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  #1   IP: 192.0.216.133
Old 06-18-2021, 02:03 PM
mboulay mboulay is offline
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help with water in cylinder #4 and in oil

Hi everyone,
I'm a new A4 owner (late model, 1977), definitely not a mechanic, and have been trying to find the source of water in my oil for a couple of weeks. I recently found that cylinder #4 has a tiny bit of water and isn't firing. I've read through all of the threads I could find but still stumped. Here's a summary:
* When I launched the boat this year (this boat, and any boat, is new to me this year) and checked oil, it was milky
* I have pressure tested the water jacket in the block, to 20 psi for an hour, pressure in through the water pump outlet and capped at the thermostat outlet to the manifold. Also pressure tested the manifold water jacket to 20 psi for an hour. No leaks.
* I changed the water pump to an MMI one, since the old one was leaking through the weep hole
* I also cleaned up and changed the gasket on the reversing gear cover, there was a lot of milk whipped up in there, and the old "gasket" looked like it would have let water leak in through the cover.
* I checked all of the exhaust, thinking that may be it. It's all in good shape with no blockage anywhere. Maybe a bit of a non-standard installation since there isn't a lot of room for vertical runs near the exhaust manifold. I made up a diagram, attached here, but I don't think this is the source of the problem. Have also tried iterations of closing the water through hull right after shutdown, but no change to water in the oil.
* I have changed the oil 8+ times, every time after making a change to some part of the engine, and it is still milky
* There isn't a lot of water, I can't notice any increase in the level at the dipstick after idling for 30 minutes or so, but there is enough to change the oil to milk
* There is a bit of water (a drop or two on the plug, and a few drops if I crank it out with the cylinder open) in cylinder #4, and that cylinder isn't firing. I *think* there is spark getting to that plug, but I have yet to confirm that directly. When I pull the spark plug wire while the engine is running, there's no change to idle, but there is a bit of discharge between the wire and plug when I pull it off. The plug has been dried/cylinder blown dry several times attempting to get cylinder#4 firing. I did have to clean up the inside of the distributor cap, which was corroded, and it looks like #4 had not been making contact (but it is now)
* Measured compression, around 100 +/5 psi on cylinders 1,2,3, and 65 psi on cylinder 4 (that goes to 75 with MMO in there)

That's about the extent of what I can test on my own. I spoke with a local mechanic who's an expert on A4's and he thought it was almost certainly a blown head gasket, although I don't know how that can be consistent with my block pressure test. I was thinking maybe a stuck valve could lead to low compression/not firing, and that could then lead to a bit of backstreaming water from the exhaust. I'm not sure how I can test that.

Mechanic also suggested that I could keep using the motor for the season, keeping an eye on the oil, and then change the head gasket once the boat is out.

What do the experts think? Is there something else I can (easily) check or do, short of opening up the engine?

I can also add that the engine temp was around 140F at idle, now it's around 120F or below with the MMI water pump.

Thanks in advance for any advice!
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  #2   IP: 104.174.83.118
Old 06-18-2021, 02:28 PM
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Your test results and diagram strongly suggest to me water incursion up through the exhaust. As a result of a recent case study (not yet published on the forum), engines with minimal hot section rise and side inlet Centek mufflers are particularly vulnerable. There are other factors such as muffler position (boat centerline or off to the side) and inlet orientation (parallel to the boat centerline or not). Also, I did not see anti-siphon protection on the hot section water injection loop in the diagram.

It sounds to me like your mechanic is ignoring the successful block pressure test result. If you're going to ignore the result, why take the test?
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  #3   IP: 192.0.216.133
Old 06-18-2021, 02:53 PM
mboulay mboulay is offline
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Thanks for the reply. The exhaust is about a foot and half to port off of the centerline, with the inlet to the muffler in the fore-aft direction (shown in the attached). All of my issues have been in the slip, so without heeling. I assumed the exhaust design would be OK since this is how I got the boat and everything seemed pretty well maintained. Correct that there is no anti-siphon valve. Is there a way I can test the setup, or would you suggest I add an anti-siphon and increase the hot exhaust height and see if that fixes the water ingress?

