Archive for the ‘corrosion’ Tag

This weeks crop

Several items of interest this week, the first is regarding seat belts and their associated mountings.

When a seat belt is attached to the seat, then the seat mountings are checked for security and corrosion in the surrounding area.

On checking a seat on a Ford Ka it was noted that the seat seemed to move a little more than normal when rocked lightly. As the mat above the seat mount was easily lifted, then a further check was simple and disclosed the securing bolt sat beside the seat bracket.

The vehicle presenter had no idea that there was a problem. The vehicle had been regularly serviced by the main dealer and as far as she was aware the seat had never been removed.

The second item concerns standards of corrosion repairs.

A Nissan micra in for MoT had previously had a repair to the rear sill because of corrosion, looking at the repair from outside the vehicle there were signs of welding with a thin skim of body filler and paint to tidy the repair up. The repair felt sound and didn’t “give” under thumb pressure.

Inspection from underneath revealed however that the bottom edge of the patch had had no weld applied at all. The testing standard for patch repairs requires that the repair should be seam welded along every edge.

The third item comes from a vehicle we had in for repair as the brakes felt spongey and was losing brake fluid. On inspection it was immediately obvious a rear brake hose was bulging, we’d had no need to apply pressure to see the problem.

The inner core ofthe hose had deteriorated and was allowing fluid to seep under the outer rubber covering, had it been on a front brake the outer covering would probably have split and caused a serious brake balance problem.

This second image shows how badly the outer covering had stretched when the fluid had seeped into it.


Corroded brake pipes.

When testing a vehicle, the mot tester often has to make decisions based on his experience and knowledge when there are no specific standards in the manual. One component without any written hard and fast rules regarding corrosion is the metal brake pipes. Nowadays most vehicle’s brake pipes have an anti corrosion measure applied at the factory, in many cases the brake pipes are plastic coated, in general however the last inch or so doesn’t have this coating. Also this plastic coating can crack at any bends in the pipework , leading to corrosion at these points. In such cases the only remedy is to replace the affected pipework .
The guidelines we’re generally given refer pitting of the brake pipe such the pitting penetrates more than 1/3rd thickness of the brake pipe, not easy to visualise. Here are 2 examples of brake pipe corrosion, one an acceptable amount, one too badly corroded to be acceptable.

As can be seen in the example above the corrosion has penetrated far enough into the metal to cause it to expand and flake. When the above brake pipe was eased out of it’s fixing clips to facilitate removal and replacement, it fractured at the bend approx 1 inch above the brake pipe union.
The example shown below whilst having corrosion on it’s surface, the corrosion hasn’t penetrated into the pipe itself to any degree. A quick rub down with wire wool and a coating of grease is likely to save this brake pipe for several more years before it needs replacing, assuming corrosion isn’t more advanced further along some where in the rest of the pipe.

Unfortunately there are areas of the brake pipes in many cases not visible, they run above fuel tanks and above subframes and can be hidden by other underside items.

Excessive corrosion.

What is excessive corrosion ?

To see what Vosa consider excessive corrosion see and reference to presrribed areas.

· The load bearing parts of the vehicle to which the testable items defined in Sections 2, 3 and 5 of the Inspection Manual are mounted,
· any load bearing or supporting structure or supporting panelling within 30cm of the mounting location.

Sections 2,3 and 5 refer to steering and suspension, braking and seatbelts respectively.

Section 6 and Appendix C should also be studied to assess any corrosion in non prescribed areas.
Even with all this information available as testers we can still get it wrong though.

A couple of examples found on a Nissan Micra.

Seatbelt prescribed area.Seen from the underside the inner sill is holed within 30cm of the seatbelt mounting.

Suspension and seatbelt.

Again seen from the underside this corrosion is within 30cm of a suspension component mounting point and the rear seatbelt mounting point.

An example of where a tester has unfortunately got it wrong can be found at

This again refers to a Micra, I have had several discussions with my local Vehicle Examiner (ministry man) about Micra crossmembers, having seen several examples like this, in each case I have been told to pass and advise as it does not meet the fail criteria in the relevant sections in the testers manual.

I’ve heard others say “it’s dangerous to drive, what if the engine mount breaks away”. ¬†Unfortunately nobody can predict the future. However, when I do come across a Micra like this I pass and advise but add that I consider it dangerous to drive. It seems silly that I cannot fail a dangerous item, but those are the rules that Vosa stipulate we have to abide by.

Excessive corrosion of a suspension component

I don’t seem to see many vehicles nowadays that suffer with excessive corrosion, but today I had an example of excessive corrosion in a suspension component.

The rear suspension arm on a 1996 Fiat Cinquecento had rusted through beneath the rear spring.
Owing to the nearly perfectly round hole,I had to look twice and compare with the arm on the other side of the car to confirm that it was indeed corrosion rather than the design of the component.
As a highly stressed component replacement rather than repair is called for in this case.

Some VW’s , Skodas and various other makes and models do have the rear springs sitting in a similar shaped seat but the hole in the centre of the seat is by design.

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