Cooling System

Originally Posted by hd750Li

OK, please allow me to summarize the problem based on your perspectives, experiences and knowledges:

Root cause: N62 and M62 engines equip with 105C-thermostat which was introduced by BMW in 2001. These are simple facts that we all know, BMW cooling fluild is a 50-50 mix of distilled water and BMW antifreeze, and 105 C is above water-boiling point. High-operating temperature can deteriorate rubber gaskets and eventually cause engine or coolant leaks. In addition, coolant being pressurized at high-pressure (by the water pump?) can also put cooling hoses at greater risk of failure.

Preventative Actions: Retrofit 95C-thermostat and replace OEM-plastic-propeller water pump by a metal propeller one. More frequent oil change. Any others?

Please feel free to correct me. Any information for the appropriate replacement parts and associated cost?

105C thermotronik tstat was introduced in 1997 with m62b44, though first versions had 95C.
Coolant is being pressurized by hot running temperature, waterpump has nothing to do with it. That's why we have 200 radiator cap which keeps the pressure so it won't start boiling, but even 50/50 under 200psi will give you 125C boiling point, so imagine any tiniest leak in the system and your system is not at 200psi anymore so it starts boiling right away.....
I'm not saying its a design flaw... Moreover i consider N62 engine to be the most advanced and fuel efficient and super powerful for 4.4L, it doesn't have direct injection, but DI has some drawbacks still. It's just on the edge so everything works at very high risk of failure, that's why all rubber gaskets start leaking very quick and they become plastikish vs flexible rubber.
Preventative actions I would suggest 90C but 95 is still okay.
Even waterpump will last longer with plastic impeller in that case. The advantage of plastic impeller is its weight, so it won't kill the bearing that fast.
Oil change every 5000km or once a year is good.

I know it's embarrassing but I could not install that bleeding hose!!! The driver side is very uncomfortable to reach and no space to install it!!! I really don't want to remove the intake manifold!!!
Any tricks?? It's real pita!

How can you tell it's boiling,by the temps only?I see no evidence of boiling in my expansion tank.I was meaning to ask awhile back where you see these bubbles?I have found no sight glass.Not doubting anyone just need more info.

SFbay I have a very long pair of needle nose I used. Harbor Freight is your friend for one time use tools.

Originally Posted by dolfan13

How can you tell it's boiling,by the temps only?I see no evidence of boiling in my expansion tank.I was meaning to ask awhile back where you see these bubbles?I have found no sight glass.Not doubting anyone just need more info.

How to tell if its boiling?? Simple:
If your temp goes to 107-110C
Then shut down your car, set your heater on hot without starting it and listen to aux waterpump you'll hear lots of bubbles going through it will also be jumping kinda bc of intermittent flow.
Called my mechanic, so hopefully he will help me with that damn hose.

Originally Posted by SFbay

How to tell if its boiling?? Simple:
If your temp goes to 107-110C
Then shut down your car, set your heater on hot without starting it and listen to aux waterpump you'll hear lots of bubbles going through it will also be jumping kinda bc of intermittent flow.
Called my mechanic, so hopefully he will help me with that damn hose.

Damn sorry to hear about hose.. I am going to be doing mine soon.. hoping I wont run into same prob. Even with TB off no room?

u need to use a longpair of needle pliers... this is why i dont use bmw clamps... when i did mine on driver side its hard but with long screwdriver and long needle nose its quick

Originally Posted by 745iguy

u need to use a longpair of needle pliers... this is why i dont use bmw clamps... when i did mine on driver side its hard but with long screwdriver and long needle nose its quick

Yeah only long pliers might help, without it I just wasted an hour and scratched my hands.

SFbay: a few questions

1) What are the potential downsides of using 90C-tstat for our cars that you can think of?

2) Do you have a part number for that 90C-tstat?

3) Do you mind writing up a quick DIY to retrofit the tstat? Pictures would be great.

I'm asking all these questions because I believe your theory. I'm not exaxtly sure why BMW engineers decided to risk the engine life expectancy by operating the cooling system at such a high temperature.

Much appreciated!

Originally Posted by hd750Li

SFbay: a few questions

1) What are the potential downsides of using 90C-tstat for our cars that you can think of?

2) Do you have a part number for that 90C-tstat?

3) Do you mind writing up a quick DIY to retrofit the tstat? Pictures would be great.

I'm asking all these questions because I believe your theory. I'm not exaxtly sure why BMW engineers decided to risk the engine life expectancy by operating the cooling system at such a high temperature.

Much appreciated!

