Can over cooling be caused by air?

[Javier]

tstat is OK and tstat housing cover is OK, if cold, tstat would simply close rising temp.

It should be a metering error, I mean, sender unit (you change it already), wiring defects, or even gauge miss-adjustment.

There is an easy check, just unbolt sending unit (or get the old one that seems to be OK as problem continues), keep it plugged in the connector, look for a camping stove (or other means of getting boiling water), pan, water, a cooking thermometer 0-100 degrees C, turn key to energize gauges, and check your gauge readings at various temperatures from 0 to 100. (if no thermometer, at least you know boiling is at 100, and its pretty close to 1/2 (center gauge is about 84, 100 is about one needle past center).

This is what I would do myself, not having handy the sophistication of an infra red gun. Also this will confirm your metering system is/is not OK.

This link should help.

http://www.bmwe34.net/e34main/troubl...e_overheat.jpg

Javier

No, stays cold all the time.... if it was getting to 12 o'clock it would be perfect.... it's pretty much rock solid on the 1/4 way mark.

[Dave M]

Well everyones hard at it, I may as well add my $0.02. Whether (pardon the pun) its +30 degrees celcius (90 F) or - 40 celcius (_40 F), the needle in my 91 525 sits at 12:00. If Javier's proposal doesn't provide the answer, its hard to ignore the thermostat. Is is possible to test these thermos in the classic " heat some water and drop the thermo in"? This may tell you if its a bum one and save time lookng elsewhere. Someone may know if this trick works.

Good luck,

Dave M

[632 Regal]

that trick works, the thermo should not open up at all untill the water gets damn hot, just before boiling since they are supposed to only begin to open at their specified temperature rating. You can get a candy thermometer at almost any hardware store for a few bucks and throw that in the water and really see whats going on, and then you can drill a hole in your smoker/bbq and use it there for perfectly smoked ribs! mmmmmmm.

[Javier]

weeks ago, this confirmed the tstat was OK (wrongly mounted, though).

Javier

[Kalevera]

True.

[doogie]

OK..... did some messing today.... put brown sensor in a cup of just boiled water, powered up car, barely moved needle. Tried shorting the connector and the needle also barely moves.... looks like a wiring fault somewhere..... d'oh!

The brown sensor has a brown earth and a brown/yellow wire coming from it. The connectors on the back of the instrument cluster don't have a brown/yellow wire on them... from what I can see I should be looking for a brown/violet at the instrument cluster end..... anyone tell me (or point me to the page in Bentley) that shows me where the brown/yellow goes before it ends up in the instrument cluster so I can find where the break/ problem is?

Thanks

[632 Regal]

might be a dash capacitor if you dont find a short.

[Javier]

I only have info for 525i and 535i that year. But the 1994 European wiring in this link:

http://www.carsoft.ru/avtorepair/bmw...0.3/index.html

reveals a brown/violet wire all the way to the instrument cluster (Pin X16-4).

In 1989 USA cars, the sensor is wired with Brown/Violet and Brown/Yellow wires all the way to the instrument cluster. Brown/Yellow gets ground from the cluster to the sensor, and Brown/Violet send back the variable resistor signal to the cluster, pins X16-24 and X16-26, but again, I understand that 520i instrument cluster is not the same that 525i/535i.

Did you check resistance to ground in both wires at the sensor? Are you sure Brown/Yellow is the signal wire? May be it is intended to be grounded and is opened! The said brown wire, wasn't Brown/Violet, and may be worn out the violet strip? Is it grounded? Have you checked continuity from Brown/Violet wire at cluster connector, and wires at the sensor?

Javier