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stevebfl · #9 07-13-2002, 11:44 AM

You might be thankful for the sensitivity of MB gauges.

I suppose I got to tell a story. The story hinges on the sensitivity of gauges.

I have been driving automobiles for fourty years. I am a repair technician probably because early in life I excelled at making things work and that included many cars of my own and family and friends. I can mostly say that I have never been stuck on the side of the road. I could write reams of the individual instances where i got the car/truck/bike home.

That all came crashing down two weeks ago. My 50k 97 BMW 540 finally got me and gauge sensitivity was most of the problem. A little info on the system first. In the continueing interest of emissions and performance the BMW engine management system uses an electronic thermostat that changes engine temp by about 20-30 degrees. Mostly the car runs hot with no power to the thermostat, but at idle the t-stat is powered and opened and the same occurs under heavy load.

Because this ranging of temp would be very noticable the gauge like many gauges is stabilized, retarded, or otherwise delayed in the actual indication.

So I am headed North on I-75 after standing in the sun all day trying to see the "Tall Ships" in St. Petersburg harbor. About in the middle of Tampa in a driving rain my display flashes the low coolant warning. Well I know all about this and know that the sensor in the coolant tank has been exposed and that level is nothing to worry about. There of course could be a serious leak but I still got the gauge, right? Well 50 miles further down the road its gourgeous out and I'm leading the pack when I get the instantaneous warning "ENGINE IS OVERHEATING" on the display. Knowing I have pushed my luck I dive for the shoulder and the temp gauge is buried in the red (I had been watching this). Within 10 seconds the key is off and I'm still doing 50 on the shoulder while braking hard and watching traffic.

Once totally off the road, in the grass, and stopped, I again switch on the ignition and the find that the gauge is just slightly over the midpoint where it always runs. I get out to view the damage. I am in high grass so i can't judge the size of the leak. The steaming under the hood appears to be the overflow not the leak as the pressure can be felt in the hoses. It is not very hot in reality and in about ten minutes I have the cap off with no boil over only steam. Thank God for rain as a few hundred yards further there is a large puddle in the swail. So I drive the distance and take off my shoes (I'm in shorts anyway) and use the two spring water bottles we have to gather pond water which I then strain through my sock into the radiator.

All filled up I start the car and quickly view the situation and boogie down the road at reduced speed and with A/C off. Again I have the temp gauge right in the center for all 15 miles to the next exit, which I take, learning from my previous arrogance.

I pull into the gas station/mini market, pop the hood and as i am walking to the front I pass over a three inch wide stream of coolant (still pretty green) running just in front of the drivers side front tire. I don't even open the hood. I call my buddie (who owns a wrecker - we are only 40 miles from home).

The point here is complicated. Fifteen years ago I had virtually the same thing happen on the way back from Orlando airport in a 450SEL. I pulled into a mini- market with a quarter inch stream visible from water pump vent hole. I purchased two gallons of milk and emptied it into the toilet. Filled the jugs and the radiator with water and started off. I left the rad cap loose to prevent pressure and decided to go till the gauge moved or 15 miles whichever came first. The milage came first and I filled the radiator from my bottle using about 2/3 of a gallon. I then headed back to Gainesville on 441 rather than the turnpike allowing me to stop about every twenty miles. The leak actually got smaller as I proceeded. I got home in about double the normal two hour drive.

In the recent situation I couldn't do the same for two reasons. The first is that with the t-stat control that is used the system will boil water unless pressurized (normal, unseen, activity brings the temp at times to near 220 I think), I couldn't run without a cap and the second reason is the gauge is closer to an "idiot light" than a usefull idicator of coolant temp.

Personally, I prefer gauge sensitivity!