Recently purchased 1991 300D, noob questions - PeachParts Mercedes-Benz Forum

isved · #1 07-25-2013, 06:53 PM

Hello,

Long time Mercedes freak, noob to diesels here. My other half and I recently purchased a 1991 300d with 309,000 miles on it. The car was owned by one person up until recently and was always/almost always serviced at a Mercedes dealer. The car runs/drives absolutely great, apart from a few things. I've searched and searched, and got mixed answers, so I was hoping some of you friendly folks could clear up a few things for me.

1. It has a grey/white smoke cloud on start up. Starts great, glow plug light seems to work as it should, and after the initial cloud at the first "puff" it seems to be perfectly fine. smokes on harder throttle at times as well. My question is, is that normal? I've read everything from possible head gasket problem (coolant is good) to simple fuel burning and that it's normal. Just wanted to get a more clear answer.
I've read that a quart of ATF with a full tank will clean out some deposits that might be causing the smoke. Any input regarding this is appreciated.
The car has no leaks except at the injection pump, I see a bit of fresh dark staining on it. Is that my problem?
I mainly would just like to make sure that the car is okay to drive, the smoke itself doesn't bother me much.

2. The A/C was converted over to R134A, there must be some type of leak because I refilled it. It seems to blow alright, but I am wondering what type of pressure I'm supposed to have at the low side. I charged it to ~35, it falls to 32 or so when the compressor kicks on. Can I charge it some more? Or is that the optimal level?

3. I'm a noob to diesels. Even though the car runs/drives great as I indicated above, any overall input and suggestions are appreciated. As far as what i should look into, check over, inspect, and overall ownership input is appreciated.

Thanks in advance!

shertex · #2 07-25-2013, 07:21 PM

Congrats on your purchase! These are great cars....I've got two of them and love them!

As to your white smoke, I had virtually identical symptoms on my 92 and it turned out to be the head gasket (at 244k miles). Is the oil level going down? Do you any oil by the exhaust manifold by #1 cylinder? Those were symptoms of mine as well. So some searches on smoke....I'm sure others will chime in as well.

On AC pressure, see AC Pressure Chart.

This is a great forum....lots of extremely knowledgeable (not me!) and helpful (I try to be) people.

shertex · #3 07-25-2013, 07:26 PM

Is it diesel that's on top of the injection pump? If so, probably delivery valve seals need to be replaced. A common, once-in-a-great while repair.

joegolden · #4 08-18-2013, 05:23 PM

I just purchased a 91 300d 2.5 today with 288k on it. Man is it a quiet diesel. But guys it will not get out of its on way

slower than my 240d if that tells you something. The car idles and sounds wonderful hardly a puff of smoke under any condition. It just winds out holds the gear for a second ...then a firm shift with very little momentum..

It almost has a hesitation like its holding back. She acts like she wants to go but wont. Is the turbo suppose to be audible during acceleration with these cars. I do not here any spooling I don't believe.

Sorry to hijack your thread. Just want to hear what you are experiencing. Thanks Joe