Heater Valve o-rings

[PeterPortugal]

Hello fellow enthusiasts,

I have a 63 W111 and have just completed a heater overhaul. There are many existing topics out there on this subject but I couldn't find an answer to my specific problem.

The valves originally moved freely in the housing. They rotated easily and slid longitudinally. However with the new O-rings fitted they are quite stiff. Too much for the cables to work effectively I feel. I have used grease but this has little effect.

I guess in order to seal effectively the o-ring has to be a tight fit but this seems too much. I bought the O-rings from a Mercedes dealer - part number 0008355898.

Any thoughts or tips would be highly appreciated. I don't want to refit the heater and find it can't be operated.

Regards

Peter

[Benz Dr.]

I've used a liquid silicone with good results.

[PeterPortugal]

Thank You Dan Caron. I shall give that a try and post my findings.

[wwheeler]

You have to make sure you are using metric O-rings, and hopefully the dealer supplied you with those. If you use the common 1/8" imperial size, it will be too tight.

I used plumbers waterproof silicone grease when installing on my W111 and they work perfectly smooth. Possibly the O-ring came out of its groove and is binding? If there is not any antifreeze in the system, the valves are easy enough to remove and recheck. O-rings should only have .015" squeeze fit and that is not enough to bind. 

[PeterPortugal]

Hi Wallace,

The O-rings were genuine Mercedes parts so I have to assume that they are correct. They are staying in their grooves ok. The heater is out of the car so it's easy to remove the valves and check this. I am still trying to source some of the silicone lubricant suggested by Dan. Not easy in Portugal !!

Can you or Dan suggest what sort of pressure I should use to leak test the heater cores? I was just going to use a hose pipe to provide a head of water using the 10m = 1 bar rule  (or for you guys 33ft = 15 psi). If you know a simpler method with no special tools then I'm open to suggestions.

Regards

Peter

[tel76]

For silicone lubricant (in a tube)  try your local plumbers merchants, plumbers use it for fitting plastic pipes.

[Jonny B]

Not clear on something you typed. You type about "O-rings" in the plural. There is only one O ring in the heater control valve. At least that is what is shown in the technical manual, and that is what I put in my (and my friend's) car. Is there another place where you have installed o-rings??

[mbzse]

.../... You type about "O-rings" in the plural. There is only one O ring in the heater control valve.../...

Jonny,   Certainly correct for a Pagoda.
However, PeterPortugal mentions he is servicing a W111; these Mercedes cars have two heater elements (one each side) and thus dual valves.
/Hans in Sweden
.

[PeterPortugal]

Hi All,

Many thanks to all you fellow members for taking the time and effort to post responses.

I managed to find some liquid silicone - in a supermarket of all places - and as promised my feedback is IT WORKS !! Thanks again to Dan Caron for his suggestion.

Should anybody read this post in future, based on my personal experience, I can confirm that liquid silicone spray (I used the brand "3 IN ONE") certainly results in substantially easier movement of the valve than using grease (I used "Wurth Multi Purpose Grease II")

Jonny - Hans is correct. I have 2 heater valves on my car.

Regards

Peter

[Jonny B]

I continue to learn.

[PeterPortugal]

So do I Jonny. After a day or so the valves were stiff again.

I am going to take the chance that once the heater is refitted and they get a bit of hot water in them they might loosen up !!

[batman]

My valve would not turn partly because the old O ring was in poor condition & had twisted on itself. I replaced the ring, applied silicon grease and it turns very easily and can be lifted out with a minimum of ease (almost with bare hands!) - all this when the coolant is stone cold. Whether the cooling fluid is warm,hot or cold should not make any difference.