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1984 633CSi Rises again!

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songzunhuang
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Re: 1984 633CSi Rises again!

Post by songzunhuang » Tue Oct 13, 2020 5:40 am

hornhospital wrote:
Mon Oct 12, 2020 8:50 pm
It tells me your temperature sensor that feeds the gauge is perhaps bad, or (unlikely) there's a local obstruction in the system adjacent to the sensor. I believe there is a test method for the sensor, but I can't recall what it is, and my Bentley manual is packed away.
So I checked out the Bentley Manual and the process seems very inexact, but then again, I guess they would know best. I'll try that out later. However, I did get to do a detailed measurement of various spots as the car heated up. I couldn't get it to go past about 5/8 on the gauge today after running the car for just over 40 minutes. Here are the readings.
Screen Shot 2020-10-12 at 10.36.59 PM.png
Cooling System readings
Screen Shot 2020-10-12 at 10.36.59 PM.png (783.71 KiB) Viewed 153 times
Does anything look awry? Ambient was about 78 degrees today when I did this.
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Song Huang
1984 633CSi
Last 7 of VIN: 6997383

olympia57
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Re: 1984 633CSi Rises again!

Post by olympia57 » Tue Oct 13, 2020 9:13 am

Mmmm......
A word of caution when using these cheap low cost hand held thermometers .
They are sold as a one shot measure everything device but are anything but.
Consult the specifications of the unit to determine the FOV ( field of view ) as this will determine the target size and distance from the point of measurement .
Image
As you can see from above this has a huge effect on the accuracy of any measurement taken.
The target size MUST be greater than the FOV or you will be measuring anything else that is in the FOV , if it is a greater temp. then it introduces a positive error , if it is less then the opposite.
That's the simple bit .
The material and surface of the target is crucial to the accuracy of measurement , this is called emissivity .
Any Infra red measuring device must have an e adjustment to compensate for this .
Rubber , steel ( painted or raw) ,plastic , all types of alloys , water , oil ,SKIN , timber etc, ad nauseum all differ greatly , get the picture ? :roll:
I could spend a long long time explaining this .
Basically black is 0 and a shiny reflective surface is 10 but is not linear between the two. This has a HUGE effect on the accuracy and again is non linear across the measurement range of the device .
A crude , but reasonably effective , way around this is to either paint the surface black or wrap it in black tape and set the e value to 0.
Lastly the target "L" in the diagram above is circular . In essence the device takes a cross sectional average of the IR transmission in that area .
If you are not at 90 degrees to the target the circle becomes ellipsoidal and again greatly effects the measurement.
Most , if not all , of these low cost thermometers will have a minimum target size of 50mm + , I have a hand held with a MTS of 9mm and that cost over £3000 ( yep that's right ) ......
Just remember all this when the wee girl at the door of the supermarket you are about to enter points a £15 hand held thermometer at your forehead and says " Ah ,you're OK , on you go ...." [-o<
I hope this is of interest to you .
Good luck :lol:
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camera_fov.png
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1981 635 series 1

songzunhuang
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Re: 1984 633CSi Rises again!

Post by songzunhuang » Wed Oct 14, 2020 2:38 am

olympia57 wrote:
Tue Oct 13, 2020 9:13 am
Mmmm......
A word of caution when using these cheap low cost hand held thermometers .
They are sold as a one shot measure everything device but are anything but.
Consult the specifications of the unit to determine the FOV ( field of view ) as this will determine the target size and distance from the point of measurement .
Image
As you can see from above this has a huge effect on the accuracy of any measurement taken.
The target size MUST be greater than the FOV or you will be measuring anything else that is in the FOV , if it is a greater temp. then it introduces a positive error , if it is less then the opposite.
That's the simple bit .
The material and surface of the target is crucial to the accuracy of measurement , this is called emissivity .
Any Infra red measuring device must have an e adjustment to compensate for this .
Rubber , steel ( painted or raw) ,plastic , all types of alloys , water , oil ,SKIN , timber etc, ad nauseum all differ greatly , get the picture ? :roll:
I could spend a long long time explaining this .
Basically black is 0 and a shiny reflective surface is 10 but is not linear between the two. This has a HUGE effect on the accuracy and again is non linear across the measurement range of the device .
A crude , but reasonably effective , way around this is to either paint the surface black or wrap it in black tape and set the e value to 0.
Lastly the target "L" in the diagram above is circular . In essence the device takes a cross sectional average of the IR transmission in that area .
If you are not at 90 degrees to the target the circle becomes ellipsoidal and again greatly effects the measurement.
Most , if not all , of these low cost thermometers will have a minimum target size of 50mm + , I have a hand held with a MTS of 9mm and that cost over £3000 ( yep that's right ) ......
Just remember all this when the wee girl at the door of the supermarket you are about to enter points a £15 hand held thermometer at your forehead and says " Ah ,you're OK , on you go ...." [-o<
I hope this is of interest to you .
Good luck :lol:
I appreciate the tips. I did take the reading several times before averaging and writing down result. Weird thing is that the engine running hot isn't consistent. It was hot once just sitting in traffic and then again when I was on the freeway. It didn't make a lot of sense to me. Something has changed as it went many years without an problem running hot.
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Song Huang
1984 633CSi
Last 7 of VIN: 6997383

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Re: 1984 633CSi Rises again!

