Unsticking corroded bolts/nuts etc.

[notsofast]

What's the best way to unstick corroded bolts/nuts/plugs etc?  Having finally found a bit of time to do a bit of work on my M49, and having bought some sockets etc., I find I can't do anything cos all the bolts are corroded solid - first I couldn't undo the sump plug, so rather than changing the oil today, I thought I'd change the exhaust tailpipe instead, but the nuts on the clamping bolts have also corroded solid and refuse to budge. Any handy hints? I've tried WD40 but to no avail.

[Tomcat3]

Best stuff ive used is Plus Gas if its really stubborn it may need a few soakings over a few days. If it still doesnt play ball I up the stakes with gas torch or angle grinder.

[notsofast]

Thanks. I see Screwfix sell PlusGas - I'll givie it a go.  Does it loosen things better than WD40?

[Tomcat3]

I just use WD40 as a lubricant and to clean parts but not on electrical components, ive used plus gas for years and it seems to work better than most.

[saskak]

I use PB blaster, rather difficult to find but it has worked quite well for a few bolts/nuts. I'm not sure you will have much luck with any liquid for the exhaust clamps/bolts. Due to the extreme temperatures, these will have corroded so much that it is more than unlikely that you will be able to unscrew them. I cut mine through and replaced the whole bracket/bolts.

[ffrenchie]

I thought I'd change the exhaust tailpipe instead, but the nuts on the clamping bolts have also corroded solid and refuse to budge. Any handy hints? I've tried WD40 but to no avail.

Exhaust clamps are consumables, don't bother undoing them just put the grinder through them in any convenient place and get new ones. Also cut as much of the old tailpipe away as you can don't mess about trying to get it off in one piece if it's going in the bin anyway.

[oilyrag]

With exhaust bolts I usually hammer an old socket onto the nut and then do it up - shearing the bolt off - safer and sometimes easier when there's no room for grinder or heat. If you have oil central heating or use diesel a good soak over a couple of days is cheaper than the sprays and no less effective.
The sump nut may take some moving and if your sump is as rusty as mine it could fail instead of undoing. You can buy reasonably cheap pumps that suck the oil via the dipstick hole. They will be slow, but may do the job.https://www.ebay.co.uk/itm/223990786089?hash=item3426e42829:g:Mw0AAOSwp7xepoZk

[ffrenchie]

The sump nut may take some moving and if your sump is as rusty as mine it could fail instead of undoing.  You can buy reasonably cheap pumps that suck the oil via the dipstick hole. They will be slow, but may do the job.https://www.ebay.co.uk/itm/223990786089?hash=item3426e42829:g:Mw0AAOSwp7xepoZk

 A 12v sump pump, don't be tempted to run the engine so you don't flatten the battery though 

[notsofast]

The garage that sold me the tailpipe also supplied a new clamp, as they said they're usually buggered too - though I didn't realise this meant the old one won't unscrew. I've only got a large-bladed (10-inch?) angle grinder that I usually use for masonry - don't think I'd feel confident using that in this situation (bit unwieldy, and what if it kicks back? - not much room to maneouvre). Would a hacksaw cut through the bolts? Not sure how to use an old socket to shear the bolt off.

In the Haynes manual it says "where joints are secured together by a clamping ring, apply a smear of exhaust system jointing paste to the flange joint to ensure a gas-tight seal" - can I get that from Halfords, or is it OTT and not really necessary?

[saskak]

Last time I did this, it took me 3 days to file through it. Too tight space and could not fit a hacksaw of any size. I had a file set and just filed through the bolt a mm by mm.
Upon fitting a new one i did not use any paste, I guess the exhaust gasses with the associated diesel carbon will seal it pretty good.