Procedure for acid flushing and pressure flushing

[Don Moyer]

Here is the procedure for acid flushing and pressure flushing as taken from our FAQ and service and overhaul manual (http://www.moyermarine.com/cgi-bin/shopper.cgi?preadd=action&key=MANL_01_98). You'll find our flushing kit (http://www.moyermarine.com/cgi-bin/shopper.cgi?preadd=action&key=CSOT_02_71) very helpful in performing this essential maintenance task.

ACID FLUSHING: The following acid flush is most effective when used as a preventative maintenance measure every 3 to 5 years:

CAUTION: Be sure to wear proper protective clothing (including eye protection). Always add acid to water when mixing, and if possible, hang a bucket over the exhaust outlet to catch acid solution when discharging from boat.

1) Mix 1/3 gallon of household muriatic acid (30% concentration) into a 5 gallon bucket of water.

2) Draw the entire 5 gallons of acid solution into the engine through an inlet "T" fitting between the raw water through-hull and the inlet to the raw water cooling pump (the same "T" as used for winterizing the engine). For best results, thermostat should be removed and the by-pass hose temporarily clamped off. All the acid solution will then be pumped through the block by running the engine. Stop the engine as soon as the bucket is empty.

NOTE: Some of the acid solution will find its way into the exhaust system, which might loosen up any crud that may have built up within the water lift muffler and connecting plumbing.

3) Start the engine after letting the acid sit in the water jackets for about 15 minutes and run it long enough to thoroughly flush out the acid.

4) If it has been possible to retrieve the acid solution from the back of the exhaust system, add approximately 1/2 pound of household baking soda to five gallons of acid solution prior to discarding.

PRESSURE FLUSHING (PRELIMINARY STEPS):

1) Remove starter and alternator.

2) Remove the three 1/8" pipe-threaded water jacket drain plugs. Two of these plugs are in the block (one is located at the forward end of the block beside the starter, and the other is located beside the distributor base). The third plug is in the lower rear corner of the manifold.

NOTE: If the cooling system has not been serviced in many years, the plugs may have to be drilled out. If, after drilling out the plugs, the threads cannot be cleaned up with a 1/8" pipe tap, the drain hole(s) can be drilled out to 7/16" and threaded using a 1/4" pipe tap. Pipe taps and replacement 1/4" brass pipe plugs are available at most hardware stores.

3) Probe into each drain with a coat-hanger-sized wire to insure that it is open. If the drain on the manifold is clogged, it will be virtually impossible to open it without removing the freeze-out plug nearest the drain and probing the drain from inside the cooling jacket. While the drain in the manifold is not used to inject pressure water, as in the case of the drains in the block, it is still preferable to open the drain if at all possible.

FLUSHING THE BLOCK:

1) Install a 1/8" pipe-threaded 6" long brass nipple in one of the drain holes in the block and a 1/8" hex-headed brass pipe plug in the other block drain.

2) On early model engines, use a 1/8" brass 45 degree street-el (provided in kit) to facilitate reaching the drain hole behind the distributor.

NOTE 2: On late model engines, the 6" nipple can be left installed in the aft block drain after the flushing operation is complete to facilitate draining the block for winterizing or other servicing (use a 1/8" brass cap to close the end of the nipple). On early model engines, there is insufficient space for the nipple after the alternator is reinstalled; however, the 45 degree elbow can be left in place with a 1/8" hex-headed pipe plug installed to make subsequent draining somewhat easier.

NOTE 3: Early model engines have a cast iron crossover tube between the head and manifold which makes it difficult to flush the block and head separately from the manifold. In some cases, this cast crossover tube has been replaced with a rubber hose and 90 degree fittings. If this is the case on your engine, you may be able to install a discharge hose on the fitting on the head to be run overboard. You can then proceed with the following steps as in the case of a late model engine.

Steps 3 through 7 apply only to late model engines.

