Can I clamp off the cabin heat circuit with no ill effects?

[bradley6]

Hello, for my 80 300 td, I'm seeing a new leak under the dash somewhere. Given the season, I'd like to just clamp off the circuit. Is there anything I'm not thinking of?

Thanks!

[Rogviler]

That would be fine, although you'll probably have to clamp off both the in and the out. I've found that just closing off one doesn't fully stem the flow.

[Alec300SD]

To bypass the heater completely:

Run a 6 foot length of heater hose to permit coolant flow from the rear of the head to the the port on the thermostat housing.

Connect one end of the bypass heater hose to the short heater inlet hose (located by the #5 cylinder on the DS).
Route the hose along the firewall to the PS of the engine bay.
Connect the other end of the bypass heater hose to the short heater return hose located at the thermostat housing.

You will need 2 barbed plastic hose connectors, and 2 additional hose clamps in addition to the 6 foot length of heater hose.

This is what I used when I bypassed the heater core to remediate the cooling system for 'Stormcloud'.
‘Stormcloud’ – Cooling system remediation – Part 1

[jay_bob]

This is important on the later OM60x engines too. They rely on that heat flow out the back of the head. The 606 (at least in the W210) has a 4 port valve that keeps the coolant circulating out the back of the head even when the heat is off in the cabin.