As Thorin has posted an excellent radiator replacement thread, which I'll be following in a couple of days, I thought I'd post up my temporary fix for the cracked radiator upper tank problem that seems to affect all stock Toyota rads at some point.
Tools you'll need:
2mm Drill bit & drill
Stanley knife
Screwdriver (small thin flat bladed)
Bucket or syringe
Solvent and a clean rag
180 Grit sandpaper
A pack of JB weld
This is the crack that you normally see weeping coolant & bubbles out of:
Copyright Thorin and blatently stolen without his permission
Step 1:
Let the engine cool down until its safe to remove the rad cap. Even though there's a hole in the rad it may still have pressure in it. Wait until the bubbles and hissing stop at the very least and USE A CLOTH OVER THE RAD CAP.
Step 2:
Check the coolant level. If its bone dry in the rad then you may have also overheated it. Can you remember what the temperature guage was at when you stopped the engine?
If its still running ok and there's no mayonaise on the underside of the rad cap and in the radiator then you're probably ok.
Step 3:
Drain the coolant down to below the level of the crack. This is to stop the coolant getting into the glue. If the rad is bone dry move to Step 4.
Either drain some coolant from the bottom of the rad drain cock (into a bucket), or use a syringe to suck it out of the top.
The syringe is best as there's a bit of dead volume around the top of the tubes and the syringe can suck all of this out. If you're feeling particularly clinical about it, stuff some rag down the cap hole with the screwdriver (keeping one end of it out to pull it back out again) and dry the inside of the top tank around the area of the crack.
Step 4:
Take the drill with the 2mm drill bit and locate the very ends of the crack. Drill into the top tank so the cracks are on the inside of the holes (i.e. just overlap the end of the crack with the hole so that the hole is slightly further out than the crack). This stops the crack going any further across the rad.
Step 5:
Take the stanley knife and use the point to cut into the crack to make it deeper. Then use the blade on its side to scratch a V groove into the crack. Make it just deep enough so that the tip of the blade just starts to break through into the inside of the tank.
Step 6:
Use the sandpaper to sand about 1/2 an inch around each side of the crack and 1/2 an inch beyond the drilled holes. Make it as rough as you can. Then take the stanley knife and scratch it up some more. The rougher the better as this is the keyed surface for the glue to hold on to.
Step 7:
Clean the area with the solvent and the rag to remove all traces of antifreeze.
Step 8:
Mix up equal amounts of the JB Weld on a piece of cardboard with the screwdriver. About 1/2 an inch from each tube is sufficient.
Use the screwdriver and dollop this into the crack. Work it in well so some goes through to the inside. Use the rest to build up the area around the crack to about 4mm proud of the surface, tapering off towards the edges.
Stick what you can (little fingers if you have long small ones) in through the cap neck and smooth the glue around on the inside), then smooth the outside off with a wet finger. Stick some selotape over it to make it smooth if you like.
Step 9:
Wait 24 hours before filling with coolant and testing.
I've done this a couple of days ago and its holding out perfectly. I even gave it full beans to get it hot & pressurised & still no leaks.
Should work as a temporary fix while you wait for a new rad if the Supe is your daily transport.
I'll post a pic of the finished article when I can get the camera to work