So my heat hasn’t been working on my 01 S500 and I took it to Tires Plus to get it checked out and they tell me I have silicone in the reservoir and there is some tech bulletin that says I have to replace the ENTIRE cooling system ($4,500)

somebody PLEASE say it ain’t so!!!

They are lying

Take it to any jiffy lube they can do a coolant flush for $100 . They can’t upsell more repairs as they only do fluid flushes

that’s exactly what I’m gonna do

here is the tech bulletin that he was referring to and says he did see silicone in the fluid

I recently had the car checked out at an indy benz shop and while they said they didn't see any silicone in the fluid the fluid was dirty. They also said they didn't bleed or drain the entire system.

they said what they found is that the heater control value is sticking and that is why I am not getting heat.

They said they don't know why its sticking but they recommend that I replace it and flush the system and add a VPS additive to the system.

That should fix your issue

I'm just wondering if it is all worth it...he is also saying that I am having a problem with the harmonic balancer

This is a guess...

There is a "duovalve", which controls the flow of coolant to the left and right heat exchangers (heater cores), and also pumps coolant for the "residual heat" function. The duovalve is located between the two rear bulkheads in the engine compartment, under the wiper system. It is pretty common for the duovalve to get stuck. Often, you can solve duovalve problems by removing, cleaning and replacing the duovalve.

This might help.
https://www.benzworld.org/threads/so.../#post-5094753