But what temp did it open at? Boiling water 212F approx, quite a bit higher than the rated 195.

Try again with your old thermostat and let the water heat up with the thermostat already in there. Monitor the water temp with a thermometer and see at what temp it starts to open at and what temp it is fully open at. Then let the water cool and see what temp it closes at.
Try this a few times and see if the open and closed temps are stable. Make sure the thermostat and thermometer don't sit on the bottom of the pot or it will skew your results.

I did this when I had a wildlyfluctuating temp gauge with a 180 thermostat. Turned out to be a junk thermostat that never opened and closed at the same temp. I reused my original 195 which actually opens at 199-200. works for me and gauge is stable.

 

Well, this is odd. I put the old t-stat back in and now the temp gauge went to 200ยบ today and then dropped between the '2' and the '0' versus pegging between the zeroes in 200. It was about 35ยบ and she stayed below 200ยบ. I wonder if it had to do with my filling the upper radiator hose, clamping it to the radiator, and then filling the radiator, yesterday. I had let it run for a while and as soon as the level started to rise I capped it. I even checked the upper hose after a bit of driving and it didn't burn my hand like it normally would.

I'll see what this does for a couple of weeks and report back!

 

It looks like I fixed the problem. The past two mornings have been very cold on the morning drive (between 25ยบ and 34ยบ) with this morning being the lowest. The needle pretty much stayed on the '2' on the temp gauge, whereas before I had performed this repair it would have rocketed past the mark above the first '0' on the gauge. I consider this morning's reading accurate and expected as colder weather make keeping a V8 warm a challenge. So, SUCCESS!

Tomorrow I have plans to pick up my new daily driver, a 1971 VW Super Beetle. Once I get it running I'll be saving funds to get the transmission rebuilt in the Dodge, after which I will put the 2-core radiator back into the truck. Thanks to all who offered suggestions.

 

Figured I'd resurrect this thread from the dead as I never really resolved the issue of my truck running hot.

To recap, at various times, and especially under load, my truck runs hot -- hot as in coolant spits out of the overflow and the overflow is filled with coolant. Also, even after having cooled off, the coolant is not sucked back into the radiator as it should.

Earlier this year, I took the truck to a local mechanic who diagnosed the truck as having the timing too far advanced, the solution of which is to have the PCM reprogrammed. Recently, I took my truck back to the shop that rebuilt/upgraded my transmission for the 30K mile service. The tech there recommended another shop, which is local to where I live. I chatted with the owner for a few minutes regarding my problem and he insists that I have a bad head gasket. He mentioned that there is a chemical test he can run which will tell him inside of 10 minutes if chemicals from the combustion process are present in the coolant.

BINGO!!!

I told him I was aware of this test and that for a few years I've been asking shops around here who does it, only to have people look at me like I have two heads. This gentleman's response was that there are "only about 10 shops in the whole state that have a clue. All the other guys are idiots." He further stated that there's no way in hell the timing is off on my truck and even the tuner programs won't touch the timing. His explanation of the head gasket is that there's some type of micro-fracture that's allowing combustion gasses to leaking into the cooling passages which then results in super-heated coolant. The resulting pressure causes coolant to fill and subsequently shoot out of the overflow.

I'm assuming that he is correct and that I do have a head gasket issue, but I'm waffling over whether or not I should address this right now. The problem is that I'm already planning to pull the engine sometime next year and go through it again, the reason being is that I was rather rushed when I performed the initial rebuild and would like to be more thorough the next time through. While working on the engine I was also planning to pull the body and bed from the frame and perform a thorough "ground up" on my truck. Even though it has 213K miles on it, I really like the truck and have no desire to "upgrade". Everything I've been through is testament to the 318's hardiness.

But, there's a problem. I'm planning a trip to Colorado Springs to pick up a car, and doing so means the truck will be running hot dragging the trailer. I'm leaning toward biting the bullet and installing new head gaskets (assuming the chemical test yields a positive result) to be on the safe side. I'm also debating on stroking the engine to a 383 when I go through it a second time.

Thoughts, ideas, suggestions, and observations are all appreciated.

 

I just can't get a grasp as to why a head gasket would do that.. If it's blown in that manner, then it would do it from that point forward regardless of 'load' or not, right? Once the h2o finds a gap and infiltrates, that passage will be expanded and will never 'seal back' on it's own, using the same theory of water and cracks in rock, and all that jazz..

