I have a 67' benz with the exhaust heater flaps in the exhaust manifold. They are frozen. One moves a slight bit, but the other is rusted solid. Anyone know of any fixes for this? I live in Florida and probably do not need the engine to heat up quickly; however, with this car one never knows.... Any info would help. Thanks.

Somebody here fabricated a metal plate between the manifolds to permanently turn off the manifold heat. They reported good results at the time, might make sense for FL.

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1967 230S automatic
Boston, MA

Thanks Todd. Any idea how they did it? I saw where someone did a study on how many 250S were left.....as of 2008 - 438....does that sound right? They made 76,000 of them.....seems like very few. Again, that's for your help.

I'm not sure exactly how they did it. I believe they just cut some metal plate into the right shape and drilled holes for the bolts, they might have used aluminum but I doubt it matters. Whoever it was is currently on this forum, this was around 2 or 3 months ago and there was a thread about it. Due to living in the frozen north (east) I'm personally going to try to get my flaps operating properly eh. They are currently wedged in the no-heat position, but they will move if coaxed and I'd like some carb heat for the mornings. There is a specific heat riser grease that is available to keep them happy. There are all kinds of home remedies for getting those flaps to move again, ranging from soaking the manifolds in various fluids to hitting with a big dumb hammer.

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1967 230S automatic
Boston, MA

I was the one who did that. I live in Chicago and the car stays in the garage during the winter, so the heat risers are not that important to me.

Here is the thread: 1972 250C - want to convert to fuel injection

I used 1/8" steel plate that I cut to shape. I ground the bottom of the intake manifold for extra space and bolted the plate to the exhaust manifold. My heat risers were frozen in the "hot" position so they were not restricting exhaust flow. I left them alone.

My car is a 1972 250C is that makes any difference.

If you want to disable your heat risers the easiest way is to leave them sticky, and then muscle the counter-weight to the open position. You will be raising the weight off its resting stop to do this. Once you have both valves open the rust will hold them in place forever. It is a tight space to get at, but you should be able to get your hand in there...careful to not bend the shaft, pry gently.

230/8

soak them in white vinegar for a few weeks, or kerosene. they will eventually come loose.

Thanks everyone. So if they are OFF of that little stop??? they are open? My car is running now, and I want to make sure I'm not going to make it worse by turning these the wrong way.

This can be somewhat confusing as they are referred to by states of the engine: hot through stone cold, and function of the flaps: no heat to carb through full heat to carb.

The Bypass or "Hot" position thorsen is referring to is the position the flaps are supposed to be in if they were working properly and the engine was hot. Confusingly, in this position, they are not applying heat to the carbs, so from the POV of the carbs, it is the "Off" position

The other extreme is when they are applying "full heat" to the carbs and the flaps are "Open" and if the springs were present and the flaps working as designed the engine would be "Cold". This is NOT the position you want your particular flaps in because if the engine warms up and they are stuck they will roast your carbs.

It's confusing because people refer to them based upon the temperature of the engine and also the application of the heat they provide. There is a page illustrating them on the ponton site:
http://www.mbzponton.org/valueadded/other/heatriser.htm
You can see there the difference between open and closed pretty clearly.

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1967 230S automatic
Boston, MA

So if the Weights are pointing toward the right fender, they are letting heat into the carbs? Is this correct? IF they are not pointing toward the left fender they are not letting heat into the carbs? Even with the pictures it's confusing. Thanks for the info tho Todd.

Regards, Dave