[jonl1983]

Hi

Did a run down the motorway this morning and after 90miles my coolant temp was at 76c. I had the cruise control on at 70 for practically the whole trip and hardly touched the accelerator. It only went to 81 when I got off the motorway and drove for about 1 mile before parking up.

Is this normal after a long drive and no acceleration? The outside temp was 1c if that makes any difference.

If the stats need changing should I change the EGR and Main or do I only need to do the one?

Cheers

[Falmouthboy]

How can you tell your coolant temp? My 330d doesn't have a temp display.

[xenon]

Sounds too cool but I don't have a 335d to compare it with.

@ Falmouthboy - you need to access the hidden service menu to see this.

[dxb335d]

The BMW diesel engines coolant temp varies so much BMW didn't fit a coolant temp gauge as they thought the varied fluctuation changes would scare owners.

[jimmylad]

As DXB says coolant temp does vary quite a bit. Every car I have ever had the temperature guage never really moved once warm.

76 degrees wouldnt bother me greatly as the extra cooling on the motorway due to relatively high road speeds / low temps & driving at 70 in a 335 isnt working it too hard. You would probably find it rises into the 80's on tickover due to no moving air through the rad.

Changed my egr stat but made sod all difference to be honest. May have warmed up slightly quicker but made no difference to me at all.

Lat year it would have worried me but now it wouldnt.

Last winter mine took ages to get up to temperature (monitoring it all the time back then)

[dxb335d]

Wish I knew about the secret menu when I had mine.

Any pics??

[xenon]

Should find it from a search - instructions on how to get it and then what all the items are, coolant temperature is one of many.

I'm guessing LCI cars have automatic radiator louvres (blanking) ?

[briers]

I haven't checked for a while but i only hit 91 - 93 in town after a longer drive.

It was about 82 - 85 normally but does drop on light load and higher revs.

[jonl1983]

I think il leave them for now then and keep an eye on them over the next couple of months.

I had in my mind the temp should be between 88-91.

Local stealers wanted £396 to change both stats and local specialist indie wanted £192. Apparently one of the stats is a pain in the arse to change.

Not got any pics, will see what is like on the way home an take some

Cheers all!

[dxb335d]

Cheers Jon!

[HighlandPete]

Originally Posted by jonl1983

Hi

Did a run down the motorway this morning and after 90miles my coolant temp was at 76c. I had the cruise control on at 70 for practically the whole trip and hardly touched the accelerator. It only went to 81 when I got off the motorway and drove for about 1 mile before parking up.

Is this normal after a long drive and no acceleration? The outside temp was 1c if that makes any difference.

If the stats need changing should I change the EGR and Main or do I only need to do the one?

Cheers

No, not high enough. Best 'normal' range is 88 - 91-degrees. Main thermostat is rated at 88-degrees, opening temperature.

EGR 'stats often fail in the first stage element, the 70-degree opening temperature, and that causes the low range figures, typically mid 70's as the system is open circuit to the radiator and bypassing the main 'stat. Also often responsible for very slow warm up times and low mpg. When removed, you can blow through the 'stat without any or very little resistance.

The second stage element (higher than the main 'stat at 90-degrees opening) becomes obsolete, as it is already out of range and messing the coolant temperature.

EGR 'stat is easiest to change and will then give an indication if the main 'stat is fine, or opening a bit low. Many main 'stats in the BMW diesel engines, (BMW and Rover models) have mid 80's working temperature, with fluctuations due to load and ambient temperature. Seems a lot of main 'stats settle in the mid 80's even after a relatively short life.

HighlandPete

[jonl1983]

Originally Posted by HighlandPete

No, not high enough. Best 'normal' range is 88 - 91-degrees. Main thermostat is rated at 88-degrees, opening temperature.

EGR 'stats often fail in the first stage element, the 70-degree opening temperature, and that causes the low range figures, typically mid 70's as the system is open circuit to the radiator and bypassing the main 'stat. Also often responsible for very slow warm up times and low mpg. When removed, you can blow through the 'stat without any or very little resistance.

The second stage element (higher than the main 'stat at 90-degrees opening) becomes obsolete, as it is already out of range and messing the coolant temperature.

