my e70 after it drank some water in mexico and hydrolocked (long story). It was at least 3 days solid of labor and probably 4 which is likely $3000 even if you find someone to do it on the cheap. That does not include the cost of an engine which is likely another 2-3k for a good used one.

I did mine in about 6 days of work while fixing up a bunch of other stuff and changing all of the seals on a used engine. Trust me you don't want to do it.


-Rich

Last edited by rbryantaz; 01-30-2019 at 08:52 PM.
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  #381  
Old 01-30-2019, 08:38 PM
rbryantaz rbryantaz is offline
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Originally Posted by David.W View Post
How do you re-calibrate a thermostat? I don't see how it is possible to disassemble the wax motor... Sure it can be removed from the thermostat housing and possibly replaced with another but I don't see how it could be modified other than possibly to squeeze in the sides of the copper body and reduce the internal volume of the wax motor which might make it open sooner. It is riveted together and this is one time assembly at the factory.
Our thermostat has a heater element that runs up the inside of the wax motor. My understanding is this turns on under engine control and raises the temp of the wax motor and so opening it sooner. I doubt the heater would last long if it were energized continuously.
You might be on to something with the squeezing of the wax housing...

Lets say you have a method for making a slight and controlled squeeze permanent...

1990 Mustang Stant thermostat from Amazon.
Click image for larger version

Name:	stant thermostat.jpg
Views:	126
Size:	16.2 KB
ID:	838307

Developing a process to do that at home would be a bit time consuming though and doing it would require a lot of experimentation. Given the effort and research involved in something like that I am happy to pay someone to specialize at it.


As a side note:

I am not sure how long the heating element would last if always turned on but that is mute because that isn't the best way to modify the t-stat.

I can say that the heating element is pretty fast. I put 12v across the terminals on an old one got hot to the touch in only a couple of seconds. Given that it is touching the wax enclosure directly all it has to do is heat that enough to fight the lower temperature water it doesn't have to work super hard.

-Rich

Last edited by rbryantaz; 01-30-2019 at 08:39 PM.
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  #382  
Old 01-30-2019, 09:33 PM
amandash amandash is offline
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Rich - How long should it take to reach normal operating temp. I have no codes now. Tomorrow I will take it for a highway run.
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  #383  
Old 01-30-2019, 09:57 PM
rbryantaz rbryantaz is offline
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Originally Posted by amandash View Post
Rich - How long should it take to reach normal operating temp. I have no codes now. Tomorrow I will take it for a highway run.
That will depend on the ambient temperature and a number of other things.

If it is cold outside it would likely take longer to warm up.

Even if it doesn't throw a code it can still cause extra wear while warming up.

-Rich
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  #384  
Old 02-03-2019, 11:13 PM
amandash amandash is offline
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Anyone used Royal Purple. Is it compatible with BMW coolant?
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  #385  
Old 02-03-2019, 11:19 PM
rbryantaz rbryantaz is offline
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Originally Posted by amandash View Post
Anyone used Royal Purple. Is it compatible with BMW coolant?
Just use the bmw coolant, it isn't that expensive compared to everything else on the car.

ZEREX makes it for BMW and you can also buy it as ZEREZ G-48.

-Rich

Last edited by rbryantaz; 02-03-2019 at 11:20 PM.
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  #386  
Old 02-04-2019, 08:35 PM
amandash amandash is offline
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I am inquiring about Ice coolant additive instead of 90c thermostat swap.
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  #387  
Old 02-04-2019, 10:01 PM
rbryantaz rbryantaz is offline
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Originally Posted by amandash View Post
I am inquiring about Ice coolant additive instead of 90c thermostat swap.
#1 rule with car maintenance: There is no magic in a bottle.

Add it if you like but it would probably already be in the coolant from BMW if it should be in the coolant.... They spend a lot of money to make oils, coolants, etc have the right formulas.

