[_TB_]

Originally Posted by Mark M

- Transmission shifts feel more crisp and precise. I know this sounds odd, maybe placebo effect.

No it is not - shift patterns are affected by the temperature.

[nicklockard]

Originally Posted by Mark M

Not to beat a dead horse on this one.....but the thermostat change really has made a world of difference.

- MPG is up at 37.9 mpg. I have done 320 miles on half a tank and OBC is projecting this to be a 635 mile tank based on current consumption. Previously I was only seeing about 550 mile tanks or less ~34 / ~32 mpg.
- Warm ups are shorter. The car reaches ideal running temps in about 10 minutes.
- Transmission shifts feel more crisp and precise. I know this sounds odd, maybe placebo effect.
- Low rpm performance feels more responsive, pulling away from a light or slow driving, the pedal feels more linear, again maybe placebo effect.
- And less soot on the rear (ABC delete car)

This might classify as one of the best and cheapest 'mods' done to the car.

You're not imagining things. Since changing thermostat, my 335D's performance is way up and 0-60 times down. Got 31 mpg on a tank where half of it was hauling ass and doing top speed runs. Car is much more responsive to transient throttle movements too. The DDE's parameters are strongly affected by coolant water temperature.

[TorqueAddict]

Originally Posted by Mark M

Not to beat a dead horse on this one.....but the thermostat change really has made a world of difference.

- MPG is up at 37.9 mpg. I have done 320 miles on half a tank and OBC is projecting this to be a 635 mile tank based on current consumption. Previously I was only seeing about 550 mile tanks or less ~34 / ~32 mpg.
- Warm ups are shorter. The car reaches ideal running temps in about 10 minutes.
- Transmission shifts feel more crisp and precise. I know this sounds odd, maybe placebo effect.
- Low rpm performance feels more responsive, pulling away from a light or slow driving, the pedal feels more linear, again maybe placebo effect.
- And less soot on the rear (ABC delete car)

This might classify as one of the best and cheapest 'mods' done to the car.

^I Agree 100% on that!!!

I was amazed on how transmission behaviour changed!! not jerky anymore. I also thought it might have been a placebo but your observation confirms my doubts. WIN!

[rulonger]

This thread has possibly answered my concern with my car and the cold. My car seems to be jerky on cold mornings and I have noticed that the mpg is definitely affected to the negative.

Today on my 30 minute commute I decided to pull up secret menu #7 and monitor the engine temperature. Ambient was 1 C and the engine was at 14 C when it cranked. Temperature never got above 66 C on the entire drive and seemed to hover around 63 - 64 C. Obviously well shy of the optimal 88 C cited in other threads.

I again monitored my temperatures on the drive home when ambient was right at 17 C. Again, the temperature just made it to 70 C. I am certain that I need a new thermostat.

[dmanb2b]

Originally Posted by BB_cuda

+1, with cooler out the way, job was fairly simple. I did loosen the mount points of the plastic water pipe as it winds it way around drivers side of engine. This was to give for flexibility of line that connects to thermostat. I did job from top except for the catch pan below for coolant spilling.

Thanks for the tip on the plastic pipe With EGR cooler out of the way, about a 1hr job and my temps are now at 86-87C, up from 75-76C.

Took me about 1.5 hours from start to finish as the lower coolant hose clip decided to shoot out on me and play hide and seek up in the turbo area

[Torqu3]

Looks like this will be the next "mod" on my list. Seems like general consensus is that this is rather simple work. However, I'm a little unsure about draining and refilling the coolant. Is there a good DIY guide somewhere for that?

[TDIwyse]

As another data point... changed my thermostat this week. Previously the car would warm up to ~172-176F, unless in town stop and go driving, where it might get to mid 180's. New stat car warms up to ~186-190F. Based on cars predicted mpg's, under my normal drive cycle, and doing ~300 ml of Thanksgiving interstate driving, there is no noticeable change in mpg behavior. However, to really know if it affects mpg's, I'll need more data points. Fortunately, I've got every single fillup and hand calculated mpg data point since the vehicle was new, to compare against.

Chart of my vehicles lifetime hand calculated fuel economy and a studies of direct injected diesel engines lack of sensitivity to coolant temp can be seen here:

http://www.e90post.com/forums/showpo...8&postcount=31

and here

http://www.e90post.com/forums/showpo...5&postcount=34

I'm curious if those posting significant fuel economy benefits from changing their thermostat could describe their before/after coolant temps, and plot hand calculated mpg results over an extended period of time before/after their thermostat change? That would give some interesting comparison to see if the trend line significantly changes.

[kydiesel35]

Thanks for posting. I'm still on the fence, haha. Looks like it calls for 4 hours labor, is this true? Including flush?

I'm thinking I will wait... I usually leave all hvac off until the car fully warms up anyways.

[TorqueAddict]

Originally Posted by TDIwyse

As another data point... changed my thermostat this week. Previously the car would warm up to ~172-176F, unless in town stop and go driving, where it might get to mid 180's. New stat car warms up to ~186-190F. ......

I'm curious if those posting significant fuel economy benefits from changing their thermostat could describe their before/after coolant temps, and plot hand calculated mpg results over an extended period of time before/after their thermostat change? That would give some interesting comparison to see if the trend line significantly changes.

