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Old 06-27-2013, 02:39 AM
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Low water flow

Hello All,

I'm hoping for a few specific directions, having found that my water flow is significantly reduced when it should have been improved.

I'm working with an early model A4. Over the winter I was able to replace the valve springs and generally clean up and relap the valves, all in the service of resolving a stuck #2 exhaust valve. She started right up but uncovered an exhaust leak in the original Tartan muffler. When that was fixed by replacing the pipe that had rusted out, I was left with a well running, 140 degree motor that puts out little water and steams when run hard. The throaty roar is new. I don't remember the flow being so low but I can't say I ever measured the quantity before. She now moves 5 gallons of water in 7 minutes. I noticed a dribble out the tailpipe when the engine was off but there was a gallon sitting in the bucket draining into the engine.

She has the Indigo thermostat, which I think is working OK. I checked the strainer and the flow into the open pump body from the throughhull when it was open. The head and the manifold were tank cleaned and pressure tested before reinstallation.

I went to use the MMI Manual's directions for flushing but I cannot find an aft cleanout plug. Accessing the forward cleanout plug is going to require removing the starter motor, which I would rather not do unnecessarily.

So, I am looking for other ways to improve the flow, assuming that I have to clean up the obstruction which has developed and hoping to avoid removing and rebuilding the water pump which worked fine before all this was done. I'm thinking that if I disconnect the hose that runs from from the thermostat to the water pump output, plug the opening to the thermostat and use the hose that normally goes from the thermostat to the muffler to connect the thermostat to the water pump output with a small pump inline, then I can circulate water under some pressure until the obstructions dissolve. Or I can plumb a garden hose into the water pump output and watch all the water come out of the tailpipe. This would force water into the block through the usual plate and circulate it or run it out the muffler and the exhaust pipe. I think the only risk is the water backing up the exhaust into the manifold. However, that seems unlikely because it would have to rise over the hot section of piping to come back through the manifold to get into the cylinders.

Looking for some direction before I start replacing the muffler or rebuilding the water pump, hoping that some easily removed obstruction has been dislodged.

Tartan 27
Providence, RI
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Old 06-27-2013, 02:48 AM
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romantic comedy romantic comedy is offline
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Did you check the impeller? That is the first thing to do.
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Old 06-27-2013, 08:20 AM
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Have a look for leaks as well. Worked on one this spring that had a small leak around the impeller cover. The guy said "that's not much of a leak...that can't be the reason". I put a new gasket and tightened it up and discharge returned to normal.

1976 C&C 30 MKI

The pessimist complains about the wind.
The optimist expects it to change.
The realist adjusts the sails.
...Sir William Arthur Ward.
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Old 06-27-2013, 10:34 AM
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I have rechecked the impeller. No cracks or stiffness. I can replace the gasket but I don't see any leakage.

Is there a quick way to test the pump output?

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Old 06-27-2013, 11:56 AM
hanleyclifford hanleyclifford is offline
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The first thing I would do is bypass the thermostat arrangement to eliminate it as a suspect. Then, working backwards from the water to hot section injection fitting, remove and clean each connection. Don't discount the possibility that the obstruction is deep in the manifold cooling chamber itself.
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Old 06-28-2013, 09:47 PM
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Oh yeah - low coolant flow.
For starters, I'd disconnect the hose from the pump outlet, add a secondary hose directed to a bucket, then run the engine for a minute and see what you get. I'd expect about a gallon at idle..
Next, disconnect some hoses and try blowing through the individual parts. Is the block clear? Is the manifold clear? Is the exhaust clear? The part you can't blow through is VERY suspect. My prime suspect for blockages is the manifold outlet..
Oh yeah, take out the thermostat for starters. You can always put it back.
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