Best way to remove Cat to exhaust manifold nuts

ksweeneyjr

Original poster
Member
Jun 10, 2013
7
I have a 2005 Envoy XL. I started the replace the exhaust manifold due to it cracking. I have 150,000 miles on it so I feel I got more miles than most out of it. I took my time and sprayed liquid wrench on the bolts for a day and had no problem with the manifold to block bolts. I cant tell you how many threads I have read that somebody broke a head off. So naturally I was worried as hell. I dont know why, but I didnt even think the Cat to manifold nuts were going to be a problem, but turns out that this is the hardest part, at least for me.:confused: So I guess my question is, What is the best way to get these off? These have also been soaking for a day in liquid wrench. I tried using my impact driver with a socket attachment, but no luck. Please help.
 

gmcman

Member
Dec 12, 2011
4,656
ksweeneyjr said:
I tried using my impact driver with a socket attachment, but no luck. Please help.

Were you using an extension? They tend to absorb the torque especially when using longer lengths, ie, 6" or longer. You stated an impact driver, is this an impact wrench or driver with a 1/4" drive?
 

ksweeneyjr

Original poster
Member
Jun 10, 2013
7
I used my cordless makita impact driver not wrench. The reason is I couldnt get my 1/2 impact wrench to fit with the hose attached. I tried for an hour to angle it. I did not use an extension. I just used the socket attachment and the socket.
 

gmcman

Member
Dec 12, 2011
4,656
That driver if 18V from what I can see is listed as 1280 inch-pounds of torque, which translates to just over 100 foot pounds. I doubt that's enough to break the rusted bolts.

I assume the manifold is not attached to the head and if so you can try heating the flange with a propane torch for about 20 seconds or so, may open up the female threads just enough to break it loose.
 

ksweeneyjr

Original poster
Member
Jun 10, 2013
7
Are there any precautions I should take prior to using the torch in the engine bay? May sound like a stupid question, but I want to be as careful as possible. Thanks.

As for the driver, yes it is only around 100 ft lb torque. My impact wrench is 300 ft lb but as i stated earlier i couldnt get it to fit.
 

gmcman

Member
Dec 12, 2011
4,656
Just a light flame, enough to heat the flange at the cat. You don't need it glowing red. I would try the impact wrench with a short extension first.
 

jonbo2002

Member
Sep 27, 2012
213
I used a long ass extension from underneath and a breakerbar with a pipe for more torque and just muscled them till they broke loose. a 1/4 drive cordless impact will not break them loose
 

ksweeneyjr

Original poster
Member
Jun 10, 2013
7
jonbo2002 said:
I used a long ass extension from underneath and a breakerbar with a pipe for more torque and just muscled them till they broke loose. a 1/4 drive cordless impact will not break them loose

I assume you had the truck lifted correct?
 

ksweeneyjr

Original poster
Member
Jun 10, 2013
7
Jonbo and gmcman thanks for the replies. I took jonbo's advice and got under the car with a 24" extension and was able to get two of the nuts off no problems. The third one was a different story. After a few days of running back and forth to the store and trying to get the badly rounded nut off I finally decided to use a rotary tool with metal cutting wheels. I went through about 12 of those before i broke it loose. I also stuffed some cardboard in the area where sparks were flying. Everything is back together now. Funny how a pretty easy job can turn into a week long journey because of one rounded bolt/nut. Again thanks for all the help.
 

jonbo2002

Member
Sep 27, 2012
213
glad to hear you got it, I know it was a pain when I had to do it even with all the nuts being fine they were still a bitch:hissyfit:
 

seanpooh

Member
Jan 24, 2012
461
I used my 1/2 torque wrench with 2 12" extensions along with a prayer of not breaking those bolts. In the end, they came off pretty well. Had to twist and turn to get the right angle.
 

jonbo2002

Member
Sep 27, 2012
213
seanpooh said:
I used my 1/2 torque wrench with 2 12" extensions along with a prayer of not breaking those bolts. In the end, they came off pretty well. Had to twist and turn to get the right angle.

lol good to hear you got them, I think my legs were hanging out a different side each bolt so you could get the right angle:biggrin:
 

DocBrown

Member
Dec 8, 2011
501
Glad you got them off! I only know 2 ways to get those bolts off, heat them with a oxy/acetylene torch, or cut them. Shops just cut them off. I used the torch with an impact wrench and long extension. And yes, you have to get them red hot. The propane torch is too wide of a flame and can't get it hot enough, you'd still be struggling to get them off. The oxy/acetylene torch can get just the bolt itself hot enough and they spin right off.
 

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