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BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

in the last 2 weeks my temp gauge has slowly been reading higher and higher, i just thought its reading what it should, when i had my car on scantools it read 80 on the gauge and proper running temp of 90 on scan tools. However is has been getting even higher, the fan cuts in, but i dont know at what temp, if the rad thermister is going faulty could it cause these kind of sysmpoms?
I did take a reading from the CTS once but i forgot what it was, i will take out my DMM today and take some measurements. Can you test the rad thermister, or is it just a on at a certain temp, i guess i could take a reading from the CTS when the rad thermister turns on the rad fan.
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x2 33 16v
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BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

Ok I got a reading of 3.04 on the 20k scale on my DMM when cold, I was running late and didn’t have a chance to do anything after a 20 min journey out, then 1 hour rest, but did after the 20 min return journey on the way back.
I checked the hoses, the o/s one was king hot, but the n/s one was just warm, then the fan kicked in and the n/s one got toasty as well, King hot, so I guess the thermostat is working?
I got a reading of 0.22 on the 20k scale of my DMM when the fan kicked in and the gauge was reading about 95c.
On idle the fan kicked in every 45 secs or so and the DMM only went down to 0.21, if I held it at fast idle the fan stayed on and then went off after returning to idle and then went back to the previous cycle.
What do you think, is my gauge just reading wrong?

P.S
I have looked at bobbers post
http://www.alfa-pages.co.uk/viewtopic.php?t=5919&highlight=cts

and

Multimeter set to 20 kOhm, should get

-10C = 9 kOhm
0C = 6 kOhm
+10C = 3.8 kOhm
+15C = 3 kOhm
+20C = 2.5 kOhm
+25C = 2.1 kOhm
+30C = 1.7 kOhm
+40C = 1.2 KOhm
+60C = 600 Ohm
+80C = 330 Ohm
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x2 33 16v
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JeremyC · Posted: Fri Jul 31, 2009 8:51 am Post subject:

If the fan is cutting in then surely that's two independant sensors saying the temperature is high and therefore it's likely to be an actual temperature problem rather than a sensor problem.
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'93 Black 33 1.7 16v

bobbber · Posted: Fri Jul 31, 2009 10:39 am Post subject:

I agree with Jeremy... but I wonder what's *actually* going wrong here?

http://www.alfa-restoration.co.uk/jetronic/tempsender.html

0.22 kOhms is 220 Ohms which is about 90 degrees?! For reference the fan should cut in at about 90-94 degrees and then switch off at 85-89 degrees. So I'd say, based upon that evidence that it's running at about 90.

I think it's unlikely that both the rad and coolant sensors are wrong (after all, the one on the rad is actually VERY simple).

So :

Thermostat stuck a bit closed (or some crud in there)
Dirty radiator
Unpressurised system
Out of phase ignition
Low oil level
Duff water pump
Low coolant level
Something inhibiting normal workload (i.e. stuck brake/handbrake or similar)

Now I'm no expert at this lot (and haven't managed to sort mine out either) - but that's the basics. Mine was really bad, but got a better after I fitted a new pressure cap on the expansion tank (which looked fine apart from being able to blow through it!!!!).

Let me know about that little lot (should keep you busy for a while).

B
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Fiat Bravo 165 Sport

BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

Thanks for you replies guys,
In answer to your suggestions

bobbber · Posted: Fri Jul 31, 2009 1:23 pm Post subject:

Ok, what about lean mixture? Fuel filter replaced recently and good fuel pump pressure?
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Fiat Bravo 165 Sport

BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

It has only just started to do it, however I think my fuelling might be lean.
When I checked my emissions I adjusted the mixture with the aid of the idle mixture screw so that the car would pass on idle and fast idle, which it did/does using the correct fuel selector. However when I connected up the lambda sensor it shot up to .45 as the car has from the start of me owning it. I thought that is was a dodgy lambda sensor and got a replacement but haven’t fitted it until i can get a reading of what its correcting the emissions to by reading emissions before the cat. Now I'm leaning towards the cat being duff and maybe the lambda sensor being correct, but I haven’t been able to prove it.
I have been running without lambda correction before this temp thing started.
What you think?.....
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x2 33 16v
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JeremyC · Posted: Fri Jul 31, 2009 2:25 pm Post subject:

My Saab 900 started overheating, it would boil if I was stationary for more than 30 seconds. The rad had the tiniest of leaks.

Replaced the rad, problem went away. I think rads are a bit like exhausts, they can look fine from the outside whilst inside they are completely shagged.
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'93 Black 33 1.7 16v

BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

Thanks for the suggestions so far guys.
yer bobbber I have fitted a new fuel filter not to long ago.
When stationary the fan cuts in and out and the car doesnt overheat.
Nothing has been changed to make the temp gauge read higher pointing to that item, although when the coolant and thermostat was done the gauge did start to read between 80 - 90, I just thought, as I said to bobber in his post, that maybe the temp is where it should be or that the temp gauge is reading correctly.
I forgot to mention in the above post that there was pressure in the system, so the system does get to pressure and to add..
I did a journey until the dash gauge red 80c, I pulled over and the system was not up to pressure, squeezing both large rad pipes were soft, the N/S pipe was warm, but the top O/S pipe was cool. AS per usual I don’t take over 3k, I forgot my DMM, DOH!

