While I was out and about visiting my local Ford garage and DIY centres, I left the air heater blasting away. This is a proven method that I have used on my Alfa Romeo Spider too.
BHPian Jeroen recently shared this with other enthusiasts:
We had a problem with Mrs. D’s Ford Fiesta. This is a 2015 Fiesta with the regular little 1.0l, 3-cylinder engine. We bought it nine months old with about 12k on the clock in 2016. Mrs. D has done some 125K by now. It is our 5th or 6th Fiesta. They are lovely little cars. And all of them have been very reliable and cheap to run. This one has had all its regular maintenance, of course. And the odd other things that might break/wear out over time. E.g. I replaced the interior fan resistor, stabiliser links, suspension springs, and one or two batteries but that is just about it.
So all pretty good, my fingers are crossed for the next 125K! But the Fiesta had developed a serious leak! The passenger footwell behind the driver seat as well as the spare tire well was full of water. Time to investigate, bring some wellies and lots of kit!!
Fiestas will leak eventually. There are quite a number of good YT videos out there that will show you all potential leaks. When you find water in the front footwell, very often it is the drain of the AC/heater that is blocked. That can be caused by just dirt building up inside the AC/heater box, or even by scraping your car on a speed bump. That is known to dislodge the heat shield which will subsequently block the drain.
But our problem was the left rear. Three suspected areas. All around the rear light unit, behind the bumper or the roof trim/rail.
So I moved the Fiesta into my workshop.
The first thing is to try and trace the water leak as best as you can.
The carpet and felt underneath were soaked. Also, the trim in the boot was soaked and there was about 1 cm of water standing in the spare tyre well!
I pried off all the trim and took off the rear left light unit. Nerd fact: To undo the nut that holds it in place, you need to remove all of this side trim. Changing a light bulb in the rear light unit is not for the faint of heart!
For good measure, I decided to remove the bumper as well. It is held in place with two parkers and some 6 plastic fasteners. Easy peasy, bit fiddly on your own.
I spend most of my time cleaning and drying out everything. All the trim that I managed to take off, went back into our home. I spread it out across several of our central heating radiators. The central heater is blasting away as it is around 0oC here at the moment.
Next, I wipe up the water as much as I can with wipes and towels. I used one of these rolls of workshop wipes and five towels.
Next, I positioned my workshop air heater into the interior and angled it towards the bottom, to hit the carpet and the felt underneath. Make a sort of little tunnel so the warm air goes in as far as it can.
I had watched several YT videos but also checked my own manual for the removal of the rear light unit and my workshop manual for all the other bits.
This little flapper device is hidden behind the bumper. It allows the cabin air to flow out of the car, hence the little flaps. So it’s one way. It’s held in place with a large rubber gasket. As you will see, all these rubber gaskets, rings, and grommets become brittle over time. So I pulled everything out/off and re-installed it with the kit.
Here you see the chassis where the rear light unit is mounted. It is held in place by one central large bolt with a nut inside the boot, two little dowel pins and two parkers. In the middle, over the main holes, is a large gasket too. Rainwater just runs down the chassis, so everything here needs to seal perfectly. So I used the kit liberally everywhere.
Here is another problem. Not unique to Ford, but Ford applies this solution to bits that catch a lot of (rain) water. Ford closes off some of the larger openings in the chassis with tape. Yes, you read that correctly.
Ford does not stock or even sell you this tape. The guys in the parts department had no clue what I was on until I showed them some images. Luckily, one of the mechanics was familiar with it and gave me some advice on where and what DIY tape is should get from our local DIY store. This is so-called Bison seal tape. Seems to work well!
I have a bunch of different kinds of sealant kits in stock, so that was no problem. I decided to use the RTC kind. It sticks really well to (painted) metal, and if you have to remove it, it is possible to get it off again.
Whilst I was out and about visiting my local Ford Garage and DIY centres, I left the air heater blasting away. This is a proven method, I have used on my Alfa Spider too. Make a little tent with a blanket.
At the end of the day, everything was dried out and I put everything back together with a sealant kit applied everywhere. I had to replace a couple of the plastic fasteners. No problem, I stock several dozen of different types of those things.
That night, I left the Fiesta parked outside. I should have checked with a water hose. But it was already dark, my outside tap was turned off and drained already because of the frost. Luckily (sort of), it rained heavily and the next morning I still had the same problem!
This time, I tackled the roof trim/rail. I was a bit apprehensive about removing the rail. But the Ford mechanic had told me it is just held in place, with what else, double-sided tape! Sure enough, I pulled out the complete rail in five seconds flat!!
I think I have found the problem. If you look very carefully, you will see a little crack in the weld inside the roof line here.
I found some more potential problem areas around the hinges and several other spots where metal sheet parts were overlapping. Compliments to the Ford Mechanic who had pointed it all out to me.
I spend quite a bit of time sealing everything with the appropriate kit. It’s freezing outside and these kits won’t cure well below 5-10 deg C. It’s about 7-8 deg C in my shop. So I am leaving the Fiesta in my garage overnight.
This was a big job, time-wise. It took me the better part of about 10-12 hours. Most of the time was spent drying/wiping and cleaning everything. I checked and Ford will charge 2 hours per roof rail. Admittedly, I only did one, the left one. But I also fixed a lot of (potential)leaks under the rear left light unit and bumper.
Leaks are often difficult to trace. In the case of our Fiesta, I could not really trace the water back to a particular spot. Because you have limited access and visibility between the outer and inner panels of the chassis. I used lights, mirrors, and my little camera thingy. But in the end, you just need to rely on finding any potential ingress points on the outside. I am sort of confident that the split welt under the roof rail/trim might have been the ultimate cause of the leak. But I am equally sure that all those other bits and pieces I waterproofed were all just “water leaks in waiting”, so to speak.
Fingers crossed for now!
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