Fan clutch appears to be the culprit (archive)

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Neal.- I did the newspaper test and the fan stopped immediately. However, I also ran the car idling and the auxiliary fan did not kick as the temp began to rise. It did though, when I turned the AC on (I did the AC test first).

Is it conceivable that there may be also a fault in the Aux fan system? As you mentioned the aux. fan should help keep the temp. down.

The Bentley manual states that there are two temp. switches and relays that control the Aux fan, so I am assuming that one of the switches may be bad since the aux fan does not kick in when the temp begins to rise?

BTW- Nice write up on the accident and subsequent procedures to get the car back in shape. I am glad there were no serious injuries.

Alex.- Did you do the work on the fan clutch yoursel? If so, how much of a hassle? Any tips?

My first suspect would be fan clutch. To test, bring the car to temp and insert rolled newspaper into fan blades. If the fan stops, the clutch is bad. If the fan continues to beat on the paper, the clutch is good.

Does the E28 M5 have an auxilliary fan? If so, it should come on when the coolant temp goes over a certain temp or if you switch the AC on. If the fan clutch is bad, but the aux fan is working (they are often jammed because the seldom come on), the aux fan should be able to control the temp to a large extent.

After an accident, I drove my E30 88 iS 120 miles home with the fan jammed into the radiator. The car did not pass the normal temp mark as long as I stayed over 55mph in the OH winter. The fan clutch was completely destroyed as the fan was held in place while the pulley was being turned behind it, but I saved the car (still have it 60k miles later) and the cost of tow (grad school).

Today at the Bimmerfest I encountered a bit of overheating problem. As a preparation for the spirited drive to Santa Barbara, I topped the coolant level this morning before we head out to meet the caravans. By the time we arrived in the San Fernando Valley-some 45-50 miles north-to meet the LA guys-as we parked-a young guy came up to me and said, man, I love your car and I hate to break out the bad news-your car is leaking coolant-darn, that�s all I need�in front of all these 2002�s M3s.
Where in the world is itleaking from? At first I was afraid there was something seriously wrong and we may needed to turn back home; however, it turned out it was just the overflow, as soon as the overflow reservoir finished dumping excess??, and got just below the �max� level (the same level it was before I topped it off), it stopped burping.

The rest of the way to SB was fine, but, in stopping and waiting for cars to catch up to the caravan on the side of the freeway (sitting idling) the temp began to rise way above normal (outside temp. in the low 70s, AC was off). As soon as we got going, the temp came down to normal levels-below the half way mark on the temp gauge.

After the show there was a ride scheduled to drive further north on the 101, a very scenic drive, and then returning back to SB on the 154. As we began the drive, I noticed the temp began to rise on steep hills, and decided to turn back and go home (some 150 miles south), heck am not going to risk it, besides, them kids those M3s were asking for a BIG ticket, CHP patrols by aircraft that area, and can easily spot a few of the dozens, of bimmers getting a little out hand.

On the way back home-sweet-home, in LA freeway system�s fashion (Saturday 5PM) the traffic coming back was brutal! stop-and-go, stop-and-go, stop... for miles, from Thousand Oaks on the 101 to just past LAX on the 405 south (on the way up to Santa Barbara at 7AM on the weekend, that�s when you can let it rip :-)

So� no overheating problems on stop-and-go traffic, no over heating on, err.. 85-90+ MPH speeds, but signs of overheating on steep hills, and serious overheating idling�

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