Frame Rust in Land Rover Discovery II models - an Achilles' heel?

NOTE:  I have an update to this essay describing a repair technique we are using successfully on many trucks beginning in the summer of 2015.  Read more here

The 2003-4 Discovery was one of Land Rover’s most successful models.  Unfortunately, significant problems have begun cropping up as the trucks have aged.  I’ve written quite a bit about the engine block problems, which got a great deal worse in the late 4.6 models.

 

2003 Discovery fording a stream in Western Massachusetts

Now we are seeing a new problem – frame deterioration.  This is a particular concern in trucks that are driven off road in mud and then on road in winter New England. The frames of these “affordable” Land Rovers are suddenly rotting out.  My investigation of frames was precipitated by one truck that came here with rust after we’d looked at it and seen nothing at all the summer before.  The rust that came through this winter was so severe that the owners (and myself, frankly) had a hard time understanding how it could appear so quickly.

I looked into what went wrong with that truck, and compared it to six other Discovery II models at Robison Service last week.  What I found is, to say the least, troubling.

Take a look at this photo of the rear underside of a typical Discovery II.  You can see some surface rust in this photo, but it’s nothing alarming.  Yet a closer inspection reveals cause for concern.  If you look at the frame rails you see they have a weld running down the bottom centerline. This weld is rough on the inside, so it can trap debris if it gets into the frame.  The next problem is the braces for the trailer hitch.  The points where they bolt to the frame rails act as barriers, also trapping dirt inside the rails.

Underside of a 2004 Discovery showing beginnings of chassis rust

Now we get to the hidden part of the problem . . . I took this situation to our Land Rover tech support contacts, who told me something pretty surprising. It turns out Land Rover reduced the frame thickness of Discovery II models by more than 30% as compared to the Defender and earlier models.  So the frame in these vehicles is significantly lighter than the frames of earlier Rovers, which were themselves no paragons of corrosion resistance.  This was done to save weight and gas but it has had the result of making them weaker and less durable.

To add insult to injury, it turns out Land Rover decided not to galvanize these frames so there is little to prevent them from dissolving if corrosives get inside.

Corrosion inside a Land Rover frame, see with an inspection camera

Another unpleasant result of this weight reduction is that the thinner frame rail walls are now fracturing from metal fatigue up front where they are exposed to heat cycling from the catalytic converters.  The shock towers are another weak point.  The truck we got in last week announced its problems by breaking a rear shock mount.  But an examination of six other DII examples at our shop showed stress cracks in the same location is three more vehicles – this is a problem that will rear its head for lots more people soon.

Note the vertical line of fatigued metal to the left of the upper shock bolt.  A breakage waiting to happen

Off road enthusiasts have long known that mud can accumulate in frame rails, and they should be washed clear after driving in mud.  In fact, Land Rover frames have holes in the low spots to allow mud to drain.  Unfortunately, the DII frames don’t drain fully because of the rough welds on the bottom, and the passage of some bolts that act as barriers.  When a frame gets filled with mud, and the truck is then driven on salted winter roads, the salts get concentrated in the mud and they destroy the frame from inside faster than I would have believed possible.

This is a serious weakness that is made very apparent with the increased use of liquid snow melter on snow country roads.  When that stuff gets into the mud inside a frame it stays damp and its incredibly corrosive.  And the inside of the frame typically has no protection.

 

This frame rotted at the weak points I describe after filling with mud and winter salts

The ultimate cure for these trucks is going to be the fitment of heavier galvanized frames, like we to with Defenders today.  However the lower value of the Discovery II models is going to make that decision a tough one for many owners.  I suspect frame rust will send quite a few of these trucks to the scrap yard.  But there will be enthusiasts who fix them, just as there are enthusiasts who pay us to rebuild engines, transmissions, and everything else on these trucks.

With restored Defenders costing over $100,000 and scruffy examples selling in the $40s a Discovery II with a rebuilt motor and galvanized frame starts to look like a more comfortable and good performing alternative that's almost as trail worthy and a lot more road worthy.  Doing a frame in that context, along with a top hat or flange liner engine makes a lot of sense.  Add some trail mods and you are still under $40 with both usability and a lot of capability.

Rovers North has just started selling galvanized DiscoveryII frames.  It will be interesting to see how the changeover works out.  These trucks have more “Stuff” underneath than a Defender.  I would not be surprised if a frame change takes 100 hours and a pile of bushings, mounts, lines and pipes.  Frame replacement is likely the most expensive repair one could undertake on these vehicles, potentially exceeding the cost of a flange liner 4.6 engine job.

(c) 2014 John Elder Robison

John Elder Robison is the general manager of J E Robison Service Company, independent Land Rover restoration and repair specialists in Springfield, Massachusetts.  John is a longtime technical consultant to the Land Rover, Mercedes, BMW, Porsche and Rolls Royce Owner's Clubs, and he’s owned and restored many of these fine vehicles.  Find him online at www.robisonservice.com or in the real world at 413-785-1665