The 3 and a half commonest Mercedes problems that can ruin your holiday.

Our beloved Mercs - the 309/310 and 409/410 pre 95 T1 Transporter chassis - are world renowned for being bombproof and good for a million. But they are not 100% perfect, neither are they maintenance free.

Over the last 17 years from my own experiences and being an active member on forums and Facebook groups, I have come to a conclusion that there are three and a half common problems that have the potential to bring a trip, or worse, a holiday, to a miserable stop. The first three are the cooling system, the gear selectors and the fuel delivery system ... and the half is the brakes - it's only half a problem with the brakes because usually they don't actually take you off the road, they just give you a fright!

All of these have been covered elsewhere in this blog, the purpose of this article is just to give a heads up to new and existing owners in case it ever happens to you.

Cooling system. 

All our vans are now over 20 years old and are usually still on their original radiators and fans. The radiators get clogged up inside and out and their efficiency reduces over the years, and the visco coupled fan gets tired and doesn't cut in when it should. Because we live in a cool country with not many mountains, you usually don't get to find out you have a problem until you are climbing up some Alpine pass in the middle of summer. Keep an eye on the temperature gauge. It it creeps up towards the red on a long hill, this is a sign your cooling system isn't 100%. A quick fix is to have all the accumulated crud blown out of the rad with a high pressure airline. This will often alleviate the problem - temporarily. Ultimately a new radiator and/or a new visco coupling mechanism may be needed to get the van back to normal performance. A system flush and fluid replacement can also work wonders. DO NOT run a Merc engine into the red or boil it over - you will crack the head and worse. The temp gauge is usually accurate - It will run to just under the red zone, but don't go there if you can possibly avoid it. Your radiator cap is also likely to be original, so if you have any cooling work done, always have a new rad cap and thermostat fitted. The water pump can also go on high mileage vans. Hoses rarely cause a problem, but should be checked.

Gear selectors.

Between the bottom of the gear stick and the gearbox is a system of rods and levers that select the gears. These can work loose, and bushes get worn leading to gear selection problems. It is rarely terminal - I have never known a Merc manual box to actually break - it is always the selectors. There are a couple of articles on here about it. Search for "gearbox".

Fuel system.

There is a gauze filter on the bottom of the fuel lifter in the tank, an inline filter between the tank and the main filter/pump, a breather pipe on the top of the tank, and the main fuel filter itself. All need maintenance and cleaning, and often have had no maintenance for 20 years. If the van is underpowered, especially on hills, or even just stutters and stops, then it is usually the fuel system. It is rarely the pump or injectors. This is a very common problem. Search for "fuel filter" for more info.

Brakes.

The back brakes on the Mercs do most of the heavy braking, especially on the 409/410 bigger vans. They need regular checking and maintenance, especially the "load balancing sensor". You don't know you have a problem until you have an "Italian Job" moment coming down 28 hairpins on the St Gotthard Pass and the pedal hits the floor. If the back brakes are not up to scratch then the fronts get overworked, get hot, and boil the fluid. Patience and engine braking will get you down safely and to a garage. Many of our vans are still on the original fluid. In extreme cases use the handbrake, which is mechanical not hydraulic. Again, this is a problem that usually manifests itself when you are a long way from the M6 - usually on holiday in the Alps or Pyrenees. Search for "brakes".



These blog articles are for guidance - I am not a qualified mechanic. There are a few other Merc related issues, but these are the main ones - not just in my own experience, but in reading the forums and blogs.

Other problems are squeaking fan belt tensioners, leaky vacuum pipes and the occasional broken fan belt - carry a spare (they are a pig to fit). Vans with over 200k can expect to need a new water pump eventually.

Have I missed anything? Please comment below.