CHT Sensor readings and question.

[fallingat120mph]

EDIT: My CHT sensor is a modern 2 wire




So, had major problems on the road.

Got the car home and here is where I think the problem lies.

When cold the CHT was showing 2.11 which is in specs (1.4 - 3.6 ohms)

When I barely warmed up the engine I was getting .203 which seemed at least I was going in the right direction. Still the car was nowhere near 105-175 degrees so this seemed off.

I decided to let the car idle for a while and got the temp close to 194F/90C per dash/gauge and the reading I got was 99.1 all the way up to 118, which is quite away from the .150 to .300 I was expecting.

Has anyone had these kind of readings before???



These are what I was using for comparison:







If I am reading things right it would seem my sensor is going completely in the wrong direction

I know these fail but can these technically fail this far off?

I am looking into making a resistor for my on the road kit per old threads and carry that, DME and other bits all the time.


Hopefully someone with similar experience can chime in.





Thanks!
Erik

[Mr. Merk]

Did you mean 2.11kohm (not 2.11ohm)
It should start at 2000ohm (2.0kohm)
warming up scale down to 1000ohm
then down to 90ohm as it reaches 265F

A laser thermometer would help with testing here as you cylinder head temperatures and the oil temperature gauge will not coincide.

When my CHT sensor started to fail, the symptoms began as random cutouts while driving. Eventually, it stalled in traffic, cooled off, and restarted. The issue got progressively worse over the weekend. The final failure happened once the car was fully warmed up — we unplugged the sensor, grounded the wire to the intake manifold ground point, and drove it home from Luft in Indianapolis without any trouble.

Bypassing the sensor worked fine when warm but made cold starts nearly impossible.

[fallingat120mph]

Originally Posted by Mr. Merk

Did you mean 2.11kohm (not 2.11ohm)
It should start at 2000ohm (2.0kohm)
warming up scale down to 1000ohm
then down to 90ohm as it reaches 265F

A laser thermometer would help with testing here as you cylinder head temperatures and the oil temperature gauge will not coincide.

When my CHT sensor started to fail, the symptoms began as random cutouts while driving. Eventually, it stalled in traffic, cooled off, and restarted. The issue got progressively worse over the weekend. The final failure happened once the car was fully warmed up — we unplugged the sensor, grounded the wire to the intake manifold ground point, and drove it home from Luft in Indianapolis without any trouble.

Bypassing the sensor worked fine when warm but made cold starts nearly impossible.

Correct with the readings, "K" ohms.

Numbers were all in spec at start up, room temperature etc.

Numbers were all over the place when warm and on the road.

Sadly the problem was (I think) - when I went to remove the CHT it was very loose and I removed by hand easily, so not sure it was tight and that might have led to the bazaar numbers I was getting at temp, and causing the engine to run bad, cutting out, etc...

Made a new CHT socket and really learned a lot in regards to that part of the engine and function.

Always a positive?

Erik

[fallingat120mph]

Originally Posted by Mr. Merk

Bypassing the sensor worked fine when warm but made cold starts nearly impossible.

I will have to get with you on this. Someone told me a paperclip can actually be used but I did buy some 300ish ohm resistors also. Was told if the engine is warm already this works well enough to get you home.


Erik

[darrin]

Originally Posted by fallingat120mph

Correct with the readings, "K" ohms.

Numbers were all in spec at start up, room temperature etc.

Numbers were all over the place when warm and on the road.

Sadly the problem was (I think) - when I went to remove the CHT it was very loose and I removed by hand easily, so not sure it was tight and that might have led to the bazaar numbers I was getting at temp, and causing the engine to run bad, cutting out, etc...

Made a new CHT socket and really learned a lot in regards to that part of the engine and function.

Always a positive?

Erik

Erik -- does your CHT have one or 2 wires leading into/out of it? The old, original to my '86, CHT had one wire and failed similarly to yours around 25 years ago. The 2 wire replacement has worked flawlessly since. Doubt the looseness of the current CHT contributed to your problems, as (If I recall correctly), there's some thermal compound between the CHT and the engine block, instead suspect yours needs to be replaced. Best of luck!

[fallingat120mph]

Originally Posted by darrin

Erik -- does your CHT have one or 2 wires leading into/out of it? The old, original to my '86, CHT had one wire and failed similarly to yours around 25 years ago. The 2 wire replacement has worked flawlessly since. Doubt the looseness of the current CHT contributed to your problems, as (If I recall correctly), there's some thermal compound between the CHT and the engine block, instead suspect yours needs to be replaced. Best of luck!

Yes sir- it was brand new and two wire.

Seems I got a bad one out of the box although I still wonder about it being loose from install, but none the less have one new socket I made especially for the job and know what the process entails so there was a positive out of it?

Sleeping in the gas station parking lot, renting a truck and trailer and living on a coffee diet for three days was not the positive - but I finally have a cool Porsche "left me on the side of the road" story.


The new one seemed to be the fix, by the way


Thanks!
Erik