[daveleach]

I have accessed the hidden menu today and cheked the coolant temp. After 30 mins of normal driving the highest it reached was 82.
Is this about right?

[bazz780]

see here:

http://www.e90post.com/forums/showth...ng+temperature

[NJ 1161]

Thats the same as mine is reaching. Car runs perfectly but after reading all the threads i've ordered both stats? not sure if needed or not?

In answer to your question.....don't know...., but everyone says must run at 90 degrees!

[daveleach]

I'm going to change seals in red boost hose at weekend and then see what temps I get after that. As some people say they could be related

[mistryn]

In brief before my temperature used to hoover around the 72 degree mark, changed the EGR thermostat and never got above 79-80 degree even on the motorway. Changed the main stat and now stays constant 91 degrees. Ive seen a slight improvement in mpg as well.

however last week my mpg has taken a slight nose dive and noticed my red boost pipe leaking oil again so could be related to that

£70 odd quid for both parts well worth spent imo

[Dr Dave]

Could take a long time to recoup the £70 in saved fuel costs though?

[NJ 1161]

I've just had my red boost pipe done. still get 82 .....

[NJ 1161]

Can anyone actually explain why running at 80- 82 degrees gives poor mpg, as aluded to in several threads??

[HighlandPete]

Originally Posted by Dr Dave

Could take a long time to recoup the £70 in saved fuel costs though?

That's true, but don't forget a hotter engine is normally a cleaner running engine. Also those with slower warm ups, and/or lower average running, can have DPF issues, due to not meeting regeneration parameters.

HighlandPete

[HighlandPete]

Originally Posted by NJ 1161

Can anyone actually explain why running at 80- 82 degrees gives poor mpg, as aluded to in several threads??

It's not due to cold running management, as that is <60C. But diesel combustion efficiency is greatly affected by cylinder wall temperature and flame temperature. We really want optimum efficiency. But the kind of driving and journey types can have varied impact on mpg. Some of us won't have much mpg variation when the temperature is running in the low 80C range.

Personal experience with diesels over the years, it is usually the lighter load constant speed cruising that shows the biggest variations, when combustion efficiency is involved. Temperature and other injection issues.

There are users who have had quite large differences in mpg, before and after issues with coolant temperature. EGR and EGT are involved, an open EGR thermostat could be causing recirculated exhaust gas to be too cold, and chilling the charge too much. Remember combustion temperature is cooled for reducing NOx levels, not for improving combustion efficiency. I do wonder if there is another factor involved, but researching the subject haven't yet identified what it could be.

HighlandPete

[JTMR360]

I went to BMW Oxford today after a 30 mile drive, I asked that my temps be checked, he took my key, plugged it into a computer and told me that my car was at 81 degrees c.

I was pretty amazed he was able to do this but also amazed that I'm getting half decent mpg on low 80's.

With this in mind I am now contemplating changing the thermostats although the guy said there was just one in a 335d, is this true?

Does anyone have a guid on replacing the thermostats?

[superflyguy9]

Originally Posted by JTMR360

Does anyone have a guid on replacing the thermostats?

http://www.e90post.com/forums/showthread.php?t=775793

There are 2 - the EGR and the main.

[confused.com]

Originally Posted by superflyguy9

http://www.e90post.com/forums/showthread.php?t=775793

There are 2 - the EGR and the main.

You will need the O ring too, and coolant. I've just had mine changed and the coolant heats up very quickly now and will sit at 89-92 on a motorway run, about the same in town too.

For info, i had mine changed at a local indy, cost 280 including geniune bmw parts.

[philmots]

Mine's hitting early 70's at best.

Getting changed tues night by a BMW tech - 2 hours apparently.

The whole job for me is around £150.


The issues is the thermostats are generally stuck open. While the car is warming up it should be shut so it reaches temp quick. They're meant to open when it's getting too hot. Basically keep between 88-92.

[HighlandPete]

Originally Posted by PhilM

...The issues is the thermostats are generally stuck open. While the car is warming up it should be shut so it reaches temp quick. They're meant to open when it's getting too hot. Basically keep between 88-92.

It is a little more complex on the BMW diesel engines, as the EGR thermostat is a two stage design. The first stage is designed to open with a reduced flow at 70C and cool the EGR heat exchanger ahead of the full engine working temperature. The second stage is designed to open at 90C after the main thermostat begins opening at 88C, when the ECT is up to operating temperature. (88 - 92C ideal normal range). EGR 'stats do fault in the open position, allowing too much coolant across the engine coolant circuit, even from cold temperatures. It messes with the ECT control, even if the main thermostat is in the acceptable range.

A failure of either stage (element) of the EGR thermostat causes issues, often very slow warm up and/or erratic temperatures. Not common for the main thermostat to be open, usually opening at a lower than ideal temperature. Typically the main thermostat performance drops off gradually.

HighlandPete

[JTMR360]

Originally Posted by superflyguy9

http://www.e90post.com/forums/showthread.php?t=775793

There are 2 - the EGR and the main.

Thanks for the link, I found the PDF and I'll be changing them as soon as weather gets better.

BMW wanted £300 but suggested I have the car remapped to see better fuel economy which to come from a BMW dealer was shocking!!!

He was actually trying to save me money and add more grin factor into the 335d ownership!!

[335DEE]

I'm having my main stat changed tomorrow ( Had egr done some time ago and made no difference to temps) , £35 for stat and £20 to fit by my indie. My temps are 74-78

I track my mpg via my signature below and as I spend my life doing ...

Originally Posted by HighlandPete

lighter load constant speed cruising

I'll be keeping an eye out to see if i get any variation in fuel consumption.

[335DEE]

Stat was changed and now car sits 89-92 regardless of ambient.

One thing I have noticed is that I have finally become aware of a regen. All this talk before and I never sensed it happen until today.
Did a motorway drive from Manchester south for around 140 miles. Kept it at a steady 70+ a bit , during this time the car went into regen twice ! around 30 mins into journey and then about 90 mins after , temps up to around 95/96 for about 10-15 minutes. Exhaust tone went deeper , it also seemed heavier on the throttle , kind of less responsive if you know what i mean. The best part is my MPG , even though it clearly went into regen it's up from an average 35 ish to 40+ ! ( it's a regular trip i do , so the speed and fuel are regularly monitored). I'd add this to the list of things to do to the car regardless ( red hose and vac pipes type stuff)

[philmots]

That's basically what I found..

Since having my stats changed I've started to notice regenerations... Never did before.

I can't help but think that knackard stats must be a contributing factor in DPF's packing in early.

[Dr Dave]

Originally Posted by PhilM

I can't help but think that knackard stats must be a contributing factor in DPF's packing in early.

Without a shadow of a doubt, these £60 items are causing big buck damage elsewhere. Many people won't realise it until its too late..........

[badgerbrock72]

Sorry to hijack thread but can someone advise on whats considered acceptable warm up times, my 330d lci is reaching 89/91 but only after about 15 mins (5 miles - although this is urban commute)

I guess its also attributed to the current low overnight temps but being slightly paranoid lol, im just after reassurance that my warm up times are ok

Cheers all

Garry

[Dr Dave]

I'd say you have absolutely nothing to worry about.