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

RLNAMERCEDES100 · #1 08-13-2003, 12:46 PM

Hi, My car has been running a little on the hot side this summer. So I hope it's the t-stat thats at fault. It hasn't been changed for at least three or four years! So I am sure it could use a new one. The reason I put it off for so long is because I have no repair manual or anything of that sort witch can contribute to getting it working right the first time without braking something. So if anybody can help me out with detailed instructions on how to change my thermostat I would appreciate it very much. It is a 1987 300D turbodiesel 603.960

HGV · #2 08-13-2003, 01:44 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

toknow · #3 08-13-2003, 03:05 PM

Hi, I might need a radiator in the near future, how much you want for it, is it with the new re-enforced neck..
thanks

RLNAMERCEDES100 · #4 08-13-2003, 04:19 PM

the thermostat is located on the right side of the engine below the air intake hose? If so does any body have any easy methods or tips on how to remove it? If it is where the t-stat is located I am having a hell of a time getting to it. Oh and one more question do I remove the housing that has two bolts or should I remove the whole thing (five or six bolts). And also what would I have to remove to get to the housing? Man it already sounds like it's going to be a PITA fix. oh well that means that I have nothing to fix on the car after this except for the sunroof brackets witch should be no problem at all ( hopefully).

HGV · #5 08-13-2003, 05:06 PM

I can not remember the specifics. I will take a look at the engine the car tonight and post a response.

toknow, the radiator I have has the reinforced nozzle neck. It a Behr. I purchased it for about $375. A Nissens sells for $275. I think $250 would be a fair price. I ran the radiator for 2 hours and decided that the one I took out was good. I pulled it out and put it back in the box with the tranny caps on.

Henry

HGV · #6 08-14-2003, 12:49 PM

Took a look at the car last night and again this morning.

All you need to do is remove the 3 10mm bolts. It looks harder than it is. Use a box wrench and make sure it fits well over the bolt head or a socket. I forget to mention another piece of advice. Remove the temp sending unit that is located on the t-stat housing first. I remeember when I changed my t-stat I snapped the tip of the sending unit. Cost me $15 to get a new one. Take it off first. It is very exposed and easy to break.

This is a simple job. Attack the bolts from above and below the car. Let me know how it works out.

Before you do any of this work. Let me know what you think "hot" is on your car. Put the AC on, and go up a steep hill under load. Leave the car in 2nd and rev up to 4000rpm. If the temp gets above 110 you might have a problem. There are many reasons why these engines run hot, and IMO it is not usually the t-stat.

Henry