Temp gauge/ sensor /alarm questions
 

Hi everyone,

1. What is the actual temperature in the cylinder head when the instrument cluster's gauge shows 1/4, 1/2, 3/4 and at red ? (My engine is an M50 but do the figures apply to all E34 engines as well ?)

2. The two coolant temperature sensors which are screwed into the cylinder head (on to inform the dme and the other to inform the instrument cluster's gauge)...are their probes in direct contact with the coolant itself ? Or are they just in contact with the metal of the cylinder head ?

3. Is there a simple way to create and install a buzzer alarm as an overheat warning, say when the needle reaches 3/4 ? Can it be fashioned from the instrument cluster's existing wiring ? Or do you know of any simple, cheap and easily installed device that will generate an audible alarm in the cabin when the temp reaches 3/4 ?

Thank you.


rgds,
Roberto

1. Instrument clusters (temp readings) are slow and I would say not very reliable due to lag.

2. In 540I as I can recall you have a switch sensor and coolant sensor in rear and in radiator. All 3 sensors are exposed to coolant.

3. This is pretty simple, take a coolant sensor and splice the wires, all coolant sensors have Ohm spec that represents temperature state once it reaches certain Ohm you can sound the buzzer. I would avoid doing anything directly with cluster because of lag problems.

Yes, splicing the cylinder head sensor's wires are my preferred way to do this too. Checking that out now..

Any good off the shelf solutions ?

And do you know what the actual temp readings on the gauge are in degrees ? Can't seem to find that information....

Borrow an infrared thermometer and let us all know. BTW when my E23 boiled the temp at the rear of the block was 97C - according to Blue Point.

I have the infrared gun. I wish to know the actual thermometer readings according to published data or something similar...which I can't seem to find. If I do find it somewhere else, I'll post it up here for sure.

And from the second part of your statement, you seem to suggest that no overheat alarm covers all situations ? I know for sure that 97C should not cause a boilover situation. In fact it might well be the normal temperature. The aux fan's coolant sensor is rated at 90c/99c. Are the engine temp environments different, even across different BMWs ?