weasley

I remember my dad’s 1978 Chrysler Alpine did this - I always wondered why modern hatchbacks didn’t do it.

Exhaust manifold leak?

To add some background info (for interest but not specifically to answer the question asked) - it is called the "reductant" pump because it is pumping a fluid that is used as a reductant in a chemical reaction. The emissions system this works with is called the "selective catalytic reduction" system, or SCR. In chemistry (in basic terms) "reduction" is the opposite of "oxidation". What the SCR is doing is reducing the levels of NOx (or nitrogen oxides) in the exhaust gasses. The NOx has been formed by the oxidation of nitrogen in the air during the combustion process. The SCR effectively undoes this, by "reducing" the NOx back to nitrogen and oxygen. It does this through the use of a catalyst (the box in the exhaust) and a "reductant"; a chemical reagent used to perform the reduction of NOx. Ideally what you need is ammonia (NH3) but this is a hazardous chemical to handle and carry around so a solution of urea dissolved in water is used - this is known colloquially as "AdBlue", although AdBlue is actually a trade name and the generic terms is "diesel exhaust fluid", or DEF. The urea breaks down to form ammonia in the exhaust which then reduces the NOx to nitrogen and water (plus a bit of CO2). Hence you need a reductant pump and an injector to spray this stuff into the exhaust stream so that the SCR can do its job and we all get to breathe slightly less toxic air. If the pump is not working then the SCR is not working so your emissions will be higher than they should be. It doesn't stop the engine from working per se, but in some cases a car's ECU will either limp or even shut down to prevent high emissions, which may be a requirement of the type approval and qualification.

A quick look in the fusebox will tell you if there is any towing wiring fitted - the fuses for towing will be in place if so, or missing if not. Towbar prep also came with the bumper cut-out in place (or it did on my pre-FL SE).

Scuffing/rumbling was one of the symptoms we had when the clutch finger spring failed and machined the inside of the bell housing.

You can read about how I discovered all this here.

It’s a screw-linear actuator- the motor turns the gear, which has a worm gear type of shaft, which moves the white plastic block up, which pushes on the latch to pop it open. The motor only turns a few revs until the plastic block reaches the end of its travel. When power is released the mechanism rewinds back to the beginning. The characteristic symptom of a failed unit is a ‘drilling’ sound when trying to use it, as the motor keeps spinning.

If it helps, this is what it looks like inside. The white plastic lever is the emergency release. The plastic shaft from the gear on the right can shear, leaving the unit unserviceable (this is what happened to mine).

I just looked this up - in the description text of the product it claims: PRODUT [sic] SPECS ACEA A3/B4 (2012) ACEA C3 (Chemical limits differ) VW 504.00/507.00 BMW LL-04 MB 229.51 Porsche C30 Please check your service manual to find out which oil you need Let me break this down: ACEA A3/B4 (2012) - the latest version of the ACEA specs is 2016; you are not allowed to make claims against obsolete versions. Furthermore, in order to make an ACEA claim you are required by ACEA to be signed up to their code of practice - guess which company isn't signed up? Furthermore ACEA A3/B4 (2012) is incompatible with most of the other claimed specifications by virtue of having too high an ash level. ACEA C3 - same applies as above regarding code of practice signatory, but also the "(Chemical limits differ)" caveat is nonsense - the whole point of ACEA C3 is that the chemical limits differentiate it from other specifications; the limits are on ash, sulphur and phosphorus, which are important factors regarding DPFs - you can't simply disregard these limits. VW 504.00/507.00 - given the lack of compliance with fundamental industry specifications (ACEA), I find it unlikely that they hold a VW approval (also see @Kenny R's list above). 504.00/507.00 requires that the oil meets ACEA C3 (in its entirety). BMW LL-04 - again unlikely; BMW LL-04 requires an oil to meet ACEA C3 (2016) in full. Porsche C30 is equivalent to VW 504 00/507 00 so see above. MB 229.51 - this one we can verify by checking the Mercedes-Benz published list of approved oils (last updated 11 January 2021). As you'll see, no mention of Brit Oil (in fact no mention of them at all in any MB approval categories). Furthermore notice what MB themselves say (my bold): We recommend using only products which are: distinctly marked with the label indicating the approval of Mercedes-Benz, e.g. “MB-Approval 229.51”. Labels referring e.g. to “MB 229.51” don't have an approval of Mercedes-Benz. Which are listed in the current MB BeVo. Only listed products are tested and approved by Mercedes-Benz. MB229.51 demands chemical limits aligned with ACEA C3. I can't say whether the oil is actually good enough to meet these specs, but the above evidence is worth taking into consideration when making a choice. As I said earlier in this thread, I've never heard of them (well I have as a consequence of this thread, but that's it). My personal opinion: I wouldn't use it.

Nope. All false.

Fast idle also helps compensate for extra electrical load (heater fan, a/c, heated rear screen, heated mirrors, heated seats (if fitted), lights etc).

When I did mine the car had towbar prep so I only had to remove the trim in the boot to access the pre-fitted wiring loom. That was a bit awkward but not difficult - sorry, I don’t know about the front trim.

