view CTS coolant temp sensor with Elanscan

[perel]

Hello, I have a problem with the operation of a random hot motor. I suspect the CTS coolant temp. sensor.
Is it possible to visualize the defect with elanscan? which parameters should be analyzed to see the anomaly?
Thank you for your answers. Welcome to Normandy.

[MPx]

Hi perel. I've just replaced my CTS in the ongoing battle to solve an issue only occurring under track conditions. The elanscan graph that led me to do it was this one

Which as you can see simply plots Temp against time - this one covers a 5 lap track session. The advice I've had is that once warm/hot the engine temp should stableise and stay within a few degrees no matter how hard the car is working (assuming not stopped in traffic etc.). My graph clearly shows it actually cooling significantly from the initial high from some time into the second lap - most odd! However I've not yet had time to capture a post CTS replacement graph so don't know if its now behaving differently to this or much the same.

On a related matter, the Wiki suggests taking the CAS off to get at the CTS - which is a bit of a pfaff to put back. I found that simply by removing the plug leads I could get an extended (deep) socket on the CTS and undo/replace with eveything else left in place. You do need to take care not to disturb the wire from temp sender for the guage though.

Best of luck with it.

[perel]

Hello MPx, thank you for the answer that makes me progress in my research. Your information is very useful to me. Could you tell me what parameter is saved by capturing the graph with CTS Low? There is also CTS Hight. Simply maximum and mini temperatures, perhaps.

[MPx]

Hi Perel

Sorry, I'm afraid my knowledge of Elanscan is very very basic - and I don't know how to answer your question. I can't even see CTSLow and CTSHigh in the capture that RonR did for me at Castle Combe. You'll have seen that my graph was just from plotting Coolant Temp vs Time which is half way down the displayable fields on the left.



Hopefully someone else will be able to help further.

[Tuga2112]

Hello MPx, thank you for the answer that makes me progress in my research. Your information is very useful to me. Could you tell me what parameter is saved by capturing the graph with CTS Low? There is also CTS Hight. Simply maximum and mini temperatures, perhaps.

given the way the parameter is worded. im curious if its values are 0 and 1 by an chance ? because if they are. its a flag, and if that is correct. then it would probably be only usefull as a guideline that the reading is outside expected values, but not actually telling you the value the CTS is returning.

[lotusflasherman]

I had problems with a CTS many years ago and been looking through my notes I made, before there was the useful page on WikiLEC. http://wikilec.com/view/CTS
It is a thermistor, which is 'electrical engineer speak' for 'thermal resistor' meaning a resistance that changes with temperature.
If you have a simple multi-meter with ohms scale the key information, easy to check, is : in iced water it should be about 8k ohms, in boiling water 185 ohms.
They are fairly robust and not prone to changing values, just stop working. Mine went open circuit, so very high resistance (infinity is high ) so ECU thought engine was cold. It was fine on first start up but soon too rich as the engine warmed up. (I found an old volume control 'pot' that covered the approximate range so 'lashed up' a manual adjustment until a new CTS could be purchased and fitted.)

I'd be very interested to see the graph from MPX with his new CTS fitted. On track, a full throttle blast down the straight will generate a lot of heat in the head so CTS will then read high, braking and part throttle will allow it to reduce, then high again for blast down the next straight. The graph covers 1000 seconds so 16 mins 40 seconds and range approaching 110°C doesn't surprise me - that's why the system is pressurised, to elevate boiling point ... 15 psi elevates it to 125°C. You get more power at higher temperature, particularly with cold air, which is more dense. Variation for 110° to 90° is within my expected range. BTW I run on an Everest chip and a diesel Astra thermostat which opens about 5°higher than the OE 'stat.

If you do the boiling water / iced water check and figures are about right I'd try a new thermostat before replacing the CTS. Thermostats can get a bit sluggish and not fully open - I usually check mine boiling it up in a saucepan - but only when my wife is out ..

[lotusflasherman]

I forgot to mention this .. "I have a problem with the operation of a random hot motor. I suspect the CTS coolant temp. sensor." That will not be the CTS, the CTS just provides temp information to ECU for mixture (slightly rich on cold engine), and restriction on Boost level until engine is up to operating temperature. It will NOT cause random hot engine, only collect data about a random hot engine. That is far more likely caused by a 'sticky thermostat', though a weak mixture from a leaking inlet manifold gasket can cause hot running but on turbo boost you can usually hear it whistling/hissing out. I'd put my money on a new thermostat as your solution.

[MPx]

I'd be very interested to see the graph from MPX with his new CTS fitted.

