SPY PICS: Benz makes over SL, SLK and its four-door coupe

Mercedes has debuted a number of key new models lately -- not least the all-new C-Class (more here). But that doesn't mean it has been letting the grass grow under the rest of its model range. In particular, the latter half of this year will see makeovers for the SL, SLK and CLS-Class vehicles.

The SL will get the most attention -- to ready it for the second half of what will end up (in current terms) a mammoth decade-long model life.

The changes will be considerable -- they need to be, the next all-new SL is reportedly not due until 2013. And it's clear where all the work is taking place -- check out the heavy disguise affixed to the front end of the car photographed.

Though the SL underwent some minor surgery last year, the luxury sportie is about to get a new face. The transformation involves a new bumper, air-intakes, grille and headlights -- the latter reminiscent of those of the CLS four-door coupe (see more below). There also appears to have been some re-profiling of the bonnet and front guards.

Though there's been speculation that the car captured hereabouts, by our spy-connection Carparazzi, is actually a test 'mule' for the new generation SL that is unlikely.  Mules are usually heavily disguised or testing running gear (and therefore not at all). As can be seen here, 'our' SL's tail is only lightly taped. Thus we reckon the taillights and the rear bumper of this facelifted model will be only slightly re-jigged.

Perhaps the cost of reprofiling the boot lid and so on would blow the budget -- especially given the close-coupled nature of the folding steel roof-top?

As Mercedes has always kept engines of the SL up to date don't expect many changes under the bonnet -- yet. Stuttgart will continue to offer the SL 350, 500 and bi-turbo V12 SL 600. The SL 55 AMG, however, will be replaced by a more powerful SL 63 AMG with around 390kW.

Like its CL stablemate, a revised range-topping 65 AMG version will also debut... Later... With at least 450kW!

Meantime, the SL's little brother, the compact SLK is set to reinforce its (still somewhat formative) styling link with the maker's F1 racers. The changes, to debut at Frankfurt, are likely to feature triangular bars underneath the bumper and a softening of the prominent nose (so that it does not dip down into the frame of the grille).

Other new features will be reprofiled front underbumper ducts and slightly modified taillights.

As the driver of the prototype snapped undergoing tests in Stuttgart was very keen on covering the dashboard, we reckon that this is going to get some minor changes, too.

And finally (for the moment!), to the CLS. The first update for the car since its international launch in mid-2004 -- in which time the 'niche' model has topped 100,000 sales internationally -- the freshened CLS gets a new grille in the style of the latest CL and also taillight and rear bumper tweaks. Expect the updated model to surface later this year or early in 2008.

-- with Carparazzi