Unseizing the front brakes

I am moving my Daimler V8 to a new home but the front discs are badly corroded so all seized up. I remember the fragile nature of the cylinder bolts so these will likely snap. The caliper bolts likewise will be well seized so I am wondering if there is a magic way to release the pistons from the discs without major damage.
I will be replacing the discs etc. but do not want to remove broken bolts if I can avoid it.I am soaking in WD40 but think this will be of little use!
Any experience suggestions to just get it onto a trailer?

If the trailer has a winch then just drag it up onto the trailer. If it has sat that long, then the tires will need replacing anyway, so you’ll hardly be worried about a barely detectable flat spot. The wheels will usually start to turn after a couple of meters. You may need to winch it back off the trailer.

Failing that, I would remove the pads before I started trying to unbolt cylinders.

Or put the car up on a set of wheel dollies.

Nothing magic involved. WD wont do a thing. it is not an antisieze fluid. Plus gas or one of the other brands may help, as will heat cycling. You might try and removed the caliper bolts and leave the whole assembly off.

Thanks guys, I think fluids will be pushed to make any headway as this has been standing for a number of years. The structural integrity of the front subframe is almost 0 so dragging it will likely cause the whole front cross member to detach! The caliper bolts won’t move yet and hard to find a socket to fit snug anyway. I think making some dollys is the best solution although we did use them for previous moving they failed eventually so I need some serious wheels to make them up.
The car has a nice California bodyshell waiting to be fitted out so the majority of what I have will be scrapped but I have to move it to a new location before that happens and remove some of the innards.

If you can get a really big screwdriver or jack handle in there you can pry the pads away from the discs enough to move the car onto the trailer.

After you are at your new home, I’ve had luck with Kroil brand penetrating oil, alternating with heating cycles with a propane torch.

I tried that yesterday but pads well stuck. I would have to chisel them out. I suspect the cylinders have rusted too. Hopefully I have complete running gear on the new bodyshell so can give up on my rusty suspension.

I’ve resurrected many dead cars, and haven’t seen seized caliper bolts yet. They’re pretty beefy. Spray them with whatever lubricant/penetrant you want, try some heat / cool cycles, then try to turn them with a good (preferably hex) socket and a 1/2" breaker. If that doesn’t work, try a 1/2 air impact driver. Make sure you’re turning things in the right direction. Go back and forth. Don’t make the bolt hot by forcing it to turn against resistance. It may get brittle and break. If you get the bolts out, soak the pad/rotor interface, heat/cool, then try getting off the caliper with a BIG pry bar. Be careful. You (or your car) can get damaged if things go south!

Thanks - do you know the actual bolt size for the caliper as nothing I have seems to fit snug? I will get a decent hex socket

Sorry I don’t. Try calling the boys at SNG Barrat - they have bolt
diameters and can usually give you a hex head size off that. Good luck,
David

hey just did this the other day your calipers are probably not seized…crack the nut that goes to your rubber hose on the caliper. stick big screw driver in between pads and pry and see the fluid come out mine were stuck because that rubber swells inside and wont relieve the pressure…good luck hope this works for you.

I actuallyalready cut the hose as I will not be reusing it and then hammered a screwdriver between pad and disc. No joy!
It will be dollies onto trailer then I can remove engine and front suspension elsewhere without chance of leaving half the car on my drive if it all breaks apart.

I just did calipers on a 420G, bolt size is 3/4"…they are “open” holes too, not closed, so saturate area with penetrant, bolt size MAY be Whitworth, which = 18mm, otherwise there is only a few bolt head imperial sizes to choose from!..an impact socket is 6 sided, I use a long 1/2" breaker bar, and tap it with a hammer, as a “manual” impact wrench. You will still need to hammer a brass drift to get the caliper free of the disc

I have absolutely no affiliation with this You Tuber but he is doing some amazing tear down ad rebuilding of a MK10. He already has seven videos. Note that he is using a special tool that electrically (??) super heats the bolts like a blowtorch would and then he easily cranks them off with wrenches.

Gerard

Found a more detailed description at:

G

the el-cheapo way is hold an arc welder stick on a bolt, this heats them to red-hot

3/4" socket is “sloppy” and 18mm will not fit. 19mm is slightly sloppier than 3/4"!! Bolts are only surface rust so will get a hex socket and long breaker bar and in meantime soaking each day with Plusgas.
Interesting video! Trust the Yanks to have an answer.

If the bolt head is undamaged thats weird, but a solution exists, Metwrinch sockets cover variations in size, they are indespensable for rounded heads, also Jags, they are expensive quality tools, I have sets, but you could order an 18 and 19mm X 1/2" sockets

the candle idea looks especially good, as the caliper mounting holes are open?, so the wax should penetrate extra well.

a magnetic induction tool exists specially for frozen fasteners, heats to red hot, with minimal heat transfer