EGR 'stat is easiest to change and will then give an indication if the main 'stat is fine, or opening a bit low. Many main 'stats in the BMW diesel engines, (BMW and Rover models) have mid 80's working temperature, with fluctuations due to load and ambient temperature. Seems a lot of main 'stats settle in the mid 80's even after a relatively short life.

HighlandPete

Hi Pete

Thanks for the advice. I will keep an eye over the next couple of weeks and if it stays te same I will get the EGR stat changed and see if that does help. The car does take at least 15-20 miles to get well into the seventies. The wife's 118d is up to 88 in around 10 miles.

[acerboo]

mine started running at 76 and using more fuel whereas normally 86 struggled to make 82 changed the EGR and went back to normal you can do these diy and cost about £25 from bmw

[shane55]

Interesting post given that yesterday I was observing my coolant temp on a 60 mile round trip when the ambient temp was between -1 and +2 degrees!

It took about 20 mins to reach the early 70's and fluctuated between the lowest 68 (when I changed to DS mode) and highest 78 degrees for only about a minute! The magic number of 75 being the minimum coolant temperature that the ECU allows for a regeneration of the DPF was only held for a few minutes and I'm sure it did not stay over 75 for long enough to regen... Most of the time it hovered at 73 degrees.

[dxb335d]

Man, how cold is it where some of you guys live... faaacckkk!!!

Sill 10+ here.

[HighlandPete]

The EGR 'stat should only initially crack open at 70-degrees to keep the EGR cooler down to temperature. (It bleeds water just to heat soak the element, to govern its operation at all times). The second stage should only open the valve and mushroom head completely, at 90-degrees, after the main thermostat is in its operating range. But if the EGR 'stat is opening prematurely, or shot, it is possibly wide open from lower than 70-degrees. There is enough flow to keep the engine cool, with little chance of warming up, particularly at low loads, worse at low ambient temperatures.



Pictures of a CAD model of the EGR thermostat, I made up last winter.

HighlandPete

[dxb335d]

Surely this part should not be going on 4+ year old cars?!

[jonl1983]

Originally Posted by HighlandPete

The EGR 'stat should only crack open at 70-degrees to keep the EGR cooler down to temperature. It bleeds water just to heat soak the element, to govern its operation. But if the 'stat is opening prematurely, or shot, it is possibly wide open from lower than 70-degrees. There is enough flow to keep the engine cool, with little chance of warming up, particularly at low loads, worse at low ambient temperatures.



Pictures of a CAD model of the EGR thermostat, I made up last winter.

HighlandPete

Thanks Pete, Always helpful. Would you recommend changing the EGR stat sooner rather than later?

Cheers

[HighlandPete]

Originally Posted by jonl1983

Thanks Pete, Always helpful. Would you recommend changing the EGR stat sooner rather than later?

Cheers

I'd do it before you get possible DPF issues. It is easy to do, you don't even need to lose an eggcup full of coolant, if you do it correctly.

HighlandPete

[acerboo]

Originally Posted by dxb335d

Surely this part should not be going on 4+ year old cars?!

neither should the red intercooler hose!

[HighlandPete]

Originally Posted by dxb335d

Surely this part should not be going on 4+ year old cars?!

It does surprise me. I've chatted to a Master Tech' on this issue and asked what the official line is, for what temperatures an engine should be running and where the temperature breakoff point is on the main thermostat, before BMW recommend a replacement. Nothing on their system, we looked but couldn't find a definitive.

What is apparent, the control strategy allows for a fluctuation of temperature, it can drop off rapidly, as EGR flows are also involved and cooling a high EGR ratio flow will mean a wide open ERG 'stat. I wonder if there is more thermal load, on the EGR 'stat than we would expect and it cooks up the low temperature element.

Even the main thermostats are not too durable it seems, why replacements (OEM 'stats) drop to mid 80's in a short life cycle, just months with some users, I also find hard to understand.

My main 'stat is running mid 80's, stayed like it for a year, so in two minds whether to change, or just leave it, if it drops no further. Regen's push it up into the 90's, so no issue there.

HighlandPete

[jonl1983]

Originally Posted by HighlandPete

I'd do it before you get possible DPF issues. It is easy to do, you don't even need to lose an eggcup full of coolant, if you do it correctly.

HighlandPete

Cheers will get one ordered and fit it over the weekend. Luckily I had my DPF replaced under warranty about 10k miles ago so fingers crossed that should be ok

Thanks again