3) Remove the thermostat housing, both fittings, and the thermostat.

4) Install a 3/8" brass street-el in the outlet of the thermostat housing (the side marked "MAN"), and a 3/8" pipe plug in the inlet (the side marked "WP").

5) Reinstall the thermostat housing, but leave the thermostat out until after flushing is complete.

7) Install bushings on the end of the 6" nipple in the aft block drain as necessary so as to be able to install a swivel type garden hose fitting. It's also very convenient to install a small ball valve before the garden hose fitting so that you can stop/start the pressure from the hose for more aggressive flushing.

8) Flush the block until the effluent from the discharge hose is clear.

9) Move the 6" nipple to the other block drain, and flush that end of the block until the effluent of the discharge hose is clear.

FLUSHING THE MANIFOLD:

1) Remove the 1/2" fitting at the rear discharge of the manifold. Inspect and clean the 1/2" pipe thread opening as necessary.

2) Connect a garden hose to the rear outlet of the manifold for overboard discharge. A 1/2" male pipe thread by 3/4" male garden hose fitting is ideal for this purpose.

3) Install a second garden hose fitting to the front (inlet) of the manifold. Connect a garden hose to this fitting, and flush the manifold with as much water pressure as possible. As in the case of the block, it's a good idea to install a ball valve between the garden hose fitting and the manifold to enable you to stop/start the pressure from the hose.

4) When flushing is complete, remove garden hoses and all flushing fittings. Reinstall the thermostat, and reassemble the rest of the cooling system.

Best regards,

Don

[vain]

Hi Don,

Are you aware of any danger of damage to the impeller and/or oberdorfer pump assembly when using it to draw the acid/water mix into the engine block?

Over the years I have read many tutorials on how to flush the engine with the muriatic acid mix and many of them recommend bypassing the engine driven water pump and using an external (ie: drill driven pump) because of fear of damage to the pump and or impeller?

Has it been your experience that is is safe to use the engine pump itself to draw in the solution?

thanks!

-todd
catalina 30/A4 Atomic

[Don Moyer]

Todd,

There is no need to remove the water pump in performing an acid flush as described in our Service and Overhaul Manual or elsewhere in our technical support documents.

Don

[Ericson32]

Don,
Last weekend I successfully used the acid flush procedure - and a fair amount of gunk came out. Later that weekend, cruising out of the harbor, I noticed the water temp went up to about 170 - it had been running at 160 or so fairly regularly. Any clues on the increase in temp? The engine runs smoothly and idles down nicely. I'm using the hotter thermostat in the MM enclosure. I'm not terribly concerned, since its still within "normal" temp limits - in fact running a bit hotter is fine with me if it will also run a bit cleaner.

[Don Moyer]

It is rather unusual to see temperature go up after an acid flush, even though (as you say) 170 degrees is still in the very normal range. I would look at the amount of water coming out with the exhaust to be sure it's still a normal amount. You could have loosened enough crud to partially block the fitting where your cooling water enters the exhaust system or perhaps the 90 degree elbow at the rear of the manifold.

Don

[Jesse Delanoy]

Is there any possibility of damage to a heater core in a hot water heater by doing an acid flush with the exhaust water running through the hot water heater core?

[Asa Kirby]

Is there any reason to not leave the flushing fittings on the 6" pipe nipple if you include a ball valve before the garden hose fitting? This is for a late model engine.

Capping the nipple is fairly easy, but leaving the fittings attached would make doing the flush fairly simple in the future. I assume that the ball valve would provide enough of a seal to prevent any leak during normal operation. I only worry about the mass of brass at the end of a 6" pipe nipple. Could it cause stress or other problems through normal operation vibrations?

As a quick follow up, is there still value in doing the high pressure flush if you are unable to bypass the manifold? By this I mean only attaching the high pressure flushing fittings to the 6" nipple and pinching the the over flow circuit hose (or turning off the flow with the ball valve provided by the back pressure kit,) and just letting the water exit the engine through the manifold and out of the engine exhaust port. I assume it is less effective, but is it in any way harmful or dangerous?

