D.FYLAKTOS

This is the end of the hose that feed hot air the air filter box. From the factory was a cover above the exhaust manifold and while this was getting warm was send warm air to the box. Since that cover was gone before 18+ year ago (they removed and never gave it back to me) i put the hose some cm lower, still has enough space to suck air (it's not visible by the photo). According to the chart is look like this: but here it the factory heat shield how is for real: https://www.drive2.ru/l/1349135/

No problem, i forgot to mention that this happened after the ''flushing process" of removing old coolant-adding distilled water-after few days remove etc. I have posted 2 photos from the results: https://i.imgur.com/5DsAznt.jpg https://i.imgur.com/dfnsge9.jpg Then i added the Amsoil additive and maybe this reacted chemically with the remains of the old ''bad'' coolant and the result was that black sludge inside the plastic reservoir. After i removed that expansion tank plus about 700ml that had inside i installed a new plus a new cap.I had it for a week now and everything looks fine. I am not Chemist but i think that by boiling the remains of the old thick coolant were pushed to that expansion tank and stuck on his walls, i there were any remains would show-up inside the new reservoir after a week? I hope not but if there is a change i will let you know.

I have checked the thermostat sensor, crystal clear, the thermostat wasn't sticky, no overheating, the gauges are working as they should be, no smell inside the engine bay. I have replaced the expansion tank and the cap, so far absolutely nothing suspicious inside, everything is blue colour and no signs of black sludge on the walls of it. For sure i am not a Chemist but i think by boiling the system push all that black ''tar'' higher (as the lathe and the bubbles of the boiling water go to the top) and stuck in the plastic tank as for example when we boiling the meat. I will post some photos from the new reservoir soon, everything is clear.

Does not go always this way, for example DOT5 brake fluids MUST NOT used by DOT4 users although these can use the DOT5.1

Here are two older examples, one from 2019 and one from late 2021 Everything fine, blue colour and the reservoir plastic tank was clear and may times i have checked the interior. The MoCool chemically reacted with those 2 Antifreeze blends and then...came the mess!

No, for all these years i have never-ever saw a phenomenon like this, only after the installation of MoCool additive and after few days my expansion reservoir looked like had liquid tar inside. I was terrified, i though that everything in my coolant system had this black sticky substance, water pump-thermostat-sensor-hoses etc i thought that all would be covered and this meant a fortune from me for repair.

Skoda says for Felicia every 60.000 Km but for sure i won't wait till that point. Castrol, Motul, Liqui Molly, Mannol, FUCHS at 75W-90 give their products as GL-4 which can cover the GL-5 RED LINE 75W90 GL-4 only but has 28 euro per 946 ml bottle (!) YUKO, Amsoil has 75W-90 GL-4 only

See the photos plus the description to that topic. I use Motul which covers the API GL-4, API GL-5 ,you have post the link few posts back https://www.motul.com/gb/en/products/motylgear-75w90 I have about 22.000 Km with that gearbox oil.

Correction: The Motul MoCool has bordeaux (is US call it burgundy) colour and not blue as i wrote. @Thefeliciahacker : Although was sort of sticky i didn't show any marks on the thermostat sensor when i removed him, it was very clear. Also with my finger i didn't felt anything on the thermostat itself nor the cap which also was no sticky. The weird thing was that i didn't had any overheating signs and the digital gauge below expansion reservoir was working normally. The whole situation remind me the lathe and the bubbles when we cook in a pot, when the water is boiling close to 100 'C they stick to the walls, here is an example: I will post some photos more from inside the plastic reservoir.

As for the previous thick coolant i have opened a new topic: Till now the factory design with the 2 hoses and the flap works perfect in city traffic,the @Thefeliciahacker was right that Felicia does not need too mush air. The fuel consumption is lowering (10,55 ltr or 22.29 US mpg yesterday) but i don't know how this combination will work in national highway or in mountain routes in high rpm.

