E39 528 Temperature gauge playing up.... sensor?

[sparks_E39]

My temperature gauge has always after a few minutes of driving remained at 12 o clock. Earlier whilst driving to Plymouth after about 40 miles and some "spirited" driving, it dipped to the 11 o clock position for a minute, then back to 12. Later on after some more "progress" it happened again. On the 120 mile trip back 1 hour later it behaved fine, and I used kickdown a few times. I didn't experience a loss of power. A year ago the radiator was replaced along with the thermostat, and at the end of the journey the engine was hot like normal. Could it be a sensor? The car isn't overheating and there is no sludge under the oil cap or a lot of smoke from the exhaust. MPG is fine to, 240 miles not hanging about was 31.3. I have no idea if this is related to the problem, but my friend topped up my washer fluid for me and the plank didn't shut the bonnet properly and I only noticed when I got home (yes I have told him he's a plank and I yes I should have checked it) Is it possible that more air was getting to the engine bay, thus keeping the engine cooler than normal?... a bit far fetched I know but anyway...

Edited by sparks_E39 on Monday 3rd January 02:16

[roofer]

The only time E39 guages read low is when the thermostat goes into failsafe open mode. I would keep an eye on it.

[physprof]

I'd go and get it changed - its on it way out. I've been through 3 now in ten years with a e39.

My observations is that when it is working fine irrespective if how vigourous you drive on road it will sit at 12o'clock. From a cold start it should gradually work up to that position - if you see it over a short period starting to make the transition from say 10O'clock to 12 very quickly that is the sign that it is on its way out then you start to see fluctuation as you've seen ....soon it will go. Worthwhile getting your viscous coupling and the water pump checked at the same time. Less expensive than a full on overheat and being stuck at roadside.

[miniman]

Almost certainly thermostat.

[soda]

Hidden OBC menu should give you a temp reading if you want to double check you have the right running temp. Too low and thermostat needs replacing.

[sparks_E39]

Cheers everyone. What sort of price would I be looking at for a replacement thermostat and fitting?

[miniman]

Most places will say that the rad has to come out, however the stat CAN be changed without doing so. You'll need the stat itself and the tube it sits in.

[4rephill]

sparks_E39 said:

Cheers everyone. What sort of price would I be looking at for a replacement thermostat and fitting?

I had Mine done at a BMW Dealership in 2009 on an E36 328i sport for @ £130 if that helps.

[sparks_E39]

Hmm yes, to be honest I'm not impressed if it is the thermostat, it was brand new in October 2009 12000 miles ago.

[physprof]

soda said:

Hidden OBC menu should give you a temp reading if you want to double check you have the right running temp. Too low and thermostat needs replacing.

steps for this please...?

[physprof]

sparks_E39 said:

Cheers everyone. What sort of price would I be looking at for a replacement thermostat and fitting?

my last one - at indi...

24.68 for thermostat
15.49 for housing
1.11 ring seal


and 99.60 for viscous coupling.....

and labour was buttons....

[soda]

physprof said:

soda said:

Hidden OBC menu should give you a temp reading if you want to double check you have the right running temp. Too low and thermostat needs replacing.

steps for this please...?

Not sure how on E39 off the top of my head, I've an E46. I'm sure I have it saved somewhere though, I'll post it up later on.

[4rephill]

physprof said:

sparks_E39 said:

Cheers everyone. What sort of price would I be looking at for a replacement thermostat and fitting?

my last one - at indi...

24.68 for thermostat
15.49 for housing
1.11 ring seal


and 99.60 for viscous coupling.....

and labour was buttons....

That's interesting, My bill from BMW reads:

£21.30 for thermostat
£15.69 for housing
£0.82 for seal
£0.82 for gasket
£12.60 for antifreeze
£69.91 for labour

And I had the viscous coupling changed at the same time as a precaution which cost:

£124.92 for the viscous fan
£38.14 for labour

As I say though, that is for an E36 328i sport but it gives you an idea on pricing.

[soda]

I can't find the file I was looking for but this site explains it pretty well.

http://www.ideaphile.com/bmw/540-obc.html

[Gman85]

Although you've prob got enough good advice to go on now I will just mention that I had exactly the same symptoms on my E46 330 and it was simply the thermo sensor as already mentioned.
Simple to repair without breaking the bank.

[sparks_E39]

Well in 200 miles it didn't do it again and it should have if its faulty, gave it a 15 minute run around after work as well and it stays at 12. When I parked up the "check engine oil level" warning came on, but the oil is at the same level it always is... re-started and turned off and the message didn't come up. I think I'm having electrical issues rather than mechanical, I noticed the lights flickered yesterday too for a second or two.... hmmm. Thanks all for the help, I'll keep an eye on it.

Edited by sparks_E39 on Monday 3rd January 16:37

[miniman]

Random electrical gremlins are often the sign of (a) a dying battery (possible given the cold weather) and (b) a dying ignition switch.

[sparks_E39]

My abs light came on and the speedo stopped working this morning. Battery is a year old, so I'm thinking ignition barrel?

[miniman]

I reckon so, mine caused radio and wipers to go on the fritz - seems like pretty much any electrical malady can be traced back to it!

[sparks_E39]

Well its fixed itself, the speedo works and the abs light is out, and the rear parking sensors which haven't worked in two years are suddenly working. I suspect my abs is fine and I have to trace this electrical bug, starting with ignition barrel! If it was the abs sensor it would be permanently have the light on, surely?