23 minutes ago, KenONeill said:

Also @RicardoM 

 

The thermostat will be fully open well before the radiator thermo-switch starts the fan. "Overcooling" is a technical condition where the actual coolant temperature drops below the design "normal running temperature" due to the fan duty cycle being excessive (or the thermostat being removed, but I think we can rule that out on this vehicle).

Yes, tuermostat will be open. And even if fan was running constantly, thermostat valve closes again and won't allow coolant in engine to drop below 90°.  

How does running fan differs from airflow during normal driving? Coolant in radiator is always cooler than coolant in engine, thats why it's there.

1 minute ago, Papez said:

Yes, tuermostat will be open. And even if fan was running constantly, thermostat valve closes again and won't allow coolant in engine to drop below 90°.  

How does running fan differs from airflow during normal driving? Coolant in radiator is always cooler than coolant in engine, thats why it's there.

Did you seriously just claim that you get significant cooling in the radiator top hose!!?

No. Where do you see such claim?

 

Do you claim that fan somehow cools radiator top hose or how it's related to this issue? I'm just saing that purpose of radiator is to reduce coolant temp. And it doesn't matter if airflow is provided by fan or vehicle movement.

Edited 21 June, 20188 yr by Papez

@nimbus

Most (90%) overheating issues that I know of are thermostat related. Then comes corroded contacts at radiator fan thermo-switch connector that prevent the fan from starting. Last, head gasket related issues.

56 minutes ago, RicardoM said:

@nimbus

Most (90%) overheating issues that I know of are thermostat related. Then comes corroded contacts at radiator fan thermo-switch connector that prevent the fan from starting. Last, head gasket related issues.

I would also add partialy clogged radiator (in older cars with badly maintained cooling system) and thermoswitch itself failing or changing characteristics over time. It's simple bimetalic switch, which is not exactly reliable. In times when estelle and Favorit was common workhorse here, it was common to use switch button to bridge thermal switch in case of malfunction

Edited 21 June, 20188 yr by Papez

4 hours ago, Papez said:

No. Where do you see such claim?

 

Do you claim that fan somehow cools radiator top hose or how it's related to this issue? I'm just saing that purpose of radiator is to reduce coolant temp. And it doesn't matter if airflow is provided by fan or vehicle movement.

I actually know how a radiator works well enough to not make a "broad-brush" statement like "coolant in radiator is always cooler than that in engine". For that statement to be true the coolant has to lose temperature in the top hose rather than as it descends through the radiator. Actually, your statement also implies that coolant is heated in the bottom hose.

18 minutes ago, KenONeill said:

I actually know how a radiator works well enough to not make a "broad-brush" statement like "coolant in radiator is always cooler than that in engine". For that statement to be true the coolant has to lose temperature in the top hose rather than as it descends through the radiator. Actually, your statement also implies that coolant is heated in the bottom hose.

 

You take things too literally on purpose... You know i meant "part of exchanger where air goes through" and not top hose... And coolant stays cool even after it leaves radiator, yes... Still, you didn't explain how running fan undercools engine, if thermostat valve works properly

36 minutes ago, KenONeill said:

I actually know how a radiator works well enough to not make a "broad-brush" statement like "coolant in radiator is always cooler than that in engine". For that statement to be true the coolant has to lose temperature in the top hose rather than as it descends through the radiator. Actually, your statement also implies that coolant is heated in the bottom hose.

Take it easy guys

 

3 hours ago, RicardoM said:

@nimbus

Most (90%) overheating issues that I know of are thermostat related. Then comes corroded contacts at radiator fan thermo-switch connector that prevent the fan from starting. Last, head gasket related issues.

Aha okay thats good to know

By the way I found this one that had a range of 92-87 degrees, is it this @Papez ?

https://www.autodele24.dk/8177760-jp-group-temperaturkontakt-kolerventilator

5 hours ago, KenONeill said:

Cheers; you're good to not boil until at least 115C with the standard pressure cap then.

okay, 115c should be the red mark

30 minutes ago, Papez said:

 

You take things too literally on purpose... You know i meant "part of exchanger where air goes through" and not top hose... And coolant stays cool even after it leaves radiator, yes... Still, you didn't explain how running fan undercools engine, if thermostat valve works properly

You do know that the thermostat isn't an on-off switch? And that it opens and closes below design running temperature? On the presumption that you do, why are you arguing that an engine can't be cooled below its ideal running temperature by an otherwise standard system with a fan that has a lower than design disengagement temperature?

34 minutes ago, nimbus said:

https://www.autodele24.dk/8177760-jp-group-temperaturkontakt-kolerventilator

 

It doesn't look like that in picture, but parameters look similar. That one I have bought is this:

https://www.autobyznys.cz/x3552/cidlo-chladice-skoda-105%2F120-cz%3B-113095070

You can se "TH470.1" engraved into it.

Its parameters are: turn on temperature 85°C +-3, turn off less than 77°C. 

