2000 E46 Overheating - BMW Forum

dslim88 · 07-12-2008, 04:10 PM

My girlfriends 2000 328ci expansion tank exploded, so I replaced it and filled the coolant back to proprer levels. I did my best to get the air out of the system, but the car still overheats. The car seems to only overheat when driving. I let it idle for 10 minutes and it was fine, but less than a mile driving at 30 mph and it went to red. I noticed that the radiator fan is not coming on even when the A/C is on. Radiator is only a year old and system doesn't have any leaks. So my questions are...
How do I test the water pump?
How do I test the fan?
What is the best way to get air out of the system?
And what other issues could be causing this?

Thanks for all the help...I'm new to fixing Bimmers!

Numark318i · 07-12-2008, 08:23 PM

check that the fan is plugged in. (assuming its an automatic, the manual's have just one fan which is clutch operated.

If water pump is bad it would usually be leaking water out. umm otherwise...im not to sure. when our expansion tank went it was caused by a faulty water pump and thermostat.

dslim88 · 07-12-2008, 11:05 PM

It's a manual...sorry I should have mentioned that. Thanks for the info.

Classic320i · 07-12-2008, 11:11 PM

I am not sure if your engine has a bleeder valve at its highest point, some times you have to jackup the front of the car high up purge the system. cannot stress how important to get all the air out! 2. after this process and if condition still exist! 2. if it was a water pump or stuck thermosatic it would over heat in within a few mins. 3. coolant sensor/ fan switch is mounted high up on the enigne where the air pocket is it would never come on. reason to make sure all air is purged out.

dslim88 · 07-13-2008, 09:02 AM

It does have a bleeding screw at the top right above the expansion tank. I will try that today and see if it resolves the issue. Thanks!

dslim88 · 07-14-2008, 03:52 PM

Thanks for info...I got all the air out and it is no longer overheating, at least for the time being. Now I'm just curious as to why the expansion tank failed.
Thanks again you saved me lots of $$$.

Numark318i · 07-14-2008, 04:37 PM

Quote:

Originally Posted by dslim88

Thanks for info...I got all the air out and it is no longer overheating, at least for the time being. Now I'm just curious as to why the expansion tank failed.
Thanks again you saved me lots of $$$.

might have worn out.

check the radiator hoses to make sure they are still in good condition while your at it.

TRuckee · 07-14-2008, 11:25 PM

Had the same thing happen with my 2000 323i. The plastic just fails after repeated hot/cold cycles. Mine had a crack from (almost) top to bottom. And these things are kinda hard to purge of air, I'd agree. Kudos for sticking with it & success! These cars are not easy/simple to DIY, but it's possible and practical.

enginesavers · 07-23-2008, 02:45 PM

You may want to check out this site. It can save you thousands for the life of your car and keep your baby running.

Welcome To The Engine Savers Website

dslim88 · 07-23-2008, 07:31 PM

And how does this help anwser my questions? I want help and info, not a lame product. Please keep stuff like this off this website, thanks.

enginesavers · 07-23-2008, 11:11 PM

Quote:

Originally Posted by dslim88

And how does this help anwser my questions? I want help and info, not a lame product. Please keep stuff like this off this website, thanks.

Sorry, I thought this may be of interest to you as it should be with anyone with overheating issues. Overheating is the worst thing you can do to your engine and can ruin your engine in a matter of minutes costing you thousands.

I have this device install in my 540i and it works as good as it says it does. It makes you engine impossible to overheat, thus protecting you engine from major repair forever. I drained my coolant and ran my engine until it kicked in and stopped my engine after 60 seconds of audible and visual alarms. It f--n works. Otherwise you could end up like the guy in this article.

<http://sandiegobmw.wordpress.com/2008/06/06/the-cooling-system-killing-your-bmw/>

Anyway, back to your problem, see if you have a bleeder screw next to your coolant filler cap. Undo the bleeder screw (small plug with a cross for a slot screwdriver). Add coolant only when cold and only on a flat surface until it comes out the hole with no bubbles. Screw on both caps and you should be good. Sometimes your radiator passages can be clogged (if it is not new) and they need to "rodded" out by a radiator shop. The get fouled from the bottom up and will slowly reduce the effectiveness of your radiator. One thing, never use tap water with your coolant. It is full of dissolved minerals and overtime with clog all your water passages. Use any kind of filtered water. Evian if your anal.