E 46 overheating ... again. - BMW Forum

TRuckee · 05-12-2007, 10:01 PM

I was almost home today when the "low coolant" light came on... by the time I got it in the garage, it was steaming from under the hood and, indeed, low on coolant. I topped it off and took it out for a short ride around the block(s) and it was doing the same when I got back home. Since my earlier problem with the cooling system ( leakng expansion tank), I've had a SMALL leak/ loss of coolant, but have required only an occosional topping off, maybe 4-6 oz. per 1000 miles. When I took my first look under the hood , I could see steam coming out of what I would call the upper radiator hose. Is this because this is the (by design) weak link or is this hose failing under pressure? I question the BMW method of making these connections. <OH, THE HERESY!!!> While the clips that secure these hoses are esy to install, are they as tight as ordinary hose clamps? What does the comunity think I should check first?

bimmerguy82 · 05-13-2007, 02:49 AM

when was the last time you changed all your hoses? when mine got old they started to get hair-line cracks one by one. this caused an annoying coolant leak over a period of 2 months until i ended up changing every hose. also check your hose clamps. i use the ones that you can tighten with a flathead screwdriver. hope this helps.

TRuckee · 05-18-2007, 10:31 PM

Well, Ive never changed any of the hoses and,having bought the car used, don't know if any have ever been changed. I do wonder about the integrity of the hose connections. BWM's system of o-ring sealed, clip secured hoses doesn't seem to be failure-proof. I'll take a look to see if I could add clamps; when it overheated, I could see steam escaping at one of the connections.
I wonder if my overheating didn't occur because of low coolant level, which could be the result of a small system leak. I can often get a whiff of antifreeze when the car is stopped while driving around town.

bimmerguy82 · 05-19-2007, 04:02 PM

Hey you can try filling up your coolant, park in your driveway, and let your car run at idle for 10-15 mins and watch for any leaks. put a piece of cardboard under your front end to catch any coolant.

GRIDLOCK · 05-25-2007, 05:58 PM

Check your expansion tank, hairline cracks are very common.

TRuckee · 06-08-2007, 10:52 PM

I replaced the expansion tank about a year ago and it did have a crack that let coolant escape. And low coolant level let the thing overheat.
This time the upper radiator hose was leaking where it connects to the radiator. I probably could have just replaced the o-ring at that connection and fixed the problem, but I replaced the complete hose. I've had no further problem .

bodyman · 06-09-2007, 03:08 AM

Could be your water pump. They have a plastic impeller that can sheer off and your engine will overheat. This would cause increased pressure in your cooling system, pushing the plastic hose connectors apart enough to leak, and loose coolant. It only takes overheating the engine once to make it break off. Its quite a common problem with the inline six cylinder. There are quality replacement pumps with a metal impeller available.

TRuckee · 06-09-2007, 12:44 PM

The first time I had an onerheating incident, I thought it was probably due to a failed plastic water pump impeller. I removed the water pump and confirmed that it had metal.