Like a bomb went off under the hood...

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Hemihead2

Hemihead2

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I let a day or two pass before writing this because I still don't know what happened. Here it goes...

Our 340 doesn't get run much, in fact it only gets out at most once or twice a year usually it just sits in a climate controlled garage...As such, I began to notice a considerable amount of antifreeze had built up (crystallized) around the intake water neck. Two weeks ago I took the car for a drive and lo and behold it began to overheat badly...So much so that it was getting blown out of the overflow tube and trailing on the ground into the driveway. I looked at the temp guage (factory) and it was nearly spiked. I blew water through the radiator with a garden hose and finally got the temp down and I parked it. Later I pulled the thermostat and found it was completely corroded...Last Saturday I replaced the thermostat and the water neck housing with another one that I had laying around. I cleaned everything up and even used a new band clamp instead of the factory squeeze type that was on it to safely secure it (or so I thought). I filled the system, took it for a short spin around the block and brought it back home. Once it cooled down I topped off the radiator and took it for a 2 mile trip....bad idea. About 1/2 way into it after it had reached operating temp I noticed the gauge was creeping up once again (ambient air temp was 80*) ....by the time I got it home it was holding steady but up in the range... I coasted the car into the driveway and let it sit- engine off...A few minutes later all hell broke loose...There was a small explosion under the hood and the steam began to roll. The force was unbelievable. It turns out that the top radiator hose blew off at the water neck and spewed antifreeze all over the underwood area...and I mean everywhere! I can honestly say it was so violent that if the hood had been open at the time I would have been scalded badly...The car runs and accelerates, no miss, no antifreeze in the oil, no leaks.

So here I am....asking for help. Has anyone ever had this happen before? The car was completely restored in 2001 with everything new or replaced. I have a 160* T-stat in it with a flow-cooler water pump, radiator was recored, etc. In the early years after it was restored we had drove the car well over 100 miles one way with no issues. Where do I begin? Collapsed lower hose, plugged radiator? HELP!
 
The radiator cap is supposed to release pressure at 16 psi. If it doesn’t, it allows pressure to build in the entire cooling system until something blows. At that point, it is the path of least resistance. You were probably lucky that the hose popped off instead of something else blowing.

I’d say replace the rad cap and test it while running it at home.
 
That was another thing I failed to mention. I just stuck a new repop radiator cap on because the one before was corroded. You may be right though because this last time after the refill nothing came out of the overflow...
 
I agree, cap didnt release.
Most cooling ststem pressure test kits come with a cap testing adapter.
The mightyvac kit i got was 45 dollars. Money well spent for me.
 
A different or new thermostat does not mean it is a good one. You might put it in a pan on the stove and see at what temperature it starts to open using a thermometer. I have had it happen.
Yote
 
Hemihead2 said:
I let a day or two pass before writing this because I still don't know what happened. Here it goes...

Our 340 doesn't get run much, in fact it only gets out at most once or twice a year usually it just sits in a climate controlled garage...As such, I began to notice a considerable amount of antifreeze had built up (crystallized) around the intake water neck. Two weeks ago I took the car for a drive and lo and behold it began to overheat badly...So much so that it was getting blown out of the overflow tube and trailing on the ground into the driveway. I looked at the temp guage (factory) and it was nearly spiked. I blew water through the radiator with a garden hose and finally got the temp down and I parked it. Later I pulled the thermostat and found it was completely corroded...Last Saturday I replaced the thermostat and the water neck housing with another one that I had laying around. I cleaned everything up and even used a new band clamp instead of the factory squeeze type that was on it to safely secure it (or so I thought). I filled the system, took it for a short spin around the block and brought it back home. Once it cooled down I topped off the radiator and took it for a 2 mile trip....bad idea. About 1/2 way into it after it had reached operating temp I noticed the gauge was creeping up once again (ambient air temp was 80*) ....by the time I got it home it was holding steady but up in the range... I coasted the car into the driveway and let it sit- engine off...A few minutes later all hell broke loose...There was a small explosion under the hood and the steam began to roll. The force was unbelievable. It turns out that the top radiator hose blew off at the water neck and spewed antifreeze all over the underwood area...and I mean everywhere! I can honestly say it was so violent that if the hood had been open at the time I would have been scalded badly...The car runs and accelerates, no miss, no antifreeze in the oil, no leaks.

