glowplugs
 

i am going to replace glowplugs in my 85 300d turbo diesel where are they located also how do i tell what size engine i have

oh boy... they are on the engine block (drivers side). You have a 3.0L I-5. Dont put gas in the tank either..

good luck!

is there some things i should know about when replacing them ?

There's some things you should know about posting a question such as letting us know what model and year Mercedes Diesel you're talking about :)

Sixto
87 300D

i believe i did
well i did some research and its pretty much unscrew the old one, screw in the new one

Is pretty rare for all of them to be bad; have you tested them, or are you changing all of them for some other reason.

Make sure you get Bosch.

Go to dieselgiant.com and follow the glow plug testing procedure before changing them. No need to change them if they are all working correctly.

When you go to the Diesel Giant sit and his pages open up it often looks like what you were looking for is not there. You have to scroll down the page to see the text and pics.

Bosch or Beru Glow Plugs are the only ones that hold up well. The Bosches are easier to find, cost less and are just as effective.
Totally avoid Autolite Glow Plugs. After 3 months use the tips of 2 of mine had swelled up and I had trouble getting them out.

You also might want to consider reaming/cleaning out the Carbon in the glow plug holes. They will work better and some claim the Carbon build up can shorten the life of the new Glow Plugs.

We also have a DIY, Do it yourself section on how to do many of the jobs.

well i already have them ordered the problem is it is really hard to start in the morning or any time its cold so im just doing the process of elimination
no harm in replacing 23 year old glow plugs right
yes i did order bosch plugs $12.00 a piece

Put a little anti-seiz compound on the threads, then in 23 years they will come out easier.

Have you done a valve adjustment? that will help on the cold starts also.
the valves tend to tighten up as they wear, then the engine looses compression making it harder to start.

Charlie

Hey Sixto, there are also some things you need to know about reading a post.....:D:D
[we've all been there] ;)