Weird Slightly Overheating Problem

[E34 530]

I am having a weird problem in my 530ia. Ther car seems to slighty "overheat" when I go in reverse or let it sit and idle after driving it. When I say overheat, it doesn't go to the red, it goes anywhere from the middle (where it always stays) to a tad before the 3/4's mark. As soon as I start driving again, the needle quickly goes back to the regular temperature mark. It doesn't do this while at stoplights though. It doesn't happen all the time, maybe about 2-3 times a week. The problem only started about one week ago. The thermostat was replaced by the PO back in July of 04 at the dealer and I just had the water pump replaced 1 month ago. Also, corect me if I'm wrong, but the fan shroud is the plastic housing that surrounds the fan its blades correct? If a piece of it is broken, (about 3 x 2 inches) should I replace it? Thanks you for your comments.
-Andrew

[F4Phantom]

The shroud is vital to get correct air flow. It allows the fan to have proper force in sucking air as the fan would get air from elsewhere at a stand still if the shroud was not forcing it to get air from through the radiator.

[DanDombrowski]

I've had no shroud for 2 years in south florida. Doesn't affect it that much.

[Guapo]

I had the exact same symptoms.

http://www.bimmer.info/forum/showthread.php?t=16791

I decided to replace both temp sensors, the water pump, and the thermostat.

I don't know which part was causing it, but the problem is now gone. When all else fails, brute force method.

[E34 530]

I had the exact same symptoms.

http://www.bimmer.info/forum/showthread.php?t=16791

I decided to replace both temp sensors, the water pump, and the thermostat.

I don't know which part was causing it, but the problem is now gone. When all else fails, brute force method.

Maybe I should just try the temp sensors for now? Where did you find them , is it an easy fix, and how much were they?

Thanks, Andrew

[Robin-535im]

Well obviously it gets hotter in reverse... you're running things backward and the fan pulls the hot air through the radiator.

Two things come to mind when it overheats at idle. The fan clutch might not be pulling air across the radiator or the water might not be pumping around as much. Since the water pump is fairly new, I'd put my money on the fan clutch. I don't think the shroud will affect it at all. Old coolant can sometimes run hot, but that's usually all the time, not at idle; either way it's a cheap first step to check the fluid level if you haven't already.

A bad fan clutch can be hard to diagnose without a heat gun / thermocouple. It should lock up when hot (Bill has the spec sheet somewhere) and spin freely when cold. Here's one test: if you're sitting at idle and the temp is past the middle mark, open the hood and watch the fan clutch as you kill the engine. If it's locked up, it should snap to a halt with the rest of the engine. If it's not locked up, it will spin a bit after the water pump stops. You'd expect it to be locked up if working properly, so if it spins you have a clue that the fan clutch may be kaput.

Increase in temp while in reverse is interesting. If you've got an auto with the tranny oil cooler in the radiator, perhaps it's flushing hot oil through when you put it in reverse, and hence the cooling in the radiator is reduced? Hmmm.

HTH

- Robin

[632 Regal]

2 quick things to check first, when its cold and you start the car, does it sound like a school bus? if so the clutch fan is most likely good. The next thing to check is the Aux fans infront of the radiator. They should turn on if the car is getting anywhers over the middle, if they dont then check if they come on with the AC on. If they do come on with the AC then you may have a temp issue.

check all your fuses too...

[E34 530]

2 quick things to check first, when its cold and you start the car, does it sound like a school bus? if so the clutch fan is most likely good. The next thing to check is the Aux fans infront of the radiator. They should turn on if the car is getting anywhers over the middle, if they dont then check if they come on with the AC on. If they do come on with the AC then you may have a temp issue.

check all your fuses too...

Yes, my car does sound loud when I start the car in the morning, even though I park it in the garage where it's a little warmer than outside. Next time it happens, I'll keep your suggestions in mind. Should the auxilary fans come on at regular operating temp with the ac on? I just don't really understand it. I drove around in the summer (90+ degrees)with a half broken waterpump spewing coolant all over, the air conditioning on, and in mild traffic with no temperature fluctuations I don't appear to be losing coolant, but when I shut the car off, I still get a whiff of coolant, but I think it might be excess coolant that is still stuck to various engine parts from when the coolant was hitting the fan and being thrown around the engine bay. When the engine warms up, I think the coolant on the parts gets hot and gives off an odor because I don't think I am losing any collant.

---Regal, I still haven't forgot about the pictures, but I'm having no luck trying to send you the large images, but I still haven't given up yet....

Thanks all for the helpful insights, Andrew

[E34 530]

Just remembered. I blew a fuse while installing my satellite radio. I'm going to check them out right now. I wish that was the problem. Don't get me wrong, I love my car, but recently it seems like I can never just enjoy the car for how it is or how it looks. Every time I plan on getting the bottoms painted or some suspension, something else breaks and halters my plans.

[E34 530]

For some reason, I think I read somewhere that you don't have to pressurize the M60 cooling sytem. I could be wrong though. Anyone know if this is true??