There is a large group of Members that insist that Mercedes are so precision and the Dealer Gaskets are so well made that you do not need any Gasket Sealant/Glue.

I can't see any issues that would come from using Permatex on a Water Pump Gasket. Don't plug holes with it and don't let it get in any threaded holes and everthing should be fine.

Personally I almost always use something on at least one side of Gaskets if for no other reason then to stick them to the part.

There is an old product called Gagachinch that is just a high temp Rubber Cement. If you coat the Gasket and the part and let it dry and tacky it works like a Contact Cement. Like Rubber Cement it is thin and after it drys there is no chance of it clogging any holes which many Members have an intense fear of.

The other thing I use is Copper Kote it acts in a similar manner except that the Copper Kote is a lot thicker (has copper particles mixe in with the Cement) and messier to use.

The non-hardening and hardening Permatexes are extremely reliable but can be a mess to clean off the next time.

In the end it is your Car.

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84 300D, 82 Volvo 244Gl Diesel