Thanks Phil, and so would I. Two issues are 1: I can only generate the symptoms in track conditions not the public roads - I will do a public road run to see what happens but it wont be conclusive whatever the result. 2: I'm currently in a Covid household and went positive myself on Sunday so I'm grounded anyway!

On track, a full throttle blast down the straight will generate a lot of heat in the head so CTS will then read high, braking and part throttle will allow it to reduce, then high again for blast down the next straight. The graph covers 1000 seconds so 16 mins 40 seconds and range approaching 110°C doesn't surprise me - that's why the system is pressurised, to elevate boiling point ... 15 psi elevates it to 125°C. You get more power at higher temperature, particularly with cold air, which is more dense. Variation for 110° to 90° is within my expected range.

And thanks again and very much chimes with Joao's expected variation as he told me on the Castle Combe thread. On the other hand...That graph isn't going up and down between corners and straights. Its slightly under a 100s lap for me if I'm trying - clearly not when I'm coasting if its gone bang - but anyway the temp warms up over the first lap or two then drops like a stone for a couple of laps then reverses again so these are more than whole lap swings. The symptoms start on about lap 4 and terminal on 5 and 6. Also very recent advice from Phil Webb at SWLC was that once the car is properly warm and thermostat open then temp should be stable and vary by very few degrees no matter how hard its used (obvs excluding traffic issues etc - and there weren't any!).

Anyway, I'll get my new graph and post it in my own new thread, and migrate all the other posts there too so that I stop hyjacking other's threads.....sorry!

[lotusflasherman]

Two issues are 1: I can only generate the symptoms in track conditions not the public roads - I will do a public road run to see what happens but it wont be conclusive whatever the result.

I had no issues on track in L100ELN which runs an Everest Chip and big brakes and was great fun, that was till the lunch break when I went to refuel at closest filling station to ' Combe and found they didn't sell Super. Put in 'rubbish' and it was 'flat' and running hot with Knock Sensor working overtime in afternoon session, came off after 3 laps before I damaged something. I'd only half-filled so topped is up with Super a.s.a.p on my way home as soon as I could..

I was building 998cc Mini engines in the 70's for Mini Miglia formula and we did a lot of work on water pumps and water gallery for racing, as well as the oil pump end of things. Peak power of around 95bhp was between 9,000 rpm and 9,500 and went to 9,800 but cavitation around the impeller was an issue solved with some grindstones and a bigger pump pulley to slow down rotation a bit. I trained as an Engineer in Electricity Supply Industry and we did Mechanical Engineering as well as Electrical and Civil. Water pumping and water turbines for hydro-electrical power normally run at 3000 rpm (50Hz) so design is much easier than a car that ranges from below 1,000 rpm to nearly 10,000 rpm, where it will be very inefficient most of the time as the optimum rpm band is very narrow. The big danger is cavitation causing air bubbles in the impeller housing. I thought about electric water pumping at constant speed but Mini 7 Club suggested that was outside their Regulations.

I seem to remember Rock Auto sending me an Elan pump that needed attention with a grindstones before fitting, wasn't quite the right alloy casting externally, and impeller was a bit messy and big. Had 4 M100's since 1995, still got 3, but can't remember which car that went on.

Just a thought - You are using a thermostat with a 'jiggle pin' fitted at 12 0'clock I presume ... ? it's there to prevent air getting trapped in the thermostat housing which can cause overheating... and probably will do on a track day.

[lotusflasherman]

Just thinking back .. I did once have a leaky header tank through the horizontal seam and the replacement I bought from a nearby Vauxhall Dealer* came with a black cap marked with "120" which I guessed meant 120 kPa. The old Yellow one had "110". (* iirc the Part No moulded on it identified as used on Vauxhall Nova's of that era, but I may be wrong.)

Lotus Service Notes (Section TDH, Page 6) says 110 kPa/15 psi, though in my world of engineering 110 kPa is much closer to 16 psi.
120 kPa is 17.4 psi so coolant boiling point would be raised by about 3°C over the 110 kPa cap, so about 128°C, instead of 125°C. I run a higher set thermostat for reasons of thermodynamics, and the heater is much better for winter use, so was happy to use the black one.

There was a discussion on LEC several years BC (Before Covid) about 'operating pressure' and I posted a link to a YouTube video of how I checked mine.
Just remove the upper small bore tube and plug it towards the engine and blow with an electric tyre pump into the header tank through the pipe.
I'll repost the link here in case anybody wants to check theirs >>> Pressure Cap check

[Tuga2112]

and thanks to the marvels of IT you can also see the video without going to youtube