Technical 100HP catalyst fractured

[DaveMcT]

Last weekend my exhaust snapped off the bottom of the catalyst. The support clamp I had assumed (stupid I know) was welded to the outlet pipe was just completely corroded away. All that leverage eventually cracked the pipe. Strangely I has no warning. The crack has obviously been growing for a while but there was no undue noise.

Ive welded it up and added support brackets between Cat case and the pipe. I need to make a new pipe clamp but the original bolt had seized into the sump. The threads are stripped (bad enough) but the cast boss has cracked and will need to be TIG welded. The threads are open at the back causing the threads to bind.

I've looked at using the engine steady mounting bolt to link a bracket to the two-bolt exhaust flange. Sadly that has open threads at the back and it's jamming in similar ways. I can't afford to crack the gearbox case so will have to support the pipe some other way.

 

[koalar]

I snapped mine a few years ago

I found one at a breakers

then sold the scrap one for the precious metals

however finding the secondhand one wasn't easy as most breakers cut them off and cash them in


front bracket isn't strictly needed. My two cars never had them for several years. I snapped mine on a pothole. But I have seen a car with an advisory for it.


There's two bolts at the bottom of the bellhousing just use the other there only two or so inches apart

 

[koalar]

off topic

But why oh why so many different size bolts on the bellhousing


Pretty much all the bolts on a Panda are odd sizes except for the smaller 10mm


13mm 15mm 17mm 19mm then they throw a random 18mm in. There no logic.
its next door to a 17mm ahhhhh

 

[chris3234]

13 15 17 and 19 arnt odd sizes?
The the most common sizes


The caliper slid pin bolts on my Tipo are 14 to be odd

 

[dac69er]

13 15 17 and 19 arnt odd sizes?
The the most common sizes


The caliper slid pin bolts on my Tipo are 14 to be odd

i found 15mm odd as im used to jap cars. they use 12mm and 14mm instead of 13mm and 15mm!!!

 

[chris3234]

i found 15mm odd as im used to jap cars. they use 12mm and 14mm instead of 13mm and 15mm!!!

Probably why
But 13-15-17-19 are standard iso metric sizes used for most bolts in Europe

 

[koalar]

shame. if they all got together you could half the amount of tools you'll need to carry around.

Which would add up, Deep socket, normal, ring and so on

The bellhousing to engine had a ridiculous amount of different sizes. I even think the two on the rear support are different sizes

 

[Pugglt Auld Jock]

i found 15mm odd as im used to jap cars. they use 12mm and 14mm instead of 13mm and 15mm!!!

Oh yes! My daughter in law's Jazz used to regularly catch me out when she first bought it. Even now, several years on, I'm careful to check before leaning hard on a spanner.

 

[koalar]

I am slightly confused with the original post


the hole in the bellhousing isn't threaded its a nut and bolt. Isn't it ?

 

[DaveMcT]

The 100HP has a cast aluminium sump which has a trough for the exhaust. The exhaust support bracket is probably much the same as the 1200 (mine had lost the loop entirely). But instead of bolting to the clutch bell-housing, it bolts to a lug in the bottom of the sump. The bottom end of the bolt had corroded and picked up the aluminium making it hard to extract I got it out with lost of back and forth but the picked up corrosion stripped the threads. It also cracked the lug so it can't be rethreaded without some TIG welding.

So I'm making up a bracket that will be attacked with a normal U bolt exhaust clamp. Mush as most do for the 1200.

The perfect place to support the pipe would be a bracket from the engine steady (dog bone) bracket to the two bolt flange. However, that is also threaded through the casting and, sure enough, it's going tight after 1/2 turn. It "cracked" loose nicely with the breaker bar but the threads feel like a repeat job of the exhaust steady. I cant afford to screw that up again, so tightened it back again.

 

[Pugglt Auld Jock]

The perfect place to support the pipe would be a bracket from the engine steady (dog bone) bracket to the two bolt flange. However, that is also threaded through the casting and, sure enough, it's going tight after 1/2 turn. It "cracked" loose nicely with the breaker bar but the threads feel like a repeat job of the exhaust steady. I cant afford to screw that up again, so tightened it back again.

On the 1.2 60hp engine in our Becky there is a quite large headed longish bolt right at the bottom of the bell housing which helps secure the gearbox bell housing to the back of the engine. When I was making my flywheel holding tool I had to remove this and several smaller bolts, to get the little stone shield off the bottom of the bell housing for access to the ring gear.

Same thing. cracked off nicely then tightened up over about a turn and a half. Like you, lots of tooing and froing with copious dousings of Plus Gas and it eventually came out. I cleaned the thread up with my thread file, didn't have a tap which fitted the hole but it looked ok and it went back in again later reasonably well but was difficult to get properly lined up to get started.

Then I "chickened out" of doing the clutch myself and handed it over to Kenny and his "merry men" who have done a lovely job and the car is driving beautifully but I noticed when I was having a crawl around just before the colder weather started to arrive that there is a teenzy weenzy whisker of thread metal sticking out the end of the hole it screws into! I put a spanner on it and it's not going to come slack but if I ever have to drop the box off the engine again? Mind you I'll probably hand a heavier job like that back to them again as my old body just isn't really up to abuse any more so why should i worry?

 

[DaveMcT]

I will try to find the old bolt. The threads look good but the first couple of turns are clogged solid with aluminium oxide which has ripped out the threads. No amount of Plus Gas (or anything else) was going to clear that.

I fear many of the clutch casing bolts will be the same because most are open at the back (as this was).

My new bracket is fitted like the 1.2 to a hole at the front of the bell-housing. I made up and L shape bracket, sawed 2/3 through, folded and filled the back with weld. Then welded it to a normal 50mm U bolt pipe clamp. Stainless would have been better but I don't have the right material. It will do the job

 

[jrkitching]

the first couple of turns are clogged solid with aluminium oxide which has ripped out the threads.

Most metals expand when they corrode. This phenomenon is sometimes called oxide jacking. A similar process is responsible for a lot of failures in reinforced concrete.

The only practical solution is to coat the threads with something that will prevent or at least minimise corrosion. Having two metals with significantly different electrode potential doesn't help; add salt water and you've basically created a battery; galvanic corrosion will do the rest.

 

[DaveMcT]

Most metals expand when they corrode. This phenomenon is sometimes called oxide jacking. A similar process is responsible for a lot of failures in reinforced concrete.

The only practical solution is to coat the threads with something that will prevent or at least minimise corrosion. Having two metals with significantly different electrode potential doesn't help; add salt water and you've basically created a battery; galvanic corrosion will do the rest.

Absolutely, but nobody told the factory. Who knows why they drilled all the way through as the bolts are far shorter than the holes. You would think any corrosion effects on the ends of a thread would get left behind, but on mine that rim of ceramic material was "welded" to the bolt. All the careful back and forth to avoid the bolt shearing just made a better job of destroying the threads.