BMW E39 failed radiator & failed expansion tank pictorial autopsy, new questions aske

I'm pretty sure the low coolant warning only comes on at shut down or start-up, nice huh?
Lucky for you you caught it before harming the engine.
I wasn't aware there was a coolant temp history available. One of my cars came to me with an overheated engine (resulting from a failed radiator hose nipple and an oblivious driver), I'd like to know how hot it got. Hot enough to pull the headbolt threads from the block is all I know.

Originally Posted by ross1

Hot enough to pull the headbolt threads from the block

Ouch. There was a recent thread on that exact topic that you may be interested in (it was within the past week or two).

BTW, since nobody seems to know how that second hidden black-slider chamber works, and since mine was 'locked' into position (even though it appears to be designed to slide), I opened a new thread just to answer that one question in this thread:

- Will the next person who replaces his expansion tank please cut the old tank open and snap a photograph of the "natural" position of the second chamber?

By way of easy linkable cross reference, this cn90 thread today seems to show that some people have a Behr manufacturing defect "flap" on the bottom expansion tank openings which is reputedly the cause of no cockpit heat when replacing the expansion tank.
- Anyone seen a defective Behr Reservoir before (2002 530i)

Cam references these threads:
- No heat condition caused by a faulty BEHR expansion tank
- Re: No heat condition caused by a faulty BEHR expansion tank

And, pleiades referenced a similar post here:
- What's the record for number of bleed attempts?

Apparently there is a bad batch of Behr expansion tanks with extra flaps in the bottom. So, when you buy a new one, check it with a flashlight. It should NOT have a flap AFAIK.

Hey Blue, sorry I don't keep up with all the posts and answer in more timely manner. "Magnetic" switches work in a couple different ways. When you were a child, did you ever wrap a wire around a nail and hook to a battery? You essentially can have a sensor whereby a metal rod passes through a coil and current is induced to flow in direct proportion to how far the metal rod penetrates the electric coil.

More simple (and likely) the way it works in the radiator expansion tank is a magnetized set of contacts are simply waiting for a piece of ferrous metal to get close enough to the magnet so that the magnet is attracted to the steel and it closes a set of contacts. The metal coud be covered in plastic to prevent rust or the steel could be like a 400 series stainless that has good magnetic properties and good anti-corrosion properties.

It looks like it's time for me to do a complete cooling system re-build as I have owned my 2000 since 2007 when it had 68K miles on it. That was when the radiator and expansion tank was replaced last. I'm at 130,000 miles now and have a slow coolant leak that I'm guessing is the water pump weep hole so will be doing entire deal and then likely selling to a guy at work. I will them drive the wife's 2002 540 and she may get a new SUV to replace her 2006 explorer. Having 3 carsand just 2 drivers is a luxury we really don't need and she insists on an SUV for the dogs....

Looking up how the sensor works, I saw this description at
- BMW E39 Expansion Tank Failure Analysis
http://members.cox.net/rsm540i/E39ExpansionTank.htm
"I am fairly sure this sensor works as follows: the coolant level float in the tank contains a metallic "donut", and this sensor must use this (via magnetic field, Hall Effect or ???) to determine the proximity of the float to the sensor. When the coolant level gets low, the float gets closer and closer to the sensor, until the low-coolant alert is triggered..."

In case that members.cox.net article goes away, it's reproduced below. I tried to simply print it to a PDF file, but the file was 4MB which is 3MB too large for an attachment. So I just reproduced the screen shots to help others and for reference since he cut the tank open at a different angle than I did so what you see is another angle on the same theme.

Interestingly, he didn't go into any detail whatsoever of the second (hidden) chamber with the black float, nor does his picture show that entire section. Maybe it doesn't exist on the 540?

Interestingly, today, cn90 over here pointed me to an old thread over here that explained how the (E46) coolant level sensor worked as shown below ...

