Acid flush questions

[Ajax]

I'm looking to do the acid flush on my engine this Spring, or during the winter if temperatures remain mild enough.

I've found the procedure here: acid flush procedure

#1. This procedure has 3 parts, running the engine, a pressure flush, and a manifold flush. Are you meant to do all 3 parts, or is the pressure and manifold flush meant to be done if you can't or don't want to run the engine? It seems to me, that drawing the acid solution in, by running the engine would negate the need for a pressure and manifold flush. Am I wrong?

#2. Does this damage the rubber impeller? Should I replace the impeller afterwards?

#3. My engine isn't very gunked up and runs at the perfect temperature, but I have observed a little black funk in the engine. I just want to keep things well maintained. Any opinions on whether an extended white vinegar soaking would be adequate vs. acid? How many folks here have done the vinegar flush?

[joe_db]

What I do is the same as how I do antifreeze - I put a hose on the exhaust and recirculate the same liquid over and over. For cleaning I use vinegar.

[JOHN COOKSON]

Ajax

Been down this road. Decided an HCL acid flush was the way to go.

First off I don't have a recirculating loop. So I would have to fill the cooling system with vinegar and let it sit for a week then come back and flush it out. Or I could fill the cooling system with diluted HCL and let it sit for 5 minutes then flush it out and be done with it.

When I looked at the price of 4 gallons of vinegar vs a quart of acid my mind was made up - I went with the HCL.

So check it out and do what you think is best.

The acid won't hurt the rubber impeller.

TRUE GRIT

[toddster]

I just went with the "running the engine" method. Operating temperatures did go down and became more stable, but I also re-plumbed the FWC, so changed more than one variable.

Two minor (?) issues arose. I did this after the new paint job, and the area around the exhaust port ended up looking like the boat forgot to wipe. Also, it appears that rust was all that was plugging the holes in my stand-pipe exhaust, so I immediately started having issues with exhaust fumes in the cabin. (I only just tracked this down when the weather got cold enough to see the fumes.)

[roadnsky]

...This procedure has 3 parts, running the engine, a pressure flush, and a manifold flush. Are you meant to do all 3 parts, or is the pressure and manifold flush meant to be done if you can't or don't want to run the engine? It seems to me, that drawing the acid solution in, by running the engine would negate the need for a pressure and manifold flush. Am I wrong?

The PRESSURE FLUSH is a separate procedure from the ACID or VINEGAR Flush.
You don't HAVE to do the Pressure Flush but it's not a bad idea because it'll hopefully clean out all the crud the acid loosened up.

In the link you posted, if you go towards the end there are some pics there of the PRESSURE FLUSH being done.

[sastanley]

Ajax, I did an acid flush and LOTS of vinegar soakings over the summer while I was getting my FWC in order. I let acid sit in there for an hour, and when I still was seeing black in my antifreeze, I did 100% vinegar overnight for several iterations.

This winter I have the manifold at the house & I have the side plate off the block to dig out the black mud that is still there. I even discovered that you can see daylight between cyl #2 & #3 when you poke the crud out of the middle manifold stud hole.

In my opinion, there really is no substitute for removing all the parts and digging the gunk it out, or trying the Moyer pressure flush kit.

Neil, I shoulda listened to you last spring...I probably would have found the bad manifold stud at the same time too.. (however, I would have cut the boat up to stuff the water tank in there if I had just re-assembled the freshly cleaned out water jacket.)

Anyway - Ajax, YMMV. I might pull at least the hoses/fittings/t-stat housing to allow a larger passage for the gunk to come out of the various components, and maybe the side plate to dig out what you can with various tools from around the cylinders & block drain plugs. That would be my minimum suggestion.

[ndutton]

Neil, I shoulda listened to you last spring...I probably would have found the bad manifold stud at the same time too..

I said something last spring that had merit?? Hold on, let me get my wife to read that.

FYI, that one hour acid soak concerns me. It might have contributed to the stud problem.

[sastanley]

Neil, not to hijack Ajax's thread too much, but I didn't put a stopwatch on it, & I probably had it diluted a little more than 3:1. but that is all water out of the stud hole now.

[Ajax]

I wouldn't worry about it. If the acid won't eat the rubber impeller, then I don't think it's strong enough to eat your engine block.

The damage was probably done over a long time, by RW cooling.

[ndutton]

I wasn't suggesting it would eat an engine block. Muriatic acid is however corrosive to metals which is why the recommendation is to dilute it for our purpose and limit the time it sits in the engine. My thought was if Shawn's stud was already on its way a prolonged acid bath could have contributed to its demise.

[sastanley]

Neil, that may be true. As I've said in my own manifold thread, I am glad the chain of events have occurred as they did, rather than in the middle of the Bay somewhere where I have antifreeze spewing out all over my fuel pump, pressure gauge, bilge, etc. ()

[Ajax]

Based on the advice here, I've decided to go with an acid flush, but since my build-up is very minor and I'm probably just catering to my paranoia, I'll do the engine flush but skip the pressure flush.

My boat was out of the water for years, and properly laid up so the engine was clean when I started. This is my first year of use.

[sastanley]

Ajax, it is a lot easier to stay ahead of the game than spend a weekend digging out the sludge!