Breezy_Pete

Subject being brake servo vacuum hoses. Not sure quite how universal this failure is, but I've seen so many now on friends and neighbours' cars I always check them any time I remember to whilst under the bonnet of a Volkswagen Group car. The hard plastic sections split where they are stretched over the barbs of hose nipples on the terminations at e.g. the non-return valve. If the hose completely parts company with the bit it's attached to you will lose all servo assistance for the brakes. The brakes still work, but you have to press a hell of a lot harder on the pedal. If you don't know this, you will believe the brakes have failed completely. Before this catastrophic failure, if the splits develop to the point of leaking significant quantities of air, all sorts of weird fault codes can be thrown up, leading to replacement of non-faulty parts if diligent diagnostic techniques aren't used. Lambda sensors, throttle bodies, all sorts of things could get the blame due to 'false air' entering the intake manifold through these splits. The splits I've just found were not super-obvious. The first one on the underside, I felt with a fingertip before bringing a mirror out to inspect it. The second split, and worse one was on the front side, facing the engine, and couldn't be seen or felt easily until I pulled the whole assembly out a little to inspect more carefully. How old was this hose assembly on my car? 5 years only. The original was found in a similar or worse state about that long ago, this was a new genuine replacement then. Guess what improvements have been made in materials and design of these hoses since this car was made in 2003? None whatsoever that I can see. Please check your own car's equivalent. Go on, you have some time in the next few days, right? If you find crap like I just did, please photograph it and add to this thread.

It worked again, just. Sounded even less likely to start than the previous time, but it did. It is unseasonably mild today though.

No, a day later. Did run the engine for half an hour after, as I do approx. monthly on this vehicle whilst it's off the road. Out of curiosity I'll go and try it again now. Has been disconnected from the car in the meantime.

Update on that battery: charged it for several days at 13.8V on a bench PSU. Put it in my spare Polo to see if/how it worked, and it started the engine, but only just. Unsurprising, at 15 years old.

Did the new thermostat housing come with a new temperature sensor, or did you move the original sensor into the new housing?

I'm not near my computer to look for good photos/videos just now, but search for "vw connector removal" on YouTube and you should find a few useful results. In words; push the connector body firmly onto the thing its plugged into while lifting the latch up a short distance in the opposite direction until you hear a click. Then pull connector away Find an easily accessible one to practise with. If you don't do that initial pushing, friction on the latch parts may cause breakage.

@drifter1949 are you familiar/well practiced at undoing the latches on these type of connectors? There's a 'knack' to it that's not completely obvious.

It's come to my attention that if your control unit has a part number ending in F, as found in some or all early mk2 Fabias, a different relay will be fitted, unlike the one in my photos. According to a couple of folk who have fixed their mk2s, expect to find an Omron G8NW-2U 12V DC fitted.

I missed this when posted. Glad you got it fixed @sti5300, and thanks for adding the info about the different relay. I shall add a bit to my 'wiper relay replacement' how-to accordingly.

Sorry, missed an important detail - With VCDS.

Touch/click on the three dots in the top right corner of the post you wish to report and you will see this option appear. (For the benefit of anyone unaware of such details.)

Info is probably available in a measuring block of the instrument cluster, module 17.

May well be some truth in that, but unfortunately that's just the sort of polarising thing that'll 'trigger' someone and cause this thread to descend into just what the OP was describing.

OP should check whether that little orange engine lights up in the instrument cluster at ignition on.

This may be of some relevance, depending on how you get on with the stalk. Removing plug from onboard power module - Skoda Fabia Mk II - BRISKODA If you do have VCDS, you can probably observe the stalk inputs to the onboard supply control unit (Central electronics, module 09) in real time in measuring blocks rather than pulling the steering wheel off.

Do you have VCDS (Lite) and a suitable cable?

It's a good point from @J.R., ECUs themselves tend to be massively reliable, as long as moisture hasn't got into their connectors.

I think the diagram in the catalogue is a little off, as the switch appears to mount on the underside (or a jaunty 45° angle maybe) of the MC when you look at listings like this Датчик включения стопсигнала VAG 8P0698459B для Skoda Yeti 2009-2018 в Москве (euroauto.ru). It's a brake light switch though, no hydraulic connections to be seen. Brake Light Switch Škoda 5G0698459 (skoda-parts.com) A fella changing one on a LHD Golf here,

You need to have a Freedom membership to sell stuff on here. https://www.briskoda.net/forums/subscriptions/

According to the parts catalogue, for an ASV engine built on or after 1st August 2003 the engine ECU will be part number 038 906 012 HC:

Think it's a hall effect sensor on the MC.

I think @Stewartasb may be correct.

See edit above for pinout info for shorting test.

(Dual) Relay is inside BCM. Short pins 3 and 4 of connector XP4 (with it still plugged in, just poke a conductor into the back of those two wire-entries). Wipers should start going at normal speed and not stop until you remove this short.

What year is the car? There may well be a relay involved, within the onboard supply control unit. Bypass this with a cunningly applied festive paperclip to test motor. I'll hunt down a recent thread with pinout details.