I don't really think there is any downfall to running SFBay's 95c tstat, possibly a too cool warning but I believe that would be if it were lower like mid 80's or so.

SFBay did spend about $300 or so on testing many tstats until he found the correct solution, I think it's unfair we ask for that information without helping atleast on the monetary part of the project, however, that is ofcourse up to SFBay.

There is really no reason, or should I say valid reason why they would run it at 105 other than to cause issues and make money on repairs and parts. The same model year MB cars are running at 85c, same size engines etc.. Also, if you really get on your car, say on the freeway, that temp will almost instantly drop to double digits, so they know it needs to run cooler for higher performance vehicles.. Even their "sportier" or "performance" vehicles are running the cooler tstat's... I see it as a marketing ploy. I was talking to a manufacturer about it the other day, and he said the same thing. Also, when you spend 7-800$ on cooling system parts like I just did this week, and you look at the hoses, and all their fancy little plastic ends with orings, you realize they made all this for profit, so you can't go out and buy a regular hose and hose clamp.. You have to buy their stupid hoses, with their design, that go out super soon, and cost an arm and a leg.

Well, I'm not trying to convince anybody to believe or not my theory, I'm just sharing my thoughts and some knowledge I obtained from university.
1) any drawbacks from running it at 95C?? There isn't any, bc it's still hot enough and DME will accept it as normal working condition. As long as its not lower than 80 Is good for DME tests. Boiler has to be tricked, but even without it it's okay and no cel at least.
2) lower than 80 is considered a little lowish bc during combustion process cylinder walls are too cold and some unburned sulphur from gas can damage it bc of steam H2O+S03=H2SO4... But nowadays there is no sulphur in the gas, so it's not relevant anymore. Also running it very cold <80 can clog oil passages, but it's only correct for mineral oils.
And will worsen combustion efficiency . It's only true if you run your car without tstat at 60-70C. 95C is more than enough. This engine will be okay even with 85C tstat. I'm trying to install it as well.
3) I will provide DIY thing very soon after I'm satisfied with the results. So I can print my certificate to prove it LOL. But I'm serious if we find some parts manufacturer and order 100-1000 of them it might cost us about 50$ per each?? BMW will be pissed if everybody installs it and so much less money they will get from happy N62 owners so far the cheapest option is 100$ plus some machining and patience.
This 95 tstat will prolong the life of all engine gaskets and even if they are leaking already, the leak will get a little smaller bc of lower temp. Also will save the tranny. And actually will get you more power bc even these 10C will lower the temp of the intake, which is very important.
To believe my theory simply check bmw 3,5 series forums with inline 6 engines: my neighbor E60 with 160km is crazy dry from the bottom so you can eat on it! he didn't spend a penny on this car since 2004: all original parts- tstat which was stuck open after idk how many miles!!! Waterpump and all belts are original 2004!!! Valve cover gasket is original too! Well he could not pass smog check and I found tstat open problem. I replaced it and it passed everything without issues!! So his car has been running for a while without tstat and it didn't do anything to the engine at all. Though after tstat got replaced valve cover gasket started leaking next week so lower temp actually saves all rubber gaskets. Under valve cover it was all clean without sludge. It's funny but his suspension is in perfect shape like brand new- all bc of no oil leaks could destroy it.
So if I retrofit another 85C tstat it might be even better, but keys see what smart DME will say.
Yes, all current engines have the same tstat, so F01 with low miles would benefit a lot from this upgrade.

Hmm they don't want me to post long posts;(( will not be rewriting my formulas and further staff, too much typing again.
In couple if words: my cheap neighbor has e60, bought it with 150km in 2011 from NY Jewish friend.
Well here is the story: he tried to register it and it didn't pass the smog. I checked with inpa and found out his tstat was stuck open!!! Well bmw e69 has no temp gauge so he never knew. Anyways I removed tstat and found out it was 2004 and all other parts waterpump, belts, pulleys, etc.!!!
No oil or coolant leaks at all! So I replaced everything: belts, tstat, waterpump. And it passed the smog the same day though bc of correct temp 95-96 his valve cover gasket started leaking next week so not too bad first repair after 150km??
Needles to say his suspension is all oem and no problems at all bc engine bottom is so clean and dry so you can eat on it lol. I was so jealous bc at that time my e65 had only 87k miles and bottom was covered in oil everywhere(
So now his car has 165k on the clock and he loves it!! And every time he see me working on my e65 he cannot stop laughing at me))

Hey guys, update: installing cooling system now. Have hoses in and TB back on, working on water pump now.