[keelcooler]

When power flushing you must remove raw water manifold discharge hose to prevent water trap muffler fill up and exhaust back flush.

[roadnsky]

I'd advise against leaving that much weight at the end of the 6" nipple.
You break that off and you'll regret your "time saving" shortcut for days or weeks! :eek:
Besides, you only need to do the power flush every three or four years.
Not worth the risk, IMHO.

Also, I wouldn't do the power flush without removing the Thermostat and running a hose over the side instead of running the crap thru the manifold and exhaust system.
You could just clog it up and defeat the purpose of the entire procedure.
Again, IMHO...:o

[Asa Kirby]

Thanks keelcooler and roadnsky!

Your posts confirmed my suspicions. I wanted to make sure I was not being overly cautious.

Your professional responses and courteous tone are the reasons these forums are so good. I've never posted until now, and you both have given me a great first experience.

Thanks!

[roadnsky]

Asa-
Thank you for the kind words. Obviously, if it weren't for Don and the folks at MMI we'd all be much, much poorer in the A4 knowledge department.

Here are a few pics of the 1/8" fitting with all the attachments for flushing and one with the plug I put in after the procedure.
(I just feel safer not having that 6" nipple sticking out there begging to get snapped off!):eek:

It's kind of ironic that I actually did the pressure flush today as a final procedure to replacing my Water Jacket Side Plate.

But that's another story for another thread. To come...
(More pics for you, Shawn):p

[roadnsky]

When power flushing you must remove raw water manifold discharge hose to prevent water trap muffler fill up and exhaust back flush.

Manifold flush pics...

[vabiker23518]

Jerry, that is one fine looking Atomic 4! I'm envious!

[sastanley]

holy cow Jerry!! :D - Nice pictures!

I didn't realize there was a flange around the pipe nipple (in that nice closeup where the plug is)...mine's rusted so many layers off there it is just flat.

For what it's worth, I leave my 6" nipple attached (I up-sized after the original galvanized rotted off & re-tapped new threads), although when I drained for winterization, nothing came out of that hole. I will comment that it is very close to the alternator belt, so if someone else needs to re-tap that thing, be careful to get it straight so the extension of the nipple doesn't rub the alt. belt.

[roadnsky]

holy cow Jerry!! :D - Nice pictures!
For what it's worth, I leave my 6" nipple attached (I up-sized after the original galvanized rotted off & re-tapped new threads), although when I drained for winterization, nothing came out of that hole.

Thanks. I think pics help. (At least for me):o

My nipple didn't drain either when I tried it at first. (Bill, can I say that here?!):p
I had to soak the water jacket for a couple of days to loosen some crud in there and used a screw driver and coat hanger to clean mine out.
When I did the pressure flush, it flowed fine.

When I get some time, I'm gonna post some pics and a thread about my
"Replace the Alternator - oops! replace the Accessory Drive - oops! turned into replacing the Water Jacket Side Plate - Oh NO! Broken Bolt - Oh #@$!! broken Drill Bit!!! PROJECT"...:eek:

[sastanley]

hahaa....sounds familiar..on the side plate part anyway...I have the old not-welded bracket on my side plate, and that bolt has been up-sized one from the stock size..i am waiting for it to fail and need the cool little stud kit from Moyer :D

[Administrator]

When I get some time, I'm gonna post some pics and a thread about my "Replace the Alternator - oops! replace the Accessory Drive - oops! turned into replacing the Water Jacket Side Plate - Oh NO! Broken Bolt - Oh #@$!! broken Drill Bit!!! PROJECT"...:eek:

Jerry, my equivalent was offering to repair a leaky faucet during a visit to my Mom's home many years ago. Cost me about $1,200 and the admiration of a mother who had previously thought her son's engineering degree something to be proud of.