-Rich
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  #388  
Old 02-07-2019, 04:29 AM
daka daka is offline
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My mechanic tells me that the thermostat is stuck open....(07 530 xiT 50,000 mi) I have never noticed anything...the car is in S FL, runs fine gets 19 mpg in city only use....
So what NEEDS to be done? What is wrong with just leaving it alone?
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  #389  
Old 02-08-2019, 04:18 PM
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Jaystyles Jaystyles is offline
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Being stuck open which mean your car will be running cooler than normal. Which is good if thatís your goal. Which is the goal weíre all trying to achieve with the 90c thermostat.


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  #390  
Old 02-08-2019, 04:29 PM
rbryantaz rbryantaz is offline
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Originally Posted by Jaystyles View Post
Being stuck open which mean your car will be running cooler than normal. Which is good if thatís your goal. Which is the goal weíre all trying to achieve with the 90c thermostat.


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I disagree, the goal is to regulate at a lower known temperature that is warm enough to still work properly but cool enough to avoid over pressuring the system and plasticizing our gaskets.

Being stuck open doesn't do that, it lets the car cool based on the max cooling it can achieve with that restriction, engine load, radiator capacity, and ambient temperature.

If running at a racetrack with known conditions running and the car hard non stop to the maximum of what the cooling system can handle then taking the thermostat out and running a restrictor can work just fine.

Running with just a restriction and no thermostat in daily driving where temperature changes (it could be 10 degrees out one day and 60 the next), we get stuck in traffic, etc it isn't a good idea. This is why thermostats exist!


-Rich
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  #391  
Old 03-02-2019, 08:16 PM
amandash amandash is offline
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So my car begun to throw a code which was returning when cleared. I went ahead and replaced the spacer with a narrower one and not the car is running at 194f-210f without a code for the last week or so. Also I am using a 1.4 bar cap. I am happy with that so far.I chose not to use the Royal Purple ice as there were comments that it reacted negatively with distilled water. I will keep monitoring it.
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  #392  
Old 03-14-2019, 02:26 AM
MTBnutFROMoz MTBnutFROMoz is online now
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Quote:
Originally Posted by amandash View Post
just mod my thermostat. Put a spacer. at ambient temp 20c it runs about 87c - 93c. Short distance test only. Down side is the thermo starts off slightly open and take a it of time to warm up. Any advice on this? Its quite a simple mod without the $$$


@amandash How much of a spacer did you put in?

I came across someoneís awesome e38 thermostat mods, using a thermostat of a lower temperature from a different car and adding a spacer ring to the assembly. Iíd like to ponder something similar for my e65.

Iím in Australia with a 750. I get stuck in terrible city traffic, sometimes in 40 deg c (105f) or hotter days.

Thinking of a huge electric fan in front of the ac condenser too.
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  #393  
Old 03-14-2019, 03:40 AM
daka daka is offline
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Back in the days of the BAVARIA's, overheating was a real problem, getting stuck in heavy traffic had you watching the temperature gauge and loking for a place to get off the road.
We first tried a manual switch for the aux fan, that helped, but did not solve the problem...the final solution was IIRC having a 3 core radiator made up..
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  #394  
Old 03-20-2019, 04:00 AM
4thBMW 4thBMW is offline
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Lol, my Florida garage never gets < 85deg F in the summer at night!

If you all are not just leasing or flipping cars, maybe you should worry about what your metal parts and cat converters think about screwing with your coolant temps inducing cylinder wall/ piston ring wear....making the car run richer longer...
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  #395  
Old 03-21-2019, 08:32 PM
Fruitsalt Fruitsalt is offline
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Logic7 thermostat

Quick question for the guys who have the thermostat

I have replaced the original thermostat with the one, have no leaks and the system has been pressure tested, however I still continue to run 102-105 in the city and around 99-101 on the freeway.

