300sd Glow Plug

[dieselman]

The other day I went out to start my 1980 300sd when I started it I noticed a rough idle and the glow plug light was flashing. It flashed about ten times and went out. Is this a bad glow plug? I am planning on picking up five new ones monday because I am going in for my 15000 mile valve adjustment. I think they are the original glow plugs. She now has 200,410 miles. Any info would be appreciated. Also I need to know how hard they are to remove. Are they going to be stuck tight or will they come out easy?

Thanks to all

[Crowe]

You are correct. The flashing light is an indication that one or more of the plugs may be bad. Most likely it is only one plug. You can do a search for more details on how to test and determine which plug is bad. It is not necessary to replace all the plugs if only one is bad. I found one bad glow plug on my '80 300SD and just replaced that one. In my case it came out without much effort. Some of the plugs are difficult to reach, which is another reason to only replace the ones that are bad.

[P.E.Haiges]

Dieselman,

In my opinion, 15,000 miles is too often for a valve adjustment. I check them every 25,000 miles. Last time I checked the valves in my 300SD, none of the valves needed any adjustment after 25,000 miles because they were all within spec.

So if they do not need adjustment at 25,000 miles, it is even more unlikely they would need adjustment at 15,000 miles.

If you do get them adjusted at 15,000 miles, I suggest you check them all first before loosening the adjustment nuts to see if any really do need adjusting.

I also agree on replacing only the bad GP.

The GP should not be any problem in your iron head. Where they get stuck is in the aluminum heads because of the solid state diffusion between the aluminum head and the steel GP.

P E H

[dieselman]

I guess I am over concerned about taking care of the car. I want it to last as long as possible. I bought it two years ago and have clocked over 70,000 miles on it. I have seen posts that claim you should get them adjusted every 15,000 miles. Then I have seen posts that claim they have never had them adjusted. The rough idle and blue smoke the other day gave me a good scare. I have had many Mercedes Diesels. This is the first one I have done regular valve adjustments on because before I did not realize they even needed it. I think I will take your advice and wait until 25,000 miles because I will be putting it up for the winter soon anyway. Those 116 bodies rust badly.

Thanks for the advice

[P.E.Haiges]

Dieselman,

The difference in "putting up for winter" and not makes a fantasitic difference. I have one 300SD that I bought in the south east and alway garaged for the winter. It is almost like new at 240,300 miles. The other one was used all it life in NY or PA in the winter is ready for the junk pile with less mileage than the good one.

The rusty one still runs good so I will use it as long as possible. I bought it as a parts car but it ran so good I've been using it for 4 years and 44.000 miles. I only spent about $150 on repairs so far and I did exchange some parts with the better car.

I got a kick about a mechanic on TV the other day telling how to keep your car runnung forever: check oil, check tires, yada yada yada. Never mentioned the worst thing you can do to a car is to drive it on salt covered roads.

P E H

[dieselman]

Very True,

I have a nice toyota camry v6xle I will be driving in the winter. I noticed while I was living in St. Augustine Florida for a year that my SD started to rust because of the salt air. I noticed it around the bottom of the fenders. I washed it almost every day after that. The 116 seems much more likely to rust than my 126 sd. I just like driving the 116 better. I knew a lady in Florida who had a 75 300d that ran good but it looked like it was made of rust. She said it had over 400,000 miles on it and from the looks of it I believed her. I also knew of two wagons in St Augustine that had over 400,000 miles. The first hint of salt I see on the road I will be putting her in the garage. LONG LIVE THE BENZ