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Discussion Starter #1
So, I've a shiny new Magnaflow 23511 waiting in the garage with a brand new Bosch O2 sensor.

I'm wanting to replace the originals on my '89 S3. O2 sensor looks rough and appears to be jury rigged on the the dilapidated catalytic converter.

I've already replaced the rear and center exhaust sections so I know how to get the bottom cat mounts off.

My question is how best to remove the bolts holding the cat to the exhaust manifold.

Is there a "best way" to get them loose that minimizes damaging the manifold? My first thought was to drown them in P-blaster and see what happens.

If anyone has experience with this your advise/wisdom would be gratefully appreciated-M5
 

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Yep, soak the bolts a number of times and if that doesn't break them loose use a propane torch to heat them up.
 

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My bolts looked pretty rusty and I was pretty worried as well. But a bit of a soak in PB Blaster and they came right off, no fuss. Hopefully you'll be as lucky.
 

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Soak them overnight and and when they break loose work them back to forth if you get any resistance.

The issue I had was the cat pipes did not match up to the exhaust manifold. I had to wallow out the bolt holes to help them fit better. And the pipes were too close to the steering box. After two years of living with this I ordered a header and redid the exhaust.

I wish you have much better luck.
 

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I would go with heat as a first attempt. Try to get the nut(s) almost red and crank them off. If I recall steel expands 6 millionths of an inch per degree temperature increase.
 

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WEAR TIGHT FITTING GOGGLES Get a dremel and the tiny cutoff wheels. WEAR TIGHT FITTING GOGGLES. The tiny cutoff wheels will cut through the bolts/nuts like butter for a bit then will EXPLODE. Put a new cutoff wheel on, put back on the goggles, repeat. You will be making a 1/32" slice through the parts and will do no damage to anything else other than your eyes if you don't wear goggles. Obviously don't have any body parts in the same plane as the cutoff wheel . . . .

;-)
 

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Don't forget gloves when removing the cat!

WEAR TIGHT FITTING GOGGLES Get a dremel and the tiny cutoff wheels. WEAR TIGHT FITTING GOGGLES. The tiny cutoff wheels will cut through the bolts/nuts like butter for a bit then will EXPLODE. Put a new cutoff wheel on, put back on the goggles, repeat. You will be making a 1/32" slice through the parts and will do no damage to anything else other than your eyes if you don't wear goggles. Obviously don't have any body parts in the same plane as the cutoff wheel . . . .

;-)
Be sure to wear gloves too !

 

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Dremal tools is the best way. They make a NEW cutting bit that has a spring loading cutting wheel. Best $25.00 investment. Home Depot has them. I cut everything with this bit. Buy some new hardware and your all set
 

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Discussion Starter #11
Update.

I removed air intake to have better access to the spot where the top of the cat assembly attaches to the bottom of the exhaust manifold. It is still a tight spot.

I wasn't able to angle spray bottle of P-Blaster so I used an old cut off toothbrush aand liberally scrubbed it into the 3 bolts (4th was not used for some reason). I'm hoping that after about 24 hours of soak I will be able to get them loose.

It seems they (nuts) are a good bit rusted. Was steel normally used for this or should they be brass?

The nuts are on the underside of the Assembly so I'm unable to get a good view, but they appear to be 13mm.

I'm hoping tomorrow I can get underneath with a good 13mm socket and get the nuts off without damaging the studs.

Wish me luck and thanks for the advice.-M5
 

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Dremal tools is the best way. They make a NEW cutting bit that has a spring loading cutting wheel. Best $25.00 investment. Home Depot has them. I cut everything with this bit. Buy some new hardware and your all set
Thanks for the tip. I read customer reviews and ordered one from Amazon.
 

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Discussion Starter #13
2 out of 3 so far............

Well so far I was able to get 2 of the three nuts broken loose.

There was no stud or nut in one spot (the 10 o'clock position). The 2 o'clock and and 4 o'clock are loose. The 8 o'clock is being cantankerous. I soaked it again in p-blaster and will try again after getting a different length socket extension. All the ones I have currently are either too long or too short.

I'll keep you posted.-M5
 

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Discussion Starter #14
Can I replace broke/missing studs?

Update:

Cat and exhaust manifold are off.