Bill

[Asa Kirby]

Hi roadnsky,

Your pictures are excellent! It definitely gives me something to aspire to. I've already implemented your suggestions and removed my 6" nipple and replaced it with just a pipe plug. Happily, I've included all the brass fittings into my own flush kit for future use (and by future, I mean when our marina here in Austin, TX decides to re-plumb city water to the slips.)

Thanks Again!

[sastanley]

So Jerry,

What is your procedure there with all those fancy fittings? Do you hook up a hose to each of those fittings at the same time, or are you doing one at a time, or does one end drain overboard into a bucket so you can see all the stuff you got out, or what? :confused:

Do you blast the block with fresh water thru the nipple or sideplate and collect it at the thermo housing? Same with the manifold I assume...in one end and out the other?

[roadnsky]

So Jerry,

What is your procedure there with all those fancy fittings? Do you hook up a hose to each of those fittings at the same time, or are you doing one at a time, or does one end drain overboard into a bucket so you can see all the stuff you got out, or what? :confused:

Do you blast the block with fresh water thru the nipple or sideplate and collect it at the thermo housing? Same with the manifold I assume...in one end and out the other?

First time I heard plumbing fittings called fancy!:p
Yeah, you nailed it.
The 6" nipple (I love writing that word!) has a ball valve (yeah that is fancy) on it so I can "blast" the fresh water thru.
(Luckily, my marina has really good pressure on our fresh water supply.)
Anyway, I flushed out the aft water jackets (3& 4 cyls) then move to the forward block drain and do cylinders 1&2.
The crap exits out the Thermostat housing (the thermostat is removed) thru a hose to a bucket that I filter to see what I caught! :eek:
Then, finally I move to the manifold. Intake forward and output is aft.

In the pic, the GREEN hose is the incoming pressure water. The CLEAR hose is the outlet hose going to the bucket.
You can see the crud thru the clear hose while you're doing this. Sorta like a "colon blow" for the engine...:rolleyes:

Also, while I had the thermostat out I cleaned it up with vinegar and did the hot-water-in-the-pan test.
Kinda like being in Jr High Science class again...

[sastanley]

roger thanks! More good pics :cool:

Ok, the Admiral is hollering at me so I'd better get - "what are you doing at the Moyer site, I thought you were going to work on the mast today?" :rolleyes:

[Baltimore Sailor]

I've been reviewing this thread the last couple of days, and I had a thought: getting at the front (closest to the flywheel) 1/8" fitting normally requires the starter to come off. Why couldn't a flexible line be used there that had 1/8" fittings on both ends?

A quick Googling finds an $8.99 18" grease gun hose with 1/8 male NPT threads on each end. The line has a rating of 3000 psi, so I don't think we need to worry about our marinas' water pressure bursting it. ;) Yet it should be flexible enough to get into that fitting with the starter still in place, and the rest of the bushings, etc. could be fit to the other 1/8 male fitting on the end.

Unless someone can think of a good reason not to, I'm going to give this a try. I just acid flushed the engine -- and good golly, what a mass of goo came out of it -- and I wanted to do the pressure flush as well. This looks like a good workaround for removing the starter.

[roadnsky]

You'll need the fitting/hose connection at the point where it screws into the engine to be in the 2-3" range before it makes a hard angle.
(Looking at pics I have it appears to be about that much clearance between block and the starter)
Could work though.

Another thought would be a 90° fitting there?

If you do it, be sure and let us know where you end up. ;)

[Mark Millbauer]

Last time I did the acid flush/pressure flush I was able to install a brass 90 or 45 in the flywheel end coolant drain. I don't remember which it was and don't. have pictures but it is still there with a 2" extension and a cap on it. remove the cap and it will drain. Or attach the hose to flush. Works great. it was a bit tricky getting it threaded in but only took about 5 minutes.

