Water temp question
 

I have an 84S US spec. w/ automatic. It tends to run on the hot side I think. I have an infrared temperature sensor that I used to check the temperatures at the thermostat input and output hoses. On the inlet side it reads 145-150 which seems about right. On the outlet side I get 186-190 when it is warmed up and idling in the driveway. This seems a little on the high side. These readings are after replacing the thermostat with a new 83 degree thermostat. So the question is whether the 186-190 outlet temp is reasonable?

Thanks

yes that sounds about right. Did you replace the rubber sealing ring behind the new thermostat?
It is inserted into the inside of the water bridge and the bottom of the thermostat seals on it

I replaced the rubber O ring that goes in front of the thermostat and seals the thermostat against the inlet casting. I did purchase the other rubber sealing ring, but couldn't see where it needed to go. It looked like it maybe it fits at the bottom of the water bridge where it mounts to the block?

The smaller seal goes straight behind the thermostat and you need pliers to get the old one out. Big seal is for the body, small one for the plunger to actually stop flow.

It may be possible that your water bridge doesnt have the seal, thats said it is also possible that it does and the old seal has fallen apart to the point that it doesnt look like there is a seal there. To remove the old inner seal simply tap the outer part with a long screwdriver into its center then it will fall out.
The seal in question is about the same diameter as a half dollar coin and about 10mm high

If that Water Bridge isn't leaking. I would leave it alone. That water bridge and lining up those gaskets and bolts was a serious pain for me. Unless you guys got a trick to do it easier.

FYI, I also used High Temp RTV Silicone as well as the Gasket for the bridge. Sealed with zero leaks like a Frogs Arse.

Thanks for the information on the seal. I'm not sure I would have found it otherwise. I'm just starting to learn about 928's. I've been an Italian car guy for many years so this German stuff is all new. I'll pull the thermostat when I get a little time and see about the rear seal.
I was more interested in the temperatures. The temp gauge runs pretty much at the last mark before hot one, about 3/4 up the gauge. It makes me nervous but if my infrared temp readings are correct, this is about 186-190 going to the radiator. That isn't to the OMG! range for me, but is that about where these things run?

Dano, the water bridge isnt getting moved or otherwise disconnected to replace the rear thermostat seal.
To replace the thermostat seal simply drain the radiator then remove the lower hose from the thermostat housing remove the 2 10mm bolts and the O ring then the thermosta will fall out then the seal is tapped into the housing behind it

the part number for the rear thermostat seal is 928 106 163 00

Oops, misread.