The Cat was original (said "ALFA Romeo" on it) as was the O2 sensor, which after liberal amounts of P-Blaster is still stuck to the Cat. Hopefully these Reagan era parts were the cause of my "sputtering" while warmed up issue.

The last bolt was a major PITA! After soaking for days in P-Blaster, I was able to use a set of extensions worked down so I could access from under the car near the front tire. After a few minutes of careful torquing with a breaker bar I felt it break free, so I thought.

It actually broke off!

Another stud was pretty badly rusted at the mating point with the cat and it too broke when I tried to double nut it off.

Otherwise the exhaust manifold is solid. No cracks or issues.

Is it possible to get the broken studs out? If so, what would be the best way for me to do it? Should I just take it to a machine shop?

Also, has anyone any idea as to what studs these are (from exhaust manifold bottom to CAT assembly top)?? It seems the suppliers only carry the studs for the exhaust manifold into the engine block (thankfully, all of mine are AOK). I see threads inside where the one is missing but I know that after cleaning, an 8*1.25 bolt will not work. It seems to be too big, but that is what the mounting portion of the studs are.

I'd hate to have to drop $300+ over studs.
Thanks in advance-M5
 

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I've opted for bolts when I can't locate studs. You might try ACE lumber if you have one...they have higher grade bolts in metric sizes...I've cut many of my own to fit perfectly with a Dremmel. one piece of advice...I changed all my bolts on my exhaust to stainless steel and I use brass nuts and lock washers they will never rust and will hold well. I think I purchased the bolts and nuts at Lowe's or Home Depot...just take old ones with you to match.
 

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M8x1.25 x 43mm

The studs that fit into the base of the exhaust manifold (to connect the downpipe) have an M8 thread with a 1.25 pitch. The length should be around 40mm to 45mm overall. They can be threaded the whole length, but if you get the kind with an unthreaded band in the middle, you don't want that unthreaded "shoulder" portion to be more than the thickness of the downpipe flange, which I believe is about 10mm. It's OK to get the kind that have a short thread on one end (to fit into the manifold) and a longer threaded section on the other end (to attach the downpipe). I suggest using serrated flange nuts when securing the downpipe.
 

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Discussion Starter #17
Pic requested

Everything is on the car. I attached the cat hangar to the transmission by dead reckoning. The old cat had no hanger so I just attached the current one to where it looks like it should.

I also loosened all the other exhaust hangers and connectors while installing. The first time I tightened everything back up the heat shield of the cat was jammed pretty tight into the heat shield at the bottom of the car. I loosened up and redid the connections so it sits just slightly lower and now I have the slightest of leaks at the junctions of each end of the CAT.

1. Has anyone have a picture handy of what the connection of the cat hanger on the transmission should look like once it is connected? I have the manual and the tiny exploded picture does not give much of an idea.

2. Is there any specific order for tightening up the exhaust system so that everything hangs and fits correctly? I've been trying to tighten everything just a bit at a time to get everything lined up. I'm just wondering if there is a better/easier way.

3. There is nothing on the Magnaflow website mentioning a "Break in" period for catalytic converters, but I've heard that it may be necessary. What say you Alfisti? Wives tale or not?

Thanks in advance for all your help-M5
 

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Sorry to say, but you also purchased one of those poor fitting Magnaflow POSs. I brought mine to a muffler shop where they heated it and bent the pipes just enough to stop the binding.

My CAT hanger never even came close to the transmission mount. I went to the auto parts store and purchased an exhaust hanger and attached that to one of the CAT pipes and the transmission mount.

I've never heard of a break in period for a CAT. They should work out of the box, but someone else might have a voice.

I was hoping that five years after I purchased my POS Magnaflow CAT they would have fixed the fitting issues, but I guess quality of fit is not one of their concerns.
 

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Discussion Starter #19
alignment not fitment

I was hoping that five years after I purchased my POS Magnaflow CAT they would have fixed the fitting issues, but I guess quality of fit is not one of their concerns.
I may be wrong but it seems to be more of an alignment issue than one of fitment. It is so close to being DAP, I think it can be adjusted properly with enough patience, persistence and guidance.

Thank you just the same though-M5
 

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Hey Jeff,

Sorry about being negative.

I remembered I also stacked three gaskets between the exhaust manifold and the Cat downpipes to help solve the problem you are having with the heat shields. Maybe you'll only need one extra if it's that close.

Good luck.
 
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