Strange coolant temperature behaviour

Mustard3 · 08-07-2012, 09:36 AM

Running at a constant 70mph in 6th (manual mode), and my temperature is sitting at about 92 degrees.

Without changing speed, if I drop down to 4th gear the temperature drops to about 84 degrees within about a 1/4 mile. And the reverse if I change back up to 6th.

Both thermostats have been changed fairly recently.

This seems counter-intuitive, can anyone suggest an explanation?

xenon · 08-07-2012, 09:40 AM

Engine spinning faster therefore the water-pump is turning faster

I suspect the cooling system is designed to lower the temperature towards the bottom-end of the acceptable window if the engine us run at higher speeds.

dxb335d · 08-07-2012, 09:40 AM

Quote:

Originally Posted by Mustard3

Running at a constant 70mph in 6th (manual mode), and my temperature is sitting at about 92 degrees.

Without changing speed, if I drop down to 4th gear the temperature drops to about 84 degrees within about a 1/4 mile. And the reverse if I change back up to 6th.

Both thermostats have been changed fairly recently.

This seems counter-intuitive, can anyone suggest an explanation?

In the years I owned my 335d, I never ever checked the coolant temp, I also never had an issue mate.

I have heard BMW didn't fit an actual gauge because of the 335d fluctuating temp range, they didn't want to frighten owners.
Dont worry about it mate

Mustard3 · 08-07-2012, 09:52 AM

Quote:

Originally Posted by xenon

Engine spinning faster therefore the water-pump is turning faster

That might explain it, I just thought 'more revs = more heat' It might be worth remembering if the car is ever running too hot.

Quote:

Originally Posted by dxb335d

I have heard BMW didn't fit an actual gauge because of the 335d fluctuating temp range, they didn't want to frighten owners.
Dont worry about it mate

Not worried at all, just curious!

makkan00 · 08-07-2012, 10:08 AM

Do you have electric pump same as 335i?
or do you have traditional pump?

You have answer to your question already but I'd like to know if 335d and 335i both shares electric water pump?

Mustard3 · 08-07-2012, 10:18 AM

Quote:

Originally Posted by makkan00

Do you have electric pump same as 335i?
or do you have traditional pump?

You have answer to your question already but I'd like to know if 335d and 335i both shares electric water pump?

It's a mechanical (belt driven) pump I believe. I didn't realise the 335i was different.

G82Dude · 08-07-2012, 12:05 PM

Quote:

Originally Posted by Mustard3

Running at a constant 70mph in 6th (manual mode), and my temperature is sitting at about 92 degrees.

Without changing speed, if I drop down to 4th gear the temperature drops to about 84 degrees within about a 1/4 mile. And the reverse if I change back up to 6th.

Both thermostats have been changed fairly recently.

This seems counter-intuitive, can anyone suggest an explanation?

Where can you see the coolant temp? Is it in iDrive?

Kerr · 08-07-2012, 12:24 PM

Could it be the small turbo being very small and sensitive running quite regularly with small devetions in throttle movement that is adding heat?

08-07-2012, 09:36 AM	#1
Mustard3 Lieutenant 99 Rep 403 Posts Drives: F31 340i Join Date: Sep 2011 Location: UK iTrader: (1)	Strange coolant temperature behaviour Running at a constant 70mph in 6th (manual mode), and my temperature is sitting at about 92 degrees. Without changing speed, if I drop down to 4th gear the temperature drops to about 84 degrees within about a 1/4 mile. And the reverse if I change back up to 6th. Both thermostats have been changed fairly recently. This seems counter-intuitive, can anyone suggest an explanation?
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08-07-2012, 09:40 AM	#2
xenon Major General 1397 Rep 8,083 Posts Drives: 2021 G21 330i M-Sport Join Date: Jun 2008 Location: Coventry iTrader: (0)	Engine spinning faster therefore the water-pump is turning faster I suspect the cooling system is designed to lower the temperature towards the bottom-end of the acceptable window if the engine us run at higher speeds. __________________ Ian Current: 2021 G21 330i M-Sport Previous: 2018 A6 Avant S-Line MMI+, 2014 F31 320d M-Sport, 2013 F10 520d M-Sport, 2011 F10 530d M-Sport, 2008 320i M-Sport Coupe, 2002 325i, 2001 318i valvetronic, 1998 318i, 1996 525i, 1990 Porsche 944S2
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08-07-2012, 10:08 AM	#5
makkan00 Major General 886 Rep 9,097 Posts Drives: F83 and F36 Join Date: Dec 2011 Location: Essex iTrader: (56)	Do you have electric pump same as 335i? or do you have traditional pump? You have answer to your question already but I'd like to know if 335d and 335i both shares electric water pump? __________________ F36 Xdrive for her - HUD, park assist, heated steering wheel, rear camera, Apple car play F36 RWD for him - HK, M sports pack, GTS tail light, Apple car play
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08-07-2012, 12:24 PM	#8
Kerr Brigadier General 112 Rep 4,021 Posts Drives: BMW M235I Join Date: Dec 2010 Location: Aberdeen iTrader: (0)	Could it be the small turbo being very small and sensitive running quite regularly with small devetions in throttle movement that is adding heat?
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