Cooling System

Originally Posted by 745iguy

Lower hose has nothing to do with tstat opening only fan turning on, temp at wp is what determines the tstat opening.

Lower hose has everything to do with tstat. If its cold it means tstat is closed, or open very slightly

Originally Posted by SFbay

Lower hose has everything to do with tstat. If its cold it means tstat is closed, or open very slightly

That has nothing todo with what he said. He said if 75c on lower hose then the tstat will never open which is what I didnt understand. If you took out the inside of the stock tstat why would you put an in line one anywhere else but shortly after where the real one would be? The lower hose temperature isnt what causes the tstat to open or close, maybe an indication of if it is open or closed and anywhere in between but it doesnt open or close based on the lower hose temp which is what i read inhis comment.

Idk maybe im confused and if you gut the old tstat and put a custom one right after the tstat, it somehow wont open? I dont get how that would make the water colder on the side of the tstat that is connected to the wp?

Ok ok the flow comes out of the water pump in the top hose that's why its hot,100c plus.The flow returns out of the bottom of the radiator back to the pump.The stock tstat opens at 105c letting hot coolant flow in top hose to radiator.The stock tstat sits in the flow of hot coolant inside the water pump.An INLINE tstat would need to allow or stop the HOT flow not the cold returning from the radiator flow.A tstat in bottom hose might not reach enough hot coolant as the stock housing would still need to be installed.Inline in the top hose would always see the hottest coolant and open at your favorite temp letting flow go to the rad. But the heater aux pump would need to be dealt with as it coolant source would be cut off when my inline tstat was closed.Shoo wee.

Sent from my M975 using Bimmer App

Okay now i am understanding more or less what you are getting at. I know nothing about this cooling circuit or what goes where to where. All i have done is replace hoses and havent ever looked at how the loops are.
Me personally i would rather wait for the custom tstat to arrive.

Originally Posted by dolfan13

I thought about lower hose but don't think enough of the hot coolant would reach tstat.Also might slam right back shut as cold in rush from radiator.

The stock tstat works on the lower hose so the new one should too right?

The top hose expels the hot water.. even when the thermostat isn't working and the lower hose is cold the top hose is hot, it's got water going thru it and into the radiator.. I don't see why this inline thermostat can't solve our issue, but I would put it on the lower hose right where the stock one was, or close to it.. I don't see how it can help on the upper hose, it will be open constantly once the car warms up.

Inline tstat might only work in lower hose, installing it in upper hose will change small with big circuits.
Anyhow I did valley pan and pipe job, but unfortunately I still have leak from rear plate!!! Looks like everything leaks on this engine.
Now it's better, but still I can feel that there isn't enough pressure to open tstat completely when idling...

See thats what i was saying if tstat opens into lower hose why would we put a tstat on the upper hose? Lol
Either way im anxious for the tstat

Originally Posted by SFbay

Inline tstat might only work in lower hose, installing it in upper hose will change small with big circuits.
Anyhow I did valley pan and pipe job, but unfortunately I still have leak from rear plate!!! Looks like everything leaks on this engine.
Now it's better, but still I can feel that there isn't enough pressure to open tstat completely when idling...

Did you pull the motor? How did you figure that out so quick? That was a quick install, I wrote many pages ago that I was worried about installing pipe only to up pressure and make rear fail..

Iirc hesaid a mech did it for him bc he didnt want to get sick again

Originally Posted by cmpcpro

Did you pull the motor? How did you figure that out so quick? That was a quick install, I wrote many pages ago that I was worried about installing pipe only to up pressure and make rear fail..

No, he did it simple way, and then we lifted the car and found some fresh UV residue from bell housing.
Once again in order this cooling system to work properly it has to be 100% leak free, otherwise there isn't enough pressure or flow to open tstat....
Now at 3000 rpm tstat opens completely so lower hose is 65C and temp is at 93C idling is at 98-99. So lower tstat won't solve the problem bc even if temp is lower at wp it doesn't mean that cooling is effective and heads are being cooled like they should.
Valley pan, rear plate, coolant pipe are the most important things in this system.....
Straight six has nothing like coolant pipe seals or plates: everything is integrated in the block, so it never has issues with low pressure.

