These Beru caps only have about 40 miles on them. Are these marks normal for an almost new cap on an M119? Both caps look identical and the rotors are new as well.
-
Hi Guest !
Welcome to the 500Eboard forum.
Since its founding in late 2008, 500Eboard has become the leading resource on the Internet for all things related to the Mercedes-Benz 500E and E500. In recent years, we have also expanded to include the 400E and E420 models, which are directly related to the 500E/E500.
We invite you to browse and take advantage of the information and resources here on the site. If you find helpful information, please register for full membership, and you'll find even more resources available. Feel free to ask questions, and make liberal use of the "Search" function to find answers.
We hope you will become an active contributor to the community!
Sincerely,
500Eboard Management
Normal for distributor caps?
- Thread starter Joncf
- Start date
That’s relieving, thanks!
Thats how my new Beru caps looked a week ago, didn't concern me. Just blow out all that cardboard dust and cut some more slots around the circumference for moisture dissipation.
No, I would say that the pitting in the imide lacquer finish of the black cap is not normal. Or perhaps I should say not ideal.
First, why did you replace the caps and rotors. Also, why did you inspect the caps at 40 miles? Which State in the US?
The pitting in the imide finish is generally between the uppermost HT poles and the central electrode. Moisture vapour is lighter than air. Hence affects the uppermost poles. So the marks look to be the start of moisture related arcing across the surface of the distributor cap. Have you noticed any misfiring or rough running?
I used to prefer BERU because the imide finish helped to suppress moisture build up inside the cap. But BERU, which are commonly available as reboxed Doduco parts, are known for failure of the central electrode due to heat from HT spark and tracking through the plastic material. This flaw was highlighted on the original patent submitted by Doduco, and I have had this happen to BERU caps on my R129 500 SL.
I now promote modifying BERU or Bosch caps by cutting additional vents to aid water dispersal, as described in the following link: -
Link to article on distributor caps
That’s not pitting, it’s dust/particles on the surface. Looks much worse because of the camera flash. It can be wiped right off.
I inspected them because I had a new (Chinese) Bremi rotor fail after about 30 miles of driving. I replaced those with Beru rotors and haven’t had any problems since.
Ouch - are Bremi rotors now made in China? Also, was the Beru replacement the black version (OE), or the new orange version (reboxed aftermarket "Facet" brand)?
Yep, I think you or Gerry first told me they’re made in China, but I didn’t learn that until after it failed.Ouch - are Bremi rotors now made in China? Also, was the Beru replacement the black version (OE), or the new orange version (reboxed aftermarket "Facet" brand)?
The replacement Beru rotors were the OE black ones.. same with the caps as seen in the pictures. This was a while ago, you must have forgotten
:
M119 running on 4 cylinders | M119 Engine
My left distributor is not getting any power, meaning cylinders 2,3,5,8 are dead. I was convinced it was the EZL, but I swapped in my used one today and there was no change. The distributor caps, rotors, spark plugs and coils are all new. I also tested the coil wire and its good. I guess I...
Noted, not pitting. So you had a somewhat catastrophic failure off the rotor. Other than that, and also with previous caps and rotors, do you get any running issues, misfires, hesitation?
Do you think the dust particles were present when you first installed the new caps?
It is interesting that they are arranged in a distinct pattern between the central electrode and the uppermost (when fitted) poles.
Some might say ‘so what?’ What I’m getting at is, if the dust was there when you installed the new caps 40 miles ago, I would expect there to be no particular pattern. A random distribution of dust. So I am wondering what caused it to make the pattern?
The dust was not present when I first installed them. My best guess is that the Bremi rotors caused some carbon tracking because of the poorly designed exposed contact tips. I actually never cleaned any of it, it’s still there. Even so, I haven’t had any issues since installing the proper Beru rotors. I think I might wipe it out now, since you’ve pointed it out.
I’m not sure why it’s more prevalent on the upper poles, but I don’t think it was related to moisture.
Your answer confirms what I suspected. A negative electrostatic charge in the plastic between the uppermost poles and central pole. Attracts the dust. Not a coincidence.
The electrostatic charge gradually builds up in the polymer between these poles due to arcing, probably as a result of moisture vapour in the upper part of the cap. The polymer is normally non-conductive, and once charged it is very difficult to discharge. The rate of dissipation of the static charge lags behind the generation and I surmise that the affected plastic in the region of the high energy arcing holds an electrostatic potential of say around 50 kV, but it won’t release it. Slowly building up 5 kV at a time from the 30 kV produced by the coil.
My guess is that this could be the precursor to the formation of carbon tracks, which of course may or may not occur. Depends on extent of arcing. Enough energy and the potential in the polymer is equalised when it forms a covalent bond with carbon.
Did you see any of carbon tracks in your old caps?
I have suspected that moisture vapour (due to condensation) occurs in most caps (except possibly in very dry States like Wyoming). Certainly just about every M119 cap in the UK has had moisture in it at some time. I theorised that when the moisture concentration of the air inside the cap reaches 3%, misfiring could occur.
I do my best theorising after a good pint and a fetid belch.
The electrostatic charge gradually builds up in the polymer between these poles due to arcing, probably as a result of moisture vapour in the upper part of the cap. The polymer is normally non-conductive, and once charged it is very difficult to discharge. The rate of dissipation of the static charge lags behind the generation and I surmise that the affected plastic in the region of the high energy arcing holds an electrostatic potential of say around 50 kV, but it won’t release it. Slowly building up 5 kV at a time from the 30 kV produced by the coil.
My guess is that this could be the precursor to the formation of carbon tracks, which of course may or may not occur. Depends on extent of arcing. Enough energy and the potential in the polymer is equalised when it forms a covalent bond with carbon.
Did you see any of carbon tracks in your old caps?
I have suspected that moisture vapour (due to condensation) occurs in most caps (except possibly in very dry States like Wyoming). Certainly just about every M119 cap in the UK has had moisture in it at some time. I theorised that when the moisture concentration of the air inside the cap reaches 3%, misfiring could occur.
I do my best theorising after a good pint and a fetid belch.
Similar threads