In post #29, bidman explains:
"I am afraid Critter7r's 13 years in parts and service at 2 BMW dealers did not serve him well on this one. There is no such thing as a heating element in the coolant level sensor. There is no pocket of air for heating or cooling and no readings are taken, it is a simple magnetic float switch that operates around the outside of the tube in which the sensor sits. This is fitted to ALL the E46 models."

Later, in post #32, valvtronicdude explains further:
"The coolant [level] temp sensor is a magnetic switch. if you remove the sensor no coolant comes out right it's a dry sensor. there is a float inside the jug with a magnet in it. when the coolant level is low enough the float sits down over the glass bulb of the sensor and the magnet of the float causes two contacts to touch each other inside the sensor and cause a complete circuit. The instrument cluster sees this complete circuit and then knows the coolant level is low."

The last post gives the switch a name:
"To provide enough warning time for coolant loss, the sensor needs to be located part way up the tank rather than at the bottom of the tank. By the time the sensor contact gets made at the bottom of the tank, all coolant has drained out.

Also for those interested, the proper term for magnetically activated switch/sensor is call a Reed switch/sensor ."

To better flesh out the cooling system autopsy record, even down to the little (but common) details ... one needs to be VERY CAREFUL not only with the radiator nipple but with the two tabs on the radiator itself that hold the nipple in place.

See this extensive pictorial thread which shows how to gracefully remove the nipple intact:
- WANTED: An ingenious method of removing radiator nipple

And, see this thread if you break the nipple, how to at least gracefully remove the half that is stuck inside the radiator:
- Nipple broken in half -- radiator vent hose fitting

Originally Posted by cn90

good reading on Fan Clutch with cutaway view:
http://www.aa1car.com/library/cooling_fan_clutch.htm

When I get a round tuit for my new Dremel tool, I'm gonna see if I can cut open my viscous fan clutch.

Until then, this description will have to suffice by way of autopsy:
- Squeak squeak goes the fan clutch

fan_clutch_troubleshooting.pdf (449.0 KB, 15 views)

I was able to use the old radiator to test an ingenious method of removing the radiator nipple intact as mentioned in this old thread.

"You will note that the nipple has a tri-pronged end that gets pushed into the radiator. It clips into place. In order to take out the "old" one, I put a 10mm socket into the upper radiator hose opening, and pushed it on to the "clipped" end to push it closed enough so that I could pry out the old one. I TIED A STRING TO THE SOCKET SO THAT IF I DROPPED THE SOCKET, IT WOULDN'T END UP AT THE BOTTOM OF THE RADIATOR. This worked flawlessly."

While a 9mm socket worked much better than a 10mm socket, the whole operation would be problematic because it has to be done arthroscopically through the upper radiator hose hole ...

But at least I proved over here that it theoretically is possible to non-destructively remove the radiator nipple using this method:
- An ingenious method of removing radiator nipple

For the record, people who ask what seals the upper and lower radiator hoses, will find this picture useful.

It's this large O-ring (at each end) which does the sealing.

For the record, JimLev noticed a difference in quality between the Behr crimps and the Nissen crimps over in this thread:
- E39 (1997 - 2003) > Replacement Radiator

Here are his pictures.

It would be nice if someone else runs a comparison of the crimp quality (unfortunately, I didn't even 'think' to look for that when I did my Behr->Nissens radiator replacement).

If this is true, then the recommendation to go with 'either' Nissens or Behr might have to change!

Originally Posted by bluebee

Here's a picture of the float mechanism showing the magnetic disc about in the center of that float. That magnetic disc, when it settles over the tip of the coolant level sensor, magnetically triggers "something" somehow.

How do you think the level sensor works when triggered magnetically?]

Hall Effect

http://en.wikipedia.org/wiki/Hall_effect_sensor

I would like to know what the best price is for a new radiator, considering the several online vendors that handle them.

Then I may offer the same radiator but all aluminum. I know I beat the pants off the Zionsville unit.

If anyone is interested please let me know.

For the record, Neversaynever asked today how the fan clutch works:
- E39 (1997 - 2003) > Coolant fan clutch - How does it work?

