Earlier this week I dropped the rear sub-frame of my 2008 S-Type 4.2 to refurbish it, repair a leaking output shaft seal and replace the Vapor canister.

This is a Canadian car winter driven and I wanted to tackle rust spots before they became holes.

There are 4 large bolts holding the sub-frame in place 2 forward, and 2 at the back by the mufflers.The back ones came right out with an electric impact wrench. The front ones no so much. The one on the passengers side could not be loosened with the impact wrench so I went at it with a power bar; bad idea. I sheared the head off. Over to the drivers side and the impact wrench would not loosen it so rather than risk shearing off the head I ground the head off so I would have something to hang on to. With much heat and a days worth of trying to get the stud out I have gotten it out about 1/2 inch and I still can barely move it. I can tell from this drivers side stud that I doubt drilling and an easy-out is going to get the passenger side. nor will welding a nut onto it
My question, has anyone ever gone at these from the top,maybe I can get some penetrating oil into them?


Drivers side rear sub frame bolt-stuck.



Passenger side rear sub frame bolt sheared off.

 

The stud thats moving might come out if you could heat it up with a blowlamp, I would try that and then wind it in an out rather than just out.

Could you drill out and helicoli the other one?

 

I have had the threaded tube cherry red for an hour while turning the bolt remnant for an hour to get three turns. Even with heat now it does not to seem to want to go any further. All suggestions appreciated and I will see what seems like the best.

 

If you've tried heat and no luck, then in the past I've soaked bolts that tight it in WD40 twice a day for 14 days.
They have given in eventually

 

The arrow shows the opening where you can see the threaded tube.
The threaded tube the bolt goes into. No way to get any penetrating oil in.
Has anyone had the back seat out of their Stype to see what is at the top of these subframe mounts. There is a threaded tube welded in an you will see in one of the attached photos where I was able to get some heat in. Even though I got the tube cherry red I have still only got another half inch of thread out. The interior in my car is pristine and dove and I really don't want to remove it. Has anyone got any idea what I will find on the interior side of that threaded tube?

The bolt acts like it has rust at the top that is being drawn down with the bolt as even when I turn it back in it binds after a 1/4 turn. I have gotten it this far with a back and forth motion with vice grip and heat for about 2 hours, and now it is totally frozen.

 

I have adventured on trying to remove these rear sub-frame bolts so today I removed the back seat to try and get some penetrating oil in from the top. I drilled a 3/4 inch hole at about where I thought the threaded stud should be. I was close enough tof see the top of the sleeve / bolt with a boroscope. I have now gotten some penetrating oil in from the top so we will just let it work it's magic overnight and see what tomorrow brings.

I have included a couple of photos because sometime someone else will have this problem.

Location of where I drilled acess under rear sear cushion.
Boroscope photo of top of the bolt through the access hole.

 

Good work daro31 !
I'd give it plenty of time with soaking the top of the thread, not just overnight. Give it a few days soaking it twice a day.
Get the moley's closer to the sub'frame or you might snap the stud off and leave nothing sticking out.

What paint are you using? Or is that waxoil?
I still swear by Hammerite.

 

I snapped the first one off and will probably have to drill it out after soaking with penetrating oil. I am using POR 15 on the rusty spot and then will get some rust check into the cavity. Anti sieze is going on these bolts when they go back in.

 

They certainly don't need any thread lock on them

 

After 2 days of fighting with heat and rust buster I got the broken bolt where I had a shaft to hang onto out. It was pretty obvious that ano extractor was not going to remove the other that was broken off flush. I ended up cutting the whole mount out, not an easy job in itself. I am fortunate to have a good buddy with the fabrication tools who can weld the newly made part in for me tomorrow.


New mount made to slide so it will be the right length when welded in. The old rusted part beside.

 

Good work!
I'd like to see the subframe when it's all done.

 

I got the fabricated replacement part welded in and reat end all back in. During the time out I was able to remove the differential housing and check it, everything going clean. I filled it up with Royal Purple synthetic and now I have lost the small vibration I had while feathering the gas pedal in city traffic. The steel these cars are made of is very tough and I went through a lot of drills getting the rusted stud and it's mount out. It isn't pretty but I didn't know what I was working with. I coated the under body and cleaned up all of the emmision lines while I was under there. Car is running great time and no oil leak on the driveway so wifey is happy.


The place I had to drill out from the bottom ro eemove the stud mount. It go prettier before adding the new part.



Cleaned up rear sub-frame.

 

I got the fabricated replacement part welded in and reat end all back in. During the time out I was able to remove the differential housing and check it, everything going clean. I filled it up with Royal Purple synthetic and now I have lost the small vibration I had while feathering the gas pedal in city traffic. The steel these cars are made of is very tough and I went through a lot of drills getting the rusted stud and it's mount out. It isn't pretty but I didn't know what I was working with. I coated the under body and cleaned up all of the emmision lines while I was under there. Car is running great time and no oil leak on the driveway so wifey is happy.


The place I had to drill out from the bottom ro eemove the stud mount. It go prettier before adding the new part.



Cleaned up rear sub-frame.