Just yesterday temp got up to 107c waiting in a drive thru ( AC on)

The car is a 2008 BMW 550i (n62tu) replaced the thermostat and water pump, filled with bmw coolant and distilled water have 59k miles on the car and do oil changes every 5k miles

Do you guys think it's a bad thermostat or is something else going on. Is there a way to keep the temperature below 100c in city ? Also is it a good idea to replace the 2 BAR cap with a 1.4 BAR cap or should I leave the cap stock.

Thank you in advance.

Last edited by PAPER; 03-21-2019 at 10:37 PM.
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  #396  
Old 03-22-2019, 04:38 AM
4thBMW 4thBMW is offline
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Ah, ha...a Logic 7 t-stat...

Thx for posting. Sounds like your N62 is in good order. Seems like the l is doing what the stock t-stat calls for (or what BMW calls for on the map). maybe the guy did not "re-calibrate" the stock t-stat properly??? He would not discuss what he does to them on the phone with me. I'd be interested in his response to your concerns. I've already decided *not* to alter the cooling map on my M62TU44 engine. I do not want to introduce a richer fuel mixture to the engine if it actually does that with the lower coolant temps. I'd rather not risk any combustion chamber, valve carbon deposits. I'd just keep using that unless your core engine temps get way out of wack. What are the ambient temperatures like where you drive?
I would keep that 2 bar rad. cap. If you are worried about pressure, like everyone, there is always water-less coolant....a thought I keep in the back of me mind.

Last edited by PAPER; 03-22-2019 at 09:26 PM.
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  #397  
Old 03-22-2019, 06:00 PM
Fruitsalt Fruitsalt is offline
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Thanks for the reply, I checked the temperature on all my runs today and it's averaging 102-103 city, 99 flat on the freeway. I think I'll just leave it the way it is.

For the cap I've been researching a lot and what I realized is that the 2 Bar cap doesn't mean the system is running at 2 Bar or pressure, the rating is for when the coolant caps vent opens. So with the temperatures im at I'm just going to keep the 2 Bar cap.

Also looked into running rich, I had a few screen shots saved from before I changed the thermostat and it seems I'm running barely 0.2% richer on bank 1 and bank 2 is exactly the same as before. Talked to a master tech at bmw and according to him the temperature range should not cause any issues with cat, rings or anything, per him operating temp over 97c is perfectly fine and within motor operating values.

I know the transmission has its own thermostat, however my transmission oil has been running cooler since I did the thermostat, could get it up mid 90s before when getting on it now it stays within mid 80s highest I've seen is thus far is 89, shifts are smoother as well but then again I just did a mechatronics service ( replaced the 3 tubes and the mechatronics sleeve ) and new filter and oil ( about 6 qts) so it could just be that.

Last edited by PAPER; 03-22-2019 at 09:27 PM.
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  #398  
Old 06-30-2019, 11:06 PM
Fruitsalt Fruitsalt is offline
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A question for guys running the 90c thermostat.
I have a 2008 Bmw 550i, I have installed the 90c thermostat in it using a Bmw original housing. I wanted to verify a few things.
The temps I see are as follows.
City: 96-99 ( seen 101 a couple of time)
Freeway: 94-96
Do these number look alright or do they seem off ? I was under the assumption that with the 90c thermostat car would run around 96-97 max in city

Also I monitor the temp I have two values:
Coolant outlet temp
Motor temp

I'm assuming the coolant outlet temp is from the sensor on the lower radiator hose
And the motor temp is from the sensor on the thermostat itself.

My question in regards to this is that at times ( when it's over 90F ambient temp) the coolant outlet temp will almost read the same as the motor temp. Example: motor temp is 96c the coolant outlet temp reads 90c

Is this normal ? I thought the radiator outlet temp is supposed to be much lower then the engine coolant temp, if it's not normal what could be causing it ?

The car is not overheating and runs perfect, the system was pressure tested and found no issues or leaks. Just the readings are throwing me off.

Thanks in Advance

Last edited by PAPER; 06-30-2019 at 11:25 PM.
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