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  #1  
Old 10-06-2002, 05:19 PM
Car Killer
 
Join Date: Jan 2002
Location: Northern VA
Posts: 178
Cooling system problems: 83 300D

I bought my 83 300D from Turbodiesel approx. 1 year ago.

To date, its been a great car with a few minor cooling system problems.

Around december of last year, it had a mysterious coolant loss problem, whuch disappeared just as soon as it showed up. An oil analysis revealed no coolant in the oil, and a coolant analysis revealed no hydrocarbons in the coolant. Head gasket? nope.

Just yesterday, about one block from my house the temp gauge climbed to 120C and held there. gotta be the gauge, so I shut it down and jump out. Top coolant hose is cool, but under enourmous pressure. I can hear coolant boiling in the engine. Engine is extremely hot.

So I remove the thermostat and test it. Its fine, its stamped 176C and was opened almost fully by 190C. Several tests of the thermostat revealed it was operating just fine. So I removed the water pump. It wasnt leaking and it also appears to be in great shape. its kinda jerky when you turn it, but nothing that would alarm me. the fan belts and fan clutch were operating fine and werent loose.


I cannot figure out what the heck is wrong. thermostat is fine, water pump APPEARS to be fine, new radiator, nothing else wrong, just random overheating. any ideas?

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2003 Jetta Wagon TDI 145,000MI
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  #2  
Old 10-06-2002, 06:32 PM
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Location: S.F. Bay Area
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Cooling problems

you don't say whether your car is turbo or not. Also, check for hairline cracks around the surge tank neck. If there are cracks, you're loosing pressure and your system can't maintain anything like correct temperature.

Ben
www.reproduce100s.com
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  #3  
Old 10-06-2002, 07:11 PM
Car Killer
 
Join Date: Jan 2002
Location: Northern VA
Posts: 178
it held so much pressure that it literally exploded when i pulled the cap. I should have gotten the clue when the hoses were hard as a rock.

the shaft is fluid in its spinning, but you can definently feel a slight jerk. regardless, im buying all new rubber hoses, pump, thermostat, cap, tank, ect. Im gonna flush everything and rebuild the rest of the cooling system. The radiator is less than 18 months old and is a brand new behr unit. I doubt its the cause of problems because it flows fine and the heat never made it to the radiator.
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2003 Jetta Wagon TDI 145,000MI
1999.5 Jetta TDI 287,000MI
2001 Suzuki SV650S 26,000MI
2008 Yamaha Vino 125 11,000MI
http://www.crazymatt.org
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  #4  
Old 10-06-2002, 07:15 PM
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Try an AutoZone or Advance Auto thermostat - I have had better luck with ones from them versus MB.
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  #5  
Old 10-07-2002, 02:01 PM
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Location: Fairfax County, Virginia
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In your situation, all else being as you said with system pressurized OK.

1. Tstat (95%)
2. Coolant tank cap (5%)
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1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
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former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg
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  #6  
Old 10-07-2002, 04:36 PM
Car Killer
 
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I decided to disassemble the whole system. The system was full of rust scale and I think somthing in the system may have gotten clogged. I dont know what the small steel tube with the banjo fittings does, but it was clogged. I washed out the block and got rust scale for about 5 minutes. Its running pretty clean now, but we'll have to see if that will fix it.
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2003 Jetta Wagon TDI 145,000MI
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2008 Yamaha Vino 125 11,000MI
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  #7  
Old 10-07-2002, 05:53 PM
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car54,

That little steel line from the water pump housing to the head or top of the block is a vent tube. If it was clogged it is very likely that the water pump became air bound, as any bubbles that make it into the pump housing will get stuck there. Once there is enough of a bubble, the pump stops working effectivelyas the head it generates merely squeezes the trapped air bubble and never gets water flowing.

Erratic and sudden overheating can be a problem with trapped air in the system. I usually try to fill the car with the nose pointed up a hill, and I run it until it gets to normal operating temperature with the radiator cap off. As the level goes down from air venting out, I top the system off. This usually clears the system effectively. You also need to make sure the little vent hole in the thermostat is at the top of the housing when you assemble the housing where it will vent the most air rather than trap it.

If you really have a lot of rust you may need to try something stronger than just another water flush. Mercedes uses a citric acid flush, and you can buy the stuff from them, or do a search on citric acid and find another less expensive commercial source someone had posted already. Rust may also have clogged your new radiator which may or may not be a simple flushing operation to check or clear.

Good luck and I hope this helps. Jim
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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
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1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)
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  #8  
Old 10-08-2002, 03:14 AM
Car Killer
 
Join Date: Jan 2002
Location: Northern VA
Posts: 178
this air theory sounds very likely. Ill continue flushing with water until everything is clean, then I'll use the mercedes flush or equivilent. I will search for that in a bit.

Hopefully fastlane can ship my parts asap. as soon as they show up and I can reassemble the car, we will see if thats the problem!
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2003 Jetta Wagon TDI 145,000MI
1999.5 Jetta TDI 287,000MI
2001 Suzuki SV650S 26,000MI
2008 Yamaha Vino 125 11,000MI
http://www.crazymatt.org
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  #9  
Old 10-08-2002, 04:14 AM
turbodiesel
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I replaced the radiator, expansion tank, cap and thermostat at 180K.
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  #10  
Old 10-08-2002, 04:31 AM
Car Killer
 
Join Date: Jan 2002
Location: Northern VA
Posts: 178
I guess I'll have a few extra parts then.
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2003 Jetta Wagon TDI 145,000MI
1999.5 Jetta TDI 287,000MI
2001 Suzuki SV650S 26,000MI
2008 Yamaha Vino 125 11,000MI
http://www.crazymatt.org
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  #11  
Old 10-08-2002, 04:35 AM
turbodiesel
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I just remembered - I did not replace the thermostat.

The cap is actually newer, I think I replaced that at around 200K when it broke apart when I went to check the fluid level.

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