e34 535 - coolant cap sludge

[tollytuff]

hello all.

just topped up my coolant tank, and noticed a cream coloured sludge on the underside of the filler cap. is this somthing i should be worried about? the head gasket went last august (and was fixed at great expence!) but i havnt noticed the sludge before....

cheers dani

[Fishkie]

Hi is it a clay like gritty looking substance? I have the same problem. Car drives fine, just done a 400ml round trip. Noticed just after buying it, flushed system, changed coolant, oil service then came back from trip and it as back.
To me and to a few other car ppl, it don't look like a oil/coolant mix but of course it could be. It looks a harder substance unlike a milky oily substance? I'll leave a pic of my filler cap.
Just to clarify, not oils in oil, not loss of power, no over heating, drives fine just this substance.

[Frances The Mute]

If the car isn’t used much or is only used for short journeys, then this is just a buildup on condensation as it’s not getting warm enough between drive cycles.

If there are no overheating, lack of compression or loss of power issues, you’ll be fine. Just give the car a good long run at least once a week.

[E-bmw]

And if he still has the problem since 2005 I am sure that will help immensely

[Triumph Man]

The sills will have rotted out since then, and that filler cap will be the least of his worries