The hose beneath the aluminium heat tape is this https://www.skoda-parts.com/data/items/56/50741382eef1c.jpg The long hose is factory (is for A/C) and the hose attached to the oil cap is reinforced and can stand temperatures up to 120 'C (it's for the after gas, the factory sends them back to the throttle for lubrication but i didn't like the idea).

In the past i used the MoCool of Motul, the idea was to help my car in hard city traffic conditions to don't get overheated. In the past years i had used similar products as W.Wetter, Royal Purple and i had no problems. Turning back the time i remember that i had a problem with my water pump gasket (this means change of coolant) plus few months latter a thermostat problem (change of coolant also) so i ended-up with 2 brands of G11 Antifreeze in my car because when the 2nd incident happened i was travelling so i could find the same. Those 2 coolant changes made the analogy to be very wrong, maybe i was 60-70% Antifreeze and the rest distilled water and i added the MoCool without taking proper measurements before, if i had done this i could see that my coolant was more thick (more ''strong" s we say it here in Greece). I extract some of this ''coolant mix" (blue colour both) and i added MoCool (blue colour) according to the label on the bottle, after few days on city traffic everything looked good (1-2 'C lower temperature) but soon this stopped and when i opened the cap to make a volatilization i was shocked! The expansion reservoir has full of black ''sludge" and the coolant was black, it was some kind of chemical reaction and i was terrified because i thought that this sludge would be stuck in my water pump blades, my thermostat, it's sensor, in the wall of the hoses etc. I said ''OK, this is the End of my whole coolant circuit" and i had to remove and clean everything which means time and lot of money.

Here is the new air filter box while is installed. The flap is closed, it will open when the temperature (of the air through the hose from the manifold) rises. Now it's ready, i use a heat resistance hose (as the factory had) plus in the connection i use adhesive tape which can hold till 150 'C. For heat insulation i wrapped the upper hose with aluminium tape which can stand till 200 'C

I changed the gear box oil few years back, i used Motul Motylgear 75W-90, i have to check back home my notes for the next change. ''Hey mechanic, i hear some noises when i turn the steering wheel from lock to lock, especially inside the parking'' ''What noise?'' ''It's like gggggnnnk, do i have a problem with hydraulics?'' ''Don't worry, that is an old car, they do it often, no problem you will use to it'' I didn't believe him, i checked the oil level at the reservoir, one click BELOW the Min (!) and i was continiouing to use the car i will had major problem which also could cost me a fortune to fix it.

Yes, many times this is a problem trying to ''marry'' this to the real engine parts when it's time to order an item in an e-shop. Last night i had the chance to go to a boulevard, enough distance to put the 4th gear and reach the speed of 80Km, i was happy when i returned home and the TC-6 showed 10,48 ltr/ 100Km (that's 24,650 mpg) which is my record so far for City fuel consumption. Today home to work, normal traffic and i have 10,58 ltr/ 100Km (which is 24,885 mpg) so generally speaking things are getting better. For sure the new spark plugs were a ''savior'' and i am waiting to see the contribution of the stock air filter design, keep in mind that for 20 years i was not using it so now i must apreciate some things from the beginning.

Here is the mechanism from another view. The code of this part is VW 9A 419 133129826 and i haven't manage to find it in the web to buy it separately. Here is inside the air filter box, the hot air from the exhaust manifold hits this thinner spring which after few minutes due to heat triggers the mechanism.

Modifying the entrance of the fresh air from the grill makes a tiny difference in sound and performance, i have made in the past many modifications and when there is an exaggeration you hear a ''roarrrr" sound especially at high rpm but that does not mean more Hp (as some young driver believe). What looks like a small round hole actually is a big oval hole The part No15 is hard plastic tube S style, if you remove that part then every time you press the pedal far more air comes inside the filter, the sound is more rough but the raising of performance is controversial. One drawback of that modification is when the engine bay is getting hot (city traffic) the air filter gets hot air only and that is not good. The factory paper filter (with the stock entrance) if far the most quiet combination especially in city (idle-acceleration).

