I am a brand new '85 300sd owner of one week. Have a persistent oil leak and I dropped car off with mechanic who has been working on this car for the past six years.

He told me that the car is in good shape and the only thng that he felt needed to be done was a glow plugs replacement prior to cold weather. Is this a difficult do-it-yourself for a novice? If he does it, what would it typically cost?

Love the car and this forum!

There is nothing complicated about the procedure, it's just that a few of them are challenging to get to. If you're comfortable with removing the injector lines, it will give easy access to the plugs.

Good luck,

Glow plug replacement, you're getting ripped off! The glow plug indicator or fuse will tell you when you need a new glow plug. Yes, I said "A" glow plug. You only replace the bad one. If a light bulb burns out, do you replace all the bulbs? Of course not and it is the same with glow plugs. If the indicator doesn't blink and the fuse doesn't blow out, you don't need any glow plugs.
I have most of the original glow plugs in my 300SD. At 235,000 miles I replaced only 1 glow plug when the indicator blinked signaling an open plug. I carry a spare in the glove department just in case but its been in there for a long time. ~~~~~~~~~~~~~~~~~~~~~~~~~~~PEH~~~~~~~~~~~~~~~~~~~~~~~~~

P.E.,

What year is your 300SD? Is it a loop plug or pin plug engine?

My experience has been much different than yours, and is with a pin plug engine. In the past when the cooler days come along and my engines got hard to start. I replaced ALL the plugs and my problems were over for a couple of years. When I experienced this, the continuity check would be fine and they wouldn't be shorted to the shell. Some of the shells would have holes burned in them, however.

I started replacing ALL the plugs after an experience where I replaced only the one that appeared bad, still didn't start real well, then I just replaced them all, making it start like new. Also, when I started this approach, these plugs were only about $3 each. They are MUCH more expensive now.

I'm glad you've had better luck with them than I have.

Have a great day,

L,B.,

Actually I have 3 300SDs: '78, '79 and 80. Only the '79 and '80 running right now but they both start easily with the old GP down to about 5 degrees F with very old GP in them. All have the pin type glow plugs (GP). I think the loop type GP ended with the 115 240Ds. Even with the loop plugs I can only remember replacing one and that one shorted to ground. I don't think there was any fuse in the loop system because nothing blew out. I used to carry a short jumper wire in case one of the loop GP opened. I could jump across that GP and get started.

I could never understand why MB used the 1.2 volt loop GP in the 12 volt 190D, 220D and 240D. Half of the energy was lost in the resistors. Its as though the GP were left over from 6 volt systems. Buy you would think that for all the Diesels MB made they would have changed to plugs that were compatible with 12 volt systems with out resistors. I converted one of my 190D to pin (parallel) GP and it worked good and the wait was much less.

~~~~~~~~~~~~~~~~~~~~P E H~~~~~~~~~~~~~~~~~~

Bosch has a Fast glow kit for about $200. I think it's a series to parallel conversion but not sure.

P.E.,

I'm learning something new here. I didn't know that the SD's of 78, 79 and 80 had parallel glow plugs. All the diesels in the 123's, whether four cylinder or five had serial(loop type) glow plugs through '80 or thereabouts. The parallel(pin type) didn't start in them until '81 or so.

I can easily understand how a person would be having such glow plug luck with the loop type plugs, but I've never had such luck with parallel system.

Have a great day,

I did the conversion from the loop type to the pin type myself in my old 190D. I took 4 old loop type plugs and made them into bushings by maching out the center and tapping threads in them to fit the pin type threads which are much smaller diameter. I made 3 short wires with terminals on them to go from plug to plug. Then I put a copper wire in the dash indicator to replace the resistance wire to reduce the resistance to almost zero. I waited about 10 seconds when the engine was cold and about 5 seconds when the engine was hot for the plugs to glow. It seems like the wait for the loop style plugs was 30 seconds when cold. They worked very well and only cost the price of the new pin type plugs, about $40. ~~~~~~~~~~~~~~~~~~~~~~PEH~~~~~~~~~~~~~~~~~~