Madasafish

You did change the oil and oil filter when you changed the chain? And used the correct oil and Toyota filter?

Bought Michelin Cross Climate tyres for our Jazz March 2018. Great in current snow. Highly recommended. On all year so cheaper than winter and summer tyres.

1 Use correct grade oil 2. use correct oil filter 3. Buy NEW solenoids. (Your garage are incompetents)

Two important questions: 1. Did you switch the heating to fully hot when draining and refilling. 2. Did you bleed the system of air after refilling. If the answer to both is no, you have an airlock. Bleed the system of air.. https://tinyurl.com/yayqrawn

Your battery is FUBAR (A technical term :-) Read https://tinyurl.com/y98rdr85 Voltage is too low.

A sensor may not work as it is faulty or the wiring to it has broken.... so you'll have to do some testing.. (multimeter job) First port of call is usually passenger side front - due to muck and water..

Is the battery the original? If yes, get someone to check the voltage.

Hi That is as good as anything...

Bear in mind, your Mark1 has an EGR valve and catalyst with no other emissions control equipment - as you can smell when starting from cold. Your new Yaris has a Diesel Pollution Filter when requires a regen every so often to clear the filter (I don't think it's an AdBlue system). Regens burn diesel - so consumption suffers...

Personally I would treat the surface after derusting - there will always be some rust left.. Any of the acid based derusters will neutralise the rust left and provide a good base for painting. Waxoyl based underseal is like soft cheese- it does not survive being hosed by a mix of water and stones very well. I use Dinitrol 4941 https://www.dinitroldirect.com/car-underseal/ available on ebay. Our Yaris is virtually rust free as a result - and it resists water/stones better. And you spray it on. I also treated a VW Sharan for a friend.. directly on to top of untreated rust - just wire brushed the flakey bits. OK after 2 years ,, A pit or HIGH axle stands make life easier plus eye and nose protection.. Dinitrol 4941 stinks when applied - I apply in a pit and 20 minutes work and then a rest to allow smell to clear - it vanishes when dry.

Please ignore the above - incorrect.

Difficult to find a decent diagram but it will involve the removal of the front caliper, disk and possibly the removal of the front hub (which would be a real pia as you would have to undo the driveshaft retaining nut..) Off hand I can't find a layout diagram. My mark 1 Yaris shields have holes at the bottom and have had for several years. I have not bothered trying to replace them

Lack of fuel when you accelerate.. Try a diesel specialist..

Strip down job. Probably you released a ball bearing holding a shaft in a fixed orientation.

Hmm I would only use carb cleaner - a volatile liquid which evaporates leaving no residues.. (Yes I cleaned mine using it) Brake fluid is not volatile and is heat resistant - I suggest you have left a greasy sticky mix of brake fluid and carbon..ideal to clog up any EGR valve. (I have never used brake fluid as anything but - brake fluid).. (It also strips paint)