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  #16  
Old 12-01-2014, 03:01 PM
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Yeah. This has been the most reliable car I've ever owned. And every year, I do lots of preventive maintenance on it. For instance, I regularly change my coolant every year flushing it with water.

Of late, life has been really busy and over time, the things I should check, I don't. Or I put it off and before you know it, it's completely forgotten.

I just checked my records, the last time I changed coolant was in 2011...and that too, not a full flush. I did it only because my bypass hose blew on me and I had to change it. I remember that job fondly. Not! I don't recall flushing either. Heck I last did that in 2008 :-(

Man, I've been a bad Mercedes owner :-(


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  #17  
Old 12-01-2014, 03:35 PM
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Sounds like a circulation problem. May even be a head gasket. The engine blowing a big obstructing bubble into the coolant system partially blocking circulation.

I would want to test the coolant for any signs of hydrocarbons before moving on to other things. To me the loss of coolant with no obvious leakage place and various other symptoms you describe makes it a possibility in my opinion. Still far from a certainty.

I just would not bet it is not a head gasket. Now if the coolant was just freezing up in the radiator could explain this as well.

The bottom line remains . Were is the coolant going? Placing a mirror behind the exhaust pipe when the engine is good and warm and having someone increase the revolutions of the engine substantially might be helpful. Moisture condensation on the mirror would warrant further investigation. Or with a normal mix of coolant and water in the engine you might even smell the coolant back there. I am not certain of this last statement though. Possibly depends on the amount of coolant loss. So I would not bet on it one way or another.

White smoke may also be an indicator but this depends on the outside temperature and you knowing what the normal appearance of your exhaust was. Pulling the glow plugs might reveal one very clean one in comparison to the others as well. Coolant getting into that cylinder is going to have really steam cleaned the glow plug up. This may be the actual first diagaostic test other than the mirror examination or hydrocarbon in the coolant checking. I would want to eliminate or make sure the problem is or is not the head gasket first before moving on.

Last edited by barry12345; 12-01-2014 at 03:52 PM.
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  #18  
Old 12-01-2014, 11:09 PM
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Quote:
Originally Posted by zu! View Post
Yeah. This has been the most reliable car I've ever owned. And every year, I do lots of preventive maintenance on it. For instance, I regularly change my coolant every year flushing it with water.

Of late, life has been really busy and over time, the things I should check, I don't. Or I put it off and before you know it, it's completely forgotten.

I just checked my records, the last time I changed coolant was in 2011...and that too, not a full flush. I did it only because my bypass hose blew on me and I had to change it. I remember that job fondly. Not! I don't recall flushing either. Heck I last did that in 2008 :-(

Man, I've been a bad Mercedes owner :-(


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I feel the same way. I'm a teacher and by the time I get home, it's around 4PM. That gives me an hour to work on the car before dark. I've actually considered selling my 300SD as I just don't have the time to work on it. There isn't really anything major wrong with it, just little things you know.
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  #19  
Old 12-02-2014, 02:28 AM
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Just a quick update. I drained what was in my rad...not even 2 liters of brown water came out. Ridiculous. Filled up with about 8 liters of coolant and distilled water and drove to my friends shop to borrow his pressure tester.

Well, interestingly, the temps never went over at all. There was constant heat. I thought all was good...until I pressurized the system to 15 psi. It held, but very slowly starting dropping. I felt around the area which I had repaired before. Not wet! But there was a steady stream coming from below.

Yep, the reservoir was cracked. I can't understand it. Never was a puddle under my car. Yet I always needed to top it off. My mistake was topping off with water only and not a coolant-water mix. I think that evaporated whatever leaked.

Used a plastic welder (big soldering iron) and melted another piece of hard plastic over it. Let's see how it holds. On the drive home, everything was normal. Let's see at tomorrow's commute to work.


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  #20  
Old 12-02-2014, 03:12 AM
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Based on your last post its waaay past time for a new radiator cap. If your system isnt staying sealed (air tight) the temps are sure gonna drop as you drive.
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  #21  
Old 12-02-2014, 10:47 AM
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Originally Posted by TnBob View Post
Based on your last post its waaay past time for a new radiator cap. If your system isnt staying sealed (air tight) the temps are sure gonna drop as you drive.
Well, here's the thing. I'm not sure the cap is the problem (it may be) but the reservoir itself was cracked and this crack only manifested itself with 15 psi pressure.

Well, this morning's drive was telling to say the least. The temps were great (90) and I had good heat. Climb a hill, hit the freeway and run it a little harder and they climbed to 100. They stayed there, but no more cabin heat. Slow down for a light, heat comes back on, and temps dropped to just over 80. Hit freeway again, and temps climb to 90 and stay there, with heat in cabin.

I think the reservoir is still cracked and leaking a slight bit under pressure. And the cabin heat could probably be a cold solder or mono-valve issue.

The only thing that worries me now is the correlation between cabin heat and engine temps. Makes me wonder if the water pump is on its way out, and the only thing moving the coolant around the engine is the small little electric pump for cabin heat!
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  #22  
Old 12-02-2014, 11:03 AM
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Don't fall for the idea that you need a 15# cap for the system to perform properly. I ran my signature car with a 7# cap for years, and it worked fine. Now that I switched it to NPG, I run it at zero pressure. Much easier on the hoses, radiator, and heater core.
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  #23  
Old 12-02-2014, 11:49 AM
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Originally Posted by zu! View Post
Well, here's the thing. I'm not sure the cap is the problem (it may be) but the reservoir itself was cracked and this crack only manifested itself with 15 psi pressure.

