Heater Coolant Leak

[cuisses]

The W108 has coolant leaking very slowly into the driver's footwell. Is it worthwhile putting a chemical sealant pill in the radiator as a first attempt to stop this?

[T-Modell]

Hi David,
I personally don't believe in those "wonder pills". I don't know, if you had it apart in that area, but I'd get rid of all the cladding above the tunnel and see where the leakage is coming from. In the end you have to repair it. The heater box is great fun to remove ... but doable with two people. I've attached a photo of my W111, which - I guess - is similar.

Regards
Thomas

[Bartman4800]

I agree with Thomas. And yes the heater boxes are similar between W111 and W108

There are 2 main culprits for leakage there:

1: The hoses through the firewall have perished (happens all the time). Replace them with new jubilee clips.
2: The O-rings in the taps have gone hard and need to be replaced.

The O-ring size is 13 x 1, and can be purchased in any good seal shop (CBC, Hallite etc), make sure to buy some silicone O-ring grease as well.

If this is not the cause, your heater box might need some soldering.

If you are going to replace the O-rings in the taps, ask us again.
It is not hard to do, but you can get caught out if you do not know what to expect.

Bart