# Hymer B Class seam leaks-you may want to check



## crazyhorse (Oct 22, 2006)

Hi
I have happily owned a 1999 Hymer B544 for 5 years and a trace of a leak has just appeared high up one side about where the curtain rail goes across to the rear of the pull-down bed.
It seems to be coming through either from the top seam seal there or the horizontal side gutter strip in the same area.
I had to remove three plastic cover plates to be able to get to the area to test with a damp detector and still only in a gap between two long aluminium bearers.
Anywhere visible reads completely dry.
Right inside there is a damp reading above the mastic? seal running along there, i.e. the lower edge of the roof, but completely dry below it, i.e. top edge of the side wall.

Has anyone had any experience of replacing either the top or gutter plastic seal strips? I understand they have a tongue on them that has to push right into the sealing mastic.
How do you get the old strip and mastic out? Is it a difficult job?

The first visible sign was a run stain on the inner wall a few days ago but the leak has obviously dribbling in for some time judging by the damp readings. To find out more I had to remove several pieces. If the stain had been, say, in an area where there are cupboards, they would have to have been removed to do a damp test! 

I have looked at the internal construction of this model before and it seemed that no meaningful routine water ingress test can be done along the main seals to catch the problem at an early stage. 
Has anyone actually seen if dealers/repairers check along here or do they assume 'Hymers don't leak'.

I posted last year about my concern about the nature of these seals and their ultimate life and repairability before I had any problems.
Well in my case the life is 10 years and cost effective repairability yet to be established.

If anybody has had a similar problem and has had it fixed I would be grateful for any advice.
I imagine a lot of other 'B' Class owners may be too, as this assembly technique has been used from 1998 till present day with only minor changes.
Any info is appreciated.


----------



## davesport (Nov 12, 2006)

Sorry I don't have time to make all but the briefest of replies.

Are you sure it's leaking.

My first damp check at the dealers revealed "damp" in the vicinity of the seam you refer to. It was purely down to the van being sealed up over the winter with the bed in the stowed position with all the bedding in place. Common problem he said & he was indeed correct. I can't remember the reading on the damp meter he was using but it was definitely up in the "not completely dry area" on the scale. 

He informed me that if there was ever any damp on the inside near a seam, the sealing strip on the outside was often seen to be displaced. Might be worth checking.

D.


----------



## SueandRoger (Apr 14, 2008)

I had a similar sort of problem about 4 years ago when the van was only 3 years old! I left the bed in the 'up position' with no ventilation for about a month in the middle of winter and when I pulled the bed down, the tops of the pillows had signs of mildew on them where they had pressed against the roof. Since then I have always left the roof vents open by a couple of cm's and lowered the bed slightly so that there is plenty of room for the air to circulate and no more problems to date.


----------



## jocie (Dec 24, 2006)

Sorry to hear of your Hymer 544 problem, Crazyhorse, and for what it's worth the Hymer B544 is an A class motorhome, and not a B class!! I have had two Hymer B544's, the second of which I bought new in June 2000 and traded in for my present Devon Aztec in September 2009. I never had any water ingress on either, but it is very important with these models (and with many others with similar exterior joints) to visually examine the beading covering the joins regularly. What to look for is any slight raised bumps in the beading which indicates that the stainless screw underneath the trim has started to unscrew (and will eventually raise the bead out of it's seating,letting water in). All you need to do is pull up the plastic beading to expose the raised screw,unscrew the screw,coat it's threads with non setting sealant, screw the screw back in, and push the beading back into place!! It is very easy and I had to do it about once every 3 or 4 months to a few places (different ones each time) on both my Hymers once they were a few years old. The sealant I used is CARAFAX CARASEAL non drying bedding sealant, sold in caravan dealerships for about £2 per large tube and used in a mastic gun.


----------



## crazyhorse (Oct 22, 2006)

I'm pretty sure its not condensation as the damp is only along a short length ( about 300mm )near the roof.
My year 2000 model B544 doesn't have any screws holding any beadings. It has long plastic gutter strips which are directly bonded to the body over the horizontal joins.
I spoke to a specialist repairer and they said if they leak the gutter strips must be cut off, the mastic filled gap underneath all scraped out and replaced and new gutters fitted. A prong on them apparently pushes into the mastic before it sets.
It is an expensive job as a whole side has to be done as the strip cannot be joined.

However, I think I have traced the position of the damp patch to be directly below the front screw holding the awning case to the roof. It was very loose, allowing the extrusion to lift about 3mm. Water could then probably get in over months through the screw hole. I've sealed the section and retightened the screw this so hopefully this will cure the problem.

I expect it will take weeks to dry out so fingers crossed!
Thanks for all advice.


----------



## thegreatpan (Oct 29, 2007)

My old hymer B544 let water in via the radio aerial , the plastic cover had split pobably due to UV degradation, this allowed water to run down the cable, if it rained hard it filled the overcab bed reading light, a new areial and some bath sealer sorted that.

Years back,I had a leak on a caravan that was down to one loose awning channel screw, this was made worse by the UK van manaufacturer using a zinc plated screw that also rusted opening the hole up. Resealing the awning channel and changing all screws to stainless did the job.


----------



## vava1 (Jul 18, 2005)

Hello crazyhorse

I have a 1998 Hymer S700 with water ingress to the gutter seal strip - I am on the Cambridgeshire-Norfolk boundry

Can you please tell me the name of the specialist you mention in your post about this problem?

Thanks!


----------



## JockandRita (Jun 1, 2005)

Hi Crazyhorse,

We had a slight problem with our E Klasse (yes Jocie) rear roof seal, as you do on your B Klasse.

Upon contacting Peter Hambilton, he confirmed that it was definitely the rear roof seal that needed replacing on Our E690.
I purchased enough sealing strip and tubes of Korapop mastic from the Hymer factory in Bad Waldsee, to do both the back and front seals, and I assisted Steve Ash whilst he renewed the rear seal at Newark Autumn Show. The front seal which isn't leaking, will more likely be replaced due to it's corresponding age, at one of this year's shows.

According to Peter Hambilton, it is a poorly designed sealing strip.
The old strip has to be removed completely, and all the old mastic cut out. This is a painstaking slow job, but it is extremely important that you get as much out as you can.
Once dried out and damp tested, the new mastic was applied, and the seal firmly pressed into position and trimmed. If you have roof bars, you may need to dismantle part of them to gain access to the rain gutters. Don't forget to clear them of sealant, to allow drainage from the roof.

When the old seal is removed, you'll be able to observe the cut outs which need to be copied on the new seal, hoping of course, that it wasn't a cut out that has caused the problem in the first place. 8O

HTH,

Jock.


----------

