Xoutpost.com - Cooling question?

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Quote:

Originally Posted by David.X5 (Post 1040471)

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.

Quote:

Originally Posted by bmw540san (Post 1040473)

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

Quote:

Originally Posted by trader4 (Post 1040476)

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?)

Quote:

Originally Posted by trader4 (Post 1040482)

I haven't analyzed the coolant recovery system in the X5, but in
every other car I've seen, as pressure in the system builds and
exceeds a set pressure, the cap allows the coolant to go into
a coolant reservoir. It doesn't leak out from the cap and wind up
on the ground. And then when the pressure lowers when the car
is off, the coolant flows back from the reservoir into the cooling
system.

The thermostats aren't exactly electronic. They are mechanical
with a resistance heater added. In the wisdom of the geniuses
at BMW, that complication allows them to run the cars hotter
most of the time. But under extreme conditions, ie very hot
ambient, towing, etc, that could allow the engine to get too hot.
So, under those cases, the computer turns on the little heater
in the thermostat, which forces it to open early. If your thermostat
was failing, you'd very likely see other symptoms, including
the temp gauge rising. Yeah, it's not 100% accurate. But BMW
obviously thinks it's accurate enough that it's worth putting on the
dash. And I've never seen a failed thermostat that caused a car
to overheat with the temp gauge still showing normal. Not on BMW,
not on any car.

Given that you now say you've also seen white smoke on occasion,
I agree that the head gasket is a possibility. But again, I'd first
focus on what's clearly not right, which is that coolant is somehow
coming out from the cap. I don't see why you want to just ignore
that, which is the most obvious thing.

Im not ignoring im just building a list of things to check not just one but a list ie brainstorming and i appreciate any and all feedback and ideas trader4

i dont want to check one thing come back chit chat go back check i want to have a list of stuff to look though and inspect.....

so i have a the older cap and i ll grab a new cap as its cheap insurance to see fi that helps

however like i said before why i dont think the cap is the problem is becuase how the upper hose balloons up its out of norm and im thinking its the head gasket but ill check the cap and do the combustion test

ive dont a compression test and while numbers were not off the chart they were ok for a 200K engine and i did my best to do a leak down test and i had moderate leakage in the crankcase so the rings which is another huge issue with bmws use of low tensile rings in the m54 engine its well documented issue......