It would be nice if someone has the tools/time to slice one of ours open and post pictures here.

For the record, there are some nice bottoms-up photos of the Behr expansion tank in cn90's thread:
- E39 (1997 - 2003) > Anyone seen a defective Behr Reservoir before (2002 530i)

THIS FIRST HOLE IS CLEARLY UNOBSTRUCTED:


THIS SECOND HOLE IS ALSO UNOBSTRUCTED (SEE THE WHITISH STICK I POKED IN THE BOTTOM FOR THE CAMERA TO SEE DOWN TO):


ABOUT THE ONLY THING IN THE WAY IS THE 'MYSTERIOUS SLIDER' AS CAN BE SEEN BY THIS SIDE VIEW:

It appears that folks don't care about this thread.

Originally Posted by franka

It appears that folks don't care about this thread.

That's fine. I think people just don't know the answer to the questions (e.g., what's the black float for in the expansion tank).

However, the thread is still useful. For example, I use it for reference all the time, especially the pictures (which show how the radiator is built).

In fact, I used the pictures to illustrate a point, just now, over here:
- Griffin aluminum radiator????

In that thread, a cheaper-than-zionsville radiator was suggested. Seems to me, the Behr/Nissens is already 'all aluminum' except for the two plastic crimp-on side panels ... so ... my thinking goes that 'someone' should be able to make a cost-effective set of aluminum crimp-on side panels.

Originally Posted by bluebee

In that thread, a cheaper-than-zionsville radiator was suggested. Seems to me, the Behr/Nissens is already 'all aluminum' except for the two plastic crimp-on side panels ... so ... my thinking goes that 'someone' should be able to make a cost-effective set of aluminum crimp-on side panels.

A few posts back I asked for prices of new radiators because I wanted to compare them to having a local radiator shop build one or two in all aluminum.

For example I have one out of my 540 that I could give them as an model / example to use to quote. Maybe even just put new aluminum tanks on it.

Originally Posted by franka

Maybe even just put new aluminum tanks on it.

I agree. It 'should' be feasible (and far less than Zionsville), to simply crimp on aluminum side tanks to the otherwise all-aluminum stock radiators!

Originally Posted by bluebee

BB could you clarify your statement in the picture above. Does the Aux pump (latent heat pump), pump coolant INTO the reservoir or OUT of the reservoir?

In other words what is the direction of flow through the reservoir?

Originally Posted by *****zo

In other words what is the direction of flow through the reservoir?

I don't know what the direction is of the two hoses on the bottom of the expansion tank (note: Older E39s seem to only have one hose).

As for that little bleed hole at the TOP of the expansion tank ... when 'just' my auxiliary pump was working (for the bleeding procedure), the fluid (IIRC) was spurting INTO the expansion tank through that little hole in the filler neck.

BTW, I really don't know what I'm talking about ... that's why I ASK here for someone to show us how the expansion tank works ... because I just don't know!

For the record, there have been quite a few reports of defective Behr China expansion tanks recently:
- Anyone seen a defective Behr Reservoir before (2002 530i)

In fact, just today was another report:
- E39 (1997 - 2003) > Genuine BMW Expansion Tank

Here is the defective Behr China and BMW-bought expansion tank from that post today, side by side.

Originally Posted by bluebee

How do you think this electrical level sensor works anyway?

I don't know how this triggers the low coolant light. Do you?

Someone earlier mentioned a hall effect sensor, but I'd be more inclined to think that it's a reed switch.

http://en.wikipedia.org/wiki/Reed_switch

Much cheaper than hall effect sensors.

Originally Posted by windsmith

I'd be more inclined to think that it's a reed switch

Over in post #31 above, we determined how the level sensor worked with the white float, reed switch, and magnet. It's pretty obvious just by looking at it.

The white float level sensing isn't the problem.

The enigma is how the BLACK float system works. This is the enigmatic system in the other chamber, walled off from the level sensing chamber.

Updated annotations ...