Glow plugs Purchase - PeachParts Mercedes-Benz Forum

C Holmes · #1 02-02-2010, 04:23 AM

Anyone have a preferance on Beru or Bosch glow plugs? They list both as OEM so I was wondering if anyone knows whether one is a better choice over the other. The Bosch is 6 bucks cheaper each. I have an 87 300 TDT I am not 100% sure if that is even the problem as I have yet to troubleshoot yet. I can't imagine it being anything else. It just all the sudden did not produce the light but it will still start right up but not quite as easy so I am guessing some may be working. Are they wired in series? If one fails will that kill the light?

layback40 · #2 02-02-2010, 05:00 AM

Parallel wired.
If the light doesnt work but it still starts, most likely the globe is blown.
You may be able to hear the relay click on when you turn the key on.
If you havent checked the GP's for a while, probably worth doing. I only ever replace crook GP's, not the whole set. You can test the resistance, but I have found there is no substitute for getting them out and connecting them across the battery & watch them warm up & glow. You can also have them connected through the relay & control, just earth the body of each one (not the tip) & watch them all warm up at once when you turn the ignition on.

pawoSD · #3 02-02-2010, 07:14 AM

Another good brand to try might be the German made Monark brand. I might use those next time I need any. So far I have gone nearly 3.5 years on a set of Bosch with no failures.

C Holmes · #4 02-02-2010, 11:26 AM

well mine are years old, I have had the car for 5 years and never changed any and I know the guy before me never changed any and he had it for a number of years. What is the expected service life of these things?

tangofox007 · #5 02-02-2010, 12:02 PM

Quote:

Originally Posted by pawoSD

So far I have gone nearly 3.5 years on a set of Bosch with no failures.

My '82 300D went for 22 years on the original Bosch glow plugs. They were all still working when I replaced the on principle, in 2004.

Diesel911 · #6 02-02-2010, 01:14 PM

Quote:

Originally Posted by pawoSD

Another good brand to try might be the German made Monark brand. I might use those next time I need any. So far I have gone nearly 3.5 years on a set of Bosch with no failures.

I have Monarks in my Car (got on eBay before I read the info here, I live in S CA so that may be why they have lasted). However. members here say the Monarks are no good; Bosch or Beru are the ones that last the longest.

C Holmes · #7 02-02-2010, 01:14 PM

Well I am sure it is not fireing on all six. So I am assuming if some are working then the system must be ok. In a paralell wiring system, if say # 3 fails then none past that one will work. Is that correct?

Diesel911 · #8 02-02-2010, 01:18 PM

If you pull any Glow Plugs you should Ream or find some other safe way to clean out the Glow Plug Holes.
If your car uses those Glow Plugs that are agout 4 inches long and your Cylinder Head is Aluminum; I would read up on removing them as they some times snap off leaving part of the Glow Plug Inside of the Cylinder Head.

The Diesel Giant website has an excelleng pictoral on how to test your Glow Plugs with a Digital Volt/Ohm Meter (Multimeter). (This is not an endosement to buy parts from Diesel Giant; I would shop around.)

As the members recommend never use Autolite Glow Plugs. After 6 months use in the Engine I barly got 2 of the Autolite Glow Plugs out of my Engine because the tips had swollen up.

Bosch Glow Plugs seem completely adequate, cost less, and are easier to find than the Beru Plugs.

toomany MBZ · #9 02-02-2010, 01:18 PM

C.Holms No, if one has failed it won't work, but the rest will.

tr1cky · #10 02-02-2010, 02:21 PM

I recently replaced all plugs and added a new glow plug relay. The holes were also reamed and all wiring was inspected.

I used Bosch. I'm not a brand junkie, but Bosch has measures in place to maintain a standard to quality.

I recently broke a Beru glow plug relay. It was horribly constructed.

tangofox007 · #11 02-02-2010, 02:40 PM

Quote:

Originally Posted by tr1cky

I used Bosch. I'm not a brand junkie, but Bosch has measures in place to maintain a standard to quality.

Tell that to the folks who have purchased their recently-manufactured injector nozzles!!!

oldsinner111 · #12 02-02-2010, 02:52 PM

I go thru a set every year with the duratherms.I run 50/50 wvo and diesel with heaters.I guess its normal,but next fall I will try Monarks,because their injectors are awesome.

C Holmes · #13 02-02-2010, 04:24 PM

Well a weird thing happened this afternoon when I attempted to start. After letting it warm the plugs (assuming some are working) I cranked her over and she kicked so I repeated the process. After the second time the light came on as if normal. It didn't seem to start any better. After I got her going and warm the light again did not come on when I went to restart. Is there a temp sensor that may control whether the plugs come on or not?

C Holmes · #14 02-02-2010, 06:15 PM

Well the fuse is good and the relay seems to be clicking, I suppose indicating that it is working. I put an ohm meter on the leads and got readings of anywhere from 2.8 to 3.5 except for number two which reads 18.5 or something like that. I assume that is the one causing the trouble. So I guess that #1 is working and because two is fried nothing past that one would work.

strelnik · #15 02-02-2010, 06:18 PM

Quote:

Originally Posted by C Holmes

Are they wired in series? If one fails will that kill the light?

Only the glow plug systems before the mid 70s were wired in series, as far as I know. Don't know the EXACT date but when the 123 diesels started using the smaller glow plugs, I believe that's when they made the change to parallel wired GPs. Someone here will know the date, I don't have it handy.