Hi, I recently acquired an '87 300 SDL, has 130K miles on it, looks and runsvery nice. I have an issue I want resolved. Starts fine, with a littleroughness at beginning. After warming up and shutting down within approx.6-10 miles running, when starting again it smokes and has a loud knock andis rough running. Drive it away and it clears up until starting again, samething happens. The smoke is light in colour, almost white and isconsiderable. I feel it is an injection (timing) issue, but no one in myarea has equipment or knowledge to handle it. I am heading to Florida soon,from N.B. Canada, travelling the eastern coast, and would like to getsomeone who understands this engine to take a look and repair for me. I wasadvised to contact Brian Carlton for advise on where to go as he has severalof these vehicles. Any advice?
Ralph Robertson

Welcome to the forum.

Please smell the smoke and report back as to whether it's fuel or whether it has the sweet aroma of glycol.

Although your issue could be IP timing, it would need to be off considerably to create such a scenario.

Additionally, fill the coolant right to the mark and observe it over the course of one week. Report back as to whether coolant is disappearing from the expansion tank.

Could just be the glow plugs are not working properly...

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'95 S320 LWB
'87 300SDL
'04 E500 wagon 4matic

Ralph I have an 86 sdl. The noise you here does it go away when the motor waarms up? I know on mine I have a lifter tapping a little bit when cold but go away after warm up...Any oil in coolant or coolant in water?
There is a lot of very knowledgable people on here

Hi and thanks. I normally drive my '84 300CD and bought this unit to take to Florida. I have noticed the "add coolant" light coming on and then going off again when driving. I topped it up, and noticed when it is cold, the level is down. I just topped it up and will watch how it is for the next week. I put it in a local Mercedes dealership and specifically asked to check for head gasket issues, and they told me they checked everything and it is not a head gasket, so if they know anything, they should be able to determine that, right?? W'ell see!! Will keep you informed !!
Ralph

The most important part of that statement is, "if they know anything".

The answer is very uncertain............because most of them are just slightly older than the vehicle.

Try the cold engine hard coolant hose test yourself. After the car has sat overnight the coolant hose should not be hard and under pressure. I know the test sounds strange but is more than a part of fokelore on your engine the 603 type.

I would preffer the other ideal of releasing the cap for a second on the overflow chamber to release any contained pressure. Thats when the engine is cold and really there should be little or no presure present. Start the car cold. Check to see if the hose is pressurizing or going hard fairly fast.
it should not.

The water pump is not circulating until probably 175-190 degrees is reached. So any hardness should be from a cracked head or head gasket. In fact it is prefferable to do both tests in my opinion. Yours hopefully will pass both tests.

Never loosen that collant cap with a hot engine. Especially if abnormal pressure might be present. Some pressure is going to be there by design. This applies to any car. The scalding burns could be pretty bad.

Hi and thanks for the info. Last evening when I added coolant, there was some pressure in the tank. This morning, no pressure in tank nor was the coolant hose on top of rad. hard. Started the car and waited until engine was hot, and the coolant hose was quite warm, no pressure on the hose at all. One strange thing though, there was no heat coming from the car's heater either. Removed the coolant tank cover, no pressure and there was steam coming up from the tank. Ralph

Took the vehicle out for a run, put it thru it's paces and could not get it to act strange again. The heat was coming out as it should be, so that was just an issue of not heating while idling, whatever that indicates. The car did produce some blue smoke when taking off for a few minutes, then cleared up completely. The coolant hose did get hard once I came back and checked things out, that after about a 15 mile test run.
Ralph

I personally think that the hard hose in the morning test is useless, and your experience has shown the reason why:

Your hose doesn't get hard even after the engine is starting to get warm, it is painfully apparent that there is a leak, most likely a bad cap on the expansion tank.

If there is any leak, it will lose pressure overnight, even if the head has a crack you could shove a penny through. You first need to fix the pressure leak, so that the system has noticable pressure/firmness in the upper hose as soon as there is some heat at the heater hoses off of the head. Next, you go the car with the engine completely cold, should be no pressure felt in the hoses, start the engine. The hose should NOT pressurize right away, not until there is some heat/expansion which should take at least a minute on the 60x engine. If it pressurizes right away that indicates that there are gasses escaping the combustion chamber through the head (or gasket) into the coolant. If it pressurizes after a minute or so, the head is warm and the water is starting to get warm, normal. If it doesn't pressurize even after there's enough heat to feel it in the heater hoses, you still have a leak.

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Gone to the dark side

- Jeff

Went out to the car this morning after sitting there for several days. The top rad hose was soft, but when I took the cap off the expansion tank, there was considerable pressure built up in there.
I haven't been able to get the car to smoke and run with the loud knock, but whenever there was any smoke, I smelt it, and it is definitely fuel, not coolant.
The coolant level has gone down about 3/4 of an inch since filling it up several days ago and going for one short test run. When I came back from the test run, the coolant tank was full, but today it is down a little.
In summarizing my tests, after running the car for about 15 miles, the rad hose was hard, and the coolant tank was full. After sitting and getting cold, the hose is now soft, but the coolant tank was holding pressure for several days, and is also down a little, when cold.
Running the cold engine, at idle, until engine got hot, the rad hose did not get hard, only after driving it a few miles did it get hard. When I idled the engine to get it hot, I had no heat in the heater, and the hose did not harden, but when I drove it, to get it hot, I did have lots of heat coming out of the heater, and the hose was hard.
Ralph