A tin of condensed milk.

Maren and I love our little blue car, which we jokingly call our "Cardis", since the blue box on wheels sincerely feels bigger on the inside. (People not following the DW reference can click here.) We like to think it is a very comfy, but above all a very reliable car. You can imagine that we were horrified when our check-engine light came on the other week. Not wanting to destroy the poor thing we took her to the garage to have the code read. Of course, on the way to the garage the light went out by itself, but we read the code anyway. "PO420", the efficiency of the catalytic converter is too low. This would not harm the engine, and since the light was on we decided to keep driving until the light would come back on. From there we would see what there was to repair. Unfortunately the light came back on again quite soon after it had gone off. There was definitely a problem.

We went into research-mode, and googled around for possible courses of action. We were willing to bet the catalytic converter itself was fine, since the car had none of the symptoms that go with the failing of the converter. No loss in power, no rattles, nor a noticable increase in fuel consumption. Then we found a post on a forum saying that the code can be caused by an exhaust-leak that messes up the lamba-sonde readings. This made quite a bit of sense to us, because we knew there was an ugly fix on the exhaust that we inherited from the previous owner of the car. It was here I suspected this repair had now failed, causing our problems.

To confirm some random post I found on the internet I contacted my uncle. He is a good mechanic, and his professional opinion was  very welcome on the matter. H thought that while it could be a hole in the exhaust, we had to keep in mind that this code very often is caused by a defect lamba-sensor, or a broken catalytic converter.  Without looking at the car he said he hoped we could get away with patching a hole, instead of having to go for pricier repairs. The next morning we drove to "Biltema". This is a wonderful store selling parts for cars, boats and house-repairs as well as tools and all kinds of other things. I always like going there.

The score at biltema consisted of two jack stands, two hose clamps, a tube of exhaust mounting paste and a pipe-connector we ended up not using.

We lifted the Cardis of her feet, and got started with dismantling the old repair.

Under the aluminium tape we found a layer of exhaust-bandaging. This bandaging was blackened with soot from a hole somewhere. We were on the right track.

 We found a really thick lumpy weld under all the aluminium tape and bandaging, and the edges of this weld had rusted away into a new and large hole in the pipe. To fix this in an acceptable way, we would have to grind the weld down a bit so that our tin can could lie on the pipe neatly.

Maren inspecting the damage.

Grinding down the weld.

With the weld ground down and rounded off a bit, and most of the rust and dirt removed with a steelbrush on a drill, we applied a thick layer of exhaust mounting paste. Over this paste we folded sheet of steel plate we made by cutting open an empty condensed milk can. This can was tightly put in place with two hose-clamps, and the whole mess was left to dry for a while with a running engine.

The repair. Now one day we have to do something about the exhaust-support that has rusted away...

That evening we reset the check-engine light by disconnecting the battery for a while, and we took a long testdrive. The light stayed off! Now we hope that the light will indeed stay off longer than just one ride, but we are inclined to think we fixed the problem. And the total cost of the repair was less than the cost of having the code read by a mechanic. Now we have our fingers crossed that the jack-stands can stay stored in the garage for a while.