Corroded exhaust fixings rant

[Luddite]

While reading through Flyingelburro`s interesting thread here on 911UK, the pic he posted of his 997.1 4S that included a section of his exhaust attracted my attention, and I hope that he does not mind me re-posting it on this grumble about the quality of the fixings Porsche uses on their exhausts with whatever cost and consequences that might create in time for their customers..?

I have read and watched vids on the necessity to make use of a specialist jig to assist drilling corroded and damaged bolts out of the heads of 911`s when the manifold(s) might require removal. It seems to be accepted that these fixings will just break away in some cases, and expectations on exhaust fixings elsewhere are likely to be much the same if not worse...?

I do not remember the stats though I think it may be possible that perhaps as many of 80% of Porsches ever produced still exist in the hands of their owners, and Porsche also seem to be in the process of perhaps catering for their past production as opposed to leaving the owners to rely on specialist suppliers, as they may well have done over many years...?

Back to grumbling... Knowing the likely longevity of their cars as the result of their owners pride in maintaining them, I would be inclined to think that Porsche could if not should use more suitable materials (?) for the exhaust fixings.

I suspect in this group of Porsche enthusiasts there will be a fair smattering of mechanics, professional engineers and metallurgists who might care to share their materials knowledge, on this subject, which would be much appreciated.

I have also read on the forum where someone made available alternative supplies of 911 manifold to head bolts in titanium or some such metal, how well that might have worked out in time I have no idea,

Some time back before I bought my C4S and having read of this exhaust fixing corrosion issue, I had a go at loosening a couple of the exhaust fixings on my old crate, which I have owned for 20 years, it has an alloy V8 engine, on which the stainless bolts holding the mild steel manifold to the alloy head loosened without issue. Also in the last year or so I required to replace a section of exhaust on the old crate, on which the fixings have been undisturbed during my ownership, and again the stainless steel nuts and bolts simply unscrewed without fuss or bother, so much so that I re-used these fixings along with their original spring and plain washers to hold the new section of exhaust as can be seen in the pic.

I have no doubt that the 911 engine and exhaust may well be more exposed to being showered with water than the engine bay of my old crate, and that the exhaust temps may be a fair bit higher on on the 996/7/and 91, which may have a bearing on material choices..?

The exhaust flange holding the section of exhaust that I replaced on my old V8, is located under the front wing and very close to the wheel, so likely to be sprayed with whatever road grime exists, I have used the old thing in the Winter on occasion even with snow and grit on the road over the years

Form the images below compare if you will, the difference in the fixings from both the cyl head and the underwing exhaust flange on my old crate, against the Porsche fixings on one of the flanges of my now 9 year old 991, and those of the 997.1.

Looking at the condition of the exhaust on the 997.1, let alone the later 991.1 it can be seen/imagined that the fixings seem to corrode to the degree of possible failure perhaps some time before the rest of the system...?

I am sure I have read on this forum that one owner reckons that OE fixings should be replaced every four years when being serviced, in an attempt to avoid complications should the exhaust or part thereof require removal ..?

Any thoughts..?

 

[Zingari]

I want to change all my fixings to prevent this very issue but I get conflicting 'advice' over what metal is best and then risk of expansion over heat cycling etc.

I would think either stainless steel or galvanised would be best :dont know:

 

[deMort]

Exhaust fittings corrode and always have done the difference these days is the exhaust tends to separate or spring apart when they let go ..

993 .. no fixings and it still seals .. rusted together basically and by design jammed together on the flanges .

996 .. nothing left can seal but a slight blow when shot .

986 .. nothing left and they still seal... again will have a slight blow when totally gone .

987/997 .. they seperate when they fail so a loud exhaust blow .. when you have nothing but a cone left it's time to replace .

991 .. they seperate but i've not seen many cases so far .

It seems to me the newer the car the quicker the fixings corrode ..

Why not fit stainless steel in the first place ? probably cost .. you could argue the same with the entire exhaust after all that also corrodes.

Different markets have different needs i'm afraid and to alter components like this for certain markets only would be expensive hence we all get the same regardless .

I've replaced from 996 to 991 fixings and we like any other garage use stainless steel flange bolts but for clamps we tend to use porsche supplied ones ... they last long enough .

The first image .. that's not badly corroded and won't fail any time soon ..

Second image and i'll still say a year or two and they will be approx 10 year old clamps ... things look bad .. exhaust manifold bolts for example but can often last a long time .

Just my 2 pennys anyways .

 

[Luddite]

Zingers, it seems we along with other Porsche enthusiasts may share a common concern relative to the lack of longevity in terms of Porsche engineers or bean counters choice of material used in the manufacture of their exhaust fixings. I have difficulty in believing that engineers might have chosen materials that would suffer failure as the result of corrosion well ahead of the lifespan of the clamps and exhaust system that they are used to hold in place, and harder still to believe that those same engineers might not engage in a process of monitoring in terms of continuous improvement to weed out such simple failures.

I kinda hoped that there might have been a metallurgist in our midst who might have imparted some knowledge which might provide a degree of confidence to allow us a degree of confidence in making alternative fixing material choices that might reflect the quality which we hope to find in all aspects of our Porsches...?

DeMort, many thanks for taking the time to share your hard won and greatly valued experience. For sure exhausts corrode, forgive me, but my point is that the fixings seem to corrode well ahead of the "fittings" as the images seem to suggest..? Component cost seems ever likely to be a major consideration in the volume production of machines consisting of many thousands of parts, though perhaps not an excuse for a lack of quality...? That it seems your guys may use stainless as replacement exhaust fixings is an encouragement for those like me who have found stainless to be a more long lasting and simpler to work with material choice, which in my example above was not on a Porsche, but an alloy V8, that likely runs at lower temps than a modern water cooled Porsche.

Zingers for sure there are many professionals who seem to disagree on so much given the number of likely considerations, and enough of a mix of accurate data and fake news to choose to believe or otherwise..?

I suspect a possible answer might be that either the quality of the fixings might be improved upon, or the OE Porsche parts should be replaced as part of the service schedule at a time before they become a problem to unscrew, both here in the UK and elsewhere in the world where exhaust fixings corrosion might be considered problematic..?

A couple of links below which may help or confuse ..

https://bssa.org.uk/bssa_articles/bimetallic-galvanic-corrosion/

Bimetallic (galvanic) corrosion – British Stainless Steel Association (bssa.org.uk)