Well, this morning's drive was telling to say the least. The temps were great (90) and I had good heat. Climb a hill, hit the freeway and run it a little harder and they climbed to 100. They stayed there, but no more cabin heat. Slow down for a light, heat comes back on, and temps dropped to just over 80. Hit freeway again, and temps climb to 90 and stay there, with heat in cabin.

I think the reservoir is still cracked and leaking a slight bit under pressure. And the cabin heat could probably be a cold solder or mono-valve issue.

The only thing that worries me now is the correlation between cabin heat and engine temps. Makes me wonder if the water pump is on its way out, and the only thing moving the coolant around the engine is the small little electric pump for cabin heat!
You said you kept adding water to your coolant. I would suggest sucking out a few tablespoons and leave it out overnight in sub zero temps and see if it is frozen in the morning. If so, expect the worse, i.e. cracked block/ head.
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  #24  
Old 12-02-2014, 11:53 AM
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Originally Posted by rscurtis View Post
Don't fall for the idea that you need a 15# cap for the system to perform properly. I ran my signature car with a 7# cap for years, and it worked fine. Now that I switched it to NPG, I run it at zero pressure. Much easier on the hoses, radiator, and heater core.
What is NPG ?
Zero pressure... if that is really what you mean.... means your coolant will boil at approx 212 degree F...

Internal Combustion engines need to be at some temperature to be efficient and LAST a long time.... as the thermal expansion coefficients are figured into the sizes they are made... for instance.... many pistons are made in an oval shape to fit into round piston holes... because they expand more in on direction than 90 degrees to that... due to the piston pin and associated bulk associated with that.... they need to be at the correct temperature to be ROUND while they are ' working' or they do not seal with the side of that round bore like they should...
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  #25  
Old 12-02-2014, 11:56 AM
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Originally Posted by funola View Post
.....a few tablespoons and leave it out overnight in sub zero temps and see if it is frozen in the morning. ....
Couldn't he just label it as not edible....and put it into his refrigerator freezer ?
He should not fill up the ice cube tray....
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  #26  
Old 12-02-2014, 12:02 PM
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Originally Posted by leathermang View Post
What is NPG ?
Zero pressure... if that is really what you mean.... means your coolant will boil at approx 212 degree F...
NPG Evans Cooling

The boiling point of NPG coolant is stated to be 375 at atmospheric pressure (i.e. not pressurized).
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  #27  
Old 12-02-2014, 12:06 PM
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Originally Posted by leathermang View Post
Couldn't he just label it as not edible....and put it into his refrigerator freezer ?
He should not fill up the ice cube tray....
Wouldn't it be best to test it under the same actual condition his engine was in?
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  #28  
Old 12-02-2014, 12:17 PM
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Originally Posted by funola View Post
Wouldn't it be best to test it under the same actual condition his engine was in?
Sure, if Mother Nature will cooperate....
this ' NPG'...
does it satisfy the Mercedes need for anti corrosive properties to protect the heater core... for instance ?
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  #29  
Old 12-02-2014, 12:25 PM
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Originally Posted by leathermang View Post
Sure, if Mother Nature will cooperate....
this ' NPG'...
does it satisfy the Mercedes need for anti corrosive properties to protect the heater core... for instance ?
I've never used it. Just read the comments from proponents, and opponents, on this forum and others.

In theory? It's water-less, so corrosion is a non-issue. It's supposed to be a lifetime product...
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  #30  
Old 12-04-2014, 04:55 PM
zu! zu! is online now
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Originally Posted by leathermang View Post
Sure, if Mother Nature will cooperate....
this ' NPG'...
does it satisfy the Mercedes need for anti corrosive properties to protect the heater core... for instance ?
Well, Mother Nature has cooperated in spades. We've had quite a few freezing spells and I can confirm that the "rusty water" did not freeze at all. There were a few lumps of "rust" at the bottom of the bucket that seemed like congealed porridge, but a quick swirl of the gunk and it was gone.

My car has kinda behaved a little since. I took it for a hard run up Burke Mountain to see if the temps would rise. Not a whit. Needle stayed resolutely below the 100 degree mark.

However, what I've discovered is that if I keep the car running below 90 kmh, the temps will not climb. Going faster past 100 kmh and the temps will go above 100, but not much higher. Still within MBs range.

My suspicions are the water pump vanes may be corroded. At idle, I don't feel much water rushing by when I squeeze the top rad hose. I think that's a pretty clear indication of a "weak" water pump.

The waterpump has never been changed on this vehicle. The thermostat has. And I remember that when I changed the thermostat was when the temps of the car started going higher, up to the 100 mark. With the old thermostat, it never went past 85, which someone told me was too "cool" for the diesel to be efficient.

Either way, it looks like a dodged a bullet there. I'm going to be proactive and just change the WP, and maybe even the TStat. I'll probably wait until it warms up a little, so that I can do a cooling system flush as well. Right now, everything with water in it freezes.
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