Overhauled cooling system, temp needle still past center

[youngbimmer]

Hello all, recently overhauled my entire cooling system with the help of a friend. New behr radiator, new hepu water pump, new coolant expansion tank, new hoses everywhere, new mahle thermostat, new behr expansion tank cap, new viscous fan clutch, new fan blades, new VDO aux fan. Refilled with new green coolant. Still, whenever I drive around for a while, the temperature gauge will eventually settle either just right of the middle mark or in between middle and middle-right tick mark, which is exactly the same behavior as it was on its (believe it or not) all-original cooling system. Is my head gasket on its way out, or is it normal for 88s to show temperature like this (perhaps the buffer zone on the temp needle changed in later model years?). Doesn't matter if AC is on or not, temp needle behaves the same way. Referencing one of Gale's images, mine usually sits at 195 position or very rarely, 223

gauge_overheat.jpg

Build date 12/14/87

[theBMWbeast]

Normal behavior from an m30, in my experience. You say it can go to 223, that is no good. Make sure the system is bled throughly.

[shogun]

check the temperature sensor, here the ohm at various centigrades http://www.e32-schrauber.de/bmw/s-tempsensor.htm
But in general, as the BMWbeast already mentioned, if it sometimes goes to 223, that is not that good, it should under all conditions stay in the same position. The BMW system has a plateau indication, that means it will stay a long time in the same posiition and only when iy goes out of the programmed value in the cluster chip, the indicator will move, I explained that here http://www.bimmerboard.com/forums/posts/1245033/
Do you have another cluster for testing to eliminate the temp gauge as problem?

[youngbimmer]

I do not have another cluster to test, I will check readings at temp sensor this weekend. I’m disappointed with the results, especially since I used all OEM parts. Perhaps my head gasket is ready to die, even though there is no evidence of oil-coolant mixture before or after the overhaul. Could it be a bad thermostat? My friend drilled a small hole in the thermostat to help bleed air better.

[shogun]

Is there a return flow thru the hose to the expansion tanK? http://www.nmia.com/~dgnrg/page_19.htm

[letank]

I would check the real temp at the thermostat area and at the water pump with a non contact thermometer or infra red thermometer, harbor freight has them, and so does amazon. In the jeep world notorious for the volatile mind of our gauges this is the customary way to calibrate the temp gauge.
On our 740 the gauge is dead center, even with ac on and outside temp at 108F like we had some years ago going to LA

[youngbimmer]

Is there a return flow thru the hose to the expansion tanK? http://www.nmia.com/~dgnrg/page_19.htm

Yes, I actually forgot to tighten this hose when I initially connected it to the radiator and it was leaking fluid so I know it is not clogged.

I would check the real temp at the thermostat area and at the water pump with a non contact thermometer or infra red thermometer, harbor freight has them, and so does amazon. In the jeep world notorious for the volatile mind of our gauges this is the customary way to calibrate the temp gauge.
On our 740 the gauge is dead center, even with ac on and outside temp at 108F like we had some years ago going to LA

I will use that HF 25% off coupon for one of those IR thermometers to get a real reading.