Mark
C27 'Solution"

[Baltimore Sailor]

But you had to take the starter off to get it on there in the first place, right? My plan is to never have to take off the starter at all.

I may give it a try this weekend, depends on the weather. Saturday is looking good, so it'll probably be sailing instead of tinkering. Maybe next Wednesday, which is my usual maintenance evening once the light goes away.

[roadnsky]

BS-
I did a measurement yesterday and you've got just over three inches between the starter and engine block.
Good luck. Let us know...

[Mark Millbauer]

I did not have to remove the starter. Again, it was tight but I was able to get the elbow installed (little by little)with an open end wrench. There are probably some brass elbows configured better than others for this, location of wrench flats, over all outside dimensions, etc. I just used one I had on hand.

Mark

[JOHN COOKSON]

Can I use vinegar to (successfully) acid flush my A4?
If so how long should I leave it in the engine?
Would leaving it in for a week be detrimental?

Thanks everybody.

TRUE GRIT

[roadnsky]

Can I use vinegar to (successfully) acid flush my A4?
Yes. It's a little less effective, but yes, you certainly can.

If so how long should I leave it in the engine?
I leave it for 24-48 hours.

Would leaving it in for a week be detrimental?
No, not really. I'd think after about 2 days though, you're not getting any more positive results.
If you're gonna do a week, do 2-3 treatments during that timeframe.

[Baltimore Sailor]

I must say that I've done both the vinegar flush and the muriatic acid flush, and the muriatic flush was by far more effective.

This is how I did it:

I got two 5-gallon buckets. I mixed up a quart of muriatic acid to 4 gallons of water. The sticky says 1/3 of a gallon to five gallons of water, but that's just a 1:15 solution, and if you use 1 qt in a 1:15 solution you get a total of 16 quarts, or four gallons of total solution.

I rigged the other five gallon bucket over the stern with lines to keep it right at the exhaust output. When I started the engine I waited a few seconds before putting the bucket under the exhaust to make sure I was catching solution rather than just water. I thought about using red food dye in the acid solution so that I'd know when it was coming through, but I forgot to bring it along. Still, it was pretty obvious when the solution starting coming out, as it was awfully dark and nasty.

A box of Arm & Hammer baking soda is one pound, so I put half the box in my first catch bucket to neutralize whatever came out of the engine. A good thing I did, too, as when I was done pumping in the solution and brought that bucket inboard, it was boiling and foaming like crazy as the soda neutralized the acid.

As the solution sat in the engine, I brought the first bucket inboard and set it aside, then rigged the bucket I'd used for the solution as the second catch bucket, after first dumping its dregs into the first catch bucket.

When I fired up the engine again, the outflow was if anything even darker and nastier than before, but by the time the bucket was getting near full the outflow had cleared up to where I thought the flush was done.

I ended up with two 5 gallon buckets of the nastiest looking water I'd ever seen. There was no way I could just dump it into the creek. What to do?

Luckily, I'd read up on the reaction of baking soda (NaHCO3) and muriatic acid (actually a 30% solution of hydrochloric acid, or HCl), and it goes like this:

NaHCO3 + HCl ->
NaCl (table salt) + H2CO3 (carbonic acid) ->
NaCl + H2O + CO2

Basically what I had was a very fizzy salt solution and dirty water. I dumped it into a toilet at the marina, so that it would go to a water treatment plant where they know what to do with salt water and dirt.

The only downside of the entire procedure is that muriatic acid is nasty, and actually smokes when you open the bottle . Mine came in a plastic 1-quart bottle like bleach. It was much nastier than bleach to behold.

Still, if you dump it into the 4-gallon bucket of water and keep your face upwind, there's no problem. Once it's into the water you're OK, but I'd still keep my distance from it as much as possible. Seems to be pretty active even at that dilution.

All in all a pretty simple procedure, as long as one is careful. I think it's a lot more effective than the vinegar flush, too.

[sastanley]

Nice work and good synopsis BS.

