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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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Old 01-26-2018, 08:55 AM
Erik1222 Erik1222 is offline
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Mein Auto: 1998 BMW 528
1998 528i overheating

1998 BMW 528i
So yesterday on my way to work I noticed that the car was indicating that it was overheating. I stopped to the side and let it cool down and checked the under the hood. I noticed that there was a puddle of water (I believe) in the floor. Saw that it was coming from the loose radiator cap that wasn't tight. I then tightened the cap and turn the car on and decided to drive and after 10 minutes it began to overheat again and the check engine light lit up. (decided to not run the car any further) Not sure what to do? Thinking about adding water/coolant due to the loss of it. Any suggestions what I should do first? Thanks

Last edited by Erik1222; 01-26-2018 at 08:56 AM. Reason: Mention car
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Old 01-26-2018, 09:59 AM
effduration effduration is offline
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Mein Auto: '99 528i, '03 530i '06 X5
Overheating is unfortunately quite common on these cars and usually occurs because some part of the cooling system (which has a lot of plastic in it) breaks or cracks. Your car has an iron block and an aluminum head. If the car is run for even 60 seconds when overheated it can result in a warped head (aluminum warps easily in response to heat) which can cause all sorts of problems.

As a first step, I suggest you go get a gallon of distilled water and fill/bleed your cooling system per the proper BMW "cold" bleed procedure which you can find online. Then run the car up to operating temp and see if the needle moves away from center - toward the red - and shut it down if it does.

If it doesn't overheat, I would suggest you look for leaks at operating temp in all parts of the cooling system. I would also find somebody with a code reader that reads BMW codes (not autozone) and that will connect to your round diagnostic connector.

If you are not mechanically inclined find a good independent mechanic familiar with BMWs to do it for you.
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Old 01-26-2018, 12:14 PM
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Wgosma Wgosma is offline
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Mein Auto: 2012 X3 (2.8i)
If you’re planning to troubleshoot this yourself I strongly suggest you learn how to put the instrument cluster into “test mode”, then use test #7 to display engine temperature digitally in real time.

The analog temp gauge is electronically buffered, so by the time that gauge needle begins to move towards 1pm position the motor is already quite hot.
As already stated these motors do not handle overheat well at all- never run the motor if it’s showing signs of overheat; more than a few owners have ruined their motors by doing so-
Good luck/Bill

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Bill / 2012 X3
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Old 01-26-2018, 12:55 PM
djbecker djbecker is offline
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Mein Auto: e30,e34,Z3,e39
How long have you owned the car?

I see that you are a new poster. If you just bought the car, you bought it with an existing head or head gasket failure. It's the most common story for new posters with cooling system problems. If any part of the cooling system was just replaced, the seller replaced just enough to unload the car.

If not, what recent service have you done?

It's likely that the loose radiator cap is a symptom of overheating, rather than the cause.

"Air in the system" is only a problem immediately after refilling with coolant. It will quickly work its way out on its own, and will not return unless there is a problem. Ignore the people that say "bleed the system".

The two most likely problems are the water pump and thermostat. I have an extensive collection of both, both BMW branded and aftermarket. They aren't too expensive to replace, but unless you stop immediately you will end up with a head failure.

If the water pump fails, the thermostat might have overheated and subsequently fail as well. If your thermostat failed and you don't know when the pump was last replaced, change it.

Another common problem is the coolant reservoir. it's usually obvious when that splits, so I doubt that's your problem.

Last edited by djbecker; 01-26-2018 at 01:05 PM.
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