 

34 minutes ago, KenONeill said:

You do know that the thermostat isn't an on-off switch? And that it opens and closes below design running temperature? On the presumption that you do, why are you arguing that an engine can't be cooled below its ideal running temperature by an otherwise standard system with a fan that has a lower than design disengagement temperature?

 

Yes I know. And do you know that during normal droving, coolant temp on output side of radiator goes way bellow turn-off temperature of switch, because otherwise it would never turned off?

On 1/18/2018 at 03:38, eng_ahmad1986 said:

Greetings to all members

I have a this coolant temperature puzzle that is driving me crazy !!

I'm located in Cairo, Egypt

I own a 1996 Skoda Felicia Combi on carburetor ( 43 KW )

Coolant temperature sensor is the metal one, with one terminal connector.

installed radiator fan switch rating : on at 82 C , off at 68 C

my problem is that the radiator fan kicks in too late , meaning over 90 C , probably 95 at idle , and switches off above between 70 C and 90 C

this condition worsens after driving for a while then stopping , fan kicks in at probably 100 C and off probably at 88 C ( at idle )

there is no thermostat installed

things that have been replaced so far : radiator , coolant pump , fan switch ( same rating as above )

checked head gasket for compression leaks , the mechanic confirmed that the head gasket is OK for there is no pressure build up in coolant hoses . 

my head is going to many thoughts, could it be coolant temp sensor ? could it be temp gauge out of calibration ? could it be any other thing ?

and by the way , if the fan switch is with the above rating , what would be the normal range for the fan to work regarding the temp gauge ? 

this condition is driving me crazy , I don't know what else to do , please help  I really need it urgently

thank you all very much for considering  

Please check the ground (negative ) connected to the body.because if negative is not connected to body this heating problem arises

Hello everyone,

 

Also here a little feed back,

 

So I changed the original thermo-switch with one of the Skoda 120. And it works perfectly, only little detail is that the fan runs around 1min after turning off the engine ( Because the coolant is hot ) But that's not a problem for me  

 

Thanks for all the infos.

I know i am kinda late but i will tell you what i have done in both my felicias here in greece to keep them running cool
They are both 1.3l 68hp MPI engines
For summer time 
The one with ac gets a 70-75c thermal switch for the fan and no thermostat (free flowing) and operates nominally around a millimeter below the midle point of the gauge(with the ac off) and a mm above the midle point with the ac on
The other felly that does not have an ac just gets 80-85c thermal switch and no thermostat and it operates right on midle point
For winter time
Both cars get a thermostat and an 80-85c thermal switch and operate at middle point
This way i ve completely solved my fellys heating issues
I know it is NOT OPTIMAL but it most certainly is fuctional

Please tell us what "winter" time is in Greece.

Yes yes i forgot to mention the cliamate parameters
So during summer we get 30-40c 35c on average where i live
And during winter we get 0-10c and rearly go below -3c to -5c at the most extreme conditions

Edited 15 July, 20187 yr by Thefeliciahacker

I would like to understand what is the logic behind no thermostat during summer and the hassle of putting one during winter.

On 15/07/2018 at 15:21, RicardoM said:

I would like to understand what is the logic behind no thermostat during summer and the hassle of putting one during winter.

More coolant flow during warmer times simple

1 hour ago, Thefeliciahacker said:

More coolant flow during warmer times simple

A working thermostat suitable for the specific weather conditions allows all the flow you need. It doesn't act as a restriction at typically flow values found in an internal combustion engine. Of course you can do whatever you want. I am just expressing my opinion for the readers to decide what is better.

I do NOT dissagree but
More coolant flow usally means more heat disspation in the same amount of time
And the lower the temperature (not below 75c) the happier a 1.3l engine is 

Here in greece more than 80% of 1.3l fellys have blown head gaskets from overheating
My other felly (without ac) blew its head gasket before the temperature even reached red
So the cooler the better
 

1 hour ago, Thefeliciahacker said:

Here in greece more than 80% of 1.3l fellys have blown head gaskets from overheating

What part of Greece are you living in?

On 20/07/2018 at 23:57, RicardoM said:

What part of Greece are you living in?

I live in Peloponnese

On 20/07/2018 at 23:57, RicardoM said:

What part of Greece are you living in?

 

Greece has not so predictable climate as other countries so don't try to judge by the area

especially in some islands the situation can be very different.

If you insist i will give you some examples from my own place.

 

 

On 18/01/2018 at 00:08, eng_ahmad1986 said:

 

I'm located in Cairo, Egypt

 

my problem is that the radiator fan kicks in too late , meaning over 90 C , probably 95 at idle , and switches off above between 70 C and 90 C

 

Mahle has a very interesting list of radiator fan switches,they start from

switching point 65.0 °C • Shut-off Point 60.0 °C

 

https://catalog.mahle-aftermarket.com/eu/

 

By the way in your avatar the black & white photo is Abdel el-Sisi?