Id recommend you don’t do it when it’s cold as this will increase the chance of breakage. And if you’re fitting a towing module it’ll need coding to offer all of the features.

The only broken spring I have ever had was on a Renault Mégane - there's no rhyme or reason to it, just a new normal.

Turbo piping?

I guess it’s a risk vs reward judgement. Had my Yeti five and a half years and used the hooks extensively. Never once had need of a spare wheel though.

The couple of times I needed parts I found getting them directly from a Skoda dealer to be the quickest and often cheapest option.

A bulk oil temperature of 150°C is pretty high, although still well below the maximum it would see in the engine. Of course if the bulk oil is hot that means it is getting heated up a lot somewhere around the engine, so it could be overheating there. Oil film thickness varies with oil viscosity, so a very hot oil will be very thin which will lead to a very thin oil film - possibly thin enough to prevent metal-to-metal contact. And as you discovered, an air-cooled engine is more accurately an oil-cooled engine. Even a so-called water-cooled engine gets a significant cooling effect from its oil.

Apologies if I came across as aggressive - absolutely not my intent. I have participated in so many oil topics on the internet over the years that I try to present who I am and how I know what I am saying simply to try and establish some credibility. I have great respect for engineers - I work with many and am interested in the subject, although am a chemist myself. I also tend not to say who I work for because I want to present factual, objective information rather than being seen as a sales pitch. Sometimes this means I have to bite my lip because I see people saying things about my company's products which I know to be totally untrue, but I have to be careful what I say as lots of it is confidential and to challenge any mis-truths may give away something proprietary. Not saying this is happening here, just presenting you my background and the decades of oil topics I have tried to steer in the right direction!

And just to present my credentials, if I may, I have been working in lubricant R&D for 28+ years for one of the well-known oil brands. I've worked on everything from motorcycle to ship engine oils, as well as transmissions, turbines etc.

A very cold oil will be thick, meaning a very thick oil film will form between moving surfaces. This balances nicely with a cold engine, where the clearances are larger and need a thicker oil film. However a cold oil will not be working fully - some of the chemicals used in it don't really activate until 60+°C, so although a cold oil will do a basic lubrication job, you won't get the full protection it can provide. Hence why most engine wear happens during warm-up.

That's how the nomenclature was first developed, but it isn't really like that any more. What you say is largely correct, but doesn't quite go far enough. The "5W" is saying the oil is behaving like a '5' grade would when cold and the "30" bit is saying it is behaving like a '30' grade would when hot. In this case a monograde 30 would be too thick when cold and a monograde '5' would be too thin when hot, hence the multigrade performance and nomenclature. In reality the two halves of the visc grade are tested under very different conditions. The 'W' (for "winter") number is tested under very cold conditions to determine if the oil can flow and pump when cold - one test is called the 'cold cranking simulator' (CCS) and one called 'mini rotary viscometer' (MRV). For an oil that is "xW-yy", the CCS is tested at -(35-x)°C and the MRV i tested at -(40-x)°C. An oil has to flow and pump effectively in these tests in order to pass them. The yy number is mostly derived from a simple viscosity test at 100°C (oil falling through a tube and timed between two marks).

Pretty close! Take a look here. Your "runniness" is effectively the inverse of viscosity.

As @Wino says, oil viscosity varies continuously with temperature, down to the point at which it 'freezes' and up to the point it boils or catches fire. The viscosity classification (eg 5W-30) gives some idea of how the oil behaves when cold (the 'W' number) and when at 100°C (the second number). 100°C is considered to be a typical bulk operating temperature but obviously in the course of doing its job the oil experiences a wide range of temperatures, from cold start to the top piston ring or piston undercrown. If you can look at the technical data sheet for an engine oil, the value that helps you understand the effect of temperature on viscosity is the viscosity index (VI). The higher this number, the less the viscosity changes with temperature. So, an oil with a VI of 120 will vary more than an oil with a VI of 150. If both of these oil have the same viscosity at 100°C then the lower VI oil will be thicker when cooler and thinner when hotter than this. The relationship is not linear - it is a fairly complex logarithmic relationship. I would consider an oil to be 'warm' around the 60-70°C mark - this is the temperature that some of the active ingredients really start getting to work properly. This isn't the final operating temperature and I wouldn't expect an oil temperature (measured in the sump) to stabilise here. In an engine the oil does warm up significantly slower than the coolant, largely because the coolant is thermostatically controlled and only the small portion within the block is circulated at first, whereas all of the oil is circulated all of the time, so is a significantly larger mass to heat and is exposed to the cooling effect of the sump. I recall that in my Yeti TDi the oil would just about reach 90°C on my 30 minute work commute in the winter and would cool noticeably during any time spent idling.

That’s automatic a/c - you set a target temperature and the unit blends warm and cold air as needed to achieve it. Manual systems just allow you to set a fixed ‘blend’ and adjust up or down yourself to achieve a comfortable temperature. From the symptoms I would have suspected a sensor, as described by @Scotwall.