My fellow Felicians,

from last year i am facing a problem with my coolant temperature and i call it ''weird'' because happens ONLY when i start the car and for few minutes, after this everything work as they should be.

 

Here is the detailed description:

I start the engine,for the first minutes the needle of the panel gauge is low because the temperature of the coolant is low

as usual after 2-3 traffic lights starts rising slowly to 80 'C and suddenly...it goes crazy!

Very fast climbs one click above the '90 C line which means is 91 or 92, i have a smell in the cabin that something is burning (like some coolant drops on a hot surface and i have some emissions) and the radiator fan IS NOT starting!

For few seconds i am in panic but when i accelerate to the next traffic light the needle immediately drops to the 80 'C and later as i am moving slowly reaches the 90'C line and whoa!

the radiator fan start spinning and everything looks normal.

 

No matter if i drive then for 15 minutes or 2 hours the whole system works properly, no overheating, the needle never goes beyond the 91 'C point and the radiator works every time the systems need it

So ONLY when the engine is COLD that weird phenomenon shows up.

 

What i have done to solve this?

I have changed the thermostat with a new one better quality with housing and gasket at 88'C

New Motul Inugel coolant, volatilization (no bubbles) and new blue cap on the reservoir expansion plastic tank

No leaks checked by me and later from the mechanic

New 4 PIN sensor (which is before the thermostat) 6U0919501B

New radiator fan switch 6U0959481E at 70-75 'C one month later a 75-80 'C and later a 80-85 'C and guess what...absolutely the same thing happened!

 

For one year this problem drives me crazy because i can not find from where it comes,if i give my car to another driver which in purpose will not pay attention the the panel gauge he will notice nothing strange except that few seconds odour and after few minutes he will hear the radiator fan working so he will think that everything are as they should be.

Any suggestions why the temperature is rising so fast in few seconds and later becomes normal? have you ever faced the same or something similar?

 

PS: Keep in mind that before 2 years i installed a new water pump (changed due to a leak ) and a Bosch ventilator (changed due to failure).

 

Intresting well, a check that will clarify a bit more to me is a constant idle test,
Go ahead and start the car stone cold,

Keep it idling constantly at around 1500 rpm and see how the needle reacts,

if this fast step does not happen then I am preety sure of the reason.

Then reapeat the same test with coolant cap off
My possible causes are:

A thermostat that has to heatsoak a bit before it reaches steady state and the fast rising temperature caughts it of guard per say.

Secondly felicias at idle do not have enoguh coolant flow to keep the temperature from overshooting a bit so that may be it.
Thirdly wrong cap (do you see coolant on top of the expansion tank?)

Hello my friend,thank you for your answer.

1) The thermostat is new with housing and gasket,far better quality than the previous,i had that weird phenomenon before i install him

2) the coolant is new and in the proper level,i have no leaks

3) the reservoir tank and his cap are new VAG, the level is OK, it is tight and no leaks it or smell around it.

 

Checking my notes i saw that i have changed the radiator switch (was a Calorstat 79-88) and as i remember i had not this problem for some years

my prediction is that since i started working with Mahle that ''weird'' phenomenon shown up and my mistake was that i didn't wrote in my notes the factory radiator switch what brand was and how many 'C operating range had.

I will buy a Calorstat TS6840 (identical to what i had) and i will try make a video but let's hope that the situation will turn back to normal.

 

By the way does anyone  👨‍🎓 remember what brand was the factory radiator switch and what operating range had?

How old is the cabin heater?

1 hour ago, D.FYLAKTOS said:

Calorstat TS6840

 

It is indeed possible that the thermo switch and its acting speed is different. 

But I don't know

5 hours ago, RicardoM said:

How old is the cabin heater?

 

It's from 2000 when i bought the car

i have done a thoroughly a/c service few months ago.

 

4 hours ago, Thefeliciahacker said:

It is indeed possible that the thermo switch and its acting speed is different. 

But I don't know

 

None of these Mahle manage to stop that problem but they worked as they should be after the first appearance.

Yes they are robust but maybe are not so ''sensitive'' as other cheaper brands.

2 hours ago, D.FYLAKTOS said:

It's from 2000 when i bought the car

i have done a thoroughly a/c service few months ago.

The A/C system has nothing to do with the heater for the cabin.

