Defective BOSCH parts?!?
 

I'm continuing my posting from an old thread about a "missing" problem with my '95 E420.

I had a dealer mechanic take a peak at the problem that I was having (following the replacement of caps, rotors and plug wires). Initially we were planning on inspecting the vacuums by spraying them down with brake fluid. BUT, considering that none of these problems had started prior to swapping the new parts, he decided to inspect the new caps by spraying them down with brake fluid and seeing how the engine performed. Following the soak, the engine started missing like crazy and with the lights off in the garage you could clearly see sparks arching between the wires on the cap. (Not supposed to happen because the caps/wires should all be insulated :()

We swapped back the old original caps and performed the same test problem free. The car runs great! Caps, rotors and plug-wires are all Bosch and ordered from Importec. Has anyone EVER heard of defective Bosch parts before? Caps?? Of the 30 years he's been a mechanic, he's never seen a problem like this.

This has caused me 2 months of headaches and I'm beside myself to say the least. Any input would be appreciated.

Were they really OE Bosch OR knock-off's from China.

Right now Bosch seems to have the rotors on back-order & even the dealers are selling Duduco!!

They're Bosch (Made in Spain) DOC, have you done a test like this? Is there another way to test the caps to ensure that they are in fact faulty?

That is a pretty interesting test, spraying them with brake fluid? I have never heard of that one. Has anyone ever heard of that? Anyway, the only bad cap I ever saw had arcing like you describe and carbon tracks on the inside just like they show in the Chilton manual. But I didn't put any brake fluid on it!

I'm sure he means brake clean.



but neither should be used. Brake clean does nasty stuff to plastics.

I wouldn't use Bosch parts on my lawnmower. Don't laugh, Bosch sells a fancy lawn and garden sparkplug at Lowe's.

I use a spray bottle of plain water, like another poster mentioned, brake cleaner is nasty for plastics.

How did the engine not have a missfire with the old parts reinstalled? Ditto the comments about the brake fluid or cleaner. I think NGK plugs and Beru wires are better the Bosch. Good Luck.

defective wires-yes. caps-no. that's a new 1. especially 2 new caps. i wouldn't put bosch wires on a bicycle. had lotsa problems with them. 3 sets right out of the box that i installed and a 4th where the cust did the job and brought it to me because it wouldn't start. bad coil wire. i would have like to have seen the light show on your car. i would think the new wires did not seat properly on the new cap and the spark was escaping that way. otherwise, there would had to have been lots cracks, pinholes, etc. to allow the new caps to leak spark. if the caps weren't such a bear to get on with proper wire routing, i'd like to see them on another car, with oe or someone else besides bosch wires. when i say oe, i mean factory, not oe mb wires from the dealer. those were bosch in the box at 1 time and 2 of the 4 sets i had problems with. good luck, chuck.

I remember when you could buy a "Bosch" part and look at the box and in fine print it would say "Robert L. Bosch". My understanding was that "Robert L. Bosch" was an American company that used cheap foreign parts. We saw a lot of problems with them. Maybe they are still around and selling parts made in China with lead in them. They put it in everything else they make.
Just a thought.
Paul

I decided to replace the caps as a 'preventative' measure prior to winter approaching. The idle on the car was acting a little funky and with 88k on the clock, plugs, caps and rotors seemed to be a probable cause. After pulling the caps, the condition of them wasn't bad at all but because I'd already had all of the new parts, I decided to replace them anyway. Now they're back on the car and are running fine (minus the little bit of a rough idle).

Maybe the AMF sensor needs to be cleaned? :confused:

i'll say it again, bosch wires can be a problem out of the box. a miss at idle is a problem i've had with defective new wires. have the ignition scoped by a shop and make sure they're ok. no funny patterns. good luck, chuck.