So here I am....asking for help. Has anyone ever had this happen before? The car was completely restored in 2001 with everything new or replaced. I have a 160* T-stat in it with a flow-cooler water pump, radiator was recored, etc. In the early years after it was restored we had drove the car well over 100 miles one way with no issues. Where do I begin? Collapsed lower hose, plugged radiator? HELP!
Click to expand...

Air in the system ------------trapped???????????
 
Can't be too careful with parts these days. The Chinese counterfeit market is huge
 
I’m wondering if air was trapped in the system. I topped it off once but maybe I should’ve done it twice...could that be why the radiator cap didn’t vent?
 
Hemihead2 said:
I’m wondering if air was trapped in the system. I topped it off once but maybe I should’ve done it twice...could that be why the radiator cap didn’t vent?
Click to expand...
I USUALLY AHVE TO RAISE THE FRONT OF THE CAR, HELPS TO HAVE THE cap side a little higher too !
 
318willrun said:
radiator is probably corroded as well.
Click to expand...
I would also take a look at the lower radiator connection/ hose/ water pump "input".

Different circumstance than you, but the same results. I had the same thing happen when my lower radiator hose froze. Upper hose exploded (sounded like a muffled gunshot), I am thankful the hood was closed because it sent coolant everywhere
 
If you find corrosion like that on your cap and thermostat, i would flush the entire system first and then troubleshoot from there after the system is filled with 50/50 antifreeze and distilled water.
Drilling a 1/8'' hole in the thermostat will help with bleeding the air out of the system as well...........
 
Not the problem, but what made you put a 160 thermostat in it? The proper heat range is a 195. A cooler thermostat will not make the engine run cooler. It will only open sooner. As it is, yours is open all the time.
 
If you hit over 30 mph on that last trip, with a 160 stat, and watched the gauge creep higher than normal;then I'd guess you might have a heat shedding issue, but it may just have been reaching it's normalized temp. Shoot it with an IR gun to know what's happening.
But
So long as the system was sealed, the water temp may have been close to water's atmospheric boiling point. So,the instant the hose popped off, it all flashed into steam instantaneously, and it all had to go thru that top hose........ like a cannon shot. Flashing to steam under this circumstance would be normal.

Maybe you don't have an overheat problem at all; there is no way that hose should have popped off, unless the screw-clamp failed. The factory spring-clamps were the best. I prefer the flat-band spring types myself. They seem to be a little kinder to the hose than the round-wire hog-ring type.
________________________________________________
EDIT; FWIW;
I run a minimum water temp of 205*F by IR gun, and a 7-pound cap. I trust the thermostatic fan-clutch to force the rad to shed heat, and keep the water temp under control. My theory is that the 7-pounder will start spewing sooner, giving me an earlier warning than the pokey factory gauge that I never look at anyway, except after a red-line run.
Since 1999, my engine has never made steam.And the hoses last forever.....it seems.
 
Last edited:
AJ makes a god point about the clamp. I bet either it failed, OR what I see ALL the time, the clamp was improperly positioned. I see people all the time put the clamp ON TOP of the hose barb and not behind it. Why they do this, I have no idea. If you position the clamp behind the hose barb and tighten it up good the only way it will come off is if the hose tears. Even then, it will leave the part of the hose clamped to the hose barb.
 
AJ/FormS said:
If you hit over 30 mph on that last trip, with a 160 stat, and watched the gauge creep higher than normal;then I'd guess you might have a heat shedding issue, but it may just have been reaching it's normalized temp. Shoot it with an IR gun to know what's happening.
But
So long as the system was sealed, the water temp may have been close to water's atmospheric boiling point. So,the instant the hose popped off, it all flashed into steam instantaneously, and it all had to go thru that top hose........ like a cannon shot. Flashing to steam under this circumstance would be normal.

Maybe you don't have an overheat problem at all; there is no way that hose should have popped off, unless the screw-clamp failed. The factory spring-clamps were the best. I prefer the flat-band spring types myself. They seem to be a little kinder to the hose than the round-wire hog-ring type.
I run a minimum water temp of 205*F by IR gun, and a 7-pound cap. I trust the thermostatic fan-clutch to force the rad to shed heat, and keep the water temp under control. My theory is that the 7-pounder will start spewing sooner, giving me an earlier warning than the pokey factory gauge that I never look at anyway, except after a red-line run. Since 1999, my engine has never made steam.And the hoses last forever.....it seems.
Click to expand...

