Just under four years ago, I got a MOT advisory for badly corroded front coil springs on my 2009 Focus TDCi 1.8. I got them both replaced by a Ford garage, using presumably official Ford parts.

Yesterday I was driving on a straight smooth road at steady speed, loud bang, found the o/s front coil spring has broken near the bottom, see photo.

I have only done around 25k miles since they were replaced, use my car about once per week, mainly shopping or a 70 miles (x2) journey to my parents. I haven't knowingly hit a major pothole.

I am not expecting the garage (or anyone else) to deem this worthy of a free replacement of spring etc. However I would like to understand:

(a) why it has failed relatively soon (25k miles)

(b) should I expect the other side to break quite soon?

(c) is the state of the bottom of the spring normal (right of photo) i.e. very corroded.

(d) could a 'creaking' sound when turning (very slowly) on full lock that I've had for some time be related?

(e) Is there anything else in the suspension/steering system that could cause this spring failure

(f) What is reasonable cost (inc VAT) for replacing either 1 or  2 springs (the 2 cost me £250 inc)

Any advice appreciated.

That spring looks horrendous for 4 years old, are you sure it was definitely changed then?  If the other side looks the same I would expect that to fail in the near future too.

The lack of use won't help tbf, it'll mean the suspension parts stay damp and stationary for large amounts of time compared to a car that gets daily use.  Do you also park on mud or grass at all?  I note your location as Cambridge so salty sea air shouldn't be an issue like in coastal areas.

Creaking sound could be related, I'd also want to check the top mount bearing(s).

Cost really depends where you go and what parts you use.  I'd expect around £50 a spring and £50 fitting at an independent garage as a rough estimate.

I always have them fitted in pairs, £210 and the worst bit £ 42 VAT. We have a lot of speed bumps around here and I always slow down for them but I Reckon I go over 30 a day 365 times a year = 10950 times a year and they've lasted just over 3 years the originals lasted 7 years, I've had heavy duty ones fitted this time but I've just sold the car so I won't know how long they'll last.

The top mount bearing could be stiff this puts strain on the springs, and as Tom says lack of use could be a contributing factor.

Front suspension coil springs breaking on all age Focus's is an inherent problem, the reason probably due to the inadequate strength of the springs, I had both front coils break on my 2004 Focus, N/S was broken in 3 places with bottom coil coming out of it's seat but fortunately not touching the tyre, the O/S spring broke in 4 places with one coil section missing altogether!, that happened between last March when it was last MOT'd and now. The car still drove perfectly straight but knocked a bit when you went over humps and the ride height didn't drop that much, traded in now for a 2007 5 door Fiesta Zetec 1.4 Climate Duratec. Front springs can be purchased for as little as £20 the pair but what the quality of them is I couldn't say.

I wondered if the heavier diesel engines make any difference as I have never had a spring break on my petrol engined cars.

Thabks for all tge comments. It makes sense with diesel being heavier, esp the cast iron 1.8, but I think it has to be corrosion related. The guy at the Ford garage, who seemed quite reasonable, reckons about 10 years ago they started putting something different in the road grit. And said they do loads of springs. Although I hardly ever drove in or just after ice and snow last few years. Business opportunity for someone to make good quality corrosion resistant springs??