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

[Sh3rpak!ng]

I have an s52 swapped e30 with a stewart water pump, 48mm radiator, 88c thermostat, no clutch fan, spal pusher 1600 cfm

with this combination I would expect to see the aux gauge reading a solid 190F during daily driving but it does not.

I see a solid 200-210F on the aux gauge, and as high as 220F. The cluster gauge reads either dead center, or one needle width to the left of dead center. I have never seen it pass dead center. And this is with all types of driving, stop and go, highway cruising, canyon carving and IIRC even at autox it was solid at those numbers.



What do your aux gauges read when the cluster gauge shows the needle dead center/one tick to the left of dead center?

I'd like to try to determine if the gauge is reading accurately or not before I start pulling stuff apart.

[RoccoB517]

My gauge generally shows 200-210 when the cluster needle is dead center, but my standard operating temp on the track is 180-190 and at those temps the cluster needle is showing at roughly 1/4.

[Sh3rpak!ng]

My gauge generally shows 200-210 when the cluster needle is dead center, but my standard operating temp on the track is 180-190 and at those temps the cluster needle is showing at roughly 1/4.

hmm so that sounds about right with what I'm seeing, aside from your standard operating temp on track...

I just don't get it. In my e36 I have a stock radiator, stock water pump, 80c thermostat and I see a pretty solid 180-190 on the aux gauge in that car. I would think with the cooling upgrades in the e30s52 temps should stay rock solid around whatever the thermostat temp is.




Additionally, I let the car idle at operating temp yesterday, took readings with an IR gun and checked both gauges to see where they settled.

Idling, cluster gauge showed a needle width to the left of dead center. Aux gauge showed about 203-205F and I measured a myriad of temps depending where I aimed the IR gun. The aluminum radiator seemed problematic to measure temps on... the hose inlet measured 210+ as did the radiator face.

[RoccoB517]

Is your sender for your temp gauge threaded into the head? I try to shoot the IR right next to the sender on the head to see if my gauge is reading correctly. The thermostat cover is also generally pretty accurate once you reach operating temp.

Did you get a big temp difference between the hot side and cold side of the rad?

[Sh3rpak!ng]

Is your sender for your temp gauge threaded into the head? I try to shoot the IR right next to the sender on the head to see if my gauge is reading correctly. The thermostat cover is also generally pretty accurate once you reach operating temp.

Did you get a big temp difference between the hot side and cold side of the rad?

yup, temp gauge sender is in the head. Unfortunately there's stuff in the way to get a clear shot at the head next to the sender. Also, with the big radiator, and already tight clearances, it's also nearly impossible to get a clear shot at the thermostat housing.

It's also difficult to get an accurate reading on the all aluminum radiator. Apparently it has something to do with emissivity. I wonder if striping areas with black electrical tape would help get a better reading. That said, I seemed to get a decent? reading from pointing it at the face of the radiator.

I'll attempt some more readings tomorrow and report back.

[iwantspeed]

i believe your temps are a little high.
I really dislike the stock gauges I don't really trust them.

i run mostly distilled water and 2 bottles of water wetter from redline.
stockish m20 so it doesn't totally apply
e36 m3 mishimoto radiator
stock clutch fan
stock fan shroud
e36ti temp sending unit
16inch Spal pusher auxiliary fan
MASSIVE LEE fan brackets
adhesive backed foam between the radiator and core support
stock temp rating thermostat
auxiliary VDO gauge runs 180-185 all day long in traffic or track conditions

[Sh3rpak!ng]

i believe your temps are a little high.
I really dislike the stock gauges I don't really trust them.

i run mostly distilled water and 2 bottles of water wetter from redline.
stockish m20 so it doesn't totally apply
e36 m3 mishimoto radiator
stock clutch fan
stock fan shroud
e36ti temp sending unit
16inch Spal pusher auxiliary fan
MASSIVE LEE fan brackets
adhesive backed foam between the radiator and core support
stock temp rating thermostat
auxiliary VDO gauge runs 180-185 all day long in traffic or track conditions

I also run distilled + water wetter. I don't have shrouding between the radiator and core, but I will add that this weekend plus AC install. Though I don't see that as being the issue.