Originally Posted by cmpcpro

Hey guys, update: installing cooling system now. Have hoses in and TB back on, working on water pump now.

Did you use pliers or was able to push it without it??

I regret not checking the operating coolant temperature before I replaced my tstat just weeks ago. It was stuck in the open position. I touched 105 degrees yesterday fluctuated between 101/102, doing about 80mph, outside temp was 84 degrees with the A/C on. I wished I had held on to the old tstat.

Originally Posted by First_745Li

I regret not checking the operating coolant temperature before I replaced my tstat just weeks ago. It was stuck in the open position. I touched 105 degrees yesterday fluctuated between 101/102, doing about 80mph, outside temp was 84 degrees with the A/C on. I wished I had held on to the old tstat.

Always open is not good either, it will kill your aux fan quick, plus it's too cold for the engine. As long as it keeps 105C-aux fan on-103C idling is good.

I am at 105c thru the dash

Ha! I had to use my super long needle nose, and I had to push the s h i t out of it.. It only took a few minutes to install that pipe in general, but only because I knew you had the issue and needed pliars so I just used them the second I couldn't push it on with my hand. I put the new pump in, all the hoses... I didn't have to take the balancer off but I did have to loosen it a bit to get that bolt out, it was just right on the edge with it on.. Then I got it all on and realized I forgot one of the water pump bolts, but luckily it was the one bolt I could easily get to with everything on (the one above the balancer one).. I installed the new sensors and the new expansion tank.. The lines were pretty hard to get on because they were new.. I had to use some coolant to get them on.. had to use a little grease on the tube to the cooling pipe on engine, that was a tight fit.. and the lower hose wouldn't go on for the life of me.. had to use grease on the oring and still no go, I took out the oring on the old lower hose and it looked good, so I put it in the new hose and bam, was tight but went on..

It was too late lastnight so this morning I put the coolant in per TIS, and ran the car.. my temp sensor said -128c after driving around, but I just reset codes on INPA and it went back to normal right away, must have sensed the wire being disconnected when I opened the door. So far no leaks, but I haven't driven far.. however the new lower hose is alot more firm.. and the dealer said the old ones get so soft they collapse..

Originally Posted by sirstopher

I am at 105c thru the dash

Does it go any higher ever? Or lower?

Originally Posted by sirstopher

I am at 105c thru the dash

105 means nothing, what matters is 105-aux fan-103 cycle when idling.
Finally replaced my hose with pliers.
All is good 96C max! Aux fan starts working at 97C. I really like 2 digit numbers and a car feels stronger now and tranny shifts better even if its fully warmed up. Before it was a little jerky when in traffics and slowish.
Anyone wants to cool down his e65, f01, e60, rolls Royce any V8 or V12? Custom made tstats company opened, LOL
New 85C sporty tstat is on the way)
So far it's kinda expensive mod: 98$+your old tstat housing and 3hrs hassle with machining etc.
Trying to find cheaper options

Originally Posted by SFbay

105 means nothing, what matters is 105-aux fan-103 cycle when idling.
Finally replaced my hose with pliers.
All is good 96C max! Aux fan starts working at 97C. I really like 2 digit numbers and a car feels stronger now and tranny shifts better even if its fully warmed up. Before it was a little jerky when in traffics and slowish.
Anyone wants to cool down his e65, f01, e60, rolls Royce any V8 or V12? Custom made tstats company opened, LOL
New 85C sporty tstat is on the way)

You betcha!

I am up for the custom tstat, how much you want?

UPDATE: I have installed a new water pump (After draining my system my water pump would make a horrible groaning noise for the first 30sec if I started the car cold), new tstat, new expansion tank, upper hose, lower hose, all expansion tank hoses, vent hoses, all new sensors, new expansion cap, new aux water pump. The only things left are radiator, a hose coming from the water pump to radiator which looks to be going to the tstat for trans. Anyway, I started engine this morning, was nice and quiet no more groaning noise, filled coolant per TIS directions. Drove the car just a slight bit to pick something up and came back. Car sat for an hour or so and I fired it back up. Groaning noise is back with new water pump, or coming from somewhere else and complete coincidence, but I took the car out for a real drive. Car ran up to 102 like normal, stayed at 102 went to 103, back down to 102, got on freeway, went up to 105, back down to 104, 103, got off freeway, and it stays at 105 for a while.. sitting at light and goes back up to 106.. so evidently still having issue somewhere, so.. the only things left to replace (I figured these things needed to be done for maint. anyway) are radiator, that one hose, the heater hoses/core, and then it's got to be something in the motor. What I don't understand is how I got it to run great and perfect for a day, and then replaced that aux water pump and it went to hell again, but I am hoping I still don't have all the air out yet and this tale my still be saved.. but with my luck it's unlikely. As for replacing these things for maint. the upper hose broke apart in my hands when I was removing it.. the plastic was very brittle.

