520i temp gauge/overheating?

"Flummoxed" > wrote
> One point I'd like to reiterate (as no-one has picked up on it) is that
> the coolant level in the reservoir went UP rather than down after I
> drove the car. Can anyone say what circumstances would cause that?
> Could it just be that when the coolant gets warmed up it expands into
> the reservoir? If I had a leak or a blown head gasket I'd expect the
> level to go down not up.
>
> Does anyone haev any ideas?

1) The level in the radiator/system *usually* goes up when warm.
Extra is trapped in the overflow system and gets sucked back when
the engine/radiator cools.
2) If *both* go up, that shows air infiltration (i.e., bad head gasket)
(after entire system is cool.)
3) A bad head gasket doesn't necessarily mean loss of coolant -
remember that cylinder pressure is higher than the coolant's vapor
pressure.
4) Another source of air might be a leak in the water pump inlet
pipe (from the bottom of the radiator). This isn't high probability,
since the system pressure usually overcomes the pump negative
pressure.

FloydR

In article .com>,
Flummoxed > wrote:
> "How fast were you going when the temp shot up?"

> I wasn't going all that fast, maybe 50 mph, 60 at the most. I was being
> careful and keeping my eye on the temp gauge.

Right - I'd say that rules out the fan coupling as it will be all airflow
that cools the rad at that speed.

--
*i souport publik edekashun.

Dave Plowman London SW
To e-mail, change noise into sound.

that could be air moving around teh system.. or more air pushed into the
system..

On 22 Apr 2006 12:41:48 -0700, "Flummoxed" > wrote:

>One point I'd like to reiterate (as no-one has picked up on it) is that
>the coolant level in the reservoir went UP rather than down after I
>drove the car. Can anyone say what circumstances would cause that?
>Could it just be that when the coolant gets warmed up it expands into
>the reservoir? If I had a leak or a blown head gasket I'd expect the
>level to go down not up.
>
>Does anyone haev any ideas?
>
>Thanks again for all the help.
>
>Flummoxed


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Hi again and thanks for the continued help with this.

Maybe I should have pointed out earlier: in Aug 2004 I had the
Thermostat & O rings, and fan coupling replaced, then in Feb 2005 the
waterpump was replaced. Therefore I think it's unlikely to be any of
those components, as the car has been driven since then without any
problems, until now.

I suspect it might be that the cooling system needs bleeding, so if
anyone can tell me how to do that I'd be grateful. As I said, I've
found two cross-head plastic plugs that might be the things to use to
do this - can anyone confirm this? What's the correct procedure?

Thanks again for the help.

Flummoxed

Flummoxed wrote:
> One point I'd like to reiterate (as no-one has picked up on it) is that
> the coolant level in the reservoir went UP rather than down after I
> drove the car. Can anyone say what circumstances would cause that?
> Could it just be that when the coolant gets warmed up it expands into
> the reservoir? If I had a leak or a blown head gasket I'd expect the
> level to go down not up.
>
> Does anyone haev any ideas?
>
> Thanks again for all the help.
>
> Flummoxed
>

Bad head gasket. That's the only thing I know of that will cause the
level in the overflow tank to increase. The leak injects some exhaust
gas from the combustion chamber into the water jacket. Once you have
air (exhaust) bubbles in the coolant the pump will start to act up
causing all manner of strange temperature displays.

--
-Fred W

Flummoxed wrote:
> Hi again and thanks for the continued help with this.
>
> Maybe I should have pointed out earlier: in Aug 2004 I had the
> Thermostat & O rings, and fan coupling replaced, then in Feb 2005 the
> waterpump was replaced. Therefore I think it's unlikely to be any of
> those components, as the car has been driven since then without any
> problems, until now.
>
> I suspect it might be that the cooling system needs bleeding, so if
> anyone can tell me how to do that I'd be grateful. As I said, I've
> found two cross-head plastic plugs that might be the things to use to
> do this - can anyone confirm this? What's the correct procedure?
>
> Thanks again for the help.
>
> Flummoxed
>

A cooling system that needs bleeding will not result in a higher level
in the overflow tank (assuming you are checking when cold)

--
-Fred W

In article om>,
Flummoxed > wrote:
> One thing I wondered: should the two large hoses from the radiator to
> the engine (one top right as you look from the front, and one bottom
> left) be full of coolant? I can squeeze them very easily as if they're
> empty, whether the engine's running or not. I guess they must have
> liquid in though, but I'd expect them to be hard to squeeze if the
> system's under pressure.

Correct - they should be hard to squeeze when hot and for some time after
stopping the engine.

You've got a leak. I had a leak on my E39 which you couldn't see. A dye
test showed it to be coming from the waterpump. Exhaust all possibilities
before deciding it's the head gasket.

--
*Atheism is a non-prophet organization.

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman wrote: "You've got a leak. I had a leak on my E39 which
you couldn't see. A dye
test showed it to be coming from the waterpump. Exhaust all
possibilities
before deciding it's the head gasket."

No, it isn't the head gasket, the leak's somewhere below the coolant
reservoir, but I couldn't see exactly where from. It was just a trickle
of liquid coming from somewhere round there. There's a narrow hose with
a jubilee clip coming out of the bottom of the reservoir, and I
wondered if it might be that but I the jubilee clip didn't seem to need
tightening (at least I was unable to tighten it any more than it was
already). I couldn't see any other obvious thing to try.

Anyway I've booked it into the garage now - hope it doesn't cost too
much

Thanks for everyone's help.

TP