If your car was reaching 172-176 (77-80 C), your thermostat was most likely fine. All i could get my car to was 60-63, doesn't matter how'd i drive. No hand calculated MPG's but my tank with similar driving styles and routes used to last me ~570-650kms max. After the replacement, on winter fuel, i hit 780Kms on the tank, which is quite noticeable.

Now within 10-15 minutes of my drive to work the temperature rises to 80+ C easily, and car drives and behaves differently. Tranny is more smoother. I have been driving this car for over 4 years now - everyday. I can feel the difference in behavior. May be it never got out of warm up cycle ever (never in closed loop)

Another thing that i can relate to this is glow plug controller/glow plugs. Mine failed last winter, which caused me to monitor temperature. According to BMW training document, the glow plugs also work intermittently if your engine isn't warm enough - as a result low temps = overworked controller and plugs hence leading to failure.

[Mark M]

Originally Posted by TorqueAddict

If your car was reaching 172-176 (77-80 C), your thermostat was most likely fine. All i could get my car to was 60-63, doesn't matter how'd i drive. No hand calculated MPG's but my tank with similar driving styles and routes used to last me ~570-650kms max. After the replacement, on winter fuel, i hit 780Kms on the tank, which is quite noticeable.

Now within 10-15 minutes of my drive to work the temperature rises to 80+ C easily, and car drives and behaves differently. Tranny is more smoother. I have been driving this car for over 4 years now - everyday. I can feel the difference in behavior. May be it never got out of warm up cycle ever (never in closed loop)

Another thing that i can relate to this is glow plug controller/glow plugs. Mine failed last winter, which caused me to monitor temperature. According to BMW training document, the glow plugs also work intermittently if your engine isn't warm enough - as a result low temps = overworked controller and plugs hence leading to failure.

+1. Same circumstances for me. I replaced the glow plug controller at the same time as the tstat. Controller was throwing a code. All is good now.

[TDIwyse]

Originally Posted by TorqueAddict

If your car was reaching 172-176 (77-80 C), your thermostat was most likely fine. All i could get my car to was 60-63, doesn't matter how'd i drive. ...

That's a definite possibility and my car might have been right on the edge of where the DDE was still OK with the temp and doing proper injection timing and all the other things it controls... 60-63C is much lower than what I was seeing. Thanks for commenting on that data point.

[GreekboyD]

Originally Posted by TDIwyse

That's a definite possibility and my car might have been right on the edge of where the DDE was still OK with the temp and doing proper injection timing and all the other things it controls... 60-63C is much lower than what I was seeing. Thanks for commenting on that data point.

Seems like I'm in between you and TA. Did some data logging last week and was seeing 70-72C (158-162F) temperatures with spirited driving including a highway stretch.

Next on the agenda is a thermostat change.

[sgrice]

Here is a link to my experience/DIY guide for the thermostat replacement on the 35d - includes some part diagrams and a fair number of pictures:

http://www.xoutpost.com/bmw-sav-foru...-diy-pics.html

Hope that helps.

[BB_cuda]

I drove 280 miles home on Saturday. We got stuck in a traffic jam and coolant temp got up to 89C. When cruising resumed, I ran at 83-84C. Anyone know temp the radiator fan comes on at?

[Yozh]

96deg

[BB_cuda]

Originally Posted by Yozh

96deg

Thanks!

[dmanb2b]

Not sure if it helps for another point of reference, but on my 40 mile commute this morning water temp was steady at 87-88C, after warm-up. This is with outside temps at 27F.

I'll report back on MPG after my next full tank is consumed next week.

[JTC1]

My temps are running in the low 70s so Tstat is on my list of to do's. Has anyone had any type of engine light for a T stat stuck open? My Indy seems to think that a stuck open Tstat should result in an SES light.

[nicklockard]

Originally Posted by JTC1

My temps are running in the low 70s so Tstat is on my list of to do's. Has anyone had any type of engine light for a T stat stuck open? My Indy seems to think that a stuck open Tstat should result in an SES light.

Nope, it won't set any codes in any modern (OBDII compliant) car I've ever seen. And they've eliminated the coolant temperature gauge or deliberately made them lie (Tdi's use filtering and lie by 15-30 degF, consistently).

Which is really surprising since engine coolant temperature is probably the SINGLE most important parameter for emissions. Emissions of soot and NOx are both increased with cold running engines.

I really don't get why the manufacturers do this. Well I do know: it's to reduce warranty visits and customer complaints. But it's bad for your car (running cold and longer warmups increases engine wear), bad for fuel economy, and bad for the air.

[ninja_zx11]

Originally Posted by JTC1

My temps are running in the low 70s so Tstat is on my list of to do's. Has anyone had any type of engine light for a T stat stuck open? My Indy seems to think that a stuck open Tstat should result in an SES light.

Yes it will trigger an SES light if temp stays below 60 deg.That's the minimum threshold for M57 engine.
But you will start loosing fuel economy if temp stays below approx 70~75 deg C.

[Yozh]

Originally Posted by ninja_zx11

Yes it will trigger an SES light if temp stays below 60 deg.That's the minimum threshold for M57 engine.
But you will start loosing fuel economy if temp stays below approx 70~75 deg C.

Interestingly, I have ever only got a shadow code. My stat was completely open and at around 0C/32F I was running way below 60C on the freeway. I'm sure there are potential conditions when a full ses will be triggered, but surprisingly BMW did not make it very sensitive.

[JTC1]

Where is everyone ordering their Tstat from? I know someone in another thread said they ordered from Rock Auto. Is that a safe bet?