The only possibility to have a coolant smell in the cabin is from the heater. After 20 years it is possible to have a tiny hole. Take it out and check it meticulously.

A very sudden change of coolant temperature can only happen if a bubble of hot air goes under the coolant sensor. When the temperature gauge goes up like crazy, carefully raise the coolant sensor a bit to let the air escape then put it back when only coolant seeps out.

29 minutes ago, RicardoM said:

 

The only possibility to have a coolant smell in the cabin is from the heater. After 20 years it is possible to have a tiny hole. Take it out and check it meticulously.

 

A very sudden change of coolant temperature can only happen if a bubble of hot air goes under the coolant sensor. When the temperature gauge goes up like crazy, carefully raise the coolant sensor a bit to let the air escape then put it back when only coolant seeps out.

 

It's too difficult for me,i work mainly on the side of the road which is dangerous and only with my own tools

i will have to ask for my mechanic to do it.

 

This suddenly movement of the needle happens every time (no matter if it's once or twice a day) i start the car so the engine is cold and happens only one time which means if my eye don't pay attention i will not notice this.

I remember few years back i had a similar problem and guess what was the cause? some dirt in the round base of the coolant sensor,i wipe it out when the coolant was cold and the problem solved.

I will do what you suggest tomorrow,few minutes driving and i will pull aside,i will wear gloves and after i wrap some paper around the sensor i will pull him out

let's hope that this will be the solution.

By the way is there a possibility for the Calorstat thermo-switch to be more ''sensitive'' than Mahle?

More sensitive or rather improperly calibrated

5 minutes ago, Thefeliciahacker said:

More sensitive or rather improperly calibrated

 

To be honest for the cost of 3 euro i don't trust them so much as Mahle for that important task that they have to do

i say to put again the 85-80 and do the RicardoM test,if this doesn't work then i have to turn again to the Calorstat as a last ''desperate'' solution.

 

By the way does anyone know what brand and how many 'C the Felicia had from the factory?

I run Vernet one for 3 years now no problem whatsoever. 

1 hour ago, D.FYLAKTOS said:

I will do what you suggest tomorrow,few minutes driving and i will pull aside,i will wear gloves and after i wrap some paper around the sensor i will pull him out

let's hope that this will be the solution.

Remember there is a plastic safety latch that holds the sensor. Pull it out while holding the sensor, raise the sensor a little to let all air escape, put it back down, insert the latch. No big deal.

35 minutes ago, D.FYLAKTOS said:

By the way does anyone know what brand and how many 'C the Felicia had from the factory?

The thermoswitch is 92-87 °C standard and 87-82 °C for tropical countries (Middle East mainly). Don't know the brand and frankly it doesn't matter so long as it's not the cheapest Chinese brand like Vika.

Another test this morning,the car was cold and steady (not on the move) and guess what? exactly the same thing happened,the needle (and the temperature) raised at 93 'C the fan did not worked and suddenly the needle drop down,raised again slowly and when reached the 90 'C the fan started as normal.

I have it on a video.

 

10 hours ago, RicardoM said:

Remember there is a plastic safety latch that holds the sensor. Pull it out while holding the sensor, raise the sensor a little to let all air escape, put it back down, insert the latch. No big deal.

 

The thermoswitch is 92-87 °C standard and 87-82 °C for tropical countries (Middle East mainly). Don't know the brand and frankly it doesn't matter so long as it's not the cheapest Chinese brand like Vika.

 

I have done it and later when i finish my work (the car will be cold) i will pay attention but to be honest i am not optimistic

many guys says it's the thermostat and not the thermoswitch but that phenomenon shown up not only now with the new thermostat but with the older too.

It's a mystery...😪

 

As for the Vika, i have bought 2 light switches and don't worth the money.

 

 

VIKA and DPA branded products are manufactured in China and Turkey

@D.FYLAKTOS - Well, I think you're assuming correlation between 3 separate items:-

1. The thermostat, which is a purely mechanical device in the cylinder block.
2. The sensor for the temperature gauge, which is in the block, but physically separate to and distinct from the thermostat.
3. The radiator thermoswitch, which is in the radiator, and controls the electric fan, entirely separately from (2), and only operates when (1) is open. When (1) is closed, there is no coolant flow to the radiator so (3) detects the local air temperature, not the engine coolant temperature.

