Temperature fluctuations

[boiliebasher]

Hi all,
So my little 316i is fluctuating in temperature and I still can't seem to work out why.

It's had; brand new nissens rad, skf metal blade water pump, new behr viscous clutch and two different thermostats.
First one was a cheap gates one that I wasn't happy with so I coughed up on a genuine BMW thermostat instead.

Now, when I say it fluctuates in temperature, it's probably me being a bit ocd. It gets up to temp fine, never gets hotter than say 1 o clock.

When driving about sits at tick below the middle but when I let it idle for a while or sat in traffic, it starts creeping up ever so slowly but like I said never ever gets close to the red.

Coolant system fully bled out and the car doesn't touch or lose a drop of oil or water.

I'm still convenienced it's the thermostat but please any suggestions would be appreciated.

All my other beemers have always got up to temp and sat bang on the gauge and never fluctuated regardless of if sat in traffic or not.

I'm pretty sure this one used to do the same until it started playing silly buggers a few months back.

Or am I just going mad and going ott with minor dash gauge fluctuations?! Any suggestions much appreciated guys

[Brianmoooore]

When driving about sits at tick below the middle but when I let it idle for a while or sat in traffic, it starts creeping up ever so slowly but like I said never ever gets close to the red.

This is exactly what it should do. If the temp. doesn't increase slightly when not moving, the viscous coupling is dragging more than it needs to.

[boiliebasher]

Thanks for the reply Brian.
Right okay, whilst driving back from work this evening driving at a constant 50-60 mph, the temp guage was fluctuating between 11 o'clock and 12 o'clock. No traffic at all just quiet country roads all the way.

Now I'm still convenienced it's the thermostat that is causing the gauge to mess about. I paid near on £40 for a genuine BMW thermostat and I'm sure the original one I replaced didn't move no where near as much on the temp gauge.....

[Brianmoooore]

When driving continuously at that kind of speed, the gauge should remain completely still at the temperature stamped on the thermostat.
If the gauge i moving slowly between the two points, then the 'stat is suspect. If it's jumping between the two, then the brass nut on the back of the instrument cluster, directly behind the gauge, needs attention.

[boiliebasher]

Thanks again Brian.
Checked the brass nuts behind the dash and they seem fine.
It's not "jumping" it's definitely slowly moving between the two points on the guage which is why I suspected the stat.

I bought the thermostat from Cotswold on here roughly 3 months ago. Do you think they would replace or send me out another one?!

Like I said radiator and pump brand new too so I'm pretty convinced thermostat is playing silly buggers with me

[boiliebasher]

And it's definitely bleed out correctly. No air locks what so ever and heating works perfectly.

[boiliebasher]

Right following on from this it still seems to be fluctuating between 1/3 to half on the gauge. Car is my daily driver so I can keep an eye on it.

It never seems to go beyond half way which is definitely a good thing.

The fluctuating is much more noticeable going up and down hills.

Just seems odd as I don't ever remember this happening before or on any of my previous BMW's unless there been a problem.

So to recap:
Brand new behr radiator
Brand new behr viscous clutch
Brand new skf water pump
Brand new BMW thermostat.

System bleed correctly, heaters work correctly and literally does not touch a single drop of oil or water between servicing.

I still personally think duff thermostat as there is literally nothing else it can be, or I should just live with it seeing as it doesn't overheat or ever go past half way point.

[Brianmoooore]

Assuming that it's a slow movement of the gauge, then it sounds like the engine is being over cooled. This will be because of a thermostat that's not shutting off properly, although having the heater full on when the engine's not working particularly hard can have a similar effect.

[BristolE30]

Many many 316 owners complain of having the same issue. In my opinion it’s bad design - compensated sometimes by an additional water pump to try and rectify bad circulation. I could never stop it on my one

[BenHar]

New fan clutches can be a bit sticky to start with.

Does it "roar" a bit when you rev it when cold?

Ben

[boiliebasher]

Assuming that it's a slow movement of the gauge, then it sounds like the engine is being over cooled. This will be because of a thermostat that's not shutting off properly, although having the heater full on when the engine's not working particularly hard can have a similar effect.

That was exactly my thoughts Brian, I completely agree. If I put the heaters on full chat, it seems to have a similar effect than going down a steep hill. The temperature begins to drop .

To be honest, I think I'll just live with the dodgy thermostat as its not that bad. Just probably me being a bit picky.
Thanks again for your time mate, I appreciate it.
Kind regards Marc

[boiliebasher]

Many many 316 owners complain of having the same issue. In my opinion it’s bad design - compensated sometimes by an additional water pump to try and rectify bad circulation. I could never stop it on my one

Mine is the later M40 powered 316i. I've read about this aux pump before I think it was more in relation to the earlier M10 engine?!

[boiliebasher]

New fan clutches can be a bit sticky to start with.

Does it "roar" a bit when you rev it when cold?

Ben

Hi Ben,
Nope fan clutch seems fine to me and no "roar" on start up etc. I think my problem lies with a lazy thermostat more than anything else.

I can stop the fan blade spinning when engine is running and it "feels" as it has the right amount of resistance if that makes sense.

Thanks for taking the time to reply.
Cheers Marc