The lower hose never gets hot enough to even open the stock tsat.Its the water leaving the tsat that opens it.Thats why its going to the radiator and its HOT.The tsat is 105c it let this temp coolant go to the rad except for the engine warm up bypass.The bottom is the COLD return how could it open a 105c tsat!?

On another note Ive been curious about better under hood temps altogether.Ive had a lot of hotrods and this is a fight in summer at car shows.Before you say anything Ive also has 5 BMWs over the years. Anyhow I had a new windshield put in and didnt put cowl cover back in as it was damaged in the process.Now driving for a few a days without it I have noticeably cooler all around temps.Still get to 105 at idle but takes longer and cruise is down to 101.Im might look into some nice real venting.Hate to cut hood but maybe could do something else besides venting body.

Maybe we should pressure test our engines.. if there is a leak in the valley pan or a leak in the back plate, it would have to show.. I can open my cap in the morning and still have pressure, so if I do have a leak, it's got to be a small one, not that it matters I guess.. but if I am going to drop the tranny I will probably buy a low mile one to replace it or at the very least replace the torque converter..

Originally Posted by cmpcpro

Maybe we should pressure test our engines.. if there is a leak in the valley pan or a leak in the back plate, it would have to show.. I can open my cap in the morning and still have pressure, so if I do have a leak, it's got to be a small one, not that it matters I guess.. but if I am going to drop the tranny I will probably buy a low mile one to replace it or at the very least replace the torque converter..

Well there is another thing I was talking about 20pages ago:
You test it on cold engine, right???
So..... You got the point
It might show smth, but 105 vs 10C is a huge difference, that's why you see your pressure ok in the morning.

I think rear plate is super important bc it pumps coolant into the heads!
And if it has same exact crappy profile gasket as valley pan, so why wouldn't it fail??

Originally Posted by SFbay

Well there is another thing I was talking about 20pages ago:
You test it on cold engine, right???
So..... You got the point
It might show smth, but 105 vs 10C is a huge difference, that's why you see your pressure ok in the morning.

I think rear plate is super important bc it pumps coolant into the heads!
And if it has same exact crappy profile gasket as valley pan, so why wouldn't it fail??

Well I am shutting the car off at 105c so it's taking many hours to cool down that I would think it could be loosing pressure in.. but to solve that we just test it at operating temp.

Hello community im having an problem with inpa i flash the new firmware of the trans fine but the engine mod i cant see some kind of error. As i need to see lower hose temp, my car temp is up there 103, 105, 107 etc in dash i install new aga coolant pipe new stat all new coolant hoses new bmw coolant etc (my second water pump make a humming noise come and go non stop but if shut heater off it stop making noise) trying to make this car what it was ex owner did not take care of it did not care for it. Its up too me to bring it back sharp. Thanks for all the help guys

Originally Posted by cisco150

Hello community im having an problem with inpa i flash the new firmware of the trans fine but the engine mod i cant see some kind of error. As i need to see lower hose temp, my car temp is up there 103, 105, 107 etc in dash i install new aga coolant pipe new stat all new coolant hoses new bmw coolant etc (my second water pump make a humming noise come and go non stop but if shut heater off it stop making noise) trying to make this car what it was ex owner did not take care of it did not care for it. Its up too me to bring it back sharp. Thanks for all the help guys

If you have 107 after aga pipe installed, then it's your rear plate cover.... Very common problem. Once you fix all the leaks and restore factory pressure your car will run much nicer even with 105 tstat!
Damn I don't want to drop the tranny but it seems like the only option. 95c Tstat will save our souls;$


Taken from 5 series forum:
@ 93000 miles both valve covers and both upper timing covers
@ 96000 lower oil pan gasket, water pump, radiator and valley pan (coolant leak)

Now at 103000 and the car is "under construction" again:
- upper oil pan gasket
- oil gasket behind the alternator bracket
- coolant leak behind the transmission (end cover 11147504376) ? very painful project
http://realoem.com/bmw/showparts.do?...51&hg=11&fg=10

