Already time for a cooling system rebuild.

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Chris Nicholson

Chris Nicholson

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Nashville, TN
Picked up my '74 Swinger (318) from the paint shop a couple of weeks ago. Drove it to work last weekend to repair an exhaust leak, then my dad wanted me to pick him and take him for a cruise down the Natchez Trace Parkway. The whole time, it's running fine. Bought new alternator, A/C, and power steering belts on my day off and drove it to work this morning so I could change them. About two blocks from work, the cap on the overflow tank popped and out spewed coolant and steam. Heard a groaning noise as I pulled into the shop, maybe the water pump?

Since the car is now stuck at work, I don't have the luxury of time to troubleshoot what went wrong, so I'm just going to replace/rebuild everything. There's a radiator shop nearby we use for that work, so that's easy. I've been on Rock Auto looking at the various water pumps, thermostats, etc., available. Being a Mopar newbie, I'd like to ask what do you guys recommend for replacement parts?
 
Chris Nicholson said:
Picked up my '74 Swinger (318) from the paint shop a couple of weeks ago. Drove it to work last weekend to repair an exhaust leak, then my dad wanted me to pick him and take him for a cruise down the Natchez Trace Parkway. The whole time, it's running fine. Bought new alternator, A/C, and power steering belts on my day off and drove it to work this morning so I could change them. About two blocks from work, the cap on the overflow tank popped and out spewed coolant and steam. Heard a groaning noise as I pulled into the shop, maybe the water pump?

Since the car is now stuck at work, I don't have the luxury of time to troubleshoot what went wrong, so I'm just going to replace/rebuild everything. There's a radiator shop nearby we use for that work, so that's easy. I've been on Rock Auto looking at the various water pumps, thermostats, etc., available. Being a Mopar newbie, I'd like to ask what do you guys recommend for replacement parts?
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If you are going to change parts, I’d buy either the Milodon or Flowkooler high flow water pump and a Stewart Components high flow thermostat.

It’s not that much more money and it’s better products.
 
everyone's going to want to know what else it has. radiator size and type, fan, motor stock, ect
 
kursplat said:
everyone's going to want to know what else it has. radiator size and type, fan, motor stock, ect
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Good point. It's all stock. 318-2, auto, A/C, disc brakes. I'm only the third owner, got it from my buddy who had it three years, mostly doing body and paint work on it in his spare time.
 
Just to be safe, I'd check the oil and do a compression test.
Any time a cap pops, it makes me think compression into the cooling system. I've seen it at least three times and in all cases the owner spent good money on parts that were already fine (except the radiator that exploded in two cases, but they detonated the replacements too).
 
Phreakish said:
Just to be safe, I'd check the oil and do a compression test.
Any time a cap pops, it makes me think compression into the cooling system. I've seen it at least three times and in all cases the owner spent good money on parts that were already fine (except the radiator that exploded in two cases, but they detonated the replacements too).
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I asked my buddy and he said he did a compression test when he owned the car. A few were lower than others, but all were in range.

He suggested doing a Prestone flush before taking anything apart, to make sure it doesn't have decades of gunk built up.
 
Chris Nicholson said:
He suggested doing a Prestone flush before taking anything apart, to make sure it doesn't have decades of gunk built up.
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not saying it will definitely happen, but i'm guessing your going to find a rotted freeze plug or two after stirring up all the crap that's probably in the motor. when i get a "new" mopar i like to pull the motor, pull the water pump, knock out the freeze plugs out and clean the crap out of it. sooner or later, you will
 
Do what you want, it's your car but there's no way in hell I'd ever throw mass parts at something without diagnosis. You can spend 1K on parts and still not fix it. You should find out what's wrong FIRST.
 
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Chris Nicholson said:
I asked my buddy and he said he did a compression test when he owned the car. A few were lower than others, but all were in range.

He suggested doing a Prestone flush before taking anything apart, to make sure it doesn't have decades of gunk built up.
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Head gaskets can go bad at any time. So can a dozen other things that match your symptoms. What the previous owner did or didn't do is moot. Not trying to bust your balls, but I don't think you have a cooling system issue. Replacing the entire system may not do anything but leave you poorer and still stranded.

You could be right, but I'd rule out other things first is all I'm saying. A compression check may not even reveal a head gasket issue.

If you do nothing else, please rent a pressure testing device for your radiator to make sure that it holds pressure. Autozone rents them "free", and they're cheap anyway. Much cheaper than even a water pump.
 
1K a new cooling parts..:rolleyes:.. I guess it's possible but how ridiculous....
First if you do choose to get new cooling parts head for the radiator.. I wouldn't recommend rebuilding an old factory radiator when you could get one from Summit for probably under $150 sent to your door that's a two core aluminum that has much more capacity and cooling ability... Secondly for under $50 I bought a rebuilt water pump from Napa that was a factory high volume water pump with highly sought-after Factory numbers and the pentastar... That and a $7 thermostat...
But the very first thing I would do this determine what the hell happened before I threw money at it...:thumbsup:...
 
