I have a feeling the car ain't warming up, because I can never get really hot air out of the heater. Right now I'm running a 180 degree thermostat (which IIRC is the temp recommended by Dan) and I got a LOT of garbage out of my cooling system when I backflushed it a while back. When I take it to the shop so I can put in the new water pump, I'm going to run some cooling system cleaner through it, install a new 180 degree Superstat (right now mine's just the normal Stant), and swap out the heater core for a new one. The radiator I'll leave for now since the only reason I'd replace it at this point is for aesthetics, and I figure I can just pull it out while I have the car parked once it starts snowing and paint it then.

I'm also planning on using Water Wetter when I service the system, hoping it'll help even out the temps in the cylinder head.

Oh woops, forgot to add, my temp gauge needle never rises above the left "vertical" line on the \____/ imprint on the gauge face.

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

Jopapa,

Don't feel bad. Mine does the same thing and I have all new cores, engine, hoses, etc. I just bought the new Mr. Gasket 16# radiator cap with the temp gauge in the top of it, and installed a 195 degree Stant. The new cap shows right at 200 to 205 degrees and the heat is still not very hot inside on these colder mornings going down the road at speed. If you let it sit in the yard it gets nice and toasty then drops once you start going.

I am thinking of going with a 12" electric fan so I can shut it off going on the freeway. I think the system is just too efficient with the 5 bladed clutch fan. If I put on the old stock fan it gets a little warmer but then I drop about 1.5 miles per gallon. I have tried the switch fans a couple of times now. I also have tried two different new heater cores and two new radiators. I am running the stock 18" radiator now.

Let me know how it goes for you and if you find a way to get more heat.
I wish they still made electric heaters.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Is it still even possible to get a clutch fan anymore? Right now I've got a four-blade non clutch fan (it ain't even a flex fan), and I was thinking if I swapped to a thermostatic clutch fan that'd help alleviate the issue too. I see that both Napa and Rockauto have the clutch readily available, but the only fan I can find is listed on Rockauto as "discontinued". I was planning to install a fan with a variable current controller by DC Control, but their site's gone, so I'm wondering if the company is now defunct.

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

You can semi test the temp gauge by grounding out the sending unit wire, this shoudl cause the gauge to go full hot if it is working. You will need the ignition key on ofcourse. Then you can take a DVOM and test to see if the resistance changes in the sending unit when it cycles from cool to hot. I dont remember what values should show, but it will change as the temp changes with DVOM hooked from senser to gound. These test will not tell you how acurate the gauge is, but atleast you can see if its trying.


Jess

Get an aluminum cooking thermometer. They typically have a round dial on top and an aluminum spike about 6" long. With the cap off and the engine idling put the spike down into the water flow and let it run until the thermostat opens. Your water temp should be withing a few degrees of the thermostat temp. If it is significantly cooler then you have a problem with your stat. A heater blowing cold air is usually caused by a clogged heater core.

_________________
David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

Jopapa,

My needle stays to the left also but as I said before runs at 205 on the thermometer idling in the driveway. It gets nice an warm in the drive way but cools off going down the freeway.

The clutch fan and blades are available from Summit part #DCC-4120758 for $109. That is where I bought mine to replace my old froze up original clutch. I could never find a short enough clutch in the part stores so I bought the whole unit from them. It fits just fine. I actually brought 6 different units home to try, they were all to long.

I bought the cooking thermometer, same temp and the gauge in the radiator cap. The new 16# Mr, Gasket cap is pretty good.
I wonder if a higher pound rating cap would put out more heat?
or if a lower pound rating would put out more heat?

I am wondering if a higher antifreeze content will help keep it warmer? Since I made all the changes there is only about a gallon in the mix. I had two gallons in it during break-in.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

The pressure rating of the cap will not affect the amount of heat in the car (or in the system). It will only affect the boiling point of the coolant. There is definitely something the matter with a system that behaves in the manner described, and changing to a clutch fan or electric fan — while not a bad idea for other reasons — is not the fix. Remember, when you're driving at much of any road speed, the air through the radiator by dint of the car's forward motion makes the fan (any fan...fixed, electric, or clutch) irrelevant. Also remember that these cars generally tend not to have this problem, even with fixed-drive fans. So, some more sleuthing is needed to determine exactly what's going on so that the actual problem can be fixed rather than attempting to tackle the symptoms produced by the root cause, whatever it be.

The symptoms as described suggest several possibilities. Thermostat failing to control coolant flow correctly (opening too cold and/or sticking open) is one such possibility. Always pan-test your new thermostat before installing it: Push the valve plate open, insert a piece of string, let the valve snap shut, hang the stat in a pan of water so it's not touching the bottom or sides, and put the pan on the stove. Use a kitchen thermometer to stir and measure the water temp constantly and note when the stat drops off the string.

Another possibility is air trapped in the cooling system. This isn't as common with slant-6 engines as it is in many later designs, but if combined with e.g. a clogged heater core, you can get very low flow through the core combined with a false low-temp reading on the gauge. When you replace your heater core, be sure to replace the heater hoses and make sure the supply nozzle (on the cylinder head where the heater supply hose connects) is free and clear all the way through.

You mentioned having got a lot of trash out of the system with an initial flush. From that, it seems likely your heater core is clogged and your thermostat is stuck open by bits of flotsam.

Those radiator caps with thermometers built in are OK to get a general idea of the temperature in the top tank, but the thermometers themselves aren't very precise or accurate.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Dan,

Thanks for the answers and thoughts. I am not sure about the air bubbles though. Would higher concentration of antifreeze help to minimize any bubbles? or the wetting solution Jopapa had mentioned?

If so, what brand is the best? or does it make a difference?

I just rechecked and all hose clamps are still tight. Head has been re-torqued so I doubt that there are any leaks from it. All the spark plugs are cinnamon colored.

Everything looks good under the hood, no odd smells such as antifreeze.

Is there any difference between a Stant stainless steel stat verses a Super Stat?

Any other thoughts you may have are much appreciated.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

No. 50/50 or so is about where you want to be.
Again, no. It's not necessary.
Yes, but while I prefer the SuperStat's more robust construction, if the ordinary stat is working correctly there's nothing wrong with it. Our cars worked fine with them for years.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Good info Dan. I'll troubleshoot as best I can next time I have a free day to take the car into the auto shop (I just moved off base so it's not as convenient as it used to be to go wrench on my car).

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me