I just bought an 08 Cooper S convertible with 82K miles and noticed a bad exhaust smell in the driveway. Also I noticed it seemed loud but I assumed that was just a Mini thing. Well I took it to a local indy exhaust shop and they say the flex pipe is bad, but they don't know which one, and he's not certain that the manifold isn't cracked! He said he'd replace the flex pipe first to see if that fixes it, but he said it will be $1,000 to do it This doesn't seem right as I see a Mini Cooper flex pipe listed for $75. He said he wants to replace it all past the catalytic converter. I am going to take it somewhere else but wanted to know if anyone else has run into this and what was the cheapest fix?

 

Now is this an R52 or an R57?

The second gen cars used a fairly weak flexpipe and I wouldn't doubt that it broke, because they break if you look at them wrong, but the first gen cars use a very small section of flex pipe and I've never really seen problems with them.

If there is a leak on the header I would almost guarantee that it's at either the bottom of the smaller cat (filter), or that the weld is blown out between the collector of the four runners.

I would find another shop to fix it if they cant' properly diagnose the leak, you could buy a used low mileage header for a gen 1 car for under $500, or a good condition full exhaust for a 2nd gen car for about the same price.

 

It's an R52

 

Okay, just wanted to confirm.

I would have the diagnostic done elsewhere, I've yet to see a failed flex pipe on that car.

 

I think it must be the header but I see the header isn't replaceable without also replacing the cat. Is it possible to weld a header to fix it?

 

Wow! That is expensive.

 

Please explain the "they don't know which one" as there is only one flexible connection on a stock manifold. What we normally see here is that the manifold breaks at the "precat" that is between the flex connector and the CAT.

I see complete used manifolds on Ebay for less than $150.

 

The most common failure on the SC R5x exhaust is at the weld joint of the precat, and not at the flex pipe farther upstream. $1000 is Wells Fargo money coach robbery unless it includes an entire OEM header.




Most "professionals" will tell you it is SS and cannot be welded. Go find a lesser professional that is motivated.

fixed

 

I did a fair amount of pharmaceutical work and can tell you with no doubt what-so-ever that SS can be welded.

 

I probably should be more clear in the context. To repair the failed weld joint at pre-cat, most pros will look at the very little meat that is left on the cat side which is SS, as well as the cup shape flange on the other side. They will think to TIG weld it but will tell you it cannot be done as there is no meat on the other side.

My guy is smarter. He MIG weld the SS to the pre-cat heat shield which is mild steel. I found out with this experience that you can MIG weld SS to MS or even SS to SS if you are not too picky about the appearance and some sacrifice in oxidation resistance.

In the first photo SS and MS are labeled. The only MS is the heat shield of the pre-cat. The failed weld joint is SS to SS.

My guy spent 45 min on this job, and he does this repair at least once a month. It is that common on R52/53.

 

So the precat was what the exhaust guy was saying is a 2nd flex, so obviously he doesn't know what he's talking about. I got looking around and took the heat shield off the manifold and noticed black soot on the shield above where the manifold gasket is. Is it possible the leak is from the gasket? The noise seems to be coming from further down the pipe.

 

Take the header off the car, cut about 3/4" off the heat shield bell around the pre-cat, the find where the two pieces of steel "key" together, most times you're able to get it to key together where it should be and throw a few quick tack welds on them, after that move the header to a more comfortable station and weld it all the way round, let it cool and reinstall it.

 

This is so helpful, thanks all! This thread is a year old, but I have the issue now. I guess I need to get some gaskets on hand and set aside time to pull the header out to weld it. You guys have welded this a couple ways - cut back the shield to access the old weld and re-do it, or weld up the gap at the end of the heat shield, incorporating the shield as part of the structure. How important is this heat shield? With either of the above methods, it's effectiveness is greatly reduced because it will get much hotter on its outer surface than it does stock, or part of it is no longer there.

Thanks, Jeremy

 

Hi, my header cracked after the Cat on my 2005 R53. My mechanic welded it back and it worked fantastic, passing Massachusetts inspection. I installed a Miltek header later at 74k and have this solid reinforced OEM header for sale. I can provide photos... Paws

 

the heat shield is needed both for performance and heat management in engine bay