to those with aux water temp gauge - cluster vs aux readings??

[Sh3rpak!ng]

Yeah I used the adapter that goes on the radiator hose. Knowing your coolant temp is actually rather useless because it changes so fast. I had 240 degrees showing at coolant temp but the head was only slightly hot. on top of that, there is way too much coolant flow in the radiator hose to come to any conclusion on how hot the engine actually is. I wish I could move it but the mechanical sensor is just too big to fit into the port on the head.

I run an external temp sensor on my lemons car. It bolts onto the side of the block. It's way more reliable and steady than the coolant sensor I was running. I also moved my coolant sensor so it has good contact with the aluminum on the head. The coolant temp always made drivers unsure whether they should come in or not. Now it's very clear that if the block temp goes anything over 110 C there's a problem.

BMW knew what they were doing when they put it there. The aluminum head is ultimately what will cause engine failure when your car overheats, so knowing the exact temperature of the head is the best measurement.

Block temp is a backup in case the cooling system explodes again. (Which is rather hard to notice at 100mph and 7000rpm)

Just for reference my supercharged s52 sits right at 200F. Goes up to 210 when the fan turns on. Running the e36 koyorad and Stewart waterpump. 88C thermostat I believe. When I ran the s54 z3 rad it was at 205 and 215 respectively

And to answer the original question.. Your temps look exactly the same as mine. I was expecting it to be around 185-190 but I guess the engine coolant runs a bit hotter than the engine itself.

As long as you don't go over 230 you should be golden.

Thanks for all the details. So I guess I might just leave it as is for now. I mean, obviously it's not overheating, it just bothers me that the cluster gauge and the aux gauge don't seem to agree. And the aux gauge seems to read too high. I might eventually try another gauge/sender.

On my supercharged e36 with spal fan, mishi aluminum rad, 80c tstat and oem water pump it stays down 185 while cruising and will climb to ~210 while stopped in traffic but the fan drops it back to ~190. It's just driving me crazy that on that car with almost identical setup the temp readings seem appropriate, but on the e30 they don't.

[pandaboo911]

And to answer the original question.. Your temps look exactly the same as mine. I was expecting it to be around 185-190 but I guess the engine coolant runs a bit hotter than the engine itself.

As long as you don't go over 230 you should be golden.

[pandaboo911]

to those with aux water temp gauge - cluster vs aux readings??

Yes, thanks for that. I have been wondering about the quality of the head location as a source for temp. Do you use that aluminum splice in the radiator inlet hose for the sender? I want to see TRUE engine coolant temps, and I want to see those changes and fluctuations reflected on the gauge.

Yeah I used the adapter that goes on the radiator hose. Knowing your coolant temp is actually rather useless because it changes so fast. I had 240 degrees showing at coolant temp but the head was only slightly hot. on top of that, there is way too much coolant flow in the radiator hose to come to any conclusion on how hot the engine actually is. I wish I could move it but the mechanical sensor is just too big to fit into the port on the head.

I run an external temp sensor on my lemons car. It bolts onto the side of the block. It's way more reliable and steady than the coolant sensor I was running. I also moved my coolant sensor so it has good contact with the aluminum on the head. The coolant temp always made drivers unsure whether they should come in or not. Now it's very clear that if the block temp goes anything over 110 C there's a problem.

BMW knew what they were doing when they put it there. The aluminum head is ultimately what will cause engine failure when your car overheats, so knowing the exact temperature of the head is the best measurement.

Block temp is a backup in case the cooling system explodes again. (Which is rather hard to notice at 100mph and 7000rpm)

Just for reference my supercharged s52 sits right at 200F. Goes up to 210 when the fan turns on. Running the e36 koyorad and Stewart waterpump. 88C thermostat I believe. When I ran the s54 z3 rad it was at 205 and 215 respectively

[Sh3rpak!ng]

The gauge hardly moves because it's located on the head, even though the temperature in an engine is in constant fluctuation, the gauge is steady because it has very good thermal contact to the head.
I have an autometer ultralite mechanical gauge and it's reading temps coming out of the thermostat. the temperature fluctuates 10-15 degrees F as the engine heats up and cools back off with the fan.

The gauge seems damped because there isn't much coolant flow in that location. They use that as a location because even if you lose all your coolant it'll still read hot.

I found that out the hard way when I built my lemons car. The coolant temp was measured at the heater core hose. A wrench from the trunk of the car in front of ours flew out and went clean through the radiator, the coolant temp didn't register any change because the coolant was draining so fast, so we kept racing for 2 laps on no coolant and the race was over.

Yes, thanks for that. I have been wondering about the quality of the head location as a source for temp. Do you use that aluminum splice in the radiator inlet hose for the sender? I want to see TRUE engine coolant temps, and I want to see those changes and fluctuations reflected on the gauge.

