How to do a water pump - 1 Hour on W202 C180


Senior Member
Nov 11, 2008
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Your Mercedes
1995 R129 SL500
Okay, so this may be an easy one for a lot of people, but i thought to do a how to would be a good idea for someone who wants to be able to do such jobs on their car, but perhaps isnt confident enough to just go out with a Haynes manual and mess about with it for an afternoon.


New waterpump [GSF £30 or £50, Europarts £50, Or Mercedes £££££££££££. i used a cheap one from GSF but the quality seemed fine. i would have got the more expensive one but they were out of stock and i wanted to do it that weekend.]

New fanbelt [check yours, if it squeaks and has cracks in the grooves, thet it changed. £30 ish from mercedes. dont bother with any where else IMHO for this bit, they arent much cheaper anywhere else. save your old one in your boot for an emergency.

Blue Gasket sealant


Coolant from Mercedes - aparrently this contains particular inhibitant chemicals that other coolants do not. you only need a 2 litre or so container so its worth getting from the stealers.

De-Ionised water. chances are your merc hasnt needed anything doing on the coolant system since birth, so you would want to keep it like new in there. mine certainly was like new. see pics in how to below!


standard socket set with 5 - 10mm sockets at least.

Torx drive sockets suitable for a medium sized ratchet.


the Mrs or friend to stand there and go "ooh" and "is that meant to be like that"

first off, because the engine is longitudinally mounted in most mercs, this job is a doddle for the smaller engined models. i would imagine you would have to remove a lot more items on a C43 [but to be fair, unless you are me if you could afford to run one you probably wouldnt want to get your hands dirty] for example.

okay, so first off, open your bonnet up fully [there are some clips on the hinges that let you extend it higher] and remove your underbody tray.[if you have serviced your car before you will already know and would have already done this] on mine it was 4 8mm [IIRC] washered self tappers. i would also use a large tray to catch coolant [unless you have a means of disposing liquids, i'm not sure they are supposed to go down the drain] we used an old baby bath. LOL

it is your choice if you want to raise the car up, i didnt...

loosen the 4 10mm bolts on the water pump pulley. if its like mine it will have a rusty left handed thread where a visco fan goes. if you have a visco fan you will need to remove that, which as aforementioned is a left handed thread. you would probably need a big spanner. if you dont have th right size spanner using a chisel and a hammer to tap it loose will work too [done that on an E30 before]

remove your fan belt. on mine you put a torx drive on the end of the tensioner pulley and pull it back on its spring. i didnt remove it entirely and looped it over the power steering reservoir [see photo]


then once you have that off, and the pulley that you loosened the 4 bolts on removed, you can get to the pump.

remove the hoses for the waterpump by loosening the jubilee clips. i always use a 5mm and 7mm socket rather than a screwdriver on these. note when they are loose and leaking twist them behind something suitable as shown in the pictures:



there are about 6 or 8 bolts on the pump [use the new one for reference where they are] that are two torx head sizes on mine. cant remember the sizes but if you want to buy the tools you might as well get a set of sockets rather than the individual stuff. Halfrauds or Machine mart is the way forward [i love machine mart.... like a woman in a shoe shop in there]

once they are removed, you should be able to crack the pump off by grabbing the big extened pipe thing and twisting/pulling it off. it will come off very easily. after its off, you should be able to see the condition of the impeller. mine wasnt too bad, it looked like new but had a bit of a squeak on it. directly comparing the GSF one to the old one i coudlnt see an immense amount of difference in quality at all tbh. see pic:


before putting the new one on, make sure you remove all the residual gasket off the engine block using the stanley knife blade. it should look like this:


smear your blue gasket sealant thinly but evenly around the mating surface, affix your gasket, wipe off excess stuff, and apply the same thin amount of blue to the pump. then fix it in place. refitting is the reversal of removal.


once its all back together and tightened up nicely, you will need to refill with coolant/deionised water.

once you have filled it to the max line, start the car up and let it run with the radiator cap off, until it starts to get warm. it should start to swirl in the bottle, and while you are waiting i'd give the pipes a bit of a sweeze to get the air out. run it till it gets a bit arm [like its been in traffic for a while] and keep topping it up when needed. once the coolant is staying at a constant level and the blowers are blowing hot etc you are sorted. stick your tray back on, check you havent forgotten any bolts/parts and take her for a drive to check everythings okay.

then you are done! go have a beer.

Uncle Benz

Senior Member
Mar 31, 2006
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West Sussex
Your Mercedes
Mainly Mercedes
The top right pump bolt (as you look at it) is much longer than the others, and often feels like it is going to snap. If you work on a warm engine it minimises the risk of that happening. (In my experience!!)


Feb 8, 2006
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Grange Moor
Your Mercedes
R171 SLK280, Smart R451, Land Rover 110 County SW, 997 C2S, R1250 GSA TE 40th, CBR600FP
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