Thermostat location question

[Runningwhenparked]

Good morning

The restoration of my 1973 450se continues. After getting the engine to run it seems like the thermostat must be stuck as no coolant is circulating to the rad. I've got a replacement but am struggling to find the thermostat location on the engine. Could anyone help point me in the right direction?

Thanks in advance!

[daantjie]

Make sure it is fully warmed up. On the 6.9 at least it has 3 different circuits the coolant can take based on temp. Radiator gets bypassed full cold. Then at operating temp it sends coolant to rad with some bleed off to bypass. At max high temp of 102C the bypass is closed fully with all coolant being sent to the rad.

[jmperkins]

I would follow the upper radiator hose (coming from the radiator) to the thermostat housing.

There's also a service library in the mechanicals section that likely has a photo and verbiage to help you!

Good luck,

Joe

[TJ 450]

On later 450s, the thermostat is on the lower hose (3 bolts on the cover from the right hand side of engine), not sure if it's the same on the early D-jet ones.

It should be in the service manual.

Tim

[s class]

THe lower main hose attaches to a cover plate on the side of the water pump.  THe thermostat is under this cover. 

[Runningwhenparked]

Thanks for the assistance everyone. The thermostat must of unsiezed after we ran the engine for a bit as the temp dropped to normal.

[TJ 450]

That can also happen if there's an air pocket as well, anyhow great news it's operational again.

Tim