I got a phone call from a guy once in regard to his 2002 3-series.  Here’s how it went:

Guy – ‘Hi, yesterday I was driving on the freeway and all of a sudden I lost my power steering, the battery light went on and then I noticed that the temperature gauge was in the red.  So I pulled it over and had it towed to my house and I’d like to tow it over to you to see what is wrong’

Me – ‘Well, what most likely happened is that the water pump failed and you lost the belt that operates your power steering and alternator.  Unfortunately, with the car over-heating, you are most likely going to need a new engine in the car as those engines cannot survive an overheating without major damage.’

Guy – ‘Well, it runs fine except that in the morning it runs pretty rough for about 30 seconds and then it’s really smooth.’

Me – ‘You are definitely going to need an engine, but feel free to tow it in.’

This is the number one killer of BMWs built after 1999.  The Cooling System.

The Problem:

In every BMW there is a large amount of plastic components through which coolant flows in order to keep the engine at it’s normal operating temperature.  In the old days, coolant would travel through the engine via rubber hoses and metal radiators and thermostats.  Today the radiator has an aluminum center, with the side tanks made of plastic.  The water pumps are partially plastic in many BMWs, as are the ends of the coolant hoses, the thermostat housing and the coolant tank.  Unfortunately the plastic has a limited life span as each time the car warms up and cools down the plastic gets weaker and weaker.  When it fails, the damage is usually catastrophic.  With an operating temperature of 108-112C, the engine is on the brink of boiling but won’t as the coolant is under pressure.  When one of these components fails, the pressure is released and the engine boils itself to death.

The Solution:

With every BMW we service in San Diego, we educated our customers to have all of these components replaced at either 70-75k miles or when the car reaches about 7 years old.  The only warning you might get is your check engine light will appear due to a failed thermostat.  Changing out these components before they fail is your only protection from winding up like the guy on the phone.

What needs to be done??  With any repair, your goal should be to get the most bang for your buck and only pay for labor once.  You don’t want to pay parts and labor for a water pump, and then pay parts and labor for a thermostat.  The labor process is the same for both, so change both and pay the labor once, make sense?  What you’ll need to change is the following:

Radiator, water pump, thermostat, cooling reservoir, upper and lower radiator hoses, all belts and belt tensioners.  There are a few other tid bits as well and any shop familiar with BMWs should be providing this service to its customers on a daily basis.  Back to the the phone call . . .

So the guy doesn’t take my advice, but feels compelled to keep me up to date on what has become his crusade to save the engine.  He took the car to a local machine shop to have them remove the cylinder head, which of course was cracked and now worthless.  So he gets a used head, has the machine shop refurbish it and then has the car towed to us to install the new head.  At this point he is now up to about $5500 in parts and machine shop labor, still with no running car.  He also had the machine shop address the block, or bottom-end of the engine, to allow the head to be re-applied.

So . . . we install the cylinder head, as well as all the new cooling components that should have been purchased in the first place, all at the customer’s request.  When you install a cylinder head, the cylinder head bolts need to be very tight and there is a specific procedure to tighten them.  In the final tightening sequence, the aluminum in the block crumbled around the cylinder head bolts.  Game Over.  I called the customer and let him know that he still needs an engine as I had informed him 3 weeks prior.  By the way, the machine shop told him this as well before they did all the work for him that he insisted on.

In the end, the car was towed away from our shop, the guy had spent a total of about $7600 on saving this car and he was still at the same point he was when he pulled the car off the freeway to have it towed.  It’s actually a sad story and extremely frustrating to the customer.  Since then I have replaced about a dozen engines, most of the cars being less than 8 years old and with less than 100k miles.  Don’t let this happen to you!  Get your cooling system changed out before it cashes you out.

Chris Keefer

Independent Motorcars

5836 Autoport Mall

San Diego CA 92121