Heater core blow out again....

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spl440

spl440

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Have 67 Dart with mild 360 with 4 speed stick. Seems that when I shift it above 6500 RPM, and back off of it, I either have a hose come off, or blow out the heater core. has happened about 4 times over the last 3 years. The motor does not have a blown head gasket, standard pulleys, standard water pump and thermostat. Would a high flow thermostat help? Since it happens usually after I back off from a higher RPM, was thinking it has to much water flow can not even out in time so it pops a hose or blows the heater core. Factory bypass is there.
 
The Rad cap controls, and releases excess pressure , whether for coolant expansion, or other pressure souces. The water pump is not a positive displacement pump, so really doesn't add pressure per say, it just circulates. So, either your rad cap is too hi, or the heater cores are weak,. Or you have a compression leak that spikes pressure at hi rpm. Jmo.
 
Some late model Ford applications use a heater hose restrictor for that very purpose. You might check with your local auto parts store and see if they can round you one up.
 
RustyRatRod said:
Some late model Ford applications use a heater hose restrictor for that very purpose. You might check with your local auto parts store and see if they can round you one up.
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The old Dodge truck has a lever right from the driver's compartment heater controls to a on off valve right on The Middle of one of the hoses going into the heater core.
 
Four heater cores! Good Lord that Dash has to be on quick release hinges!
 
j par said:
The old Dodge truck has a lever right from the driver's compartment heater controls to a on off valve right on The Middle of one of the hoses going into the heater core.
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That's a heater control valve.
 
Rad cap.
After engine work, while watching resevoir as air purges,rev engine i see coolant drop,and as i reduce rpm’s coolant rises and air escapes from cooling system.
Wat you are experiencing is a version of water hammer.
 
Upper rad hose once, 3 heater cores. Standard water pump, New proper gates rad cap for dodge application. heater control valve in and working, a/c car and newer aluminium radiator. Wondering if swapping heater hoses may help, not sure if supply hose to core is going to valve first or core first. Either way would not effect upper rad hose blowing off. No bubbles, air in cooling system. thanks for all the suggestions, car gets driven hard all the time, so only happens once in a blue moon. It just happened to be blue this week.
 
spl440 said:
Upper rad hose once, 3 heater cores. Standard water pump, New proper gates rad cap for dodge application. heater control valve in and working, a/c car and newer aluminium radiator. Wondering if swapping heater hoses may help, not sure if supply hose to core is going to valve first or core first. Either way would not effect upper rad hose blowing off. No bubbles, air in cooling system. thanks for all the suggestions, car gets driven hard all the time, so only happens once in a blue moon. It just happened to be blue this week.
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I would shift at 6495, problem solved.
 
could be wrong but, I would thing it would be plumbed to the valve, then the core and back to the engine. I believe the inlet on the core is 1/2" the outlet 5/8"
this helps to slow the water flow thru the core allowing for heat transfer.
 
Same hose size, but will double check which way it is plumbed and add a restriction to the heater core.
 
spl440 said:
Could, but right foot has mind of it's own...:D
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LOL , Just a little humor,wasn't trying to be a smart ***. I've the same problem . Got rid of all the race cars so now I'm trying to make my slanty Van go faster. It's a sickness that there is no cure. Hope you solve the problem so you can mopar on.
 
Thanks, Smart *** myself so no worries. Just bypassed heater core for now, back to +6500 for a while....
 
spl440 said:
Thanks, Smart *** myself so no worries. Just bypassed heater core for now, back to +6500 for a while....
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YA NOW On to blowing up bigger and better things!!!!
 
Sorry, do not want to blow up the turbine helicopter at work ! And the Rolls Royce in the aircraft spins to 30,000 RPM
 
Post #3 Has a lot of good points. I would also check your bypass hose and the passages into the water pump and intake nipple.
spl440 said:
New proper gates rad cap for dodge application.
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Proper rad cap for a 1967.... or proper rad cap for a 360... 1967 no 360. I would again check your cap for the psi and to be sure if its for a recovery tank fitment...if you have a tank. You could have the wrong cap for your application. I would lower my psi on my cap and give it a try, it would be cheaper. Proper radiator for the application?

Adding a restrictor in the heater hoses will not work, you will have the same pressures before and after the restrictor. Ford indeed used the restrictor to slow down the coolant because of the noise the flow was making going through the heater core.
 
Some caravans used restrictors also. Late 90’s.
The lower pressure rad cap may be the answer,the pressure raises boiling point,and also prevents lower rad hose from collapsing.
You need a pressure gauge on the cooling system to see whats actually happening.
 
I have run a 7psi cap since 2004, and often shift at 7000/7200. I'm guessing you have big and little hoses, and that they are correctly routed. I run a 205 hi-flow, and a hi-flo pump. All with no problems, thru a 1973 Dart A/C rad.
Oh, and my bypass hose is severely restricted, making my heater-core my actual bypass,lol.
Oh, another thing I forgot, I slowed my fan speed down some with pulley sizing. Not much, cuz there were not a lot of factory choices in those early years.

But I don't live in Hot Springs,AZ,lol.

And; I don't often back off at 7200, except maybe to shift into the next gear. Being geared for 200plus mph in overdrive,I run out of balls waaaaaay before gear or rpm, lol.

If I had to guess, I'd say your rad might be restrictive, or restricted, or the stat might be defective. I suppose you could install a restrictor washer in the stat-house and try that.
 
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16 psi cap with reservoir, and Hot Springs Arkansas. Does not overheat. Will install 180 degree high flow stat with lower pressure cap and make sure water feed to heater core hits the valve first. Aluminium rad with dual 11 inch Spal fans.
 
I'm clueless. I've seen cases where a radiator hose would flatten at high rpm and there were hoses with a wire coil inside to prevent this. What I don't know is what might happen if the hose does go flat at high rpm ( and flatter when hotter ), and the water suddenly tried to return fasten than the hose could reform/open. A surge in system pressure that the radiator cap doesn't sense, can't relieve? Just pondering the cause of random/"blue moon" occurrence.
 
RAT ROD AL said:
YA NOW On to blowing up bigger and better things!!!!
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I have an aftermarket heater under my dash, "no room for anything sticking out the firewall."
mine just did the same thing , thinking shes building too much pressure, a 15 pound cap, instead of a 16 ???
 
That spring was for filling cooling systems in the factory. Pressure keeps hose from collapsing.

Thats why no rad hose (aftermarket) comes with a spring in it.
 
I do not know if this will help, scanned from my Chrysler, "Learn to Earn" series of books.

rad.jpg


rad1.jpg
 
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