High Temperature

[Silverado]

Driving home in traffic yesterday temperature rose to red and warning light came on while stopped. Couldn't pull in immediately but turned heat full on and in a break of traffic was able to accerate and temperature immediately fell to normal position.
Coolant/Radiator level was not low enough to cause this. Any ideas before I meltdown?

'97 E39

[EuphoriaII]

Sounds like the thermostat is stuck in the closed position. Either that or the water pump died but I am betting on the thermostat.

[brokenbat]

go for the thermostat- I'm going to get a spare in the next day or 2 maybe get a water pump to have on the shelf as well. About a 2 hour job from what I can tell. Would have been nice to stick the thermo someplace eaiser to get to. '85 318 was like replacing upper rad hose took about 5 minutes this is more involved. Experience says you will have cooling problems every 60.000. I have 56,000 now so I'm getting the paranoia.

Another thing to check is the thermo fan switch which turns on the aux fans when the ac is on or if it gets a signal from the radiator. If this is bad the fan won't come on in traffic which is what happened to you and just getting moving again solved the problem. I wired my old one in the "fans on all the time" by jumping the wires on the sensor. It took about 5 minutes to warm up in the morning because the fans were blowing as soon as the ignition was turned on but the thing ran cool even in the mid July bumper to bumper LA traffic. I would go ahead and replace this fan switch when you drain the coolant to do the thermostat or just bypass the switch and have the fans on all the time

[Maz]

brokenbat is 100% on the money!!! Those are the same problems I had with my 535 last year and what he said was the exact thing wrong with it, and once changing those parts out and doing what he mentioned in his reply here, the car ran perfect!! Good Luck with it

[SoonerE39]

Thermostat is my guess too. Good luck with it.

[Silverado]

Thanks for the detailed info - whatever about LA Bumper to Bumper traffic - at least it moves somewhat... This Dublin crawl doesn't move and the temp is only 3 degrees.
All the more reason to worry when that needle climbs! Will get the fan switch and thermostat checked out.

[Furious]

either two things, thermostat or waterpump, open the hood and see if there is any grey crap around the cooling system components, (looking for baked on antifreeze) if you do find it , you might have a cracked thermostat housing or waterpump, if not then i think your thermostat is stuck slightly closed. that would explain why your car is overheating while at idle, not enough coolant getting to the engine. when mine went it was the opposite, stuck full open, so the car ran cold all the time, when at idle the temp would drop below 1/4 and when running it would reach up towards just past 1/4