Cooling question?

[ArtMan]

Originally Posted by David.X5

Don't forget over pressure in the cooling system is one sign of a failing/failed head gasket. A combustion gas test (measures combustion products in the coolant) is a cheap way to check that.

This is what i was thinking also because even tho i bleed and bleed (and yes i know how to bleed the sysstem not to mention i already said ive been driving for yrs and no problem like this before so this is something that has recently developed) im leaning toward the idea that i have a on its way out head gasket (i do have cold misfires that some times has produced white smoke (twice only) any way im thinking it might just be this....time for a test.

Originally Posted by bmw540san

I thought by now every person on the planet knows that temp gauge dial at 12 clock position means nothing and the real temp is accessed through OBD. Temp at 12 clock position could be anywhere form 75 C to 115 C. It's well known that BMW buffered the temp gauge on many BMW models.
As somebody else suggested, do head gasket failure test and watch temp through OBD as I mentioned, then go from there.

Yes your totally right the 12 oclock is not 100% accurate as in it does have a huge margin in fluctuation but if the temp stays there for hours with out overheating then i consider that to be accurate enough for the time being ...but ill double the check the obd just incase...thanks

Originally Posted by trader4

If the temp gauge at 12 o'clock means nothing, then perhaps
you should tell those wonder engineers at BMW to take it out
of the car......

He can do what he wants. Go change the water pump, thermostat,
do head gasket failure tests. But from what I've heard so far,
there is no indication of an overheating problem. He does
have a leaking coolant cap that is producing a coolant puddle
on the ground. Why not just start with the obvious?
But then, to each his own. Oh, and when my thermostat finally
went at 160K miles, the temp gauge took a long time to get
to 10 o'clock and stayed there. Previously it had been at 12 o'clock.
Put in the new thermostat and it went right to 12 o'clock. So there's that.....

yea the 12 is not that accurate its been well documented from many generation of bmws lol google it if you do not believe the members here. but your missing my point in that the CAP only holds pressure to a certain limit. so my cap DOES NOT LEAK one bit till it hits that pressure get it. if you dont look at it like this. The coolant does heat up and expand hence why you have cold level mark so in a normal system it should heat up and rise up and the system will get pressurized that is totally normal. so the top and bottom hose should start to feel a bit firmer especially the top hose as its has the hotter temp liquid which has hotter gases so it will be stiffer but mine is going beyond that meaning when i opened up my cap after the first time the hose visably deflated half most half its size that is tooooo much way too much.

also thermostats are electronic on these cars....so it can fail any time not as often but it can. and ive heard of ppl saying that they had soft failing ones where it works and it does not so mine can be that exact case it opens when it supposed to and it might close for a brief moment then open idk

that being said not of this still does not explain why bottom hose has no pressure i mean i can almost totally squeeze it shut and i dont feel any flow or sounds of coolant trying to flow passed this narrow passage just nothing. i tested this on my e36 and the ml320 and the e30 and they all had some form of pressure feedback you can feel and you can hear the flow of coolant....

so how is that the top hose gets ballooned up and bottom has nothing... (lets say once i do the combustion gases test and lets say it comes back negative what else is left that i can check?)