Request advice with stalling engine

[jbsoukup]

IMHO #1 replace the coil - easy to do and relatively cheap.They are hard to test for heat related failure (you would have to first heat the coil to what temp?) #2 pressure test exhaust manifold - where else is all that coolant going if not inside or outside the engine

[Jon K]

More data points

Thanks to all of you for following up on this thread.

I finally got some time to continue gathering information, including what a Schraeder valve is, and why not to buy a bicycle pump at Walmart.

Here is what I know:

1. Engine loses coolant during regular use.

2. Engine stalls after 45 minutes to an hour of full speed, will not restart until it cools again.

3. Exhaust manifold cooling jacket holds 20 pounds of air pressure for 20 minutes.

4. Block cooling circuit from Obendorfer freshwater pump output hose to thermostat output coupling, with no thermostat, holds 22 pounds of air pressure for 20 minutes.

5. With the heat exchanger cap off, there are visible bubbles in the freshwater coolant, frothing when the engine revs to 2000 - 3000 rpm.

6. Freshwater pump looks good -- newish impeller and I sealed the gasket and tightened the screws.

7. Thermostat housing looks good -- cleaned and sealed the gasket, tightened the nuts.

8. Oil looks good -- no froth or other indication on the dipstick.

9. Cold compression test looks good -- no liquid, 90 - 105 compression.

10. Coolant hoses look good, and circuits test with good pressure.

11. Plugs are carboned, but mixture is rich.

So where is the steam coming from, and why does it lose coolant? At the beginning of this testing cycle there was no water or coolant in the bilge. Now of course there's lots because of changing the hoses and so on.

Where do I go from here? I could pressure test the heat exchanger, take her on a test run, or do the head gasket.

Is the head gasket a lot of work? I have access to the engine top and a few tools. The head bolts or nuts are rusty but I think they would come off.

If so, do I have the head machined or just add silicone to the gasket, or put new gaskets?

If I pressure test the heat exchanger freshwater circuit I might find air coming in. I could also replace all the hoses, although they and the heat exchanger look very new and clean.

I did hope that Neil was right about the exhaust cooling sleeve, but it holds tons of air. I got a tire valve stem, put it in a hose and clamp, and clamped it on. The other end I got a garden hose nipple, clamped it into a coolant hose, and added a garden hose close cap off my sprinkler to close it up. It took two tries tightening up until it held air, but the block cooling circuit and the exhaust manifold cooling circuit are tested without leaks. So I think it's not a cracked block, at least when cold.

Thanks in advance for your advice,

- Jon K.

[ndutton]

Your pressure testing indicates a sound block and manifold. I wouldn't touch the head gasket given these tests and your reported compression. The heat exchanger is next, cap on. It and the Oberdorfer FW pump are really the only components left.

Sounds like the coil is shot too.

Great testing and report. It's nice to have solid information.

[Mo]

I`m with Neil.

My thoughts as well Neil and that sounds like it if there is no engine performance problems.

[Jon K]

Day 3 of 7

So if I close the saltwater cock to heat up the engine, where does the steam come from?

1. Pressure test of FW side of heat exchanger failed. It won't hold 5 pounds of air pressure.

2. Going to sail today, visiting friends cabin on Gambier Island. Change hoses to send raw water pump output to freshwater pump inlet, through engine to exhaust manifold cooling jacket, change hose to send manifold outlet to exhaust. Two pumps, lots of cooling. Engine at or below 100 degrees.

Voila, raw water cooling. Left the thermostat out so temp never got beyond 100 degrees. Checked that water temperature gauge sending unit was still in the system, it is beside the thermometer housing and reads correctly.

3. Ran under power for 1 hour, stopped then ran again for another 1 hour. Dropped to idle to lower mainsail, engine stalled. (Stall on idle is ongoing problem). Engine temp read 140 degrees. Possibly less cooling during idle, engine still hot?

4. Waited a few minutes, engine restarted and ran fine for another 20 minutes, had dinner. Came home 1.5 hours, engine temp 100 degrees, no issues.

Stall on idle problem happened at 2 hours, engine temp 140. When engine was cool, did not fail as before. I think this points to a temperature related problem.

Neil, the cold coil resistance is 3.1 ohms. I just read the coil thread, will try to think about that. Measure when hot?

Great to be on the water today/tonight, full moon guided us home. Trying not to think about the saltwater cooling the engine.

Answer: Steam caused by freshwater and antifreeze pushing into the saltwater circuit at the exchanger and out the exhaust. Seems a likely scenario.

- Jon K.

[ndutton]

Great post Jon

You have it surrounded Jon. Install a new heat exchanger and the cooling system issue is resolved. Nice work with the pressure testing. It took you directly to the problem without guesswork.

Your coil seems to be Okay although I'd still like to see one of slightly greater resistance for longevity (suggested on principle only). Given your history of shut downs I'd change it anyway.

As for the occasional stalling at idle, at what RPM do you customarily idle in gear? This could be as simple as a minor adjustment. Dare I ask, do you have a PCV valve installed?