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Definitely let us know...
... this problem mostly with cars that are kept outdoors, as opposed to mostly garaged.
Yes, I will report back for sure.

My car is always kept in a dry garage, so this is not the solution unfortunately. If only it was that simple! :wink
 

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We don't seem to have the problem here in the desert dry air.

... I wonder if one of those silica gel desiccant packs would help...
Thanks for the helpful info. Interesting that you don't have this problem in desert environ. This suggests that the theory muted in earlier posts concerning humid blowby gases leaking past the cam seals may not be the primary cause, otherwise you would be experiencing problems too. Although its fair to say it could be a contributory factor if the seals are worn out I guess.

I have been looking into this misfire issue for several months (if not years!). Certainly looks like ambient humidity is the main ingredient. Coupled with differential temperatures caused by thermal conduction through dissimilar materials (alloy - very conductive, phenolic resins etc - insulating), thermal convection, vapour drive from hot to cool (direction subject to cooling or heating cycle), partial vapour pressure, and also that some of the resins I believe are hygroscopic. I plotted the cycle on a Mollier diagram and it all points to a dew point on the inside face of the distributor cap. This dew point can occur even with a hot engine, so long as there is sufficient temperature differential and partial vapour pressure. The temp differential only needs to be around 6 to 9 degC for all the other magic ingredients to come together to create the moisture.

It appears that the Designer was Little Bear in this instance, and he managed to create a Goldilocks distributor where 'Everything was just right'... to produce moisture inside the cap! :wink

With hygroscopic resins, like silica gel desiccant, the moisture is adsorbed, not absorbed, and both these materials release their moisture when heated. The point I am getting to is that silica gel would release its moisture when the engine gets warm, which would lead to the same running issues after a short journey, park up and restart. I don't think silica gel is the answer unfortunately.

For the benefit of all reading this: -

Vent the caps.

I would also suggest trying out Beru caps, because I think that their design is more compatible to solving the problem due to fact that they have an added layer of protection - a smooth imide polymer varnish layer inside the cap.

Don't think that Beru is the cheap option either. It isn't. :wink2

Hope this helps you all.
 

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Our humidity here in the desert is commonly below 30 percent, sometimes in the teens. 75k to 100k cap and rotor life has been my experience. Perhaps there's some other type of desiccant / drying agent would work.
 

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I have a r129 which was running inter motor caps for years, since changing to Bosch have the moisture problem. So beru caps and rotors here we come. It's the only parts I've changed so the caps must be designed differently. When I get the berus I will compare them.
 

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Discussion Starter #66
I have a r129 which was running inter motor caps for years, since changing to Bosch have the moisture problem. So beru caps and rotors here we come. It's the only parts I've changed so the caps must be designed differently. When I get the berus I will compare them.
Beru caps and rotors worked for me :wink
 

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I just think I bought genuine Bosch caps and rotors, this was about £240. This is a lot of money. They are way past 12 months old, it’s took me this time to realise they are the problem.
The question is it’s a cap and rotor. What is the difference between a beru and a bosch? Especially as bosch has the design rights according to the internet and the vehicle would of had bosch from new.
There must be a vent missing or a redesign by beru. I think I will email bosch technical first
 

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Discussion Starter #69
I just think I bought genuine Bosch caps and rotors, this was about £240. This is a lot of money. They are way past 12 months old, it’s took me this time to realise they are the problem.
The question is it’s a cap and rotor. What is the difference between a beru and a bosch? Especially as bosch has the design rights according to the internet and the vehicle would of had bosch from new.
There must be a vent missing or a redesign by beru. I think I will email bosch technical first
See post #36 in this thread.
There is a link to my Beru caps topic and also a link to my engine dies topic that shows a photo of the tracking across the old Bosch caps.
 
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