[bazz780]

Hi Guys,

Just wanted to share a problem and hopefully solution to the issues i have been having with the car

After noticing poor mpg and checking the hidden menu for coolant temperature, it appears that the thermostat is not letting the car reach normal operating temperature,

From my understanding the normal temp should be approx 90 degrees, my car does not get past 80 degrees and thats stuck in traffic, on the motorway after a 2 hour journey temperature was only on 66 degrees which climbed up to 77 through local traffic.

I have ordered the parts (2 x thermostats) from the dealers and will hopeflly fit myself this week,

Will report back on here to share my new findings with you all:

Hidden menu instructions can be found by searching 'e90 hidden menu'

Regards

[IceMan007]

Check the red boost hose in your engine bay and the the oil drip tray underneath. If the hose has oil and/or you can see remnants of oil on the drip tray then you need to replace the red boost hose.

It's a common fault with the 335ds and may be another reason for the poor mpg (I'm experiencing this too).

My hose is due to be replaced over the next few days so will report back too!

[xenon]

That engine is running way too cold though.

[flying_scotsman]

http://e90.wetpaint.com/page/BC+hidd...us/revision/37

is the link to get to the hidden menus too :-)

[bazz780]

Originally Posted by xenon

That engine is running way too cold though.

Thanks mate, hose has been corrected last month, it has made a good difference in the way the car drives

Im assuming the poor mpg due to the low running temperature,

[briers]

I don't think 90 is normal for the 335d. Only time i see 90 is with a DPF re-gen and then its about 92.

Mine typically sits at 84c.

High 70's is not that far off but if you are seeing mid 60's to mid 70's it seems like a clear problem.

[HighlandPete]

Originally Posted by xenon

That engine is running way too cold though.

+1

And correct to get both thermostats fixed as OP is doing. I'd wager EGR 'stat will be open in the first stage, (70-degree element) and main 'stat running low as well.

HighlandPete

[HighlandPete]

Originally Posted by briers

I don't think 90 is normal for the 335d. Only time i see 90 is with a DPF re-gen and then its about 92.

Mine typically sits at 84c.

High 70's is not that far off but if you are seeing mid 60's to mid 70's it seems like a clear problem.

Main thermostat should be opening at 88-degrees, engines typically run 88 - 91 degrees.

Failed EGR 'stat will cause a low range (low 70's is typical), with slow warm up. The first stage EGR 'stat element is set to open at 70-degrees and that is the part that fails in the open position, preventing initial warm up. It is supposed to just 'bleed' coolant from the first stage, until the main 'stat is open and then the EGR thermostat second element fully opens at 90-degrees and above.

Main 'stats typically start falling off optimum range, and gradually drop through the 80's.

Mine is now sitting at about 84-degrees, dropped about 1-degree since last winter.

HighlandPete

[bazz780]

Thanks for all input, i will try fit asap as will be a good comparison with weather still stable, when i did this on my 530d with same symptoms, 15 minutes into a local drive coolant temp reached 92 degrees.

Hope it works just as well on the 335d and hope it helps others with same problems

[acerboo]

this has been covered in other posts also, but mine did the same thing and it was the egr stat, this seems to be a common failure on the 335d

[F104]

I'm not arguing, but fail to understand the EGR thermostat impact on (low) coolant temperature. I thought its only purpose was to avoid cooling exhaust gasses when the engine is cold, as that results in acid condensation. So when engine is warm, I assume it can fail such that no coolant passes thru the cooler, and then coolant picks up no heat. That does not result in cold running though. Or it fails open, engine should be able to cope with that, but cold starts will then results in acids killing the cooler.

I also question the coolant temp increase during regeneration. I'll check it next time, but i would say the late fuel injection does not result in any heat (that fuel should only ignite when passing thru the oxydation catalyst just before the DPF). And the EGR valve closes during regen, thus putting no heat into the EGR cooler. The EGR valve closes to avoid unburned fuel going thru the cooler and into the plastic manifold. I'd expect coolant temp to drop when regeneration starts, and then recover depending on where it was vs thermostat opening.