So... Thinking that you're lucky after 100k miles and 9-10yrs is just not smart, right?
This is where we lose that coolant pressure. Lower tstat will not help here much..... But for future safety -yes. Think about it: if you fix coolant pipe with vp, more pressure will destroy half dead rear cover, this is what happened to me;(
Some nice pics:

Originally Posted by SFbay

So... Thinking that you're lucky after 100k miles and 9-10yrs is just not smart, right?
This is where we lose that coolant pressure. Lower tstat will not help here much..... But for future safety -yes. Think about it: if you fix coolant pipe with vp, more pressure will destroy half dead rear cover, this is what happened to me;(
Some nice pics:

That is exactly what I have been saying for weeks now.. My cooling pipe is okay, but I am probably going to buy the AGA pipe and swap it anyway.. what pipe did you use again? As for dropping the trans.. is that a really hard job?

When my car is started from completely cold and I drive it right away it would surge RPM's between a couple hundred RPM's for the first minute or so when it was at a low RPM.. well changing fluid made a big difference, but at 500RPM I can hear the TC, but at 700RPM it goes away.. also I notice my shifts are a little on the soft side.. sometimes can be rock hard, so I know the clutches have to be okay.. do you think I should replace TC while I'm at it? They're like $1,200 or something I think..

Originally Posted by SFbay

If you have 107 after aga pipe installed, then it's your rear plate cover.... Very common problem. Once you fix all the leaks and restore factory pressure your car will run much nicer even with 105 tstat!
Damn I don't want to drop the tranny but it seems like the only option. 95c Tstat will save our souls;$


Taken from 5 series forum:
@ 93000 miles both valve covers and both upper timing covers
@ 96000 lower oil pan gasket, water pump, radiator and valley pan (coolant leak)

Now at 103000 and the car is "under construction" again:
- upper oil pan gasket
- oil gasket behind the alternator bracket
- coolant leak behind the transmission (end cover 11147504376) ? very painful project
http://realoem.com/bmw/showparts.do?...51&hg=11&fg=10

Thanks for reply im going to change water pump and secondary water pump too and see im taking it in for the sleeve and trans pan on tuesday if guy can do the rear plate ill do that too hope after that im set.

Originally Posted by cmpcpro

That is exactly what I have been saying for weeks now.. My cooling pipe is okay, but I am probably going to buy the AGA pipe and swap it anyway.. what pipe did you use again? As for dropping the trans.. is that a really hard job?

When my car is started from completely cold and I drive it right away it would surge RPM's between a couple hundred RPM's for the first minute or so when it was at a low RPM.. well changing fluid made a big difference, but at 500RPM I can hear the TC, but at 700RPM it goes away.. also I notice my shifts are a little on the soft side.. sometimes can be rock hard, so I know the clutches have to be okay.. do you think I should replace TC while I'm at it? They're like $1,200 or something I think..

I used URO parts and believe me there is nothing wrong with it, ppl get problems with the plate after the pipe.
URO parts is pretty good pipe and URO has been around for years unlike aga and other blah blah overpriced pipes. 200$ is a good price for 2 pieces if brushed aluminum with orings, but not 500-700$!
Have you done mechatronik adapter yet?? If not then fluid change does nothing almost, replace that gasket adapter and your tranny will be back to life.
And yes valley pan and rear cover are way more important than coolant pipe. After I replaced my vp, I noticed that pressure is much better now, but still not there.
No, there is nothing wrong with your TC, just mechatronik adapter... Check willson DIY and you'll be fine!!! If you wanna perfect shifting back you need new solenoid pack or complete valve body

Thanks.. the one thing that really made me not want the URO pipe is, well they could be around longer than AGA, but they clearly copied them, it's easy to see.. and they used a rubber seal, where AGA used Viton.. so I believe the AGA pipe will solve the problem for good.. though I have no proof of course..

Originally Posted by cmpcpro

Thanks.. the one thing that really made me not want the URO pipe is, well they could be around longer than AGA, but they clearly copied them, it's easy to see.. and they used a rubber seal, where AGA used Viton.. so I believe the AGA pipe will solve the problem for good.. though I have no proof of course..

They all use the same front seal. The price is even the same for the front seal. Who copied who doesn't matter, what matters that it holds pressure enough to destroy rear cover lol