Many customers call us during the first hot days of summer and complain that their Mercedes-Benz 190 SL is stuttering or even stalling. This is due to an overheating problem that we are very familiar with: high temperatures in the summer, traffic jams, etc. cause the temperature of the water in the radiator to rise to 90-95°C. The entire system then heats up. The manifold also radiates heat, which rises directly below the carburettor. This causes the fuel in the carburettor float chamber to boil, adding air bubbles to the fuel entering the jets and preventing the systems from working properly. The engine will begin stuttering or even stop altogether.
The only thing you can do about this is to wait and hope for the best once the system has cooled down.
Fortunately, there is a simple fix for this problem.
Heat protection tape on the exhaust manifold reduces heat transmission to the carburettors
Applying heat protection tape to the exhaust manifold has proven very worthwhile in our experience. Heat protection tape wrapped tightly around the exhaust manifold prevents heat from being transferred to the carburettors. To do this, the air intake pipe has to be dismantled and it is easier if the carburettors are also removed. When you test-drive the vehicle upon completion of the job, you’ll notice that the engine is quieter because the tape not only prevents heat radiation but also acts as a sound insulator. It smells a bit unpleasant at first, and it can produce a small amount of smoke (the heat protection tape must burn-in a little), but that settles down once you’ve completed a long test drive.
Auxiliary electric fan for extra cooling
An auxiliary electric fan means much less worry about overheating.
We have been installing electric auxiliary fans for many years. Their extra cooling power offers a solution to overheating problems whether on the move or stationary. You don’t need to do anything to operate this particular fan, as it is temperature-controlled. A thermal switch activates it at 85°C and switches it off again automatically at approx. 75°C. The additional cooling provided by the fan also prevents the formation of air bubbles in the fuel line. The electric auxiliary fan is attached to the radiator and, as the name suggests, provides additional cooling right next to the radiator fan blades. It also helps to cool the manifold system and carburettor. It is not visible from the outside; you can only see it if you look inside the engine compartment. We can supply you with a complete installation kit with thermal switch and installation instructions; we are also happy to install it for you if you bring your vehicle in to us.
Radiator with high-performance core
Another upgrade that we now include as standard in our restorations: the installation of a radiator with a high-performance core.
But which version do you currently have in your Mercedes-Benz 190 SL? The W121 has a water pump and a fan blade attached with four screws.
Another problem: a fault in the water pump can also result in damage to its aluminium housing, as play in the bearing can allow the impeller to scrape against the housing. If you then fit a new water pump to the housing, the bearing play will reduce the water throughput.
We install a thermostat with a ball valve and a lower opening temperature. The ball valve lets air bubbles through and allows the thermostat to work more precisely. If the water pressure in the cooling system rises above 1 bar, a valve in the cooling water seal opens and releases the excess pressure. This takes care of the problem because, if the pressure in the cooling system is too low due to an incorrect or defective seal, the cooling water boils earlier and produces air bubbles.
All versions and spare parts are available from us and we can also fit them to your vehicle if you wish.