Temp gauge and sender

[CorvallisBMW]

I know the m30 runs a 78C thermostat which is a lot cooler than the m20 88C piece. Because of this the normal operating temp of my engine makes the temp guage needle sit at the first hash mark, "1/4", instead of reaching the middle mark. Will swapping out the brown temp sender in the thermostat housing with an m30 unit fix this?

[CorvallisBMW]

Anyone?

M20 temp sending unit 12-62-1-710-512
http://www.pelicanparts.com/cgi-bin/...81987-91%29%20

m30 temp sending unit 12-62-1-747-281
http://www.pelicanparts.com/cgi-bin/...C%20Each%20%20

[CorvallisBMW]

Why on earth would I do that?

In an m30 swap car, the car has an m30 engine. The M30 runs a 78C thermostat.

The m20 runs an 88C thermostat.

Since I swapped the brown temp gauge sensor from my m20 in to the m30, it causes (I think) the needle to sit below the halfway mark. The temp sensor is looking for 88C, but since it sees 78C it reads "low". I just want to find the correct temp sensor that will make the gauge read 1/2

[Brian D]

So you want to take an accurate gauge and make it inaccurate? ;)

I see what you're saying, but the senser and the gauge are matched electrically. If you use the M30 senser, if it's matched to the gauge, it will still read at the 1/4 mark. If it's not matched, it may read at a different level, but now you have no idea what the actual temp of the engine is.

The gauge is reading accurately. If you want it to read higher, you have to change the actual temp of the engine with a higher temp thermostat. Why does the gauge reading low bother you?

[Jean]

So you want to take an accurate gauge and make it inaccurate? ;)

I see what you're saying, but the senser and the gauge are matched electrically. If you use the M30 senser, if it's matched to the gauge, it will still read at the 1/4 mark. If it's not matched, it may read at a different level, but now you have no idea what the actual temp of the engine is.

The gauge is reading accurately. If you want it to read higher, you have to change the actual temp of the engine with a higher temp thermostat. Why does the gauge reading low bother you?

This

[CorvallisBMW]

If 78C is the normal operating temp of the engine, then why shouldn't the gauge read 1/2?

The gauge is NOT accurate currently. It reads that the engine is running cool even when it isn't.

Am I just not making myself clear? It doesn't seem hard to understand :shrug:

[Jean]

The e30 temp gauge is calibrated for the e30 temp sender.

You can try the m30 sender but most likely it wont even register on the e30 gauge.

One option is to ship the cluster and have it calibrated or add aftermarket gauge to use with m30 sender.

[CorvallisBMW]

Or just swap in an m30 gauge and sender.

[Brian D]

I know the m30 runs a 78C thermostat which is a lot cooler than the m20 88C piece. Because of this the normal operating temp of my engine makes the temp guage needle sit at the first hash mark, "1/4", instead of reaching the middle mark.

If 78C is the normal operating temp of the engine, then why shouldn't the gauge read 1/2?

The gauge is NOT accurate currently. It reads that the engine is running cool even when it isn't.

You're contradicting yourself, and you had it right the first time. I have a lower temp thermostat in my M20 currently and the temp gauge sits at 1/4 most of the time, which is where it should be.

Actually, looking at the parts catalog, both the M20 and the M30 thermostat part numbers are for an 80C thermostat (the same part, in fact). Are you sure of your numbers?

I guess the only way to be truly accurate would be to use an aftermarket gauge and sender. Then you would have a real number, instead of just where the needle is on the gauge.

[LowR3V'in]

Mine is an 80c I think. Whatever autozone gives you for a stock replacment.

Holds at 194f. Middle of a gauge is about 200/210f.