Author: John Thorne

Mclaren and ‘corrosion’ seem to go hand in hand sadly as its quite likely that nearly every model will need rectification work at some time which is disappointing, however its all covered under warranty so its inconvenience rather than cost but we thought we would explain what is the cause and what to look for on your own car.

First off here is a video we’ve done that explains it all;

There are actually two causes for paint problems on Mclarens and the cause depends on the panel material.

Super Series Cars (12c, 650, 675, 720)

The majority of panels on super series cars are composite, on these panels the issue is moisture inside the laminate structure which expands and bubbles up the paint, it can be repaired (digging out the issue, filling and painting) but Mclaren simply replace the panel and repaint.

Common areas are front wings, front inspection panel, rear wings and engine covers, the bubbling is nearly always at the edge of the panel.

Sports Series and 720

The sports series cars (540, 570, 600, GT) have more aluminum panels and here the issue is that the surface was not properly treated before painting so over time the bubble pops up, again its not the paint as such but the material underneath. Again, these can be repaired (strip down and paint) but Mclaren again simply replace the panel and repaint.

Common areas are doors, front and rear wings and engine cover, and again the issue is localised to the edge of the panel.

The good news is that all of this is covered under warranty, so at least its not a cost.

We first came across some issues with the power steering pump 2 years ago, an owner commented on issues he was having with multiple canbus failure due to water ingress into the front compartment but as we never saw the car nor inspected the issue we put in in the ‘keep an eye our for it’ section for Mclaren and moved on, but this week we had two 12c Coupes both recovered/limped in with multiple ECU faults and on both cars a complete electrical break down.

First car was reported as complete electrical failure, multiple ECU faults, power steering, ABS, traction, suspension you name it, every light was on and the car was stuck – pretty much screams canbus failure and the fact it happened in the pouring rain meant we assumed water ingress of some kind. Initial inspection confirmed this, water in the footwell and carpet area so we started the process of chasing down the fault ECU by ECU. Having the full Mclaren wiring diagrams and diagnostic kit was essential and we eventually tracked it down to three ECU’s all in the front of the car, the main dash ECU, power steering ECU and suspension ECU.

After taking apart the whole front end section we found the issue – the power steering pump was heavily corroded and the lower case seal had failed allowing water into the pump unit itself causing it to ground out and as its part of the main canbus system caused a multiple cascade affect of ECU failures (think of it as a weak link in a chain, if the link goes the whole chain does).

In UK spec cars the power steering pump is ‘protected’ by a plastic cover, which is designed to keep the noise in the cabin down from the pump.

The problem is that this plastic cover (despite costing £85!) is a bit crap and it has split allowing water into the foam which acts like a sponge resulting in the power steering pump sitting in a pool of water, this has corroded the casing causing water ingress and ultimately the pump to fail.

We can dry out the pump easily enough but if enough water has penetrated the mechanism it means the pump motor will fail so needs replacing at a cost of £1300 plus VAT. A lot of this water ingress comes from the washer pipes which split quite regularly resulting in washer fluid leaking directly onto the power steering pump cover which leads to the question of whether this is something that should be covered under warranty?

The answer is probably no, the water ingress is caused by a split pipe (wear and tear) but after that its a split in the cover that makes it worse (trim) and then corrosion on the pump itself, all of which one could argue is a design fault with the car though. For us, we will cover it as a goodwill issue for cars with our warranty but we dont imagine anyone else will for the above reasons. To help prevent the issue happening to your car – check your washer pipes regularly – they do split, often, but we are adding this to our list of checks to cars for warranty and purchase inspections. If you want to know you have an issue just try your windscreen washers, if its not on the screen from both arms then its going somewhere and is most likely going over your power steering pump.

Whilst its disappointing that a supercar has such an issue at least it is fixable.

Just a few shots of the recent Mclaren Owners club meet at Salon Prive.

Great had by all, 36 cars in total so a great display. Strongly recommend owners join up as its great value at £50 and has a mass of meets, events and deals on offer as well as 10% discount on our labour rate!

For details see here: Mclaren Owners Club UK

Another great Greystone track day, this time at Goodwood where we again provide full technical support for everyone attending. As well as the Mclarens (12c, 720, 570, 650s) we also looked after a couple of Aston Matins, AMG mercs and a lovely 911 GT3RS.