Webasto Air Top 2000 ST Diesel heater - leaking diesel fuel tank

Submitted: Wednesday, Jul 18, 2012 at 21:44
ThreadID: 96956 Views:5831 Replies:3 FollowUps:3
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We have the above heater installed in our Phoenix off road c'van. It is a fantastic addition to our van but the fuel tank, which is located on a specially made frame on the rear bumper bar, leaks continuously. The leak appears to be via the fuel cap. It is only a very minute leak but it is enough to attract all the road dust etc and is not a good look! The same occurred on the original tank which was replaced by Webasto. Before we go back to Webasto, I was wondering if any other members have the same unit and the same problem?. ( and if anyone has a solution).
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Reply By: Member - Captain (WA) - Wednesday, Jul 18, 2012 at 21:52

Wednesday, Jul 18, 2012 at 21:52
Hi Ian,

Is it a "leak"or is it just diesel venting from the vent hole in the cap? I too have a diesel heater with a 10L tank and there is occasionally a dust trail where fuel has come out of the vent hole.


AnswerID: 491220

Follow Up By: Member - Alan H (QLD) - Wednesday, Jul 18, 2012 at 21:54

Wednesday, Jul 18, 2012 at 21:54
Me three

FollowupID: 766686

Follow Up By: Member - Ian G (NSW) - Thursday, Jul 19, 2012 at 01:01

Thursday, Jul 19, 2012 at 01:01
It is leaking via the threaded cap, not the breather hole. When turning the cap, it gets tight, then slackens off again. It won't make a tight seal.

FollowupID: 766690

Follow Up By: Member - Captain (WA) - Thursday, Jul 19, 2012 at 10:46

Thursday, Jul 19, 2012 at 10:46
My cap screws on about 3-4 complete turns and then cannot go further as the filler pipe is wider than the cap. It sounds as if your cap has been over-tightened and the threads have been damaged. Can you see if the threads are damaged on either the cap or the tank?

FollowupID: 766700

Reply By: Ozhumvee - Thursday, Jul 19, 2012 at 08:09

Thursday, Jul 19, 2012 at 08:09
I fitted our tank inside the Oka, to do it I cut the threaded section of the filler neck off and used a bit of silicone hose to extend the neck to the outside and then refitted the end and cap externally and it does the same.
You will have to expect some leakage through the cap as there is no breather on the tank and any pressure build up from movement or heat expansion must escape through the neck to cap gasket as the valve in the cap is one way in to prevent a vacuum when the heater is drawing fuel from the tank.
The only solution would be to drill and tap a fitting into the top of the tank and run a breather hose up high with a small fuel filter on the end.
The easier solution might be to never fill it past 1/2 or 2/3rds so that only fumes not fuel are expended.
AnswerID: 491227

Reply By: Gone Bush (WA) - Thursday, Jul 19, 2012 at 17:19

Thursday, Jul 19, 2012 at 17:19
I put a piece of duct tape around the cap just to stop it loosening a little.

Seems to work.

I'm glad I ain't too scared to be lazy
- Augustus McCrae (Lonesome Dove)

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AnswerID: 491249

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