Webasto issues

[Staarek]

Hi there,

I’ve got bit of an issue with my Webasto Heater. It’s a 90 St version (9.1Kw). It’s been working well for years and I never had any issues with it. I always made sure it was working hard, I would only switch it on for 1,5 – 2 hrs max at the time, so I doubt it was ever going to “low flame” setting. Since last week it’s been switching off due to overheating. I vented the system, flushed it, vented again (numerus times) but still the same things happen. I checked the water pump, it seems all good, there’s a good flow and I cannot see anything wrong with it.

What basically happens is Webasto runs for 20-25 minutes (sometimes longer, sometimes shorter) and then it seems that the coolant after the unit boils and the unit switches itself off. I think that it generally heats up the entire systems quicker than usual, it is quite of a big system, 6 rads, towel rail and a calorifier – give or take 100 lts of coolant so it was normally taking around 1hr or more for the rads to get proper warm, this now happens after 20 -25 mins.

Any help will be appreciated!

[Tony Brooks]

Can you hear the boiling or are you surmising it is boiling because it shuts down?

If the latter then are you moored up so the bank/fenders are blocking the exhaust or has thee exhaust coked up?

If its heating the ENTIRE system then the water pump must be working tolerably well and you have circulation so I doubt its an airlock and I suspect it is probably not boiling (unless you can hear it).

 

 

 

[Staarek]

Hi Tony,

Thanks for your reply. The exhaust is not blocked. It seems that the coolant is boiling as the pipes are making weird noises and you can see steam after removing one of the hoses from the unit.

EDT. I will investigate the exhaust though, might be worth removing the silencer.

Edited February 26, 2018 by Staarek

[Tony Brooks]

In that case it sounds like an airlock, is there a bleed point on the circulating pump or very close by? Not sure what you mean by "venting the system".

[Tony Brooks]

A further thought although it does not accord with "heats the whole system". Does your installation have a header tank or has it been done "domestic wise" and uses an sealed expansion vessel to give a supply of "top up" water. If by any chance its the latter how can you be sure there is enough water in the system?