Keeping a closer eye on the aux gauge, I see a solid 200F while highway cruising. This is driving me crazy. Idk wtf is going on. Basically every part involved in the cooling system of the car is new, and or a major upgrade to stock.

[Sh3rpak!ng]

Food for thought:

I couldn't remember what aux fan switch I installed, just looked up the invoice. It's an 82C switch 6131136427282 with one speed (only 2 prongs, so its either on or off)

It cycles on and off if I let the car sit idling. Probably 10 seconds on, 30 seconds off

So that means the switch is seeing a normal fluctuation of coolant temp around the 82C mark on the "cold" side of the radiator. Couple that with what I see on the cluster temp gauge (needle width to the left of center, give or take a little more or less) and I am becoming skeptical of the accuracy of my aux water temp readout.

I just ordered an 80c thermostat which I'll install this weekend along with AC parts. We'll see what happens at the gauges.

[TobyB]

standard operating temp on the track is 180-190 and at those temps the cluster needle is showing at roughly 1/4.

Me too.

OP, try another thermostat.

t

[Sh3rpak!ng]

Me too.

OP, try another thermostat.

t

ordered an 80C wahler. Installing this weekend. Though, I'm not sure that's the full issue. It still seems like my aux water gauge is being weird. I have an extra sender I'll swap and see if anything changes

[iwantspeed]

ordered an 80C wahler. Installing this weekend. Though, I'm not sure that's the full issue. It still seems like my aux water gauge is being weird. I have an extra sender I'll swap and see if anything changes

On the new sender for auxiliary gauge you can do a mod to it.

Get a 1-2foot section of thin wire 16-20 gauge would do it.
On one end crimp an eyelet large enough for a 10mm
Bolt
On the other end strip the insulation about and inch from the tip
Twist the strands
Tin the tip of the strands of wire with a soldering iron.
On the sending unit get some sand paper and scratch the coating off a spot and solder the wire you just prepped to the sending unit.

Then find a suitable grounding spot.
This might help the sending unit ground properly and get a more accurate reading.

[Sh3rpak!ng]

On the new sender for auxiliary gauge you can do a mod to it.

Get a 1-2foot section of thin wire 16-20 gauge would do it.
On one end crimp an eyelet large enough for a 10mm
Bolt
On the other end strip the insulation about and inch from the tip
Twist the strands
Tin the tip of the strands of wire with a soldering iron.
On the sending unit get some sand paper and scratch the coating off a spot and solder the wire you just prepped to the sending unit.

Then find a suitable grounding spot.
This might help the sending unit ground properly and get a more accurate reading.

Thanks, sounds like a solid solution. However, if bad ground is the issue, I'd rather check the engine grounding, as I'm sure it would affect more than just the aux temp sender. All other gauges seem to be functioning appropriately

I didn't have issues like this in my e36 with the same gauges, senders setup the same way :hitler:

[CorvallisBMW]

I'm not sure what brand your gauge is, but on my VDO gauges the instructions called out very specifically for at least a 14ga grounding wire. They said that anything smaller could affect gauge accuracy. How thick is your ground wire on the gauge itself?

[Sh3rpak!ng]

I'm not sure what brand your gauge is, but on my VDO gauges the instructions called out very specifically for at least a 14ga grounding wire. They said that anything smaller could affect gauge accuracy. How thick is your ground wire on the gauge itself?

Hmm, good call. I forget what I used though it might have been a smaller gauge. Also I wired them all together for power and ground. I think I'll give that a shot first.

[irish44j]

My VDO aux water temp gauge (which goes to the port in the head of my M42) consistently reads about 205* in highway cruising and around 210 when on-course (rallycross). IIRC our Chumpcar (M20B27) also runs about 205 during long enduro races pretty consistently. Neither has ever had any overheating issues (both cars run high-CFM Spal fans). Both have the sender in different locations, FWIW.

BTW, both cars use 12 or 14ga wiring.

Chumpcar runs distilled. Rallycross car runs a standard antifreeze/distilled 50-50 mix (since it runs in very sub-freezing temps in the winter).