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Discussion Starter · #1 ·
W211 E350 water pump torque specs needed

The water pump is not leaking but the bearing is on the way out. Replacing the pump, tensioners and serpentine belt seems pretty straight forward.

Can anyone provide the water pump torque specs and any tips/tricks/advice about the job for:

2008 E350 4dr Sdn
18" wheel SPORT upgrade package

VIN WDBUF87X18B314644
Delivery Date 2/25/2008
Engine # 272972 30 90586

Thanks in advance...

137 Posts
I don't have the tq specs, but I'd assume it comes with the pump? Some basic instructions in the box? I personally would not tq it very much, and stuff like that I just do by feel. I rarely tq any bolt to the specs, but especially alum parts because I've seen too many broken alum parts and alum threads stripped. I tq rod and main bolts to the bolt mfg specs and that's it. Heads I tq less, sometimes to half or less the spec. Everything else I do by feel and to less than the "correct" spec. Of course I don't do that willy nilly, I tq to match the need. For example; wheel bolts/nuts I'll usually do more like 90% tq but it varies a lot depending on the car/wheel. Or the heads on my truck are at 25ftlbs, the oem spec is like 65. I see it like this; the mfg doesn't want anyone blaming them for too little tq, but if things crack or break then it was defective. So (imo) everything is overly tight to cover their butts, which may also increase profits due to selling you parts.

With delicate things like an alum water pump (I'm only guessing yours is delicate) I'm also very concerned about the gasket because the more tq and/or thicker the gasket, the more likely it'll break. Aftermarket gaskets are often much thicker which makes things worse, so be wary of that. Pumps vary a lot too, so when I say delicate I mean ones that have a lot of surface area and the one or more edges extend quite a ways away from the actual pump shaft. It's easier to cast a water passage on the block and cover it with a pump than it is to put the passage in the block.
I often don't use a gasket at all, but it depends on the pump and if the two mating surfaces are true. If not true then you need a gasket and lower tq is even more important. I've never broken a water pump, but I've certainly seen them and other alum parts break where I bet it would not have if only just enough tq was used.
Not sure about this eng, but on some the holes for the pump pass thru to a water jacket. This means you need to coat the threads with sealer so water doesn't weep out, which is annoying. Some bolts may even reach the crankcase and weep oil instead, which is even more annoying. I kinda doubt MB has made either of those mistakes, but you never know. Usually it's obvious as soon you remove the bolt. A blind hole will have a nice clean and dry bolt.
There are no doubt youtube vids on changing the pump and the other stuff, which should cover any weird things to be wary of with that exact eng.

I never use a water pump gasket as-is, but instead I coat the entire gasket with silicone to seal it from water damage and weeping. Plus if coated it'll come off undamaged in case you needed to re-use it, and you don't have to scrape hardened gasket residue off the block, which is zero fun.
I use regular silicone for windows etc for sealing bolts like that, and gaskets. I usually use black so it's easier to see that I've completely coated the gasket. I've yet to find anything better than generic silicone, and nothing is cheaper. You have to coat both sides and the edges, especially the inside edges which will see boiling hot water under pressure. Sealing the outer edge will prevent it from soaking up whatever rain/wash water or oil, gas, cleaners etc, but generally just oil. So the entire gasket is coated and I rub it in with my fingers to be sure it's in the material and no chance of missing some spot. Don't let the silicone cure before install, if you do it'll add stress toi the pump and would be more likely to weep. So I silicone it, stick it to the pump, then install it. I suppose you should let it cure before adding water, but many times I've had the eng running 10min later and never had an issue.
That silicone ritual may be considered overkill to most people, but the gasket is out, silicone in hand, so why not. If you install it dry and it decides to weep later (even more likely with a cheap aftermarket gasket), you'll be kicking yourself. Plus weeping is how pumps tell you the bearing is going, so then you have the added stress of wondering which it is.
If lower tq makes you worry it'll come loose, then don't. Or you can use blue loctite (the weaker and easier to remove stuff). I rarely use loctite on a car, certainly never on a water pump, and never had a water pump bolt come loose on me. The pump is a very low stress item so the bolt tq is really just there to clamp the gasket down enough to prevent leaks, which brings the whole lower tq thing into perspective. Since a silicone sealed gasket is far less likely to leak, even less tq needed.
However you tq it, do so gradually and evenly like you would a head, because like a head, that could break it. The more you tq the more careful you should to be. Sure odds are it won't break, but how much time, trouble and $ would it be if it did... Takes an extra minute to be careful.
Probably TMI, but you asked ;)
And good luck!
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