9 minutes ago, KenONeill said:

@D.FYLAKTOS - Well, I think you're assuming correlation between 3 separate items:-

1. The thermostat, which is a purely mechanical device in the cylinder block.
2. The sensor for the temperature gauge, which is in the block, but physically separate to and distinct from the thermostat.
3. The radiator thermoswitch, which is in the radiator, and controls the electric fan, entirely separately from (2), and only operates when (1) is open. When (1) is closed, there is no coolant flow to the radiator so (3) detects the local air temperature, not the engine coolant temperature.

 

After that problem occur i added in my console a gauge with an 1/8'' NPT sensor just before the new 4 PIN sensor (code 6U0919501B) ,i did as an extra insurance in case that the gauge has problem etc

but that crucial seconds shows exactly what the gauge on the panel for example 93 'c, those seconds i don't know what to do !

My thermostat is new at 88 'C, the thermoswitch is new, the coolant is new even the water pump has only 5100 km in use.

 

What is causing the temperature of the coolant (before the 4 pin sensor) to rise so suddenly and in few seconds returns to normal?

I so much air bubbles hidden inside the whole circuit?

3 hours ago, D.FYLAKTOS said:

What is causing the temperature of the coolant (before the 4 pin sensor) to rise so suddenly and in few seconds returns to normal?

Coolant temperature doesn't jump up and down so sudden. I see 2 possible scenarios:

1. An air pocket as I've mentioned before
2. The thermostat allows somehow(?) to pass hot coolant from the engine block for a few seconds. It "burps" some hot coolant.

The thermoswitch not working in those 5-10 seconds when the gauge shows 90-95 °C is not the end of the world. Remember the coolant sensor and the thermoswitch are totally separate and far away one to each other. I can guarantee there is not enough high temperature in the thermoswitch area to kick the fan. It is just a small pocket of hot air or hot coolant under the sensor.

 

I think you are overthinking the issue. It is not the end of the world. There is no danger to kill the engine.

if I understood correctly, it gives the same reaction in my vehicle.

When the cold engine warms up at the first start, the thermostat opens at 93.(88c vernet)

When the water in the radiator turns, it quickly drops to 82 degrees.

Moves normally after a few km.

but i didn't care much

Edited 18 February, 20206 yr by mturgut

It is only a transient, not harmful event.

One important thing though. The coolant level in the coolant reservoir has to be half way (in the middle between MIN and MAX) when the engine is cold.

18 hours ago, RicardoM said:

1) An air pocket as I've mentioned before

I think you are overthinking the issue. It is not the end of the world. There is no danger to kill the engine.

 

2) The coolant level in the coolant reservoir has to be half way (in the middle between MIN and MAX) when the engine is cold.

 

Reverse asking:

 

2) If the level is above that (engine cold) the system will be under bigger pressure?

 

1) After almost 20 years of use how can i compromise with this?

 

1 hour ago, D.FYLAKTOS said:

Reverse asking

Well, IIRC you've changed the thermostat and/or thermoswitch, and added heat insulation to the engine bay, and are now wondering why the fan behaviour is not "as designed"?

7 minutes ago, KenONeill said:

Well, IIRC you've changed the thermostat and/or thermoswitch, and added heat insulation to the engine bay, and are now wondering why the fan behaviour is not "as designed"?

 

I added heat insulation in the hood about 15 years ago,the problem shown up at 2019.

I have changed the thermostat at 2018 and few months later the thermoswitch because: the first one broke and the second because was many years on the car and was delaying the fan to start more than it should be.

 

On 2/16/2020 at 2:42 PM, RicardoM said:

How old is the cabin heater?

what kind of problem does it create? (clogged cabin heater)

Does this have an impact on the return of water?

1 hour ago, mturgut said:

what kind of problem does it create? (clogged cabin heater)

Does this have an impact on the return of water?

It stops the heater working (as well as it should). Other effects will be minimal beyond that you can't use the heater as an "emergency radiator".

2 hours ago, mturgut said:

what kind of problem does it create? (clogged cabin heater)

Does this have an impact on the return of water?

These illustrations should answer to your question.

5 hours ago, D.FYLAKTOS said:

2) If the level is above that (engine cold) the system will be under bigger pressure?

No, but the excess coolant will eventually exit to atmosphere as steam through the cap of the reservoir.

Less coolant could potentially create issues as described by you.