I haven't read this entire thread.. Without, can I ask a stupid question? Have you ever ran differing types of coolant through it? If so, some of those coolants don't like each other and make a nice little gel at the right temperatures.. It makes perfect sense to me that a flush, no matter how thorough, would still leave enough to have a wad of that junk floating around in your system, which if it hits the right temperature turns into a nice wad of sticky gel.. which could contribute to slower moving fluid, which contributes to not dissipating heat as you would want it to..

I'm curious to see what comes of this.. I'm likely way of base- but I just can't get a grasp on a gasket that gives when it wants to and then reseals.. I've been wrong before though.

 

It IS a condition that will get worse over time, but, really isn't out of the ordinary for a head gasket/cracked head condition. Probably what is happening is, the area of the crack is only stressed enough to start leaking when there is a sufficient load on the engine to heat it past a specific point. Trouble is, that point will continue to get lower and lower as time goes on. (or, it may just reach a breaking point, and then you will see combustion chamber pressures in the cooling system as soon as you crank the engine..... not a good scene.)

Run the test, see what the results are. If the result is positive for a problem there, good possibility you are going to need to replace your heads.... (they are notoriously weak from the factory.....) I do believe this IS something you should address before subjecting your truck to a low stint of towing.... If you replace the heads, you can always swap them over to the new motor, when it gets to that point.

 

when the enging is idling, the combustion chambers don't go through as much pressure. THe engine does not have to work hard at all to turn.

Here is a test:
1. Try to turn your engine in park/neutral. Note that you can do it.
2. Now try to turn your engine with it in first gear.

Other than #2 being impossible, you realize that the necessary force exerted to move your truck is transferred FROM your combustion chambers to the pistons...to the crank...through the tranny, through the axles.....

I know of this because I had a blown main. It was fine at idle. But when you step on it...it busts oil out of the timing chain cover and oil pan (SBC)

 

Heads are good. I upgraded to beefy aftermarket heads with all new valves when I rebuilt my engine.

 

Now how messed up would it be if you just had a bolt or two on one of the heads that simply lost a little torque and the gasket was fine.

 

Mayhaps... but I've never seen a blown head gasket on a Chrysler small block cause overheating without also putting the unmistakeable smell of exhaust gases into the cooling system. One quick sniff with the cap off tells that tale.

All of the coolant you push out while the engine is running must be replaced by whatever is pushing it out. If it's combustion chamber gas, you should be able to smell it.

Whatever else he knows, he doesn't know tuners. They all twiddle target fuel/air ratio and timing, every darn one of them, even if they touch nothing else. The primary difference between economy and performance tunes is the target mixture and the aggressiveness of the timing advance curve. A richer mixture will get you only so far, and certainly won't make the 25% increase in horsepower that an aggressive tune can pull out of one of these old beasts. To get that, you've gotta crank the timing up to get the additional fuel burnt before the exhaust valves open -- throwing more fuel at the thing than it can burn in the time it has to do it will only heat the catalytic converter (or make your exhaust stink of unburnt fuel if the cat's gutted or gone).

All that said: If you're not getting spark knock or detonation, then your air/fuel ratio and ignition advance can both be ruled out.

That part is correct in gasket fractures can and do happen -- but incorrect because the leak would be caused by pressure leakage, not superheating. Have you hit 226F (assuming good coolant at 50/50 mix) without boiling? If not, you're absolutely not superheating. I'll be astounded if you can even even make superheating happen in a gasoline fueled internal combustion engine.

If it's happening in a Chrysler small block without exhaust aroma in the radiator I'll be very, very surprised and will publicly eat crow for my previous statement.

Mystery overheating with a (properly sized) known good radiator and water pump is almost always blocked passages somewhere. An infrared camera will usually tell the tale writ so large that anyone can see it if he's got a known good reference to compare to. That damned Bar's Leaks is famous for causing this because it often totally plugs the lower water jacket so the oil is not cooled as much as it should be on the drip path down to the pan. Aluma-Seal is somewhat less likely to cause the same kind of problem, and when applied properly it's not as likely or pronounced, but it can do it, too. Similar products, similar problems.

Have you ever seen coolant leaving the overflow reservoir, leaving green puddles when you park? If not, and it's not showing up in your crankcase oil or transmission fluid, it might just be a stinky little pinhole leak somewhere. Logically, if it ain't going in, it's coming out.

This is an interesting problem, I think, since it's not me who's got to hunt it down and then pay to fix it.

If you get a positive result, by all means go for it. Would you rather pull the engine in Norman, or in Hamilton, CO? No matter what it is, it's cheaper and easier to fix it at home.