Was Fine, Then Temp Redlined... - BMW Forum

Casey3561 · 06-09-2005, 07:43 PM

Today, I stopped by the grocery store to pick up some junk for dinner. When I parked it, the temp gauge was top dead center- precisely halfway. Get in, idle for a second while I get settled, pull forward a few feet into a faraway spot to check something, and the dang temp gauge nearly redlined. Check Engine light and all.

After much cursing, I popped the hood and let it cool a little. Checked the radiator- normal. Checked the fault codes- normal. Opened the radiator and peered in, fluid nice and clean. Started it, fluid ran out, verifying that the water pump is working. So that leaves me thinking.

Is it the thermostat, which would be cheap, or the fan clutch, which would be a good bit worse? How bad will I get beat up on these? Could it be something simple like the PO not flushing the radiator, and a flush and fill fixes?

dvmotorsports · 06-09-2005, 08:09 PM

Quote:

Originally posted by Casey3561@Jun 9 2005, 05:43 PM
Today, I stopped by the grocery store to pick up some junk for dinner. When I parked it, the temp gauge was top dead center- precisely halfway. Get in, idle for a second while I get settled, pull forward a few feet into a faraway spot to check something, and the dang temp gauge nearly redlined. Check Engine light and all.

After much cursing, I popped the hood and let it cool a little. Checked the radiator- normal. Checked the fault codes- normal. Opened the radiator and peered in, fluid nice and clean. Started it, fluid ran out, verifying that the water pump is working. So that leaves me thinking.

Is it the thermostat, which would be cheap, or the fan clutch, which would be a good bit worse? How bad will I get beat up on these? Could it be something simple like the PO not flushing the radiator, and a flush and fill fixes?

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I have the same exact porblem right now. I think it is just the Thermostat. I'll let you know alittle more tommorow after the repair.

Ljk619 · 06-09-2005, 08:21 PM

After you've driven your car for a bit then parked it is normal for the temp. to go up pas the middle mark reason being, unless you've parked your car for hours on end, then chances are your engine hasn't cooled that much, and much of the heat is just sitting under the hood due to no air passing through like when you're driving. once you get the car moving to cruising speed it should go down. But if the temperature gauge is going past about 4/5 of the way then you got a problem.

Does your fan come on when the temp starts to rise past 3/4?

loftygoals · 06-10-2005, 12:18 AM

It's most likely the fan clutch. They are a fairly common point of failure. If you were close to over heating, make sure you have the entire cooling system checked out. A lot of pressure build up in the system during an over heat. Check the thermostat housing as well. The stock ones are plastic and have a tendency to crack under stress.

-bj

bad man working · 06-10-2005, 06:34 AM

The reason the gauge jump up so quickly is the gauge electronically damped to keep the needle in the middle as the thermostat and fan cut in and out When you stop for a short time the engine temp goes up because there’s nothing to cool it. Your engine must have been on the edge of the damping limit when you stopped so when you started of again it went into the red. As to the fault that causing it to overheat go for the thermostat first, they are common and M43 engine have problems with head gaskets normally high mileage for the fan coupling

Gator · 06-10-2005, 08:04 AM

It could also be that the electric fan didn't kick in as the temp started to rise. When the car stopped the temp would rise unless the electric fan kicked in. Also the electric fan does most of the cooling when the car is idling or at slow speed. If thefan doesn't start it's most likely the temp sensor screwed into the bottom of the radiator.

Bear · 06-10-2005, 08:14 AM

What I discovered with my 750 was that even with a good (new) aux fan switch that in traffic in S.W. Florida, and aux fan at high speed, if the viscous fan clutch is bad, the aux fan will not save you.

Casey3561 · 06-10-2005, 01:01 PM

Well, just heard back...

Thermostat and fan clutch. $400. Not sure on a water pump, he hasn't checked yet, but I'm fairly sure it would have been swapped for a metal impeller at 140K, right?

dvmotorsports · 06-10-2005, 09:22 PM

Mine wasn't the thermostat either. But I think it's the AC compressor.

Casey3561 · 06-10-2005, 10:06 PM

Water pump, thank God, was changed previously to a metal impeller.