I wouldn't recommend a lower-pressure cap, it reduces boilover protection and max cooling capacity quite a bit; I had to run a 10-lb cap on my original radiator so it wouldn't leak and after switching from a 16-lb one I noticed it took less hard driving or crawling in traffic to get the temp to start climbing than before.

I'd pull the rad and flush it as well as the whole system, get a new high-quality t-stat (at least a Stant SuperStat or similar) and TEST IT before installing. Also a new high-quality rad cap. Then when it's all filled and buttoned up start the car and let it warm up in your driveway or take it around the block a few times not far from where you live in case something happens.
 
RustyRatRod said:
Not the problem, but what made you put a 160 thermostat in it? The proper heat range is a 195. A cooler thermostat will not make the engine run cooler. It will only open sooner. As it is, yours is open all the time.
Click to expand...


Can you please explain why a 160* doesn’t allow the engine to run cooler? Seems that opening sooner would give the cooling system a head start to start dissipating the heat...Maybe I just never thought that through the whole way.

Has anyone had experience with the Flow-Cooler water pumps. At the time I bought it they were all the rage.
 
Air.........these mopars are easy to bleed.......just fill the system with the intake heater fitting open, fill till you "hit water". If you don't have a heater, either put a valve there or a fitting you know you can remove, like a brass plug sealed with teflon, etc.

In addition to a bad new stat, clamp problems, or a stuck cap, if you underfilled it might be it overheated badly before the temp gauge reacted. This may have added to the extra steam pressure. Hope you didn't "hurt" anything.
 
Hemihead2 said:
Can you please explain why a 160* doesn’t allow the engine to run cooler? Seems that opening sooner would give the cooling system a head start to start dissipating the heat...Maybe I just never thought that through the whole way.

Has anyone had experience with the Flow-Cooler water pumps. At the time I bought it they were all the rage.
Click to expand...

it opens at 160, unless you have a Monster radiator in there no way the system can disperse the heat created to keep it at 160.
160 is also probably not optimum to burn off the fuel & condensation that makes its way into the oil. not that the car would run at 160 the way it is.
 
In the 60s we ran caps to keep the flies out.
The cooling systems were large,with large upper tanks, more than adequate, and most ran direct-drive fans. And the engine rarely topped 300 hp. If the system is properly sized and in good condition, then hi-pressure is just hard on everything. . My rad is a 1973 model, from a 318Dart with A/C. My heater core is ancient, as are most of the hoses.
Like I said; "since 1999 my engine has never made steam". I guess I should add that while our summers are short, we do get up into the 90s for a week or three, and traffic is traffic, and idling is idling. My cooling system just doesn't care what it has to endure; the stat keeps the temp up, and the 7-blade fan keeps it from creeping any higher.But then, my HO367 is just a little streeter.
My comment was what I run, and I run it cuz it works.
 
If you run a 21st century coolant you wouldn't need to run a pressure cap. As AJ just mentioned, pressure is not always a good thing. It's just a crutch to help an outdated coolant work.
 
Why are you seeing so much corrosion in your cooling system? You're not running straight water, are you? Even in climate controlled storage and only driving in the summer you still need anti-cirrosion additives. Preston, Prestone, who needs Prestone?

Something was blocked in your cooling system (or there was trapped air) and it built up pressure which should have been relieved by the cap. (Hint) You're lucky you weren't hanging over the engine compartment when it let go or you could have been severely burned.

Chrysler was very thorough in their engineering and would spend the few extra pennies to make things RIGHT. Over the years I think a lot of this after market latest fad type of sh** became popular to fix shortcomings of pennypinching GM stuff and it spilled over to the Mopar world. My 2 old driver cars with warmed up engines have no problem staying cool. I put 120 miles on my /6 Valiant yesterday (with the top down) in 94 degree heat and it ran flawlessly with the stock radiator and fan. Oh....and a 50/50 mix of coolant.
 
I think I got mine to heat up because the system was borderline adequate, based on multiple factors... The air is not only less dense here at high altitude but also very dry which doesn't hold as much heat and in the summer temps can get well over 100*F. My 360 also had 10.5:1 compression and a too-small cam which made the cylinder pressures high and I struggled with constant detonation issues in hot weather until one of the piston ring lands finally gave up the ghost. I was running the factory HD radiator (my Duster was originally a 318 car with A/C) but have since scrapped it and now plan to get a nice aluminum one from ECP with dual extra-fat cores.
 
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