I now own a 300SDL and questions . . . - PeachParts Mercedes-Benz Forum

Big J · #1 07-10-2006, 12:24 PM

I purschased ATATEXAN's 300SDL. It was delivered Sunday. I am excited!!

And the questions begin in 3 . . . 2 . . . 1 . . .

The car loses coolant. PO said that there would be a small puddle on the floor. He had the radiator and all hoses replaced. Don't remember if the water pump was replaced or not. The system was pressure tested and passed. Where could the coolant be going? My first thought is to replace the expansion tank and cap (puddle is on that side of the car). Any suggestions?

The oil cooler lines leak (slightly larger than silver dollar puddle after 20 minute drive) and appear to need replacing. I looked at them and they appear to be straight forward to replace. IS this wishful thinking on my part? Should I let my indy replace them? Anyone have any comments or suggestions?

That's it for now . . . more to come!

Hit Man X · #2 07-10-2006, 02:07 PM

Could be thermostat o-ring...

Oil can leak from the IP, the oil level sender, or the cooler. I'd verify the easier ones first. If it is indeed the oil cooler, I have a cooler with lines if you need.

TheDon · #3 07-10-2006, 02:14 PM

the coolant could be leaking from a freeze plug like mine is.. but when i park after driving anywhere i pop the hood and vent the pressure in the cooling system by taking the rad cap off.. viola no more leak

Dervman · #4 07-10-2006, 02:34 PM

Congratulations on your purchase, the SDL is a GREAT car (not that I'm biased

).

One check to make for peace of mind is to run the car and leave it overnight. Before you start it the next morning, check the Top Rad hose to make sure it is pliable. If it is rock hard then that is really bad news because it means combustion gases are getting into the cooling system probably through a leaking head gasket or (worse still) a cracked head

This could also cause coolant to be forced out of the overflow on the expansion tank or any other weak spots in the cooling system. A pressure test may not reveal the same problem as they involve much lower pressures. Hopefully this is not the problem.

The coolant leak could be a number of things, but the most likely are the Thermostat gasket or a drain plug (possibly around the block heater) all of which are on the passengers side of the car. If the Expansion Tank Cap is faulty the coolant will leak out through the overflow which should be easy to trace. You should be able to see if it is leaking from the joint between the Thermo Housing and block.

The Thermostat is a PITA to get at but not difficult to replace. If this is the problem, change the Thermostat and seal and while you are in the area, remove the Alternator and take a look at the Brushes that are part of the Rectifier assembly on the back end. You might be able to get this off without removing the Alternator but its a lot easier if you do. If the brushes are worn replace the whole assembly as it is a real pain to get at normally.

I have not replaced the Oil Cooler lines myself (PO had already done that) but I hear the biggest issue is getting the connections undone without damaging the threads or the cooler.

TheDon · #5 07-10-2006, 02:40 PM

Quote:

Originally Posted by Dervman

The Thermostat is a PITA to get at but not difficult to replace. If this is the problem, change the Thermostat and seal and while you are in the area, remove the Alternator and take a look at the Brushes that are part of the Rectifier assembly on the back end. You might be able to get this off without removing the Alternator but its a lot easier if you do. If the brushes are worn replace the whole assembly as it is a real pain to get at normally.

.

i recomend when removing the tstat to soak the three bolts in pb blaster because they are known to break off. and when bolting it back up becareful not to cross thread it since its a steel bolt going into aluminum you'll be screwed

dervman about your info on the uper rad line being hard. i have a question.. i have a coolant leak out of a freeze plug.. its not that bad but it is a leak.. before i put a new tstat in it didnt leak.. i was told this is proably due to the fact the old one wasnt getting the pressure up in the cooling system and the new one is.. could it be the new tstat is doing what it should be doing

catmandoo62 · #6 07-10-2006, 07:09 PM

i just got an sdl myself,man what a car,anyway,after i fixed my ip leak i took both belly pans off and cleaned em out,man was there some major oil,etc on them,anyway i was just out looking and i have a small leak coming from the p.s. pump,looks like the line on the outboard side,and i see the oil level sender is leaking too,it also looks like it has a leak going on in the back around the rear main seal area,but i did just change the oil and some did get spilled out of the filter housing so i'll have to see if it grows or not,hopefully not.

Big J · #7 07-11-2006, 06:53 AM

I checked with PO and the oil cooler lines are recently replaced on the '87 300SDL. The oil puddle is black, so I am assuming it is engine oil not PS fluid (though I will check). Going to spray the area down with degreaser and see exactly where the oil starts to form.

Where is the oil sender located on these beasts. I have not bought any manuals, yet.

As for the coolant leak, I will check the top radiator hose after work today and see if it is hard or not (fingers crossed that it is soft). Parked for 10 hours should be enough cooling time. I'll also look at t-stat housing & drain plug.

Looks like it's time to crawl under the car for a better look.

Thanks for all of the replies!

Hit Man X · #8 07-11-2006, 07:12 PM

Quote:

Originally Posted by Big J

I checked with PO and the oil cooler lines are recently replaced on the '87 300SDL. The oil puddle is black, so I am assuming it is engine oil not PS fluid (though I will check). Going to spray the area down with degreaser and see exactly where the oil starts to form.

Where is the oil sender located on these beasts. I have not bought any manuals, yet.

As for the coolant leak, I will check the top radiator hose after work today and see if it is hard or not (fingers crossed that it is soft). Parked for 10 hours should be enough cooling time. I'll also look at t-stat housing & drain plug.

Looks like it's time to crawl under the car for a better look.

Thanks for all of the replies!

PS tends to get black as it runs down the block to the ground. My pump leaks on it...

Oil sender is on driver side of oil pan.

Big J · #9 07-12-2006, 06:08 AM

Yes, I'm psyched, the top radiator hose was soft after sitting for 10 hours. So no cracked head or not cracked enough for the gasses to back pressure the system.

HitMan,
I tightened the black knob on top of the PS pump, probably a full turn, so in light or your information, it quite possibly could have been PS fluid. I will remove the top of the PS pump and check the level this evening. Should it be checked hot or cold?

Dervman · #10 07-12-2006, 06:03 PM

Quote:

Originally Posted by TheDon

dervman about your info on the uper rad line being hard. i have a question.. i have a coolant leak out of a freeze plug.. its not that bad but it is a leak.. before i put a new tstat in it didnt leak.. i was told this is proably due to the fact the old one wasnt getting the pressure up in the cooling system and the new one is.. could it be the new tstat is doing what it should be doing

Sorry for the delay in replying I was away yesterday.
It may just be the increased cooling system pressure if the old Thermostat was stuck partially open or not sealing properly, but there is not that much difference in pressure between open and closed. The Thermostat just changes the water flow to go the Rad when the engine is up to temperature.

Did you flush the cooling system or replace the coolant? If you did you may have disturbed some grunge around the freeze plug and it is now leaking. I'm not a big fan of cooling system leak stoppers, but I have used them and they do work well for minor leaks. Barrs Leaks is one I have used with good success.

If you haven't already, do check the top rad hose the morning afer using the car as combustion pressures leaking into the cooling system could definitely cause leaks to appear.

Hit Man X · #11 07-12-2006, 06:22 PM

Quote:

Originally Posted by Big J

HitMan,
I tightened the black knob on top of the PS pump, probably a full turn, so in light or your information, it quite possibly could have been PS fluid. I will remove the top of the PS pump and check the level this evening. Should it be checked hot or cold?

I check mine hot and cold. Just as long as it is full but not right at the top, maybe 2/3 full? Use your best judgement.