Post by TBM » Wed Oct 14, 2020 4:56 am

Have you checked that your fan clutch is fully engaged? Common problem..If not fully engaged its of course not moving enough air.. If its bad may be a good idea to use either a high CFF electric fan on the front of the car (a pusher) or once you remove the fan clutch a low profile sucking fan on the inside of the engine compartment.. Its a bit of a job but the fan either works or it doesn't and in the future easier to diagnose or replace.

. When was the last time you flushed out the system with new coolant? If over a year ago you may have some kind of blockage (not likely, but you never know.) Coolant should be changed every year either way or it turns acidic. Also, you could just take the temp sensor out and run it outside the car in boiling wanter and measure the resistance to see if it's reading correctly (need to find what resistance readings should be..)
'84 M635csi
'86 Lotus esprit Turbo (sold)

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Re: 1984 633CSi Rises again!

Post by 86_6series » Wed Oct 14, 2020 11:49 am

What I see is the temp for the upper rad is lower
than the bottom. Usually hot water enters the rad @ top
and cools as it works it's way down to lower hose.

Other than that, temps that you measured seem normal to me.

As said, it could be the guage or the temp sending unit to guage.

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Re: 1984 633CSi Rises again!

Post by songzunhuang » Thu Oct 15, 2020 7:59 pm

TBM wrote:
Wed Oct 14, 2020 4:56 am
Have you checked that your fan clutch is fully engaged? Common problem..If not fully engaged its of course not moving enough air.. If its bad may be a good idea to use either a high CFF electric fan on the front of the car (a pusher) or once you remove the fan clutch a low profile sucking fan on the inside of the engine compartment.. Its a bit of a job but the fan either works or it doesn't and in the future easier to diagnose or replace.

. When was the last time you flushed out the system with new coolant? If over a year ago you may have some kind of blockage (not likely, but you never know.) Coolant should be changed every year either way or it turns acidic. Also, you could just take the temp sensor out and run it outside the car in boiling wanter and measure the resistance to see if it's reading correctly (need to find what resistance readings should be..)
Thanks for the input. I hadn't thought about the fact that hot coolant enters at the top. Perhaps checking the center top of the radiator is not an ideal place. I made special note of the area right by the temp sensor. As you can see, it hardly changes.

I thought about the viscous clutch, but the "newspaper test" tells me that it's not the culprit.

So yesterday I took the car to the office. On the way home, I ran an errand. All together, this was over 100 miles of driving. I watched the temp closely. I even got out once when it was at 3/4 on the temp gauge and measured the area by cylinder 6, which is what normally gets the hottest. I saw a reading of 223F, which is a bit hot but not surprising on a 91F day. Once again I checked by the temp sensor and it was 184F. Last weekend I put in a 80C (176F) thermostat so that reading didn't seem out of line. Also while running errands and driving home, I ran the A/C which had a measured 46F-48F blowing out the center vent the whole time. That made me happy since it was a hot day.

The weird part is that I could be at a constant speed on the freeway and it would rise close to 3/4 and then drop to just over 1/2 and then go back to 3/4, all within the span of 15-20 minutes. It just doesn't make sense!

I may try the coolant flush, just because I'm running out of ideas!
Last edited by songzunhuang on Fri Oct 16, 2020 8:40 pm, edited 1 time in total.
-----
Song Huang
1984 633CSi
Last 7 of VIN: 6997383

songzunhuang
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Re: 1984 633CSi Rises again!

Post by songzunhuang » Thu Oct 15, 2020 8:20 pm

86_6series wrote:
Wed Oct 14, 2020 11:49 am
What I see is the temp for the upper rad is lower
than the bottom. Usually hot water enters the rad @ top
and cools as it works it's way down to lower hose.

Other than that, temps that you measured seem normal to me.

As said, it could be the guage or the temp sending unit to guage.
The temp sensor test was mentioned in another thread as well. I actually have an extra one of those I could compare against. Turns out in the early days of fixing this car, I had suspected the sender and purchased a spare. However, when I install the spare many years ago, the reading was even higher on the gauge! This made me put the old one back. ;)

In any case, worth a shot since I have the bits on hand.
Hm, I just grabbed the spare temp sender and tried to get a resistance reading at room temp. I couldn't even get my multimeter to register anything. It's like the sender is an open circuit at room temp. I them ran outside and measured the unit installed on the car. It was 84F at the temp sender housing. Alas, when I measured the installed unit, nothing. Once again, it appears that it's an open circuit until it warms up a lot more.

Oh well, I guess I'll have to put them in boiling water and try a side by side.
-----
Song Huang
1984 633CSi
Last 7 of VIN: 6997383

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