Mercedes-benz w203 water pump replacement – (2001-2007) c230, c280, c350, c240, c320 pelican parts diy maintenance article e sampark electricity bill payment


When a water pump begins to fail, you’ll notice that the car tends to overheat at low engine speed, such as sitting at a stoplight. When you accelerate, the engine temperature will drop. Now, this is not always indicative of a water pump, but a good starting point. You may also want to try squeezing the top radiator hose with the engine warmed up and running. You should feel pressure build up on the back of the hose and surge once it is released. If you feel no pressure, it’s a fair bet that the water pump is failing.

Replacing the water or coolant pump on W203 is certainly a doable job for a DIY’er but it is not a quick job. If this is one of the first projects you are attempting on your car, give yourself at least five hours to get the job done and don’t forget to refill the coolant.

There are several things that will need to come off or out of the car to replace your water pump including the air filter ducts, engine cover, fan and you will need to drain the coolant as well. This is also a very good time to replace your hoses if they are getting on in age.

You are going to remove the Poly-V belt to remove the coolant pump as well as remove the idle pulley. Inspect your belt and replace as needed. With an E10 (reverse Torx socket) and driver locate the tensioner and using the Torx driver turn it counter-clockwise 45 degrees. You can now slip the belt off the tensioner. You can also lock the tensioner into the open position if you need both hands to install the new belt. Turn the tensioner all the way counter-clockwise and insert a retaining pin between the rotating part and the tensioner base. If you do not have a retaining pin you can use a 5mm Allen key.

To remove the coolant pump you will first need to remove the idle pulley which is located right above the coolant pump pulley. Insert a flathead screwdriver between the cover plate and the pulley and gently pry the plate off. With the plate off use a T-50 Torx and remove the pulley bolt. The bolt is extra long so make sure to label it as it is not easy to replace if you loose it.

Move to the two hoses that connect to the lower part of the coolant pump. Remove the hose that goes to the auxiliary coolant pump from the clip that holds it to the alternator bracket. Next using a flat head screwdriver, remove both hoses. You may need to run the screwdriver between the hoses and housing to help break any seal that has developed.

There are one E14, four E12 and twelve E10 bolts connecting the coolant pump to the engine and most of them are different lengths. I like to take an old cardboard box and draw an outline of the pump on it, as I remove each bolt I stick it in the cardboard where came off so I will know where to put it back when I put the new pump on.

Comments: Having followed your instructions I managed to remove the faulty pump. I’ve cleaned the mating surface. There only a metallic gasket. The mating surface is clean but looks somehow stained. Do I have to remove the stain? If yes what product can I use. Brake cleaner wasn’t helpful.

Comments: Hello I have a 2001 c240 and I’m having problems with one o the tubes on the auxiliary water pump it just popped out the one that’s missing is the one that’s missing in the picture and I don’t know where to connect it too it connects from the pump to what ?

Comments: I WISH WISH WISH I had foud this BEFORE I started in. I pickked upthe new pump at the dealership and it came with 2 gaskets, the rubber inset into the block OEM and a felpro type metal with gray gasket covering. Service dept took 30 minutes to figure it out once I brought it to their attention. The said metal coated one is th update. I looked at it and it does not seem to fill the keyway on the upper passenger side,so do I use the OEM? Both? Or am I missing something?

Followup from the Pelican Staff: If the part is updated, it may fit differently. Check with the dealer you bought it from. Could also be the wrong part, Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.

Comments: hi I have a 2000 ml320. their are two gaskets included with the pump. your article shows the small one not the flat one. I heard the gasket to use depends on the engine# you have because their were two different covers which were used?

Comments: Thanks for the advice! This time, I did remove both Water pump and the Fan clutch out. Then, I was able to remove the Fan clutch from a defective Water Pump. You know what? Finally, I just followed the instructions from this Article got my car Water Pump replaced without any issues. This is an excellent Article and details…You guys are awesome. Thanks!

Comments: I got a Fan clutch holder and 36 mm Wrench, but have tough time to remove the Fan clutch. I know that the wrench goes CCW and Holder CW to remove, but I never got it loose…Please advise…Overall, I see this Article really helps…

Comments: AWESOME. This article plus the comments save me about $400 bucks! One thing I’d like to add is be CAREFUL when snugging down the twelve E10 Torx bolts. They are SOFT, so if you torque to much, the head will snap off! Lost three of them before I figured out to take it easy

One problem with the Saleri was having to create threads on the 2 holes that hold a bracket to the left of the idle pullley. Being very careful I managed to use the e-bolts like self-tapping screws back & forth until bolts created threads. PIA but it eventually worked BEFORE installation.

**when i started the car, fan came on super high and temp gauge would not work. i found that replugging the temp sensor, the two metal filaments sticking up got pushed down, not inserted. prying them up gently with pocket knife and re-inserting connector corrected problem. Thanks for a great help in allowing me to do this by myself!

Comments: The two bolts in figure 9 do not hold the pump to anything, they just hold the bracket to the pump. Additionally, I would recommend loosening the 4 bolts that hold the water pump pully to the water pump before removing the serpentine.