Best Glow Plugs?

[328dabi]

What are the best glow plugs for our cars? I’m looking to replace mine. I’ve seen Denso, Bosch, beru. Pelican parts has oem plugs which are made by Beru I think? Any suggestions which to buy and where would be greatly appreciated. My glow plug lights comes on, but the green light does not and it’s difficult to start in this cold weather. Once she’s hot, starts up quicker than my F30 328d. So I’m assuming I need new plugs.

[Kerrvillian]

Beru are the best followed by Bosch. Avoid off-brand plugs, particularly Autolite since they tend to swell the tips and either die early, provide poor starting, or break off in the swirl chamber. Autolite failures are very well documented in the Mercedes community and the glow plugs used on the M21 are the same as those used on contemporary Mercedes diesels

[328dabi]

Beru are the best followed by Bosch. Avoid off-brand plugs, particularly Autolite since they tend to swell the tips and either die early, provide poor starting, or break off in the swirl chamber. Autolite failures are very well documented in the Mercedes community and the glow plugs used on the M21 are the same as those used on contemporary Mercedes diesels

Thank you for the reply. I’ve also found Autolite and NGK plugs.

[Kerrvillian]

Skip the Autolite unless you just need something to sell the car and make it not your problem anymore. NGK are very hit or miss with the Mercedes community. Again, the M21 glow plug is the same one used in OM61x and OM60x engines, so a much larger demographic to get data from. Stick with what's good. The cost difference is negligible, particularly long-term.

[328dabi]

Skip the Autolite unless you just need something to sell the car and make it not your problem anymore. NGK are very hit or miss with the Mercedes community. Again, the M21 glow plug is the same one used in OM61x and OM60x engines, so a much larger demographic to get data from. Stick with what's good. The cost difference is negligible, particularly long-term.

Yea no, I don’t want to sell. I own the very first North American car produced and the only 1984 model year car. So I’m doing a full restoration. My experience with the e28 chassis is limited as is with the m21. But I def want good plugs. Better than oem if they exist. But so far looks like I will be ordering beru plugs if I don’t go to my local autozone and pick up the Bosch plugs they carry.

[gadget73]

I bought OE Bosch for mine, sold as a "kit" for some 6 cyl Mercedes. Same part number.

If you find Motorcraft bagged ones, those are also going to be Bosch parts. After I put the "Mercedes" ones in my car I found a set of Motorcraft ones for so cheap I had to own them as spares, so those are on the shelf in 40 year old plastic bags.


All that said, there is no point in replacing them unless they are bad. You can unplug them from the controller and do a quick ohm check to ground. Good plugs are something like 3 ohms. Half of mine were good, the other half were open. I threw away all 6 and replaced the set.

[328dabi]

I finally swapped out my glow plugs with a set of Bosch plugs. Someone attempted this before me, the old plugs were all Bosch but the first 3 were slightly shorter and carried different part numbers. They were also labeled 11.5V vs 11V on the correct plugs. So I’m guessing this was my issue. I’ll see how she starts tomorrow. Have the battery out of the car being recharged now.

Man, plugs 4 and 6 were a royal pain to replace. I didn’t remove the manifold, but got all 6 done. Thank you again.