I would have thought if the thermostat was closed then yes the O/S pipe would be cool, but why is the N/S one warm? Is it due to water going round the closed thermostat loop of the heater matrix and header tank, warming up the water in the N/S pipe?
Is it possible that the CTS gauge sender can fail giving erroneous higher readings?
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x2 33 16v
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BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

I just had a thought, would a different thermostat and differing coolant type and strength of mixture make any difference, as this started when I fitted new thermostat and coolant.
I havent had a chance to investigate any further, mot is due.
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x2 33 16v
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JeremyC · Posted: Wed Aug 12, 2009 5:23 pm Post subject:

Coolant no but a different 'stat may well run at a slightly different temperature.
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'93 Black 33 1.7 16v

BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

Could that be the same for bobbbers???
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x2 33 16v
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BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

I just fitted the ser 3 consol and the temp gauge reads the same btw.
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x2 33 16v
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knighty2 · Alfa Arna Joined: 19 Aug 2009 Posts: 11

reading through this and other threads, am I right in thinking that the alfa boxers run about 5-10 degreesC hotter when on a summer motorway run?

I have just replaced the thermostat on my 1989 1.7 8v with carbs, and sure enough the old one was stuck open, so previously it ran cool, then flew off the scale and over heated on a summer motorway run........now it fluctuates between about 88-92 around town and country lanes........ then on a summer motorway run it gets about 5-10 degrees hotter........is this normal?????

as a point of note, my engine is rear mounted in a beach buggy, I run a Mk1 golf GTi rad, with two 9" ducted fans permanently on, due to packaging the rad is not forward facing (side mounted).......and I dont run the heater matrix......I am considering rigging a heater matrix core back in, for engine cooling only, as I'm quite sure this helps the cooling circuit in the block side.........does anyone think this will help????

thoughts please!!!

.. · Guest

i always have the heaters full on in summer Razz

... and the windows down of course...

knighty2 · Alfa Arna Joined: 19 Aug 2009 Posts: 11

very funny - ha ha Mad

......just because the heater fan is not on, does not imply its not rejecting heat, the heater matrix will still cool the block water to a certain extent........any other thoughts on this?

RBL · Posted: Wed Sep 02, 2009 11:50 am Post subject:

Knighty. You're probably not getting the extra airflow that you should normally get at higher speeds needed to cool the extra engine temps. The coolant temp shouldn't increase that much.

I have the same engine in my Spyder with a front mounted 33 radiator, and I don't have any problems even with the rad mounted at 45degrees, a small air intake grill and mid-mounted engine. Can't you mount the rad towards the front or in the airflow? (you wouldn't need the fans on then - my fan only comes on a hot day in traffic)
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Porsche 550 spyder replica with Alfa Sprint 1.7 engine

JeremyC · Posted: Wed Sep 02, 2009 1:13 pm Post subject:

With a recent new 'stat mine is rocky steady in the middle and cruising at motorway speeds it occasionally drops down a tiny bit then rises again.
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'93 Black 33 1.7 16v

knighty2 · Alfa Arna Joined: 19 Aug 2009 Posts: 11

thanks RBL and Jeremy.........great information.......RBL - whats the height and width of your spiders front air intake?

The trouble with my front end is there is literally no room for a radiator, but it looks like I may have to approach it from a different angle.........I could perhaps do it with two front mounted heater matrix cores.........I was also trying to avoid the long heavy pipe runs.........but hey ho - my current system is actually not that bad, I'm just being a bit of a tart and cautious like.

JeremyC · Posted: Fri Sep 04, 2009 7:45 pm Post subject:

Is your rad a truly known quantity.

Rads can look fine but be silted to hell.
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'93 Black 33 1.7 16v

BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

The car does not get up to temp atfer 20 mins now, where before it took 5 mins.
After 30 mins on the motorway at 3k "60mph" the temp was at 70c, after revving to red line a couple of times the temp then sat at 80c.
I am now beginning to think that the new thermostat "who knows how long it has been sitting on the shelf" is to blame.
I got the new thermostat Thu Mar 26, 2009, from CAF I think, I fitted it on Sat Mar 28, 2009. As per my post in this thread http://www.alfa-pages.co.uk/viewtopic.php?t=5986&highlight=thermostat you can see that I had problems with if straight from the bat.

What do you think.
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x2 33 16v
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BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

Well now i am thinking that the sender for the console is to blame.
I got the same as above today but i didnt red line it and it still sat at 70c, after my 30 min motorway drive i left the engine running and waited for the rad fan to cut in. I checked the gauge and it said 75.
What do you think now.
Am i right in thinking there are 3 things relating to temperature on the engine.
1 CTS
2 console red light
3 console gauge
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x2 33 16v
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Guest · Posted: Wed Nov 25, 2009 7:49 pm Post subject:

Could be a faulty(jammed) thermostat. It happens.

BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

I don’t know what to think, the rad fan came on, which is at 90c I think and my gauge read 75c, I think I need to investigate further? I could get a DMM on the CTS to confirm the temp.
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x2 33 16v
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Oggie · Posted: Wed Nov 25, 2009 8:58 pm Post subject:

I bet you knocked the needle out of line when you applied you white dials Al?, I never trust the readings on the dash just use them as a guide.
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PHAT 33