Mark
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Old 06-18-2021, 03:56 PM
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Anti-siphon is an absolute must and maximizing the hot section riser is to your advantage. Even if these items are not the problem there is no downside to making them better.
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Old 06-20-2021, 07:11 PM
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Anti-syphon in the line to the water injection can't hurt.
Your pdf diagram makes me wonder why the water lift unit isn't lower.
Is your water lift piped correctly? Inlet to the can should be high. The interior outlet fitting should be low in the can so not much water builds up. The water from the exhaust should be coming in batches. Water collects in the bottom of the water lift unit while exhaust pressure builds up. Then a batch of water/exhaust gets expelled, and the cycle starts over again.
If piped incorrectly you'll get a steady mix of water and exhaust from the transom.
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  #6   IP: 155.186.122.195
Old 06-20-2021, 09:32 PM
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I saw that the block had been pressure tested, correct? If so was the manifold included in the test? If not and as you stated things did look good so we can assume it was running fine before. A pin hole in the manifold can and often does pick on the #4 as does the exhaust.

Keep the cylinder dry and lubed.

Also try turning off the water and in 3~5 seconds shut her off, should keep the exhaust water at bay until resolved. Won't hurt the water pump.

And yes the anti-syphon is a good idea. just as "high" as you can mount it.

Dave Neptune
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  #7   IP: 192.0.216.133
Old 06-26-2021, 05:45 AM
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Hi everyone,
Many thanks for all of the great advice! I checked inside of the waterlift muffler by disconnecting the hoses and looking in. It seems to be piped correctly. The water does come out in batches when running. Would be better if the muffler was lower, I think it was just easier to mount it where it currently sits since there was already a "shelf" there to hold the fuel tank.

I did pressure test the manifold and block water jackets separately, both were good.

Since the first post I added an extra ball valve between the raw water intake and the water pump so that I could open/close the inlet water from the cockpit, and found that if I open the valve 5 seconds after starting the engine, and close it 5 seconds before shutting down, I no longer get water in cylinder #4 or in the engine. After a bit of testing I believe the water was getting in only on startup, so it had to be splashing from the water inlet line in the exhaust back through the hot exhaust pipe and into the cylinder, while cranking, just before the engine started. This is different from what I read in most other posts, where the potential issue is usually seen as water flowing back through the exhaust due to gravity - in my case it had to literally be splashing at the injection point. Took me 15 oil changes to get that sorted, but I now have a new MMI water pump, and not a single drop of anything where it shouldn't be.

Now that I know what's going on I will rebuild the exhaust properly to prevent that from happening - higher rise in the hot section and water inlet much further downstream. It's only a matter of time before I forget to open the cooling water ball valve with the current setup, so I don't want to run that way. Now I just need to get cylinder 4 back up and running, since it has likely been seeing water for some time. I'm hoping it's just a stuck valve, but will see.
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  #8   IP: 70.67.6.75
Old 06-27-2021, 06:56 PM
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Well, I'm no "expert" but what jumps out at me is the height of the muffler and the injection point. IMHP I would suggest moving the muffler down as low as you can get it and make sure the injection point in the hot section is a minimum of 4" below the exhaust manifold. An of course be sure to have an anti-siphon valve at the high point of the water exit hose.

Chuck
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Old 06-27-2021, 07:20 PM
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What I see.

What is the boat? That underwater muffler is pretty much level with the top of the manifold if you eyeball it. I have a C&C 30 and my underwater muffler is much lower...down hard on the bottom of the boat.

I realize you just picked up the boat....that exhaust looks like it will work fine for someone motoring, but once on a decent heel, well, that muffler has no trouble sending water back at the engine.

Worked on a boat the year before last with valve problem on number 4...fixed that for him. Last spring, had an issue with the same one. I looked at his exhaust and knew it couldn't be right. He swore it was...I swore it wasn't. So I told him I'm not working on it until he fixes it to what I say....so he broke down and did it. Fixed the issue, no problems since. Small mistakes make big work when it comes to exhausts.
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Old 06-28-2021, 01:02 AM
JOHN COOKSON JOHN COOKSON is offline
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Quote:
Originally Posted by mboulay View Post
. The exhaust is about a foot and half to port off of the centerline, with the inlet to the muffler in the fore-aft direction (shown in the attached). All of my issues have been in the slip, so without heeling. I assumed the exhaust design would be OK
siphon and increase the hot exhaust height and see if that fixes the water ingress?
Mark
If you can have the riser or part of the riser at or across the boat's centerline it will be equally effective on both tacks.

ex TRUE GRIT
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