Covid measures are here in Greece for 2 years. All the previous years i didn't pay attention to my night cold starts, they were brief, 1-2 times per week i was in a boulevard and i could engage even the 4th gear and the fuel consumption was good. Then came the mistake from the mechanic (wrong valve gaps) plus the NGK which didn't worked good and the very thick coolant and the fuel consumption started rising. Additionally he restrictions from the Covid made things in fuel consumption worst as ever. I have some photos to upload from the instalation of the new air filter plus the flap mechanism and for few days i will put the ''hot air'' hose in different positions to find what's best. Today my night cold start wasn't too short but not 3:45 as the old ones, tomorrow i will use the timer to see if there is any improvement in that sector. In the road things are good, one click lower noise at idle (traffic light) from the air filter box and in acceleration. I have also some photos to show from the previous coolant expansion reservoir which had a bad look like dirty with a black and sticky substance on the walls.

I have not that air filter box thermostat since 2002, has been removed and i can not find it in my closed of spare parts. I bought and installed a new at 2022 because i want to solve the problem with my ''second'' cold starts. Turning back the time it was my mistake that i removed that item but as already said i had a ''bad advisor''. ALL the ols cold starts were out in the fresh air and i was traveling 1-2 times per week in a boulevard and sometimes in the highway. I didn't gave any special attention of how many minutes the rpm were at 1100 because i was in a hurry to return home after work. For 2+ years things are different, cold starts in parking garage-hard traffic-not high rpm-mainly 1st and 2nd gear etc, all of these didn't existed in my life so far. The car was clogged and when the TC-6 arrived finally i had a tool to work, i have live indication of what's happening and that socked me. Step by step, making corrections i am lowering the fuel consumption, from the worst of 14,7 ltr/ 100 Km now i am at 10,7 (i have seen 10,6) ltr/ 100 Km and i am optimistic that i will manege to make it better.

Brand new, tested with heat gun and refrigerator and works as it should be. Cold start: allows hot air to come to the air filter helping the starting process. As the time passes and you are not in a boulevard or highway the temperature rises so it closes the hot air hole allowing only fresh air to come from grille. Yes,there was no reason to feed with hot air the filter all the time, this is no good in a trip. I cover the hole and the car had only one (and for some months two) entries of cold air only. My problem is if it stucks on the 1st position while i am in a highway or a mountain route i will have a performance problem plus poor combustion. That flap mechanism is not visible and i have to bent in a very Hot engine to find the solution.

Here is the connection, the flap has an U shape and the rod a Π shape, it clicks and thus controls it. That air filter sensor is very sensitive, a little bit of rubbing by hand and immediately reacts. The crucial point is ''for how long"?

The Mediterranean people when the joking do it obviously and in internet they add a LOL or an emoticon with smile. As @Pete_Ex-Wino said it's not a reliable item, as you can see below there is no ETKA number for this part, it's not something you can buy it separately. So if after a years or two the flap stay in the closed position blocking the cool air and allowing only the hot air HOW how will you find out? Let's say you are in a highway and the car start showing signs of poor performance, the last thing that will come to your mind is that flap. IF that air filter thermostat was reliable there would be no worry by me.

The thermostat with the pin pushes the rod and opens the flap and when withdraws the flap goes back to normal position (which closes the cool air). Hot air->thermostat warm->pushes pin->rod goes front->opens the flap. Since has wax inside soon or later there will be a leak and the rod will not moved (front or back) and will stay in one position and ''game over''. The rod is something like this: In the end has a hook and it grabs the flap so it controls the movement (Front-back). I wonder if i make a simple flap with lighter plastic or with aluminum tape, the incoming cool air after (for example) 40 Km speed could be capable to push it back and close the Hot air hole? Let's say it can, then in city traffic when the flap is back the Hot air from the manifold can push it to open a little bit?

I live in 3rd floor, i can't do this at home. I wonder if i make this flap work as manually, the strength of the incoming air (from the front grille) would be capable to make it close? I mean at 40Km speed could make it go back and ''seal'' the hole of the hot air?

Yes i saw that pin, is flat in one and and pointed at the other end. The Warm position must be blocked 100% ?