Ice Storm Overheat

[Homer]

Well- I just came in from looking at my coolant and oil and am hopefull that I have dodged a bullet. My 97 528 has been in need of an aux fan fix for awhile now as my attempts to fix it have not succeeded. I have been carefull to stay out of traffic and away from the drive-thru's. But yesterdays ice storm here in Ohio nearly got me. It was so bad on the roads that I never got going fast enough to cool the radiator and the light came on just before I reached my driveway. I have said my prayers and vowed to take it straight to my indy. Just thought Id warn everybody about how snow and ice can lead to overheating.

[Craig in Canada]

I don't mean to sound flippant, but the aux fan is not your only problem if what you say is true. As a matter of fact, it might be broken but it's probably not responsible for your recent overheats in any way.

First, in sub-freezing temperatures the E39 doesn't need any fans to stay cool. Just by having the hood open, no fans installed, no heat on, it can't get above 70C (I just did this on the weekend trying to bleed).

Second, the main fan, even when not engaged, provides more than enough airflow in these conditions to keep the engine cool. EVEN IF your main fan is failed freewheeling, it'll still move enough air to keep from overheating.

Third, add the heat sink effect from your cabin heater and the situation is even less precarious.

Does your cabin heat work solid or go cold from time to time? What is the condition of your thermostat and water pump? Does the gauge jump around, or smoothly change readings and gradually overheat? What happens if you turn the heat up to full (i.e. set for max temperature and max fan) when it starts to indicate an overheat?

I'd seriously place the aux fan aside in your mind and start checking other things. It's POSSIBLE that it could have kicked in to prevent an overheat depending on what else you've got going on, but the aux fan should not have even been necessary in these kinds of temperatures.

[JimLev]

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[Craig in Canada]

I can't say I've ever had packed snow compromise my cooling before. Again, at freezing temps I'd expect the breeze from the main fan through the kidney grills plus the heater core to be more than enough unless he was doing a hill climb race or something....

[Homer]

Though I didnt think it related-the cabin heat is there only when I get on it. Starts blowing cold air at idle. Ive been bleeding the thing for a year regarding that. I def need to get to the expert. Thanks for the comments H

[Craig in Canada]

Are you constantly getting air out of the system? Or do you bleed constantly but there isn't much of an air problem?

If there's not a lot of air in the system, maybe your water pump has issues. Maybe part of the impeller is even missing? Maybe you have a blockage somewhere preventing the easy flow of coolant. Or it could be the t-stat stuck open, I suppose, over cooling the engine with the radiator so you have no heat left.

The heater and the block are "inside" of the stat and with the exception of overcooling have no relation to the operation of the stat. If you were overheating and simultaneously not getting heat the other day - it's not just the stat.

If you are constantly getting air out of the system, it could be a head gasket issue but we'll all hope that it isn't that.

[JimLev]

Homer, take bleed screw #5 out and make sure the housing is full of coolant when the engine is cold, if low fill it thru the screw hole, put screw back in.
Then start the engine and run it until it's hot, loosen screw slowly, if no coolant comes out remove the screw and fill it again.
I've done this on a few I6's that were overheating after numerous bleeds, it cured all of them.

http://www.realoem.com/bmw/showparts...46&hg=11&fg=35

[Homer]

Theres not alot of air coming out the bleed screws. And I dont see excess pressure in the bottle when its running. I sure hope its not the headgasket or head. Could be an impeller problem-but it seems that at times the car is more forgiving than others. Ive read something about a valve that could be sticking.. ? Again thanks

[Homer]

Ill try making sure that the housing isnt holding air as you suggest. One thing I may not have right is the level I am to have the bottle. Is it to be filled to the top? I thought it was just an overflow/resevoir and low in the bottle (a couple inches) didnt mean coolant was low..? thanks

[Craig in Canada]

General comments (not a reply to JimLev specifically):

On the I6s #5 is to be open/removed when coolant is being refilled into the system after some kind of significant level drop (not just a top up). This makes all the difference in the world to a trouble-free fill. I've read the technique to fill through this hole but I've never needed it. As filling the e-tank I will eventually see the level slowly rising in this hole. Last weekend I also slightly pressurized the e-tank by mouth so that a little coolant flowed out of #5 as I tightened it. Don't overtighten and make sure that the O-rings are installed and intact at both vents.

After the system is full, bleeding, in theory, is only done at the vent near to the e-tank. This isn't to say it's not a good idea to check for air at #5 but there probably won't be a whole lot if the refill process went well. Elevating the front end seems to make this a whole lot easier. I've always had the front elevated - mostly because I need it to be up on ramps to access belts, pulleys and fans from underneath.

As to "valves being plugged", I'm not sure what that is in reference too. Sure the heater core valves could be malfunctioning but I'd expect only one side to go crazy at a time and it wouldn't be accompanied by overheating or overcooling.

[Whorse]

last week i was driving in the snow storm on the highway and after a while my headlights were worthless cause of all the snow buildup on the front. (hids=no heat) I pulled over on the shoulder to clean the headlights real quick and got stuck in some snow so i had to spin the tires for about 30-45 seconds (not constant) and i saw my temp start climbing past 110. At 114c the needle started moving, at 117c it was at the 3/4 line. I [Oops!] a brick and shut it off, i hit the rest button on the climate control and watched the temp drop sooo fast. Anyways i popped the hood and needless to say there was 0 airflow. Driving on the highway in snow clogs up all the air passages. The whole front of my car was wearing a mask of ice and snow. only the fogs lights were clear from their own heat. Headlight washer systems should of been standard on all cars with HIDS. I had to pull over every 10 mins to clean off the headlights.

Andreas
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