So can someone tell me how the coolant flows from the engine to the heater core and back in an 84 300D? I'm helping a friend with some repairs and we were discussing it a bit. It looks like the flow would be like this....

1. Out of the water pump, then out through the hose by the alternator.

2. Through that hose to the aux heater assembly, then through another hose up to the monovalve on the firewall and into the heater core.

3. Then through the heater core, and out the hose to the top of the head on the engine.

4. Through the engine back to the water pump where the circuit starts all over again.

Am I correct, or is the flow reversed from how I discussed (out flow at the top of the head instead of inflow)

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2012 Mercedes ML350 Bluetec 91K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 231K (mine)
1998 Volvo S70 T5 Turbo 196K (kids)
1994 Ford F150 4WD 249K (firewood hauler)
1983 Mercedes 300D 376K (diesel commuter)

Heater flow is: 4-3-2-1!

Hot water is supplied from the head, returns to water pump.

Ok, so basically I had it backwards the first time? How about this.

1 . Hot coolant out the hose at the top of the head and into the heater core.

2. Through and out the heater core, through the monovalve and through the hose to the aux heater assembly.

3. Through the aux heater assembly and to the hose leading back into the engine by the alternator.

4. Into the engine and to the water pump where it all starts the circuit again

Correct??

__________________
2012 Mercedes ML350 Bluetec 91K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 231K (mine)
1998 Volvo S70 T5 Turbo 196K (kids)
1994 Ford F150 4WD 249K (firewood hauler)
1983 Mercedes 300D 376K (diesel commuter)

The cooling circuit is shown in the shop manual:

Attached Files

20-005.pdf (181.4 KB, 93 views)

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

How Glysantin® coolants work ǀ Glysantin®

Play the video in the link. Not sure if this is what you mean.

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1990 190E 3.0L

Thank you all.....Got the answer to my questions!

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2012 Mercedes ML350 Bluetec 91K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 231K (mine)
1998 Volvo S70 T5 Turbo 196K (kids)
1994 Ford F150 4WD 249K (firewood hauler)
1983 Mercedes 300D 376K (diesel commuter)

Ok, another question comes to mind. I asked this before in another forum section, but did not get an answer...... Does anyone know the size of the heater hoses? I'm thinking 5/8" or 3/4. Going to do some work soon and would like to know the size (and no, cutting a piece of hose off and taking it to the auto parts store is not an option!)

Thanks,

Glenn

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2012 Mercedes ML350 Bluetec 91K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 231K (mine)
1998 Volvo S70 T5 Turbo 196K (kids)
1994 Ford F150 4WD 249K (firewood hauler)
1983 Mercedes 300D 376K (diesel commuter)

Are you getting another hose? If so, just order the specific hose from online. No measuring required. Just make sure it looks the same and you can also look it up by part number to be sure you are ordering the correct part.

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1990 190E 3.0L

No, I want to install a "T" fitting, so I need to know the size of the hose. I could disconnect it and measure, but I don't want to open the system up until I need to.

__________________
2012 Mercedes ML350 Bluetec 91K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 231K (mine)
1998 Volvo S70 T5 Turbo 196K (kids)
1994 Ford F150 4WD 249K (firewood hauler)
1983 Mercedes 300D 376K (diesel commuter)