P38A Stud removal exhaust manifold to downpipe - help please !

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AndyF07

Active Member
Posts
134
Location
UK
Hi,

Firstly apologies if this is a bit of a newbie/numpty question. I am in the process of replacing the exhaust system on my P38 4.0 2002. I don't think anything has ever been touched since it left the factory as it took an age, vast amounts of heat etc to get the cross member bolts out.

I have started removing the studs holding the downpipes / cats to the bottom of the exhaust manifold. I used an impact wrench ( couldn't budge them at all with wrench or breaker bar) after soaking in penetrating fluid and the first couple came out nicely. On the third I managed to just take the nut off the stud. My question is firstly what I am doing is the right or best way to remove them and should I continue with the others the same way? Then if not what is please ?

When it comes to removing the stud left in - it is intact (minus the nut) so would one of the 'stud extractor' tools out there be the most effective way to get it out as it's quite a tight space ? Any thoughts and advice very welcome :)

Cheers
 
We've all been there you have 2 choices
1. Drill the remains of the bolt out and retap a new thread in situ as you say not much room in there.
2. Remove the manifolds and do it on the bench this is what I had todo to mine when fitting new cats

Good luck if you do remove the manifolds the last 1 at the rear bottom left side is a real bugger
 
Usually if they are that rusty, it required heat around the studs to get them loose. Much easier on the bench.

20160507_181025.jpg
 
If you can, weld à nut on the end. The heat alone will crack the rust and then you can remove it. Just be sure to disconnect the battery unless you have a shunt device to put on the battery. In addition you can unbolt the live wire from the alternator as well. ;)
 
Is the remaining stud completely fragged? Maybe just leave it in, or use a proper stud extractor (with impact gun)... You cd also put two nuts on it and lock them together, and try and undo the stud using the top nut.
Lastly, its cold this time of year, but if you run the engine it will heat up the manifold and maybe help the assembly come loose...personally I wd leave the manifolds where they are, or before you know it you'll have created more problems.
There is one more option...induction coil on the stud will get it white Hot, so you may be able to use a few heat cycles to crack it loose once it has cooled a bit.

I dont have access to a welder so thats not in my repertoire
 
Mark Piercy said:
If you can, weld à nut on the end. The heat alone will crack the rust and then you can remove it. Just be sure to disconnect the battery unless you have a shunt device to put on the battery. In addition you can unbolt the live wire from the alternator as well. ;)
Click to expand...

If you can weld a washer on first to stud then a larger nut to washer then in fill nut with weld is what I did on an UMM exhuast...
 
Mark Piercy said:
If you can, weld à nut on the end. The heat alone will crack the rust and then you can remove it. Just be sure to disconnect the battery unless you have a shunt device to put on the battery. In addition you can unbolt the live wire from the alternator as well. ;)
Click to expand...

I have an arc welder and have done a bit of welding on the bench but not on the car. Where would you attach the earth to ? Really don't want to fry the ecu or anything else for the sake of an exhaust? Cheers
 
romanrob said:
Is the remaining stud completely fragged? Maybe just leave it in, or use a proper stud extractor (with impact gun)... You cd also put two nuts on it and lock them together, and try and undo the stud using the top nut.
Lastly, its cold this time of year, but if you run the engine it will heat up the manifold and maybe help the assembly come loose...personally I wd leave the manifolds where they are, or before you know it you'll have created more problems.
There is one more option...induction coil on the stud will get it white Hot, so you may be able to use a few heat cycles to crack it loose once it has cooled a bit.

I dont have access to a welder so thats not in my repertoire
Click to expand...

Thanks for the advice. I certainly would like to leave the manifold removal as the last resort as the bolts look even worse on that (although it sounds like where I will end up) and try easier things first. I've ordered a stud remover so fingers crossed !
 
AndyF07 said:
I have an arc welder and have done a bit of welding on the bench but not on the car. Where would you attach the earth to ? Really don't want to fry the ecu or anything else for the sake of an exhaust? Cheers
Click to expand...
Attach the earth to the manifold close to where you are going to weld. As Long as you do as Mark says and disconnect the battery and alternator, your electronics will be safe.
 
AndyF07 said:
I have an arc welder and have done a bit of welding on the bench but not on the car. Where would you attach the earth to ? Really don't want to fry the ecu or anything else for the sake of an exhaust? Cheers
Click to expand...
As Keith says, closest to the weldo g job as possible. Disconnect the battery and the alternator and cover as much as possible. Also if you have a compressor and water to hand. :)
 
I had to do this on a ford ranger 2.2tdci recently in the garage. The inlet manifold has mostly bolts but the center two to locate it on assembly are studs that need to be removed to pull it away from the egr cooler on the back of the head.
They have little male torx heads and yip, one snapped off!! Thankfully due to my extensive nut and bolt collection I fitted a 17mm nut first and then a 14mm nut (same thread), then welded the 14mm to the stud. Probably just the heat alone was enough to crack the stud free and it wound out no issues. :D
 
Well on the positive side all of the old exhaust is off. On the flip side one of the studs sheered clean off when trying to remove it from the manifold / down pipe. As predicted at the start of this thread the manifold is coming off tomorrow to drill out the little b****r. What I love about my journey working on the such a wonderful machine is how something that sounds like a '5 minute' job in RAVE is really a 5 day job if it hasn't been done since 2002 :)

On a serious note on the passenger side one of the studs between the manifold and donwpipe is still in place but intact as the nut just came off clean. Is there any reason that can't be re-used in situ ?

Cheers
 
"A quick sunday job" i tell myself or "I'll do it Saturday afternoon after work".... What an idiot I then think afterwards :p but it gets done.... I agree never 5 minutes ;)
.
If the stud is in good condition and isn't heavily rusted, then let that dog sleep! :)
 
Mark Piercy said:
"A quick sunday job" i tell myself or "I'll do it Saturday afternoon after work".... What an idiot I then think afterwards :p but it gets done.... I agree never 5 minutes ;)
.
If the stud is in good condition and isn't heavily rusted, then let that dog sleep! :)
Click to expand...

Cheers @Mark Piercy. Hopefully get it all back together today fingers crossed.
 
If you need to take the drivers side manifold off, easier access if you take the wheel and arch liner out you can reach out with a long extension and a wobble joint. You can do it from the top, if it's been off recently.. all me how i know :D
 
Thanks @kermit_rr. Will definitely go through the wheel arch. I've been reading up regarding removing the intermediate shaft which I've not done before. I've seen some comments about tying the steering wheel to prevent it turning. Also making sure the steering lock isn't on. I didn't see any of these in Rave. When you did the job did you have any issues with removing shaft or any tips that I should be aware off? Cheers
 
AndyF07 said:
Thanks @kermit_rr. Will definitely go through the wheel arch. I've been reading up regarding removing the intermediate shaft which I've not done before. I've seen some comments about tying the steering wheel to prevent it turning. Also making sure the steering lock isn't on. I didn't see any of these in Rave. When you did the job did you have any issues with removing shaft or any tips that I should be aware off? Cheers
Click to expand...
i didnt touch the steering in the end, it didnt want to come apart so i left well alone. didnt have a problem going through the arch though.
from rave...
upload_2023-2-14_10-29-40.png
 
Thanks @kermit_rr. In the end with the amount of work to remove the manifold and potential of more broken studs/bolts I decided to drill the stud out in situ which was a pita but all done now. I don't have a tap set and can't seem to find a m10x5mm tap on line. Do you know if Is there any reason I can't use a nut and bolt in place of a stud assuming it can be torqued to the right setting? The other two connections would be studs?
 
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