83' 300sd Glow Plug Mix-N-Match... Does it matter? - PeachParts Mercedes-Benz Forum

cousindave76 · #1 12-11-2006, 02:41 PM

Hello all,

I just ordered a new glow plug/relay kit which comes with a new relay box and 4 new BOSCH glow plugs. I have an 83 300sd so I ordered an extra BOSCH glow plug to complete the kit. Upon package arrival I noticed they gave me a BERU glow plug as my extra. This looks like it will thread into the block just fine but it has a slightly different style than the BOSCH plugs.

I am not a fan of installing miss matched sets of ANYTHING. When I get the opportunity to install new parts on my car, I like everything to be matched up.

Here's the question... Is there absolutely no reason to worry about the unmatched plug? Will it work exactly the same with the other plugs? Should I not be worried about it and just install it already? Or should I confront my part supplier and make them give me a matched glow plug?

I appreciate you input!

rrgrassi · #2 12-11-2006, 02:59 PM

Matched would be best, but as long as the odd one has the same thermal and electrical specs, it should be fine.

#3 12-11-2006, 03:36 PM

I wouldn't bother complaining about it, having all the same brand would be best but the Beru GP is similar quality and should last just about as long. GPs are maintenance parts, so you will have to replace it eventually anyway.

cousindave76 · #4 12-11-2006, 05:15 PM

Thanks for the input guys. I guess I will go ahead and install the BERU plug along with the others.

Spec wise the only difference I could see is that the BOSCH plugs say 11v on them and the BERU says 11.5v. Is that a problem?

barry123400 · #5 12-11-2006, 09:32 PM

There is no problem here. It is for common sense purposes like having a light fixture with 4 sylvania light bulbs and one general electric bulb of the same wattage for arguments sake. Only time will tell if one brand lasts longer than another. All five bulbs will produce about the same amount of light. One could in theory call it a missmatch I guess. But getting another boch plug from a different production run could be much the same. As for the 1/2 volt difference it is about the same principal as one light bulb rated at 115 volts and another at 120 volts. Manufacturing tollerances eliminate any reality here again for practical purposes. No point in trying to expand upon this really. I even mix old and new plugs when removal of the other older plugs is just too difficult without them being really bad. Never seems to cause the slightest difficulty in apparent general function.

cousindave76 · #6 12-15-2006, 06:19 PM

Thanks again guys... I'm installing the new set this weekend. I'll let you know how it goes.

barry123400 · #7 12-17-2006, 10:54 PM

For practical purposes the 11 volt versus 11.5 volt rating makes no appreciable difference. In my mind it is much like a sylvania light bulb rated 60watts at 115 volts ac and a general electric bulb rated 60 watts at120 volts. In theory the lower voltage bulb will burn less than five percent brighter. Manufacturing tollerance variations will tend to negate any real difference to start with. Even if you got bosh plugs from two different production runs you might have a greater spread. It is a good test to see if one brand tends to last longer than another if done objectivly perhaps. Since you only have the one differemt manufactures plug a random efffect is possible. In general though if the beru outlasts two or more bosh plugs I would buy beru from now on or at least try a set when your present plugs are gone eventually. Again though nothing is sure as a random production effect might overshadow consistancy hence forcastibility of the beru or the bosh for that matter. Maybe glow plugs are a bit of a crap shoot although the cheap brands have a poor reputation. Brands like autolight, champion etc should be avoided basically by others experiences of very short apparent lifespans on occasion. There is absolutly no potential problem with your mix though that occurs to me.

cousindave76 · #8 12-18-2006, 09:42 AM

I installed the glow plug kit over the weekend. The install went smothly. The new system works great except for one thing...

The glow plug lamp on the dash stays lit for about 3-4 seconds and turns off. The car does not start after only 3 or 4 seconds of glow. I tried waiting even after the light goes out but no start. I have to cycle the key two or three times before the plugs get hot enough to start the car.

Is there something controlling the timing of the relay that has possibly gone bad. Am I unlucky, did I just install a new defective relay unit?

I appreciate you input!