Water Temperature Gauge Reading

[its55]

Started this question on the "What did you do..." thread and thought I'd move it hear.  The below pic shows my temp gauge reading after I've driven around a bit.  I measured this w/ an infrared thermometer which shows about 195 degrees.  It was a hot day and the coolant did not gotten above this temperature.  I'm curious what others experience and what their gauge shows.

 

Both the water pump and thermostat were replaced recently by a previous owner, and the radiator is not the original so was also replaced at one point in its life.  Temp gauge grounds have been added, all other grounds checked, etc. (this gauge always went to "full hot" before I added the grounds). The radiator cap "looks" ok but I might replace it just in case.  I have heated up / burped the coolant w/ heater on hot and all seems to be functioning normally.

 

Edited June 28, 2022 by its55
added info

[jgerock]

Where did you point the IR gun? Top of radiator, bottom of radiator, coolant branch at head, thermostat all might have different readings.  Coolant branch is where the gauge sending unit is located.

 

Any idea which thermostat your car has?
 

As marked on the extreme edge of the gauge, top of blue range is 67 deg Celsius, start of red range is 115 deg. C.

[its55]

I pointed it at the sending unit, coolant hoses, and top of radiator including with cap off (directly on coolant) and got pretty much all the same readings. thermostat is the specilfied 176° opening

I don’t see any numbers on my gauge where do you see that?

Edited June 28, 2022 by its55

[jgerock]

You have to remove the cluster from the dash, remove the gauge from the cluster, then remove the cover from the gauge face to see the markings. Sneaky Germans.

['76mintgrün'02]

8 minutes ago, its55 said:

I don’t see any numbers on my gauge where do you see that?

 

[its55]

5 minutes ago, jgerock said:

You have to remove the cluster from the dash, remove the gauge from the cluster, then remove the cover from the gauge face to see the markings. Sneaky Germans.

that is sneaky!  glad to know it though, thanks!

[Dudeland]

In the FWIW department I drilled a 1/4 inch hole in the thermostat to help with bleeding the air out. 

 

I would do a flush, perhaps take out the frost plugs and see if there is a lot of sediment. 

 

Regards 

[its55]

2 minutes ago, Dudeland said:

In the FWIW department I drilled a 1/4 inch hole in the thermostat to help with bleeding the air out. 

 

I would do a flush, perhaps take out the frost plugs and see if there is a lot of sediment. 

 

Regards 

Do you believe that my 195 deg. is high?

[Mike Self]

3 minutes ago, Dudeland said:

I would do a flush, perhaps take out the frost plugs and see if there is a lot of sediment. 

Not everyone knows there's a block drain, inconveniently located under the exhaust manifold, and plugged with an ordinary-looking 17mm bolt.  When you do your flush, be sure and remove it.  If nothing comes out, you'll have to poke around through the drain hole with a stiff wire to unclog--which will be a good indication of lots of sediment in the block.  Much easier than removing freeze plugs.  You can make up a nozzle to squirt water up through the block drain to loosen things up.

 

And take the bolt to a hardware or auto parts store--I was able to find a drain cock that threaded right into the block.  Makes draining the cooling system next time much easier!

 

mike

[tech71]

My car runs in that range as well and its been hot here. Not sure what degree thermostat I'm running, probably the middle one at 75c.  A new heavy duty Radiator from Blunt is installed

One thing I noticed was the fan belt seems a little long/loose, its at the end of available adjustment. Changing belts today. Will probably order a 71c thermostat as well

Edited June 28, 2022 by tech71

[its55]

1 minute ago, tech71 said:

My car runs in that range as well and its been hot here. Not sure what degree thermostat I'm running.... A new heavy duty Radiator from Blunt is installed

One thing I noticed was the fan belt seems a little long/loose, its at the end of available adjustment. Changing belts today.

thanks, thats good to know, that mines in the ballpark. 

[its55]

8 minutes ago, Mike Self said:

Not everyone knows there's a block drain, inconveniently located under the exhaust manifold, and plugged with an ordinary-looking 17mm bolt.  When you do your flush, be sure and remove it.  If nothing comes out, you'll have to poke around through the drain hole with a stiff wire to unclog--which will be a good indication of lots of sediment in the block.  Much easier than removing freeze plugs.  You can make up a nozzle to squirt water up through the block drain to loosen things up.

 

And take the bolt to a hardware or auto parts store--I was able to find a drain cock that threaded right into the block.  Makes draining the cooling system next time much easier!

 

mike

 

Good to know! Must the exhaust be removed?

[Mike Self]

9 minutes ago, tech71 said:

One thing I noticed was the fan belt seems a little long/loose, its at the end of available adjustment. Changing belts today.

Be sure you have the correct length (and width) belt.  There were several different sizes used on 2002s, and it's easy to get the wrong one.  Also the belt width is very important.  A too-narrow belt will run deep within the pulley grooves, overheat, stretch and eventually (sooner rather than later) break.  I learned this the hard way on a trip, where I was having to stop every few hundred miles to adjust a loose belt (it was stretching).  Finally it broke--in 104 degree heat--and I had to change it on the roadside.  

 

mike

[Mike G]

That’s close to where my runs with an 80c thermostat, you might a be touch higher. 

[jimk]

1 hour ago, its55 said:

Do you believe that my 195 deg. is high?

Not if you were driving around and let it idle, the build up of heat in the block and the low coolant flow at idle will show an increase in temperature.

 

The normal running temperature at the head outlet will be around +10F over what the thermostat is controlling to (the thermostat is on the engine inlet).  EFI systems have the ability to sense these locations and is what I saw on my M10 and on the S14.

 

During a similar test, measure the radiator bottom nozzle and if it's lower than about 165-175, then the radiator is doing it's job.