The Stovebolt Site Forums The Shop Area Engine Shop Should I Change Ol' Roy's Name to Christine?

As you know, Ol' Roy has been overheating severely and rapidly. Temps went easily up to 120+ and boiled out the coolant. This would occur while idling in the driveway relatively quickly.

A fluid test on the radiator was somewhat ambiguous but indicated that there may be a small leak in the head gasket allowing exhaust into the water jacket.

Anyway, today I started it up and let it idle for well over thirty minutes. The Temp never even hinted that it would rise above 180. I decided to run some errands and put about 20 miles on the truck on local streets and interstate. Not once did it creep above 180. In fact it was even at 179 a few times.

Since I planned on pulling the head, etc, I never refilled it with ethylene glycol, just plain water. (just a refresher - new pump, T stat, radiator cap, boiled out radiator)

In the immortal words of Slim Pickins, "What in the Wide Wide World of Sports is a goin' on here?"

How much of a drop in local ambient temperature, between then and now?

Maybe 10 degrees. I don't think that is the reason, though. When the truck was overheating in the driveway, it did it when temps were in the 70s as well as the 90s. It's currently 77 right now.

And when I say it didn't even hint at going over 180, I mean it didn't go to 185, 181 or anything else that would be deemed acceptable range.

This is how it always used to run regardless of outside temps. That includes 98 degrees on the downtown connector during stop and go rush hour traffic.

Sounds like the thermostat and pressure cap are doing their jobs, and water passages are clear.

Might want to keep running clear water coolant for a while and drive it for more check rides.

The viscosity of water and water/glycol is a lot different.

If you want a test that is closer to 1:1, fill it with proper coolant and run it.

I understand that. However the over heating occurred both with a 50/50 mix and with pure water. And the engine ran just fine on a 50/50 mix prior to the initial overheating event.

Subsequent to the second overheating event, it has had nothing but water in it since I didn't want to waste coolant. And it continued the same overheating behavior. So I don't think that the viscosity of the coolant mixture was the cause of the overheating problem.

Sounds like you have driven the truck quite a bit since the first boil over event.
I suggest that you pull all 6 spark plugs and lay them side by side and look for a clean one. The clean one will have been steam cleaned.
That will tell you which cylinder is leaking water.
This test is as easy as as it gets.

Old fashioned water injection setup.

Before the first episode, no coolant loss was experienced. Since the truck has a plastic coolant reservoir, it's easy to see if the level is dropping.

After the first incident, the cooling system was pressure tested with water at 55psi. No loss of pressure was observed and no water was found in the cylinders.

I'll pull the plugs and have a look-see but again there is no visible loss of coolant and no steam from the tailpipe.

Not saying this is your problem, however:

If it were mine I would replace the thermostat. I have had more than one thermostat stick; and then decide to work, and then at the worst possible time, stick again.

Jon

Thermostat was already changed. I also tested the thermostat that was in it when this all began by putting it on a stove in a saucepan of water. It worked perfectly. I replaced it anyway.

I drove it again yesterday for 15 or 20 mi no problems I drove it today for a short test drive of about 8 mi to warm it up for another block fluid test. In this case the fluid didn't turn green or yellow but stayed blue for over 15 minutes and the engine was running for well over 30 minutes both idling and driving and the thermometer never got above 180

52 carl,

prior to my little block test a few minutes ago I took out all of the plugs and check them not a single one showed any evidence of being steam cleaned. I have pictures of all of them but I can't post them from my phone and for some reason my phone will no longer download pictures to my computer.

Any new ideas as to what was or is going on?

When I performed the block fluid leak test the first time - while the engine was still over-heating if you looked at it sideways - the blue fluid turned green. I performed that test twice with the same results.

This indicates, according to another forum member who experienced a similar "green not yellow" color change, that there was exhaust gases entering the water jacket through the head gasket or crack or whatever.

Now that the engine is not overheating, the same test indicates that there is NOT exhaust gas leaking into the water jacket.

How can this be?

For whatever reason, apparently the exhaust gas leak into the cooling system has stopped / sealed. And it doesn't repeat the problem.

Declare victory and drive on!? At least for now.

Yes. I do intend to start driving it again and monitoring the situation closely. I don't like not knowing the cause of problems, though.

Next up is pulling the speedometer and repairing/replacing it.

Could running straight water allow a small crack to rust shut???

Mike B

You mean like a small crack in the block or head between an exhaust port and a water gallery? I hope not but maybe so. i guess I'll find out when I refill the engine with coolant (after I redo the JB Weld patch near the petcock with Marine Tex).

Sometimes, when an intermittent problem occurs which presents no clue as to what is wrong, we just need to drive it. The problem will likely get worse to the point that the cause will expose itself.
I have a '49 with a shimmy in it at 60 MPH after 2,000 miles of flawless driving at 70 MPH on the highway. It has all new everything, carefully adjusted to specs. It is not a death wobble, but I find it unacceptable. I can't find what is causing it so I plan to just drive it until it gets worse in hopes to find the cause.