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  #1  
Old 10-17-2008, 10:49 AM
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No Heat

My no heat issue question is how much flow should occur at the monovalve in a 85 300TD. I took out the monovalve and it worked but was torn. When I turn on the ignition I get no flow at the monovalve(with the valve removed) and can feel the assist pump working. I start the engine and get two small streams(from the bottom of the valve?) that flow at idle, when I rev the engine it will flow over the top(it takes about 2 seconds) of the monovalve slowly. It seems slow to me. Should this be gushing out? Is the system plugged or is there a thermost slowing the flow down? It seemed to work this summer but now it's not. The assist pump sure doesn't do much, so I thinking there is a flow restriction. Any ideas will help. Curt


Last edited by dirtcurt; 10-17-2008 at 10:51 AM. Reason: Forgot car model.
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  #2  
Old 10-17-2008, 11:31 AM
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What is the coolant level in your system?

Low coolant levels and a closed t-stat can impede flow also.

Flow will change with engine speed, as the water pump speed varies directly with the engine speed.
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  #3  
Old 10-17-2008, 01:03 PM
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Quote:
Originally Posted by dirtcurt View Post
I took out the monovalve and it worked but was torn.
A torn diaphragm could be the extent of your problem. It's a problem, at the very least.
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Old 10-17-2008, 01:04 PM
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Quote:
Originally Posted by rrgrassi View Post
...a closed t-stat can impede flow also.
How?
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  #5  
Old 10-17-2008, 11:14 PM
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The car runs 80-85c 70mph and have never seen it go over that. I'm thinking the pump may be clogged but have not had a chance to tear it down other than the M valve. Most cars I have worked on, the bypass for the heater shoots like a garden hose bypassing the thermostat. I don't have a service manual so I'm guessing at this point. I'm thinking the assist pump has failed or is jammed with junk. Coolant level is correct as well. New mono valve will be installed Sat. Curt
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  #6  
Old 10-18-2008, 12:51 AM
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Quote:
Originally Posted by qwerty View Post
A torn diaphragm could be the extent of your problem. It's a problem, at the very least.
Agreed
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  #7  
Old 10-18-2008, 01:05 PM
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Check the aux pump

Quote:
Originally Posted by dirtcurt View Post
. . . I'm thinking the assist pump has failed or is jammed with junk. . .
I agree that there should be a reasonable flow of coolant through the hoses into the heater core, thermostat open or closed. It would be worth the effort to pull the aux pump, see if it's crudded up inside.

Jeremy
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  #8  
Old 10-19-2008, 11:14 PM
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Well I found the problem after replacing the Mono valve. Somebody had plugged the steel hose with a plastic hose cap just before it goes into the pump. It may have been the PO or the AC repair shop trying to "FIX" the broken mono valve. They converted to 134(mistake) and were probably trying to get all they could out of the AC with 134. Pulled the cap and now I have controlled heat! It was not adding up and I had a feeling it was a trick. Still drives you nuts when somebody does that and doesen't tell you. Thanks for all of the ideas! And now on to the next thing to fix.

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