water logged A4

[breweraz]

A week ago Friday, I went out to the mooring and ran the motor for 3 hours to charge the batteries. During this time there were no issues. The motor started great, ran strong, (between 1000 - 1200 RPM for charging).

The water temp was not coming up so I open one of the return water lines that cycles engine water back into the intake side. The temp went up to 160 and was stable.

When I turned the motor off i checked the water strainer, as I had not opened this valve this summer, to see if any crud came through. There were a few rust particles.

While running the motor I notice a small exhaust leak on the bottom side of the exhaust flange. We are a month away from haul out so I bought some exhaust putty to plug the leak and left it sit overnight.

The boat started the next morning with no problems and I let it idle to warm up. I started to head out running at 1500 RPM under power. I noticed that the engine started to heat up faster than usual as it usually takes 45 minute to 1 hour to reach 150 -160 degrees. She had a knocking sound like spark knock and I turned her off.

I started checking the usual issues, clogged intake,clogged water filter, impeller etc and nothing seemed to be the issue. I sailed the boat back to the mooring ball. The motor was cool so I started it with the sea cock closed. It started right up with no problems. I left the motor in low idle and took it to the dock (2- 3 minutes.) She ran fine. Once secured to the dock I turned the motor off and let it cool off.

After 15 minutes I started the motor up with no problems and open the sea cock. It ran for a few minutes than shut off. The motor would not start. I pulled the plugs and there was water in all four cylinders.

I took off the water pump cover and drained the block of water, pulled each of the plugs and placed my thumb over the spark plug hole and turned to motor over with the key. I repeated this for each of the four cylinders. There is enough pressure in each cylinder to push my thumb off. I turned the motor over to push as much water out and tried to start it but it would nto start.

I had to clear the dock and it was getting late so I poured some oil in each
cylinder hole and thumb tightened the spark plugs by hand.

Some other history.

In May when I brought the boat down from her winter hard I started the engine in the harbor and forgot the sea cock. I overheated the motor. I used this to event to change the oil (again), replace all of the water lines, the wet exhaust line and the Vetus water lock.

The motor has run very strong over the summer. I have logged over 1300 NM this sailing ME including over 100 hrs of motoring. It has not given me any problems. It starts very quickly and has run strong. That is why this was such a surprise.

The only things that were out of the normal or different was

1. Plugging the exhaust leak at the exhaust flange - this may have created a new pressure point and caused a failure of the exhaust gasket or head gasket at a different place.

2. Opening the return line to the cold water intake - this may have pushed some debris through the system causing a block. if the block was at the mixer loop than some water could have been forced back through into the exhaust.

Following Don's list of causes I can rule out cranking as the engine was running when the problem first came up and ran with the seacock closed. It failed when I opened the seacok when it was running.

The compression is the cyclinders all seem strong using the thumb technique

I will next try the pressure on the exhaust head and hope it is not the block.

Any other thoughts are appreciated or a lead on a A4 mechnic in midcoast ME that would come fix her up as AZ is calling me home.

Tim

[hanleyclifford]

This "return line to the cold water intake " is interesting. Could you be more specific about where it actually connects?

[rheaton]

You might want to check your anti-siphon valve.

[breweraz]

return line

This is an early model motor with no thermostat. Where the water exits the block on the exhaust side there is a T. One lines goes out to the exhaust mixer and the other lines connects into a T at the top of the seacock so it feeds hot water into the cold side of the circuit. This line is controled by a ball valve.

Hopes that helps.

Tim

[hanleyclifford]

From the description of your recirculating loop it sounds like the water did indeed come back to the cylinders via the exhaust mixer. When an engine is shut off some expansion of the water in the block can occur. Also depending on the relative heights of these components, some siphoning could be taking place internally especially if the bypass valve were left open. This addresses #2 on your first post. So why did this happen now? Now on to the #1 on the first post. The exhaust leak that you repaired could have been fulfilling one or two functions. 1. It may have provided an air leak to break the siphon circuit or 2. It could have provided a path for the water to get to the bilge and not the engine.

[rigspelt]

This is an early model motor with no thermostat. Where the water exits the block on the exhaust side there is a T. One lines goes out to the exhaust mixer and the other lines connects into a T at the top of the seacock so it feeds hot water into the cold side of the circuit. This line is controled by a ball valve. Hopes that helps. Tim

Tim, does it look like this? I did this drawing for a recent thread where the gang discussed coolant flows. I don't have an early model A4, but they said the drawing is typical.

[breweraz]

The diagram is close. Where the cold water enters the block there is a T. A hose loops around the front of the motor and connects back into t just before the mixer. That line has a ball check valve to control the water flow. It is left open all the time. I will be working on her this weekend and was going to start with the mixer anti syphon. Valve as well.

Thanks

[ndutton]

Is there any harm in plumbing the system like the late model engines, thereby eliminating the thermostat and return line? A line from the diverter going to a T in the crossover loop with a ball valve midway would nearly mirror the later engines. Temp would be controlled via the ball valve.

That return line is bugging me. If there's no anti siphon valve in it (or one not functioning properly) and the thru-hull were left open it looks like an open invitation to a flood.

[Dave Neptune]

No syphon?

I tend to agree with Niel in that the leak in the exhaust was your "anti-syphon" function of the cooling system.
Where does the engine sit related to the waterline? If it is below the waterline I don't see how it would work without a anti-syphon valve set up. If it is above the water line youu should be ok.
There are probably a couple of ways to route the water system to eliminate the thermostat, but if the lowest exhaust valve is below the waterline you will need an anti-syphon valve.

Dave Neptune

[hanleyclifford]

It sounds like some one has built into your early model engine one of the worst aspects of the late model, namely the "T" fitting at the water jacket side plate. The diagram Rigspelt posted shows a 90, but mislabeled as a "T". I would not rely on a check valve. A better configuration is to run your bypass from a "T" at the aft end of the manifold. Use a ball valve in that loop.

[keelcooler]

Sounds like you have two temp control systems. Both have ball valve controls and no thermostats. I prefer the full flow early system that Niel has displayed. You do not need or want both. When you replaced the exhaust hose and vetus did you inspect/clean the mixer? The boys are correct you must install a vented loop in that type of system. I want to know more about that manifold external leak. Is the rear manifold leak a rusted out area or a horizontal freeze type crack. If it’s leaking externally it could be leaking inside dumping down into the exhaust ports. You can pressure test the manifold water jacket to eliminate this cause. Is your patch holding up?

[rigspelt]

The diagram Rigspelt posted shows a 90, but mislabeled as a "T".

Aha - I had drawn the diagram for a late model first, then modified it for an early model, and did not change that label. Will do so.

[breweraz]

I added the lines to your diagram that show how my water system works, The blue ball and handles reflrct the location of the ball type check valves.

[breweraz]

update

I got the motor running today. She started right up after the water was cleared out of the cylinders and the carb, If I turn off the motor with the seacock open it dumps water back in the cylinders and carb. The oil has no water in it.

If I shut off the seacock and let the motor run and pump out the water for 1 to 2 minutes there is no water on the cylinders and she starts up fine. She runs strong and across all power ranges.


The mixing chamber is the old Westerbeke chamber and is well above the water line. The motor is below the water line.

Yes the exhaust patch is holding.

[hanleyclifford]

I would be interested to hear the reasoning behind that loop at the front of the engine. It seems unneccessary and if the valve is left open has the potential of admitting water to the combustion chambers.