540i

Okay, before I start I just want to mention that I did a search and didn't find anything related to this.

When I was topping off my coolant, I noticed that the coolant measuring stick was missing, which it wasn't a few months ago. After a few days I started getting "low coolant" messages. I kept topping it off until last weekend when I decided to fix the problem. I noticed that the small hose at the top that goes from the coolant reservoir to the radiator had a small leak, so I replaced it. They didn't have the exact same part but advanced autoparts had an identical plastic hose for a different vehicle, so I used that one. I didn't have any issues until...

Fast forward to Tuesday, as I was driving down the highway, I heard a pop and a "low coolant" message appeared. I pulled over popped the hood and saw coolant everywhere. Looked a little closer and realize that the big hose running from the radiator to the engine had come off. I put it back on and filled the car up with coolant so that I could limp to autozone to get a new clamp. I figured the clamp wasn't strong enough. Once I replaced the clamp, I drove for about 2-3 miles (coolant refilled) and it popped out again. While driving I noticed that there was no hot air coming through the vents.

I decided to get the car towed, which they did to the nearest "mechanic." They said the radiator and the thermostat needed to be replaced, and quoted me $1300. They said $700 for parts alone, which didn't make sense. An OEM radiator can be had for $250 and thermostat for $100. I searched and figure that I can replace the thermostat myself, which I ordered yesterday. Called my local BMW indyshop and he said he can replace the radiator for $300, parts and labor.

My question is, could it be that the missing dip stick somehow went through the system, causing all this? Could it be the new hose that I had replaced over the weekend?

Rizbel

For my car, there is a proper coolant filling procedure to do to prevent getting air in the system (ignition on without starting the car and heater on with blower at low before pouring 50/50 mixture of BMW coolant and distilled water). If you're not getting hot air inside the car it could mean coolant is not getting to the heater system. Your hunch about the dipstick might be correct; mine just disintegrated and crumbled to pieces due to old age. Good luck.

BimmerFan52

1. Usually when the coolant measuring stick "disappears" it means the plastic of the coolant reservoir tank has reached the end of its life. The next event will be the tank splitting.

2. Vent tube is the same issue. BMW used a plastic tube with brass inserts. Age and heat eventually degrades the plastic. I replaced the plastic tube with 5/16" copper for a permanent fix that was only $5.

3. Unlikely. It probably just crumbled and settled to the bottom of the tank.

540i

Thanks guys. I'm trying to figure out if anything else might be causing the hose to be popping off before I replace my radiator...

Gilgorm

My 2 cents from a non-mechanic. The hose popping off is caused by the high pressure that is building up and the heat has nowhere to go. It would seem that the rad is either clogged or coolant can't enter the rad to cool down.
It would be like plugging a kettle. It will burst at its weakest link as the heat builds up.
The rad or hoses to the rad could be plugged. Depending on your mileage you may be in line for a cooling system overall. The lack of cabin heat is caused by air in the system(as suggested already) OR a plugged heater core. The heater core (on its own) shouldn't be responsible for the popping of the hoses.
As I said, my 2 cents.
GL

540i

Thanks, that makes a lot of sense. But on the other hand I lose all the coolant when the hose pops off so there is coolant coming through the radiator. Maybe a coolant system flush would help or something is clogging the coolant after it leaves the radiator.

roskinc

the other day i saw my coolant level stick had disappeared too! and i know for a FACT it was their in the morning because i got low coolant warning too, and i checked it and it seemed fine, it was the only time i got that error, and i figure i might have done something when i was cleaning my engine bay the day before. i don't notice a radiator leak, but im going to take that disappearing level stick as a warning to replace the expansion tank, its not that expensive and its not that hard from what i can see and what ive read online.

turboawd

i thought the big hoses used metal clips to hold them on, not clamps. or is that only where they connect to the pump/engine?

if its popping off the radiator, did you see if maybe part of the neck broke off? piece would be stuck in hose.

what engine do you have?

540i

Thanks guys. This is my course of action:

1. While the thermostat is being shipped, check the top hose running by the hood latch that I replaced last weekend since the problems started then

2. Replace the thermostat

3. Replace the radiator - if the two above don't solve the problem. I already found a Mechanic who would do this for $250, including parts.

540i

So, took out the thermostat today and tested it in boiling water. It never opened up, so hopefully that will be the end of the problems. If not, radiator replacement it is.