I have to agree with pressure check the cooling system first. A small hole in a heater hose, a freeze plug, etc.. could let water get away slowly. Its gonna run hot eventually. Groaning noise would be radiator cap venting pressure. If the cooling system wont hold pressure but no visible leak, pour some water in it and start it up. If you get steam out the exhaust.... head gasket failure. Good luck
 
if you replace parts , milidon igh volume water pump is good and noy much more than factoty champion radiator is also not expensive and keeps my 426 cool on a 95 degree day in traffic . first find the problem though , then get parts as needed
 
You said the cap on the overflow popped? That overflow should have a vent on it? Was that plugged?

I agree with above. I wouldn't start replacing a bunch of stuff that might not need to be replaced.
 
what does your oil on the dipstick look like ?
 
After reading all the sage advice here, I got to work on it a bit after work.

Found the drain tube on the original overflow jug may have been blocked. Dug some stuff out of the top end and blew more debris out with compressed air.

Pressure test found no leaks, and did not even drop.

Oil level and color were fine.

Car started fine, with no steam or water at the tailpipe. Test drive around the block revealed no issues. Can still smell coolant, but that be from Saturday's mess.

Will plan for a flush on my day off (Tuesday).
 
The rule of thumb is, if the radiator is old, it might be dirtier than you think. Usually shows up by overheating at highway speeds. The thermostats that we call "high flow" now, were equal to factory Mopar original thermostats up to about 1967. In other words, most of our motors are seeing a flow restriction with a regular 'stat that has the 1 1/8" opening. Spring for the EMP/Stewart thermostat.

--- And remove the block plugs at the bottom of the water jacket on each side, when you drain each flush. They're 1/4" pipe thread. 8 point sockets make it easy if they're the square kind. Use distilled water and coolant for the final fill
 
Thermostat stuck closed and never opened at the desired temp then it finally did. I myself would start with flushing the cooling system and then replace the thermostat which could be gunked up from the garbage circulating in the cooling system. This is a pretty easy and cheap fix at a location that is not yours...
 
Demonic said:
--- And remove the block plugs at the bottom of the water jacket on each side, when you drain each flush. They're 1/4" pipe thread. 8 point sockets make it easy if they're the square kind.
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hopefully they come out in one piece
 
After work tonight, I decided to start with a Prestone 10-minute flush. Which takes more than 10 minutes, of course. Opening the petcock for the radiator only resulted in getting my fingers a little wet. About 15 PSI with the pressure tester did the trick. After that, I followed the instructions on the bottle. While waiting for the engine to cool down between sessions, I tried to replace the alternator/AC and power steering belts with the new ones I bought last week. They were all too big, the power steering belt comically so. At least the old belts haven't broken yet! :D Got them back on, finished the last drain, poured in some fresh 50/50 mix and went for a test drive around the block. Everything seemed okay as far as I know (as my luck would have it, the only gauge that doesn't work is the temperature gauge), so I eased it home. By this time it was 10 at night and only 82 degrees outside. Only interstate stretch was on I-440, which is limited to 55 so I did 53 according to my phone app (speedo reads over 20% fast, so I'm using an app for now). Rest of the drive home was in 40 and 45 zones.

Obviously, I need to get the temperature gauge working. And take the old belts with me when I return the new belts and see if they can just match them. Then another run down the interstate in the daytime to see if it overheats again.
 
Get an aftermarket temp gauge. Even a cheap IR thermometer from horrible fright (harbor freight).

The factory stuff isn't worth trusting.
 
The good news is, my car looks like this. :usflag:

Garage 12x9.jpg
 
Update:

Drove the Dart to work yesterday, determined to change the belts. Took surface streets except for the last bit which was I-440 at about 60 mph. No problems.

On my lunch break, I went across the street to a NAPA store and had them match up a set of belts. The alt/AC belts were a little shorter, but that was the closest they had. Started on the car after work. Found out I didn't have enough room to move the alternator and get the NAPA belts on. Even took the alternator off to see if I could get it under the belts and then bolt it up. Nope!

Something I neglected to mention earlier is that the alternator was replaced who-knows-when with a later metric unit. By "metric" I mean the bolt on the alternator that goes through the slide part of the bracket is an 8mm with a 10mm head. While I had the alternator off, I noticed that there is another threaded hole along that same radius that would allow the alternator to be adjusted out for longer belts. So I cleaned the threads, got a new bolt out of the parts bin with a 13mm head, added a wide washer and a spring washer, then put it back together with the AutoZone belts I bought last week. The power steering belt from Napa fit, so after that was finished I cleaned up and drove home.

Decided to take my normal interstate route home and the ambient temperature was 90, so I figured it would be a good test of the Prestone flush. Wasn't aware of any problems until the large hill just before my exit. Was doing 70 up that hill and something just didn't feel right. Exited just after the crest and could hear the radiator cap moaning from the pressure. While waiting for a chance to turn off the ramp, steam was visible at the other end of the hood. I cranked the heat up all the way and drove it gently along the backroads the rest of the way home. No more signs of steam or complaints from the radiator cap the rest of the way.

I'm thinking my next step is a new thermostat, and if that doesn't help a new aluminum radiator from Summit.
 
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