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  #1  
Old 01-22-2009, 07:48 PM
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overheating 300sd

I have a 1984 300sd. It was overheating and I flushed the system and replaced the Thermostat. It is still overheating andwater/antifreeze is coming out the AC drainage tube, and the reserve is still full??? Help please.

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Old 01-22-2009, 08:06 PM
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Sounds like a bad heater core.
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Old 01-22-2009, 08:12 PM
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300sd overheating

with my experience I would say thermostat you changed already, so is the water pump circulating, if it is then I would say radiator is proably stoped up from crud and age with it being and 84 model that is what I would say I have seen this with other cars and it happens when the radaitor gets age, so thermostat, water pump,radaitor. now you could do a presure test at 15 psi and also see what other problems you have,.
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Old 01-22-2009, 08:16 PM
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overheating?

bad heater core would either be leaking or not putting out any heat and that would be if it were stoped up and everything else was working, heater valve if stoped up coolant would still circulate through the block. check heater valve.
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Old 01-22-2009, 08:16 PM
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Do you have working heat?

Can you try bypassing the heater core? Cap off the metal pipes running to the firewall. One near the oil filter and one going to the mono valve.

My 300 SD ran hot even after a citric acid flush. I had to replace the 26 year old radiator.

Radiators.com has one for the 300SD for around $200.00
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Old 01-22-2009, 08:20 PM
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over heating

you sure can that is what I would do to eliminate my sources for blockage, run you a hose from right side of back of head to where the heater hose hooks up to the water pump and then see what happens, if it doesn't over heat now you know it is heater core heater mono valve. and so on, and not the radaitor,water pump or something with the head?
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Old 01-22-2009, 08:25 PM
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If its holding pressure its probably the radiator. If it was a water pump, you'd know im sure. Is there air in the head (meaning did you "burp" the cooling system?). Does blasting the heater help keep the temp down?
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Old 01-22-2009, 08:33 PM
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DON'T KNOW WHAT BURPING SYSTEM IS. i HAVE HEAT. i'LL CHANGE THE TERM. AND REROUTE THE HEATER HOSE. LET YOU ALL KNOW WHAT HAPPENS.
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Old 01-22-2009, 08:41 PM
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Sorry forgot this does anybody have directions for changing the heater valve and where it's located. I try to work on my car but i'm just learning thanks for the help.
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  #10  
Old 01-22-2009, 10:18 PM
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over heating 300 sd

Mono valve is on the pasenger side left side looking at the engine , you will see hoses connecting to it you can take a 1/2 inch peice of copper tubing remove the two hoses and bypass the valve going to the heater core ,by bypassing now you don't have coolant going to the heater core and no heat. if it does not run hot like this you have a heater core blockage, if it still runs hot you have a stoped up radiator,replace radiator.... now before you do any of this how hot is it 180degrees, 190, steam coming out, this is a closed system any excess should go back to the overflow tank you could have air in the system , if no air then it is the radiator......

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