[pandaboo911]

to those with aux water temp gauge - cluster vs aux readings??

The gauge hardly moves because it's located on the head, even though the temperature in an engine is in constant fluctuation, the gauge is steady because it has very good thermal contact to the head.
I have an autometer ultralite mechanical gauge and it's reading temps coming out of the thermostat. the temperature fluctuates 10-15 degrees F as the engine heats up and cools back off with the fan. It does this every few minutes. The needle moves very fast as things get hot

The gauge seems damped because there isn't much coolant flow in that location. They use that as a location because even if you lose all your coolant it'll still read hot.

I found that out the hard way when I built my lemons car. The coolant temp was measured at the heater core hose. A wrench from the trunk of the car in front of ours flew out and went clean through the radiator, the coolant temp didn't register any change because the coolant was draining so fast, so we kept racing for 2 laps on no coolant and the race was over.

[Sh3rpak!ng]

Really? I always thought it was damped. I guess I learned my new e30 fact for the day :)

Yup! afaik there is no damping on the e30 and older water temp gauges. They added the damping to the newer cars (~2000 and newer) because "people got upset/didn't like" seeing the temp gauge moving around. So basically on newer cars it's just a fancy idiot light that tells you:
A) needle to the left - engine is cold
B) needle straight up - engine is between slightly warm and almost too hot
C) needle to the right/red light - WAY TOO HOT SHUT IT DOWN NAOWWW

Now, as to how accurate that e30 temp gauge is, I have no idea. Though, thus far it seems to respond accordingly to any changes I have made to the cooling system.

[CorvallisBMW]

Really? I always thought it was damped. I guess I learned my new e30 fact for the day :)

[Sh3rpak!ng]

AFAIK, VDO is regarded as some the the best gauges you can get. I would trust them over the factory temp gauge, as it is "damped" in the middle and designed to show mostly whether you're very cold or very hot, not to show small fluctuations around your normal operating temp.

On the e36 and newer cars the cluster gauge is "damped" in the middle. On the e30 and older cars, the cluster gauge is not "damped".

Sorry if I am making things confusing. I have both an e36 and e30. I know the e36 cluster gauge is useless, but the e30 cluster gauge is not.

[CorvallisBMW]

AFAIK, VDO is regarded as some the the best gauges you can get. I would trust them over the factory temp gauge, as it is "damped" in the middle and designed to show mostly whether you're very cold or very hot, not to show small fluctuations around your normal operating temp.

[Sh3rpak!ng]

You also have to account for the emissivity (heat transfer efficiency) of certain materials when using non-contact methods. As an example, copper conducts heat more efficiently than rubber, therefor pointing a gun at the outside of a copper container full of boiling water will show aroung 99C, but a rubber container might show just 80C. Therefor the aluminum thermostat housing will likely show a different reading than the rubber radiator hose.

/enginerd

Yup exactly. I knew that but then decided not to post the full explanation. I had a feeling you guys are enginerds just like me.

So basically I have no good places to point the IR gun. Aluminum thermostat housing is unreliable, and the polished aluminum radiator is worse. I think I might make some small spots on the radiator and thermo housing with black matte spray paint so I can get good IR readings.


More OT, I changed temp senders and the thermostat from 88c to 80c last night. The thermo change is easily noticeable on the cluster gauge which now holds about a needle width to the right of the 1/3 mark. The vdo aux gauge shows "cooler" than it did before, but still not accurate (no surprise). It shows more like 195-200F now. I think I might just look for a better gauge and sender combo. This is really annoying. Guess I got lucky with the gauges I bought for the e36 since they seem to be spot on.

[CorvallisBMW]

I tried to do the same, but it seems there aren't many good accessible places to take accurate measurements...

You also have to account for the emissivity (heat transfer efficiency) of certain materials when using non-contact methods. As an example, copper conducts heat more efficiently than rubber, therefor pointing a gun at the outside of a copper container full of boiling water will show aroung 99C, but a rubber container might show just 80C. Therefor the aluminum thermostat housing will likely show a different reading than the rubber radiator hose.

/enginerd

[Sh3rpak!ng]

Hmmm, I have an IR gun at home. i'll have to check it vs the gauge.

I tried to do the same, but it seems there aren't many good accessible places to take accurate measurements...

[CorvallisBMW]

Hmmm, I have an IR gun at home. i'll have to check it vs the gauge.

[Sh3rpak!ng]

VDO gauges read high, regardless of how you ground them.
We've used IR, probe, and comparative gauge readings between a stock BMW gauge and VDO, VDO is always higher.

Hmm, interesting. Was there any trend as to how much higher?

any suggestions for a more accurate gauge?

[UNHCLL]

VDO gauges read high, regardless of how you ground them.
We've used IR, probe, and comparative gauge readings between a stock BMW gauge and VDO, VDO is always higher.