PeachParts Mercedes-Benz Forum - View Single Post - Need some help changing thermostat on 603. motor

HGV · #2 08-13-2003, 02:44 PM

When you say that your car is running a "little hot", how hot is it running? A t-stat that is 3 to 4 years old should not be broken. Changing it out is fairly straight forward as long as you get the correct t-stat. THe turbo diesel t-stat has a green dot as opposed to others. It also has a notch that keys the position so that the self bleeding ball check works.

To change the t-stat, first drain the radiator using the stop cok located on the bottom right corner and then the block drain located below the exhaust manifold. You can tell the block drain because it has a hose fitting on the end that lets you attached a hose to it and drain it into a container. Following the draining, remove the bolts on the t-stat housing and remove. You might need to remove the radiator hose to do this, can't remember. Install the new t-stat with a new gasket, making sure that the notch aligns in the housing. Tighten everthing up, reattach hoses and close all drains. If the car was jacked up or on ramps, lower prior to filling the radiator.

NOW follow the following advice!!!!!

This car is very difficult to bleed air out of the block. If you do not bleed air out, you run the risk of overheating immediatly. I found the easiest way to bleed is by removing the upper radiator hose from the radiator neck, and pouring in the radiator fluid in the hose until the block is completly filled, then quickly putting the hose back on. The car needs to be on level ground for this work best. Continue filling the radiator through the expansion tank, then lift and lower the small 1/2" insulated hose that runs on top of the radiator to the aluminum housing near the injection pump until no air bubbles exit into the expansion tank. Put the heater on high and start the engine, watch the temp gauge and when it reaches operating temp, stop and check fluid level. Be careful not to get burned if you remove the radiator cap.

If you still have overheating problems, it could be the radiator. When you remove the upper radiator hose, take a look inside and see if there is a reinforcing steel ring on the inside. This car had a problem with the radiator neck breaking off, and they solved the problem by adding a reinforcing ring. If it is not there, then you probably have the original radiator and should consider replacing it. If so let me know, I have a brand new Behr radiator for you car sitting in my garage in the original box.

Good luck

Henry