I'd advise people with coolant temp issues to try and see what it does with cabin heater off. A 330d at 70mph runs at very light load. The cabin heater might take nearly all the heat out of it. I might be wrong but it's an easy test.

regards,

[HighlandPete]

Originally Posted by F104

I'm not arguing, but fail to understand the EGR thermostat impact on (low) coolant temperature. I thought its only purpose was to avoid cooling exhaust gasses when the engine is cold, as that results in acid condensation. So when engine is warm, I assume it can fail such that no coolant passes thru the cooler, and then coolant picks up no heat. That does not result in cold running though. Or it fails open, engine should be able to cope with that, but cold starts will then results in acids killing the cooler.

I also question the coolant temp increase during regeneration. I'll check it next time, but i would say the late fuel injection does not result in any heat (that fuel should only ignite when passing thru the oxydation catalyst just before the DPF). And the EGR valve closes during regen, thus putting no heat into the EGR cooler. The EGR valve closes to avoid unburned fuel going thru the cooler and into the plastic manifold. I'd expect coolant temp to drop when regeneration starts, and then recover depending on where it was vs thermostat opening.

I'd advise people with coolant temp issues to try and see what it does with cabin heater off. A 330d at 70mph runs at very light load. The cabin heater might take nearly all the heat out of it. I might be wrong but it's an easy test.

regards,

Simply put, a failed EGR 'stat allows the coolant to short circuit, across the system, bypassing the main thermostat, so it can be as there is no main thermostat control. Then there is not enough 'spare heat' to get up to temperature.

Regen' does increase the coolant temperature, mine running mid 80's will go over 95-degrees during a regen' cutting back to around 87-degrees as it is in the last stage of regeneration. Then goes back to 84 - 85.

Cabin heating makes little difference once warm, as you'd expect with good 'stats, but will increase warm up time anyway, but worse with weak 'stats.

HighlandPete

[F104]

Originally Posted by HighlandPete

Simply put, a failed EGR 'stat allows the coolant to short circuit, across the system, bypassing the main thermostat, so it can be as there is no main thermostat control.

That is only true if the EGR cooler coolant outlet bypasses the main (radiator) thermostat. It sure doesn't on my 07 E92 320d. On mine the EGR in and out coolant flow are into the engine block; such that the EGR also assists in heating up faster. The radiator flow on mine is controlled by the main thermostat; located on the water pump inlet.
I'd be surprised if BMW had coolant systems where the EGR flow could bypass the main thermostat. But anything is possible.
BMW had Webasto heaters fitted as standard on first gen. E46 diesels as they knew it did not produce enough heat under circumstances.. I had one..

[HighlandPete]

Originally Posted by F104

That is only true if the EGR cooler coolant outlet bypasses the main (radiator) thermostat. It sure doesn't on my 07 E92 320d. On mine the EGR in and out coolant flow are into the engine block; such that the EGR also assists in heating up faster. The radiator flow on mine is controlled by the main thermostat; located on the water pump inlet.
I'd be surprised if BMW had coolant systems where the EGR flow could bypass the main thermostat. But anything is possible.

BMW had Webasto heaters fitted as standard on first gen. E46 diesels as they knew it did not produce enough heat under circumstances.. I had one..

You have an N47 engine don't you. We haven't got the EGR 'stat of the N47/57 engines.

Makes much more sense to help heat the engine, than draw cold coolant from the lower cold side of the radiator, into the EGR cooler (as the M47/57), which although the plumbing isn't directly to the radiator on the top side, means coolant must go back into the radiator, and it is warm flow, wasting valuable heat.

I totally accept the warm up issues, due to thermal efficiency and having a water-flow heater in the E46 diesels. Our E9* models have the PTC electric element in the diesel variants, to give us faster cabin heating, one reason it may appear the engine heating and coolant issues are not so bad, on colder mornings.

