E39 540i Temperature Sensor Problem - Reads too high...

[///Matt]

Recently, my temperature sensor was replaced after an accident. It has worked fine for a month or so, but now its acting strangely. When I start the car it reads 91* and slowly climbs to a max of 121*. The sensor is mounted in the normal front-right position and is away from any heat creating elements. Does anyone know of a DIY fix for this or am I going to have to shell out another $40?

[superdeadman]

matt
if you are serious about the car's performance and real temperature (which is a biggie since there are tons of failures) i'd say you get an aftermarket temp gauge and install that. The problem with bmw temp gauges is that it can be wrong by like 50 degrees which is a LOT!

[Teh Prof]

Originally Posted by superdeadman

matt
if you are serious about the car's performance and real temperature (which is a biggie since there are tons of failures) i'd say you get an aftermarket temp gauge and install that. The problem with bmw temp gauges is that it can be wrong by like 50 degrees which is a LOT!

I think he means the external thermometer rather than the engine temperature...the engine temp can be off by 50; I've never heard of a working external thermometer off by 50.

[mdimbler]

Matt,
I had a similar problem when I first got my 540. It turned out to be the front right underbody plastic engine cover. Part of it was missing, and as the engine compartment got hotter and the ambient temp warmed up (spring/summer time) the temp guage would start out in the 80's and shoot up to about 115 or so. I replaced it, and have had no problem since. The part number is 51718159426, and was about $14.

[cnn]

Originally Posted by mdimbler

Matt,
I had a similar problem when I first got my 540. It turned out to be the front right underbody plastic engine cover. Part of it was missing, and as the engine compartment got hotter and the ambient temp warmed up (spring/summer time) the temp guage would start out in the 80's and shoot up to about 115 or so. I replaced it, and have had no problem since. The part number is 51718159426, and was about $14.

You are correct the part number is 51718159426, and was about $14 at my BMW dealer.

http://bimmerboard.com/forums/posts/181068

1. Leave it in the same place: risk of curbside damage.

2. I moved it to the "outside" of the lower intake airduct: safe place away fromengine heat and from curbside damage.

See link above.

Any questions, email me cnn90 at netzero dot net