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MG MGF Technical - Corroded Cat Nuts

Having spent the past couple of hours under the car trying to remove the original exhaust, I have been beaten by the old problem of the corroded cat nuts. Having taken most of the skin off the knuckles of both hands, I have decided to take a break to gather some suggestions.

I have soaked the nuts repeatedly in WD40 and left overnight etc, but that doesn't seem to have helped much. I think now the only options left are to Dremel the nuts off or to drill out the studs.

What would be the best (ie easiest!) method? I'm desperate to get the Daytona and cat by-pass on!

Any suggestions welcomed!!

Ian Matheson

use Plus-gas* (available from halfords) instead of WD40**

Heat the nuts up to cherry red with a blow torch before hitting

Buy a nut splitter (requires access to get a drill to the side of the nut).

Destroy the nut by cutting the sides with a dremmel, then try again. Don't destroy the stud unless you really have to - putting new studs in is a real chore.

Will

* Designed for this
** designed as a water dispersant (WD!)
Will Munns

I gave up (even after the nuts were soaked in Plusgas for a week) and took it to a local exhaust place. Think it would be £40 well spent for an easy life!

Tim.
Tim Jenner

If your taking the cat off as well, then try undoing the nuts on the manifold end of the cat first, you can then take if of as 1 piece and tackle the other nuts later. I have also found these are easier to undo then the silencer/CAT nuts.
I managed to shear one of the cat studs and can confirm what Will said, drilling the studs out is a real pain and very time consuming due to the metal being very hard.
Also don't forget you will need to put the CAT back on for MOT's so I would recommend using stainless fasteners when you fit it, to make it easier to get off the next time.
Steve White

Ian,

Are you sure that you can fit a cat by-pass? You're car is a MY2000 model and so has two sensors instead of the one that the earlier cars have. Might be worth checking before you go any further.
David Clelland

Took off me nuts with a full-fat angle grinder. (The corroded nuts will simply laugh in the face of the low calory Dremmel)
Then drilled out the studs with a cobalt bit.
Used nuts'n'bolts during reassembly.

But don't worry, the angle grinding gets easier after the first four hours or so....
Swear lots too, that always helps.
Cannonball Bob

Heating the nuts cherry red with a gas torch is the only fast and easy way to get them off without the nuts and studs.
Jon

<<Took off me nuts with a full-fat angle grinder.>>
Sounds a bit sore!!!

Thanks for all the suggestions. I'll try heating the nuts up and see how that goes. The main problem will be access (how the heck do you get an angle grinder in there???), although I'll concentrate on the manifold end of the cat as Steve suggests.

DC - I think the 2nd second sensor and the new exhaust layout were introduced in 2001. I've checked the silencer-to-cat pipe and can't see any sensor plugged into it...

Ian Matheson

Ian,

I think the sensor is located at the top of the pipe, so might not be immediately visable.

Can always use an easier check, and check to see where the bend in the pipe is.

Post 2000, the pipe from the catalytic converter goes through a 90 degree bend before connecting to the silencer.

Pre 2000, the exhaust pipe does a full u-turn before connecting to the catalytic converter.

If that makes any sense.

Paul W

paul weatherill

http://www.mgf.ultimatemg.com/exhaust_differences.htm

http://www.mgf.ultimatemg.com/exhaust_pix/elbow_quarter_pipe.JPG

much clearer explanation, thanks to Rob Bell.


paul weatherill

Thanks Paul. I've definitely got a pre-2001 exhaust as I've had to buy the 'elbow' pipe from Mike.

Looks like its going to be another sunny weekend spent under the car!!
Ian Matheson

Ian,

All you need to do to rescue the cat is hammer the damaged studs out of the flange as they are a press fit, just hold the flange in a vice, then use nuts & bolts.

Alastair
Alastair McLeod

Kev says be brutal
4 inch angle grinder cut them off and throw over shoulder, job done !!!

Kev stamp of approval
Kev

Careful not to damage your cat, or you'll be shelling out £200+ like me!
Holster

Yeah! you should have seen some of the people I have seen struggling with these little******* ( Ozzy word)

Like SF in the Paddock at Brooklands! Well done Andy!

I suppose if you are going to struggle with them you couldnt think of a more heritage place to do it! but it was utterly freezing that day.

Or the old boys at Cheeseman exhausts in Woking scratching their folically challenged heads. I think eventually got the gas hammer out. I couldnt bear to watch them anymore.

With the use of replacement big nuts and bolts I can now change the cat bypass pipe for the car's annual cat-run to the MOT station in less than 10 mins and without even jacking the car up! Mike Satur does a nice line in Stainless nuts, in a manner of speaking.



Neil

I've still not had any luck getting my new exhaust on. A friend with an inspection pit and oxy-acetylene torch (!) said he would get the old nuts off for me, but then went on holiday the next day for 2 weeks. Friends, eh?

I also tried to change my front brake discs at the weekend, only to find that they've managed to 'weld' themselves to the hub. No amount of hammering, cajoling or tickling was going to budge them. Some heat required here too, I think.

I'm starting to develop a deep-seated loathing for rust...

Ian Matheson

This thread was discussed between 08/07/2004 and 20/07/2004

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