I had a similar experience with the acid flush except that I was on the hard, so I was hanging the bucket to keep from spraying on the neighboring Island Piglet's winter cover. :rolleyes:

[hanleyclifford]

Shawn - I do hope that you guys in your neck of the woods don't say that while on board!?:rolleyes:;) Regards, Hanley

[sastanley]

Haha..Hanley, only if the owner is out of earshot. :rolleyes:

[hanleyclifford]

Shawn - Actually I was refering to the word itself. When I first stepped onto a commercial fishing vessel as a newbie I was given a no-no list: 1) never turn a hatch cover or a bucket upside down on the deck, 2) never piss on the deck, 3) if anyone comes looking for the captain you do not know anything about his whereabouts, and 4) never utter the "P" word (or any of it's conjunctions or derivatives) while on board:eek:. Don't know if it worked, but we didn't sink!:) Regards, Hanley

[Baltimore Sailor]

I had a look at that 1/8" flexible hose, and the diameter of the fitting is just too small. It looks to be only about a literal 1/8", which I don't think would pass enough water to do the job.

Next plan is to see if a short 1/8" nipple, even a closer, with a small 1/8" street el can be rotated in there. It looks like it might fit, though it will probably be a long, slow, painful rotation.

[ndutton]

Balty,
Why the aversion to removing the starter to install these fittings? Once installed you'll never have to do it again and by removing the starter now you stand a better chance of a reliable, leak free installation.

Just wondering.

[Baltimore Sailor]

I have an aversion to touching things that are working perfectly in order to get to another part, if it's at all possible to avoid. If there's room in there to rotate a 1/8" street el, I'm going to do it even if it takes an hour to get it seated (which I don't think it will).

I'm not worried about getting a leak-free installation; if I can't screw in a 1/8" fitting so that it doesn't leak, I have no business taking off the starter in the first place. :cool:

[Brett]

I am planning to acid flush the engine today while I am on my mooring. Is it environmentally safe to allow the acid solution to flow out the exhaust and into the water? Should i run some baking soda through the engine after letting the acid sit for 15 min to neutralize the acid in the engine?

[roadnsky]

I am planning to acid flush the engine today while I am on my mooring. Is it environmentally safe to allow the acid solution to flow out the exhaust and into the water? Should i run some baking soda through the engine after letting the acid sit for 15 min to neutralize the acid in the engine?

It is best if you can catch the solution as it comes out the exhaust.
Add baking soda to that to neutralize the acid.

No need for baking soda thru the engine. Just flush really well.
You may want to consider doing the PRESSURE FLUSH after the acid flush.
Many find that the acid flush breaks loose crud that finds its way to little spots where they get hung up and cause cooling issues later.
See http://www.moyermarine.com/forums/showthread.php?t=5486

[Brett]

Thanks for the feedback. When performing the acid flush, can i simply remove the hose (while keeping the intake valve closed) for the raw water intake and insert it in the acid/water bucket? What is the need for the "t" fitting?

[Dave Neptune]

There is a better way if you have the access and a pump.!!
I too use a bucket with the 30% concentration but I use a circulating pump, my procedure is as follows.
First I warm the engine as the flushing solution will work better with a bit of temp. After the engine is warm disconnect at the pump or "tee" fitting which ever is easier and hook the circulating (pond or centrfugal of some sort) to the "tee" fitting. Then disconnect the exit hose on the manifold and use another piece of hose to go from the "exit fitting" back into the bucket. Turn on the pump and watch the descalling begin. I leave it on for about ten minutes or so or until the solution STOPS getting darker. Then dump the bucket into another for proper disposal and refil the bucket with fresh water and a little baking soda and run the pump again to flush a bit. After that I just hook the cooling lines back up and run the engine for a bit to finish the flushing.
Circulating the acid solution for a bit really makes a differance in how clean the block gets.

Dave Neptune:cool: