westsidebalto

Seems like I've joined a crowd with my broken coolant stick...

Two weeks ago I got my first "Low Coolant" warning on my 04 545. It would go away if I started the car warm, so I assumed it was related to the bitter cold weather. Nonetheless I topped off the fluid a day or two later. Problem solved.

....then yesterday the warning came on again. Today I finally opened the expansion tank only to find that the stick had broken in two. I was able to pull most of the stick out, but the top inch sunk underneath the float. From what I've read, it's time to replace the tank since the stick is non-replaceable. Until I can do that I have two questions:

1) Is the top inch of the stick sitting in the bottom of the tank a hazard? Should I not drive until I can fish it out or replace the tank? Obviously I don't want this thing getting sucked down the line.

2) I have no noticeable coolant leaks on my garage floor (or anywhere else). Should I still be looking for leaks? Time to take it to my indy shop? I should also point out that I can't tell if coolant has leaked by the coolant level alone, since the stick broke.

...I'm fearful that it's my time to pay the piper, since I've dodged any problems to date.

turboawd

i'd guess the worst that could happen is the piece of stick flows towards the radiator and settles on the bottom, which shouldnt cause any issues.
but i'd change the tank asap, as they are known to crack open too.

BimmerFan52

Unless the float stick was abused by jamming something into the reservoir, the stick broke because the plastic has become brittle with age and repeated heat cycles. Many times the coolant reservoir tank fails right around the same time the float stick does.

Your car is sending you a warning. You need to replace the coolant reservoir immediately. You also need to assess the rest of the coolant system. Preventive maintenance of the cooling system is the cheapest insurance you can buy on a 545i. Water pump, thermostat, hoses, vent tube and serpentine belt all should be changed if they are original. Aluminum BMW engines have almost zero tolerance for overheating. If you are caught where you can't pull over immediately and turn the engine off you could do thousands of dollars in damage. At the very least you will pay to have it towed, and if out of town you are at the mercy of who ever is available and whatever they want to charge you in labor and parts.

If you can DIY, replacing the above mentioned parts is a 4-6 hour job, or if you can't do the work yourself use your trusted indie. You will save money in the long run by doing the PM now.

Regarding the stick, there is almost no chance the stick can get into the radiator. Not only does the vent tube take sharp turns, but under the fan shroud the vent tube becomes a very small diameter plastic tube with an ID of around 3/16".

The function of the coolant reservoir is to allow coolant to overflow the closed system when the engine is turned off and the coolant is no longer circulating. Because the coolant is no longer moving and being cooled by air flowing through the radiator or by the fan, the coolant sitting in the block experiences "heat soak" whereby the hot block begins to heat the coolant in the block to much higher temperatures than the coolant experiences during running of the engine. This increases the pressure in the sealed coolant system and pushes coolant to the top of the radiator, where it slowly flows through the vent tube and into the coolant reservoir. There is extra room in the coolant reservoir past the level measured by the stick in the full position to accommodate extra coolant. After the "heat soak" period of usually 3-10 minutes the coolant temperature and system pressure slowly begins to drop. As the system pressure drops over several hours a slight vacuum is formed and coolant is very slowly drawn out of the reservoir and back into the radiator. Because this flow is very slow it would not be any where near enough to "suck" the piece of stick from the bottom of the reservoir and into the radiator.

westsidebalto

Thanks guys.

It seems like I'm driving on the spare tire of time. I shall heed the warning. Will start ordering parts today.

That was my biggest fear, as it would totally imobilize my vehicle. It would be nice to keep driving it in-town until I can replace the parts. No out of town trips for a while...

I topped off last night (maybe half cup or so) and no warning this morning.

Margal

It'is year now I've been driving my car with that broken coolant measure stick.
I do not think it will hurt anything but as advised by other members would be good if you take care of it soon.

best1

Mine has been broken for 2 years. it is on my list of things to fix, but no leaks

westsidebalto

Seems like stick itself is not really an issue, but I may have an unrelated leak. It's kind of funny that the stick is dual-purpose: measures coolant level and measures lifespan of the tank it's in.

540i

The same thing happened to me. My stick was missing and I had a leak somewhere. I kept refilling the coolant until I decided to tackle the problem.

I located the leak but also replaced the thermostat. After I replaced it I located a second leak in the upper hose. A AAA shop wanted to charge me $1300 to replace the thermostat, radiator and upper hose. I did the upper hose and thermostat myself. Total cost - less than $100 including coolant.

Another note, if you can't locate a leak, you may have a bad head gasket Check your exhaust to see if you see more (white) smoke than you're used to.

Symptoms of a Blown Head Gasket | eHow.com

BimmerFan52

As several have pointed out, you can drive with a broken coolant reservoir level indicator stick. It will not hurt anything by itself, but one point of caution is to insure that you do not overfill the reservoir without the aid of the stick to provide a correct level.

If the reservoir is filled to the top, when the engine is turned off there will be no room for coolant expansion and the weakest point in your system can rupture (often the vent tube or the o-ring on the temperature sensor on the lower hose for 545s).

advancedlogic

Welcome to the 545i club. Phantom missing coolant? Check the following:

Small diameter plastic coolant pipe on top of radiator (You will have to remove the metal plate. This tube gets very brittle with age and will fail)

head coolant hoses- near the front of the heads, under the intake manifold. Prone to breakage

The nasty and dreaded valley pan and coolant transfer pipe - would have required engine removal to replace. Now, an expandable pipe is available. Cut the old one in half, remove, and install new pipe. Tighten as directed. Install new valley pan and gasket...sounds easy? That bastard child of an intake must be removed first.

Best of luck to you. Keep us posted on the outcome!