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  #1  
Old 10-17-2002, 01:47 PM
redhdeight
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heating problems 300sd

i have a 1983 300sd that only blows cold air. i have posted this issue before:

http://www.peachparts.com/shopforum/showthread.php?threadid=47808

i got a repair kit for the monovalve. i replaced it last night. the old valve did not look damaged- the rubber gasket didn't look like it had any tears in it, but i replaced it anyway. i did have a concern because according to http://mbdieseldiy.tripod.com/monovalve.htm
there is supposed to be a small washer, a wave spring, a large washer, a coil cylinder and an solenoid coil/valve top/electrical plug. well, when i took the old valve out the small washer was missing. no washers came with the repair kit- i got a new valve and a new wave spring. i put everything back together with the new valve, minus the small washer. (valve, wave spring, large washer, coil cylinder and solenoid coil/valve top/electrical plug- in that order) i can't imagine this small washer making that much difference- but maybe it does. at any rate, with the new valve- i still have no heat.

to try and get the heat to come on, i push the top fan button, the thermostat wheel is turned to "max" and i push the "ec" button. this is what i should be doing to get heat- right?? the heater hose (the hose that goes from the block to the heater core) is new. the hoses that are connected to the monovalve look good- no tears or leaks. when i unscrewed the 4 screws to replace the monovalve- after the 4th screw was loosened coolant began to seep out of what the valve is screwed to- only a little leaked out- but i don't know if this is normal or not.

it is getting colder and colder here- i need to do whatever i can to fix this problem soon. what else can i do? what else could be wrong? can i try and diagnose anything? any advice is appreciated. thanks.

nick

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  #2  
Old 10-18-2002, 05:45 PM
redhdeight
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anyone?
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  #3  
Old 10-18-2002, 06:22 PM
RSH RSH is offline
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Join Date: Jul 2002
Posts: 106
heating problems

I have a 83 300SD, and in econ mode (ec button pressed) with the temp wheel at max my heater is in full operation.Does the heat work in defrost mode (button closest to the temp wheel) it will be hot no matter what the temp wheel is set at, if that works then you could possibly have a vacuum problem with the climate control flaps and doors not directing the heat properly or the push button control could be at fault. I cannot answer if the small washer your missing in your monovalve assy can effect operation or not, only that the instructions that come with the rebuild kits say keep track/order of all parts.Did the heat work at anytime before you replaced the monovalve?
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  #4  
Old 10-19-2002, 12:24 PM
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Join Date: Aug 2000
Posts: 106
Default on monovalve is full heat, check hoses etc. for blockage.
Do the hoses get warm? Check aux water pump, could be blocked. Aux. water pump should be unplugged if not working.
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  #5  
Old 10-29-2002, 02:42 PM
redhdeight
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well. i replaced the entire monovalve and i still have no heat. i get cold air when the "ec" button is pushed and the temp wheel is set to "max". it is also cold when the defrost button is pushed. there is power to the monovalve (the connection is not bad) and since it is all new the solonoid is working as it should, but this obviously wasn't the problem. the hoses coming from the monovalve were all cold after i drove around for 15 minutes hoping that warm air would blow through the vents. should they all be warm?? my temp gauge sits just below 100 degrees celcius when the car is fully warmed. where is the auxillary water pump located? how will i know if it's not working and what would need to be disconnected? i replaced the hose that goes from the block to the heater core so i know there is no blockage there. this hose is warm everywhere except for the few inches right before it goes into the heater core. the little hose that is connected to the monovalve that comes out towards the battery is not blocked either- i checked it when i replaced the monovalve last night. the other 3 hoses have not been fully checked for blockages. but as i said none of these 3 are warm. i've spent $150 replacing something that probably was working fine- this is just so frustrating. i'm just dreading that the heater core is bad. please let me what you guys think about all this. thanks.

nick
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  #6  
Old 10-30-2002, 08:27 AM
it leaks, its german
 
Join Date: Mar 2002
Location: raleigh nc
Posts: 1,111
Ok, first things first.

1) is the monvale getting power when its getting no heat? (quick test, unplug it, you get heat, then the fault is eletrical)

2) is their air in the heater core? This will stop all flow through the core.

3) if you get heat when the monovalve unplugged its time to run the tests on the PBP.

4) check all the fuses in f1 under the hood, I've run into weird climate control issues that were nothing more than corroded fuses making intermitent contact.

5) check the aux water pump for operation and flow, you can remove it and jump power to it for testing. if it's locked up, try freeing it and lubing it before replacment.


Joe

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