Temperature running cold

[ian_79a]

Just resently my temperature gauge has been droping down at motoway speed and then going back to normal around town.

Am i right in thinking its a sticky thermostat, and will the cause me any problems short term other than being cold and having to drive with gloves and a beanie :D
Im only concerned because of driving 360 miles to cornwall in a couple days time i will get it sorted for the trip back or when i get back

[peppernick]

Depending how low the indicator drops to. It's normal for the engine to run cooler at crusing speed. I would say it's a normal phenomenon.

It's very unlikely to be a sticky thermostat indicator.

[ian_79a]

drops almost to the blue and i lose my heating :o

[peppernick]

If that's the case something is wrong, but unfortunately I'm not able tell you anything more specific.

[Stock323iSaloon]

sounds like a thermo gone bad, 40 quid from stealers and 30min DIY

[ian_79a]

can anyone do a walk though for me? do i need to drain the rad?

[Chaos]

Pretty much sounds like a sticky stat to me, yeah. Some cars you can change them without draining the rad, I'll have a peek and see if you can with yours unless someone who knows or has done it chimes in first.

[Stock323iSaloon]

http://forum.e46fanatics.com/showthread.php?t=219433&page=2

[Chaos]

OK, to add to that, I don't believe that you have to drain the water unless you want to. Some will come out, but shouldn't be too much, so if you don't want to do a full change then you should be able to swap the stat housing and top up after.

(PS, as per your other thread, please pass on my sincere condolences to Tracey)

[ian_79a]

ill try and pick up a stat when stealers open see if it sorts my problem out thanks for you help :)
And thank you Dan

[will_uk]

My thermostat was defective and stuck in the open position. This causes the water to be circulated all around the cylinder block AND radiator which is why when you get to motorway speeds the excess cold air blowing through the rad makes your engine run cold. (Normally the stat just closes and blocks the water flow to the radiator so the engine can warm up).

If it's running very cold I presume the ECU will enrich the fuel mixture in order for the engine to be able to idle. This would probably increase your fuel consumption a little. I heard that also, running increased fuel in the air/fuel mixture can strip oil from the pistons and increase engine wear. It normally only occurs for a couple of minutes or so on a cold morning whilst the engine warms up. To be honest, it's all speculation as my knowledge is very limited in these things. I've replaced a few thermostats on some of my older cars and to be fair, it was a real doddle. However on the E46 that I have, i took one look and thought sod that, just looked too much like hard work for my lazy arse to tackle. If you do replace it yourself mate, when you fill up the water that you lost just make sure that the bleed nipple is open (It's right next to the filler cap) just to make sure you don't get any airlocks in the system.

[ian_79a]

thank will ;)

[sjj84]

Stats are only about £45 to buy along with the housing. Think it's 1-1.5hours labour to have it fitted if you can't be bothered. Seems to be alot going recently, I had mine done last week. The dealers normally have them on the shelf if you're going to do it yourself.