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> UNDERheating problem, World-of-the-strange
dante giacosa
post 28th February 2019 18:19
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Hmm,

Well; I've just completed my bi-monthly 300-mile commute to the top of the country, and was surprised to discover an anomaly on the way.

My coolant gauge- which; once up to temperature ('90') NEVER moves- was reading low. Just over 70 in fact, at motorway speeds.
Very strange. Ambient temperature; 8 degrees.

Stopping at roadworks; the temperature steadily rose to a nominal indicated 90, before the radiator fan came on...

As I was sitting at the roadworks; I could see the needle on the temperature gauge making MICRO-movements up and down, but steadily rising.

(I also have oil-temperature instrumentation; and this read an ordinary '100'- which confirmed the engine was okay. There was no loss of power, no sign of a coolant leak, or anything.)

My thoughts are: thermostat, or coolant-temperature sender?

The car does run quite rich I think.

Thoughts?




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dante giacosa
post 28th February 2019 21:16
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Hmm,

Started the car again, after an hour and a half off, and immediately drove for twenty minutes.

The coolant-gauge was reading 'stone cold' all the way- showing no temperature at all.

The oil-temp gauge came up as expected, and I was able to blow proper hot air from the vents.

Got to my destination, left the car running for a few minutes and the coolant-gauge came up to temp...


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SteveG
post 28th February 2019 22:12
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QUOTE(dante giacosa @ 28th February 2019 21:16) *
Hmm,

Started the car again, after an hour and a half off, and immediately drove for twenty minutes.

The coolant-gauge was reading 'stone cold' all the way- showing no temperature at all.

The oil-temp gauge came up as expected, and I was able to blow proper hot air from the vents.

Got to my destination, left the car running for a few minutes and the coolant-gauge came up to temp...

Sounds more like sensor to me, too erratic for the stat.
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hazeyblue
post 1st March 2019 08:48
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I'd start with the Temp Sender Unit.
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JeremyG
post 1st March 2019 09:07
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QUOTE(hazeyblue @ 1st March 2019 08:48) *
I'd start with the Temp Sender Unit.


Yes, i'd agree.

Dante - first half of your first post (low temp at motorway speeds rising when stationary) suggests thermostat but everything else suggests temp sender (or wiring).

I guess you could have both...
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dante giacosa
post 1st March 2019 11:50
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Ok team-

Thanks for your feedback.

Got an appointment for next week at my specialist.

We'll have to see...


A quick sniff at the back of the coolant-sender doesn't reveal much



This post has been edited by dante giacosa: 1st March 2019 12:17
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Ganz
post 2nd March 2019 22:28
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That's never happened on mine. I'd be guessing so see what the specialist says. Sure it's nothing serious. Water temp was one of the reasons I brought the extra gauge with its own sender. 145/6s and water temps eh?

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dante giacosa
post 3rd March 2019 10:31
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that's interesting Ganz-

Yes- it was somewhat a relief to have additional instrumentation; I'd have been quite worried if I hadn't been able to independently confirm genuine engine temperature.

Interestingly- I've driven the car a couple of times over the weekend; and it's sat at high-idle after starting for a long time- almost as if the engine isn't receiving the signals to make a descison to adjust the ICV down.

It's running fine though.
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dante giacosa
post 7th March 2019 09:47
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the 146.gif is in with my marque-specialist today for the coolant temperature issue.

This morning; I had warm air within three minutes of driving, but now a completely dead coolant-indication gauge all the way there...

Hopefully this should make it quite an easy diagnosis.
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dante giacosa
post 1st April 2019 08:45
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RIGHT,

well, a few weeks on- I think it's possible to pull focus on some every interesting outcomes from this little debacle.

In short; my garage diagnosed the following combination of issues;

* thermostat not fully closing

* possibly faulty coolant temperature sender

* faulty coolant sender wiring

I feel a bit of a fool with regard to the last item- as wiring is my area, and I should have thought of that. The loom-branch that led to the coolant sender itself had lost a core at the point that it appears from under the engine cover. There are three cores and as I understand it- two sensors (in the one housing); one which feeds the ECU and the other the gauge.
The consensus was that the performance of the sender(s) was ambiguous, and that it might be worth swapping out- I'm sure I had it on a list of things to swap out anyway, so I didn't complain.

The thermostat & coolant were swapped also.

results?

Well, somewhat tellingly; the car now warms up and very occasionally exceeds the 'dead-centre' 90 degrees which it always shows on the gauge. I have never seen it exceed 90 degrees!
When this happens, the radiator fan kicks in and immediately acts upon the coolant temperature which very quickly drops on the gauge, at which point the fan drops out again.
The 930 CF2s have two fans speeds and a relay for each; one is on the fusebox, and the other is under the bonnet under the BBoB. They are negative-switched constant positive relays, and I have cabin indication for each speed.

Classically 'speed 1' is associated with air conditioning; (which I have yet to fix), and I have never seen it in use (except VERY occasionally & fleetingly after a hot start) and now I see it all the time! Indeed both fans speeds see use with some regularity, within relatively short distances after starting.

Secondarily, and this has yet to be definitively proven until I do a to-the-top fuelling measurement after a big run- the car is more efficient.
I usually get '63 miles' in the town for 15 of fuel- I'm sorry I don't know exactly what that is in litres, but this has continued for some time.
Last week I got an easy 85 miles before the fuel light came on!
That can't be a coincidence, but as I say; a longer run will prove it.

I wonder if the coolant sensor has more to do with the general health & efficiency of the engine that could have been realised?
I think I read as much on here- but it was always behind the MAF and Lambda sensor for general performance.
My car has always run rich; and it remains to be seen if this little episode might have had wider implications.
Certainly with regard to coolant management; everything seems more dynamic and reactive.

Watch this space!



This post has been edited by dante giacosa: 1st April 2019 08:51
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JeremyG
post 1st April 2019 12:03
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Aha - so I was right when I said you could have both thermostat and wiring problems (is there an emoticon for smug grin?)!

Thanks for taking the time to feed back on this - especially re. impact on fuel economy - that's interesting!

I've always felt that the thermostat is a critical bit of kit to keep your engine running as designed, and is often overlooked (especially on older vehicles) given they're old-school mechanical items. But given they're not expensive and are generally pretty accessible it's an obvious item to change at any hint of a temperature-control issue. Only good can come of a thermostat change, in my view!
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dante giacosa
post 1st April 2019 12:15
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yes- I agree; that and the coolant pump.

I never feel I have TOTAL confidence in a car until I've swapped the thermostat & water pump out.

In this case however, I think that's irrelevant.

It's funny though, because it suggests the cars behaviour (up until this point) as being 'the best it could do' on the sensor inputs it was receiving.
Because now it is behaving differently- the fan cycles on & off within a minute now, rather than running for a few minutes.


if only they could talk!!
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JeremyG
post 1st April 2019 13:00
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Yes, agreed it'll be the faulty temp sensor info that has been foxing your ECU and causing it to run rich, not the thermostat... great to have a diagnosis and cure, though!

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dante giacosa
post 2nd April 2019 08:28
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yes indeed-

I'm not complaining though- in two years of ownership; it's the only thing that's ever 'gone wrong'...!
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