Originally Posted by cmpcpro

UPDATE: I have installed a new water pump (After draining my system my water pump would make a horrible groaning noise for the first 30sec if I started the car cold), new tstat, new expansion tank, upper hose, lower hose, all expansion tank hoses, vent hoses, all new sensors, new expansion cap, new aux water pump. The only things left are radiator, a hose coming from the water pump to radiator which looks to be going to the tstat for trans. Anyway, I started engine this morning, was nice and quiet no more groaning noise, filled coolant per TIS directions. Drove the car just a slight bit to pick something up and came back. Car sat for an hour or so and I fired it back up. Groaning noise is back with new water pump, or coming from somewhere else and complete coincidence, but I took the car out for a real drive. Car ran up to 102 like normal, stayed at 102 went to 103, back down to 102, got on freeway, went up to 105, back down to 104, 103, got off freeway, and it stays at 105 for a while.. sitting at light and goes back up to 106.. so evidently still having issue somewhere, so.. the only things left to replace (I figured these things needed to be done for maint. anyway) are radiator, that one hose, the heater hoses/core, and then it's got to be something in the motor. What I don't understand is how I got it to run great and perfect for a day, and then replaced that aux water pump and it went to hell again, but I am hoping I still don't have all the air out yet and this tale my still be saved.. but with my luck it's unlikely. As for replacing these things for maint. the upper hose broke apart in my hands when I was removing it.. the plastic was very brittle.

Yep, you have a leak prob heater hoses or heater core....
You understand your self bleeding system isn't working properly
Mostly the air is on top hoses
Anyhow you don't need explanation that running like this will kill your engine soon.
Even after you fix all leaks it only will last for a while until one hose oring starts leaking again bc of high temp!
Also you can try to get the air out this way:
Car is cold
Tilt your nose like 20 degrees smth.
Open radiator cap
Disconnect aux water pump-so you know when there is no air in the system
Start your car
Heater on high
Rev it 3-4 times 2000rpm for 20 sex each
Massage upper hose 5-10 times
Check if air is hot while idling

It worked for me for a while, but air will get there anyways soon, so better fix the leak. The worst nightmare is heater core replacement and rear plate and coolant pipe.
Now you understand why I modded tstat????

Originally Posted by SFbay

Yep, you have a leak prob heater hoses or heater core....
You understand your self bleeding system isn't working properly
Mostly the air is on top hoses
Anyhow you don't need explanation that running like this will kill your engine soon.
Even after you fix all leaks it only will last for a while until one hose oring starts leaking again bc of high temp!
Also you can try to get the air out this way:
Car is cold
Tilt your nose like 20 degrees smth.
Open radiator cap
Disconnect aux water pump-so you know when there is no air in the system
Start your car
Heater on high
Rev it 3-4 times 2000rpm for 20 sex each
Massage upper hose 5-10 times
Check if air is hot while idling

It worked for me for a while, but air will get there anyways soon, so better fix the leak. The worst nightmare is heater core replacement and rear plate and coolant pipe.
Now you understand why I modded tstat????

Well I've understood why modded stat is needed from begining, it's way too hot.. I am starting to think this BMW coolant is the cause.. when I replaced coolant the first time I used only 1/3 bottle of BMW coolant, and rest distilled water and it ran the best.. then I replaced the aux water pump and I used more coolant.. and it ran worse a little.. now I replaced the cooling system and used a whole bottle of coolant, basically exactly 50/50 and now it's running the worst..

This is the update: Drove the car again and noticed tstat stopped opening all together.. would run at 105/106.. got on freeway drove 10 miles or so and no tstat opening.. just ran at 105 solid.. got off freeway and right up to 106/7.. now when I turned around and headed back after about 5 minutes the tstat started opening again, and the whole ride home it would open correctly, got down to 102.. the last 5 minutes home it was at 102 the whole time.. hit traffic and it goes right back up to 106/7 and won't open again.. my issue is, I realize it's a good chance something is up with heater or heater hoses, but everytime I change something it either gets worse or better.. the times it's got better was with less coolant.. when I drained my orig coolant, if you shook it a little or dribbled water in it, it would start to foam with bubbles.. I am wondering if this think BMW coolant is junk!