HighlandPete

[F104]

Originally Posted by HighlandPete

You have an N47 engine don't you.

yes indeed N47. Ok I never realized BMW had such different coolant systems, and did thus not understand this, and other threads. But indeed, that makes one big difference, and also on warm up times. Thus my comments only apply to N47 powered cars. Sorry for any confusion caused!

[HighlandPete]

Originally Posted by F104

yes indeed N47. ....... Sorry for any confusion caused!

No problem at all, the N47/57 looks to be a much improved system.

The issue with the EGR 'stat in the M47/57, when the low temperature element starts working, it is only supposed to just keep the EGR cooler from overheating as I understand it, and it would be a small flow, until there is much more heat and the temperature is at full range. But if it is failing, or completely failed, the flow is far too much ahead of getting up to temperature. The flow doesn't/can't go through the main thermostat opening, it flows into the warming coolant (chilling it) preventing heat/fast heat up. In effect bypassing any low temperature regulation. When the main 'stat opens and the bypass heating closes, normal cooling can take place, the flow is drawn back through the engine via the pump, now cooling correctly.

We just don't have enough heat to get up to main thermstat temperatures, in some instances. Let alone get to the point where the second element in the EGR 'stat would normally open after the main 'stat is already drawing water the correct way.

It is this anomally, which in my understanding, is why some EGR 'stats can completely solve a coolant temperature issue. But if the main 'stat is opening low as well, it can't be identified, as it is masked by a faulty EGR 'stat.

Hence why some replacement EGR 'stats will then only improve the temperature, up to the main 'stat range, and then requires a main 'stat to get the full working temperature.

In the CAD illustration I put together, it is element '1' that is the common failure, leaves the first stage valve open at low temperatures. I believe it over cooks (prematurely), as it is rated at 70-degrees, but has a normal flow over it, once hot, of over 90 degrees, when the second element '2' extends and fully opens the mushroom head at the end of the 'stat.



HighlandPete

[F104]

HighlandPete, thanks for taking the time to explain this. Indeed N47 is completely different. The EGR cooler has constant coolant flow (6 & 7), the cooler housing (1) has the cooling element in the top 3/4 section or so, the bottom 1/4 is a bypass channel for the EGR gasses controlled by the vacuum valve (5)

[AlwynMike]

HighlandPete, F104

This is way above my pay scale, but many thanks to you both - us underlings may now start to understand these things a little better.

Mike

[bazz780]

Hey guys, an update:

Managed to change the EGR thermostat yesterday as easy to do and already there seems to be a little difference with the feel of the car (most prob in my head but anyways...)

the old thermostat was easy to blow through whereas the new one was completely impossible even though i turned blue trying.

i have not had a chance to take the car on the motorway so not sure if car still sticks to under 70 degrees and locally i am still getting around 77 degrees, will change the main one today as good weather and will post findings asap

was hooping someone with bentley or haynes manual could have sent me scanned email on DIY but no luck in another thread.

regards

[bazz780]

another small update to share,

I have not had a chance to do the main stat yet,

however since the egr stat, temperature reached 99 degrees (dont know if this acceptable) since then car reaches approx 88 or so after 20 mins of local driving

will still change main stat once i get a chance but i couldnt get the rad fan out for some reason to access the 2 egr bolts.

[HighlandPete]

Originally Posted by bazz780

another small update to share,

I have not had a chance to do the main stat yet,

however since the egr stat, temperature reached 99 degrees (dont know if this acceptable) since then car reaches approx 88 or so after 20 mins of local driving

will still change main stat once i get a chance but i couldnt get the rad fan out for some reason to access the 2 egr bolts.

Sounds as if either your main 'stat hasn't been open for a while (sticky) and/or you've had a DPF regeneration, due to being up to a high enough temperature. Either can give you a high peak, before giving you a true running temperature.

I'd monitor it for a few days, see what the steady temperature is, as you may not have any real issue with the main thermostat.

HighlandPete

[no_ball]

sorry for the simple question, but how does one get the actual ECT to display please on a 2006 e90?
Thnaks in advance