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#1
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1984 300CD Heat question
I have a 84 300CD and I am struggling to repair the heat. The problem is that when traveling over 50 MPH there is no heat. At less than 50 MPH the heat is fine. I have rebuilt the mono valve and replaced the aux water pump. The valve seems to operate normally. I can hear it pulsing, it shuts off water flow when in A/c mode and controls the air temp very well at less that 50 MPH. The aux water pump seems normal too. I can hear it running when the engine is off and the system is calling for heat and I can hear the coolant recirculating and I can hear the mono valve pulsing. I just not sure what to check next, any ideas? Again, the air at the outlets gets cold very quickly right at 50 MPH.
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____________________ 1984 300CD (sold) 1973 220DPK 4 spd (died) 1978 350SL 4 spd gray market 2003 SLK32 AMG 1988 300CE (sold) 1997 E420 (Totaled) 1998 E320 Wagon |
#2
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FYI
If you can hear the coolant recirculating, there is air in the system.
It should be virtually silent if the system is full. .
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ASE Master Mechanic asemastermechanic@juno.com Prototype R&D/testing: Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician. Noise Vibration and Harshness (NVH). Dynamometer. Heat exchanger durability. HV-A/C Climate Control. Vehicle build. Fleet Durability Technical Quality Auditor. Automotive Technical Writer 1985 300SD 1983 300D 1984 190D 2003 Volvo V70 2002 Honda Civic https://www.boldegoist.com/ |
#3
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whunter, is that the reason for loss of heat? What is the best way to bleed the air out? I would think that it would happen as all of the coolant recirculated.
Thanks for your help, I do appreciate it!
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____________________ 1984 300CD (sold) 1973 220DPK 4 spd (died) 1978 350SL 4 spd gray market 2003 SLK32 AMG 1988 300CE (sold) 1997 E420 (Totaled) 1998 E320 Wagon |
#4
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Loss of heat at highway speed is very likely to be a monovalve problem. There have been a number of reports on this forum of defective aftermarket monovalve inserts that cause that issue.
Quote:
As designed, the 617.95 engine is self-bleeding. The thermostat housing features a passage that bypasses the thermostat; any air should wind up in the expansion tank.
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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl. |
#5
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FYI
Quote:
Real world experience proves that air generally becomes trapped in the heater core / cylinder head, causing issues. If you can hear the fluid flow = there is air trapped in the system. .
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ASE Master Mechanic asemastermechanic@juno.com Prototype R&D/testing: Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician. Noise Vibration and Harshness (NVH). Dynamometer. Heat exchanger durability. HV-A/C Climate Control. Vehicle build. Fleet Durability Technical Quality Auditor. Automotive Technical Writer 1985 300SD 1983 300D 1984 190D 2003 Volvo V70 2002 Honda Civic https://www.boldegoist.com/ |
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