Hey guys, this is my first time posting on here, but I've been reading for a year or so now ever since I got my 96 4.9 F-150 (a straight 6).

Here's the problem I'm facing at the moment:

I've disassembled everything, down to just the block sitting in the truck (pistons and everything still in, etc). My goal is to do a full seal and gasket change and to get the rust out of the whole engine that has been plaguing my radiator/cooling system.

I recently got the block back from the machine shop where they trued the gasket surface and did a valve job, as well as (supposedly) sand-blasted it, gave it an acid bath, and checked it with magnaflux. I wasn't very impressed with the job because the coolant galley running all the way through the head is still coated with rust and has the same odd smell that the coolant system has always had.

As for the block, it also has a good amount of rust within it's coolant galley and I want to get rid of all of this. Taking the block out of the truck is not an option as I don't have the time or money to do that. So, my strategy is as follows:

Plug the block and fill it with an acid of some sort and let it soak for whatever amount of time is necessary depending on the acid used, then flush the acid out with water. (I've tested this out already, so the "how" is not a problem).

For the head, I would like to do the same thing which will be even easier since it is off the truck and I can move it around.

My question is, what type of acid (or any liquid) should I use?? What will work best being mixed with water (not necessarily during the actual soak, but I'm just worrying about chemical reactions for when I'm flushing the acid out). I want this stuff to REALLY work, not just convert some of the rust and leave the rest to be scrubbed off, which is not an option since these are deep, maze-like coolant galleys I'm working with.

I've read up on using muriatic acid to do this but I am hesitant. I am aware that it will strip not only rust but any coatings on certain metals (e.g. zinc on many bolts, etc), thus exposing them and allowing even more rust to accumulate, and faster (tested this with a few bolts myself and it's no lie). What makes me suspect that it might be safe to use on the head and block is that perhaps those inner galleys have no real coating to worry about being stripped away in addition to the rust... The head and block are both made out of cast iron (I assume) which historically has been pretty tough as far as holding up to acids goes. Another treatment I've heard of is using Sulphated Molasses... it takes a while (aprox. 30 day soak) but is supposed to work just as well as any acid, be safer, and comes pretty cheap. Haven't tested or researched more into that method yet though...

I have pictures of everything if any clarification is needed as to my set-up and the pieces I'm working with. Let me know what you guys think I should do.

I thank you for any and all help in advance!

- Dan

 

You should of done SEVERAL coolant flushes with the truck Running . That would of gotten rid of 90% of the rust. Now you will, never get rid of the rust unless you pull the engine and have the block hot tanked

 

Yes, I repeatedly flushed it 4 or 5 times, trying a few different different flushing products from autozone...

And, like I said, the head was given an acid bath at the machine shop which I was not impressed with because it seemed like it did not work... unless "hot-tank" is something different from "acid bath" ?? Pulling the block is not an option, but any chemical "bath" I could do to it would be the same if I just plugged the block and filled it with said acid, so that's what I'm sticking with. I'm experienced with handling many toxic materials and know how to properly dispose of them so any suggestions are welcome

 

We've poured CLR into heater cores before, let it soak and flushed in both directions. Usually a last ditch effort before replacement is necessary.