I have been working on an MGTD for four years.
The car sat in an attached garage from '84 until I hauled it out in 2013.
After going through the carbs I got it running just fine, a few minutes at a time. The water pump leaked badly.
After replacing it and and all brake cylinders and tubes the owner decided we needed to take the body apart and pain it.
Now that that's all done I installed a new radiator and started it up again.
It runs fine but boils the water in five minutes..
I removed the water pump today and found the water passages to the pump are rusted closed.
Where the water goes back around the front cylinder on each side of the cylinder it was plugged tight.
After poking a small hole in the rust a half gallon of water gushed out.
I would like to make a plate to cover the block where the water pump came off and fill the engine's water jacket with something to make rust go away.
I already tried SLR or RLS or LSR.
So what can I pour in to get the rust dissolved?
Will you, like the T blocks, probably loose your freeze plugs when you remove the rust?
Presume this is iron or steel block, not aluminum?
I have had good luck using phosphoric acid. Ospho from the auto paint suplly shops. Converts some of the surface rust back to metal and flakes off the loose rust.
Sounds like it's too gunked up for chemical means at this point. Remember that a chemical reaction consumes the chemicals and at some point one of them runs out and the reaction stops. I would clean it up by mechanical means first.
Take a stranded steel cable a couple feet long (from bicycle brakes, a speedometer, or whatever is lying around), fray a couple inches of one end and chuck the other end in a drill. Fish that through the coolant passages while running the drill and it will take out as much of the scale as you have the patience to reach. Once that's done you can just flush with a garden hose. A chemical chaser is optional but I figure if you've come this far you may as well.
It is cat iron. Block and head.
This rust is really hard.
I had forgotten about Evaporust.
I will try the frayed cable trick today. That should clear a passage for the chemical stuff.
I don't want to use rust converter..... it's bad enough having rust block the.passages, iron would be a permanent blocker.
I have lots of plastic sheets. I'll make a cover for the water pump hole a fill the engine with Evaporust.
To heat mixture I can set the engine once in a while.
Thanks so much for the ideas Guys.
That was meant to read CAST iron.
The frayed cable isn't even about making a path, picture it as a flexible, powered wire brush to clean out the passages. You should be able to feed it through the whole block and head, especially if you're willing to take a couple things apart.
You may need to run the drill in reverse, depending on the direction of twist in the cable you use. They are made in both directions depending on application.