Mercedes 190E metal thermostat housing upgrade – here’s how to fit it

The Mercedes 190E along with other Mercs from this era were originally fitted with a plastic thermostat housing. Like a lot of plastic components that are subjected to high temperature for many years, this part is prone to sudden and catastrophic failure.

To avoid getting stranded and potentially frying your engine it’s a damn good idea to fit one of these upgraded all-metal components. The part I am fitting is a direct replacement manufactured by Febi Bilstein, it’s kit no: 34700. I purchased mine from these guys for less than £20 delivered.

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Febi Bilstein kit no: 34700 is a direct replacement for the OE Mercedes part

Fitting the metal thermostat housing upgrade for the Mercedes 190E

The part uses a banjo fitting where the original does not, but includes all components necessary to make it s straight swap.

Bank on 30-45 mins to make the swap, you’ll not really need much mechanical ability but will require a 10mm and 12mm socket, a screwdriver, a dab of grease and a new sealing ring for your thermostat.

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Your OE setup should look similar to this one.
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First things first, remove the radiator top hose and the hose at the top of the thermostat by simply undoing their Jubilee clips, you may lose a tiny trickle of coolant in the process.
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Now you can proceed to remove the 3x10mm bolts holding the thermostat housing in place – keep these, you’ll need them later. You may have to shuffle the HT leads sightly to get the required access.
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Lift the top of the housing and the thermostat will now be exposed. If yours has been in a while it may require some encouragement.
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Remove the thermostat from its housing and remove and replace its seal. Don’t skimp here, this is an essential step.
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With the new seal in place it’s now time to add a dab of grease around the edge, this will help the part seal correctly.
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Prior to fitting the housing it’s important that you assemble the part correctly as shown above. The hollow bolt goes directly through the banjo fixing with a copper washer at either side.
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Here’s another angle. Got it? Good. Now screw this part loosely into the thread at the top of the thermostat housing itself
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Assembly is very much the opposite of what we’ve already done. So now, take the new component and using your three existing bolts tighten the whole assembly down – be sure to do this evenly. Position the banjo fitting at the correct angle to attach the smaller hose and slide the radiator top house back in place too. Tighten the Jubilee clips for both of these hoses .
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Do ensure the 12mm banjo fitting is tight too, mine dribbled slightly after installation as I hadn’t done it up quite tight enough. That’s it, you’re done. Now, make sure to top up the car’s coolant level if necessary, and then run the engine up to temperature while inspecting the area closely for potential leaks.