W211 cooling issue E220CDI

[Damoe]

While driving home today I noticed there was very little heat in the car interior, even when turned up to full heat.
When I got out of the car I left it running and had a look under the bonnet. The electric fan was running and the radiator was cold - so cold that I could hold my hand flat on the core. The pipe to the radiator from the thermostat housing was hot.
Squeezing the coolant pipe I could not feel any build up in pressure in the pipe.
Thinking of potential causes, I'm thinking cooling pump failure, or sticky thermostat?
I'd appreciate if anyone has any thoughts?
Cheers
D


Sent from my M2007J20CG using Tapatalk

 

[Blobcat]

Thermostat failed open is where I’d be looking initially

If the car is showing it’s at temperature then the duo-valve for the heating is the likely culprit to have have failed.

 

[Damoe]

Thanks for this. Just wondering though, if the stat is fully open, what would cause the cooling fan to come on?

Sent from my M2007J20CG using Tapatalk

 

[malcolm E53 AMG]

The stat sounds like it is sticking closed or partially closed if the radiator core is cold

 

[Damoe]

So, started the car from cold and noted with a thermal camera that coolant was going straight to the radiator, so the thermostat was changed.
So now the coolant temp gauge is sitting a good bit higher (around the 80C mark), but the cabin still feels cool.
Anyone any ideas what to check next?
I'm thinking the following are some of the potential problem areas...
- coolant diverting valve to the heater
- temperature sensor in the cabin controlling the climate control
I guess there may be others, but would appreciate any input from the learned folk on here to diagnose what is broken or causing this.
Thanks
D


Sent from my M2007J20CG using Tapatalk

 

[Uncle Benz]

The heater control valve is a common problem on these old girls. Bit of a fiddle to do, but you’ll get there

 

[Damoe]

The heater control valve is a common problem on these old girls. Bit of a fiddle to do, but you’ll get there

Cheers uncle Benz.
Where is that valve located?

Sent from my M2007J20CG using Tapatalk

 

[Uncle Benz]

It’s right up under the wiper scuttle, near the brake master cylinder