Radiator question

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Well I took the Dart out for a15 minute drive varying speed from 25 - 50 mph I shot the therm housing 165 degrees the upper rad housing 175 and the lower rad housing 113 I change from a 180 to a 160 stat and the gauge didn't go into the hot area of the gauge I want to check it out on the highway and see where the temps come in at
 
I took the Dart out for a road test and drove about 15 minutes. I varied my speed from 25-50 mph. When I returned home my readings are as follows 165 at the stat housing 175 at top of rad and 113 at bottom of radiator. The gauge ran in the normal to high zone but didn't peg all the way to the right.
 
Have you thought about installing a new gauge under the dash? They're cheap peace of mind, especially considering you might be chasing problems that aren't problems in the future (I sure know how that goes).
 
Yes, I have a gauge on order. The one thing that stumps me is that the 1969 engine ran fine by the gauge. The 65 engine shows it runs hot,
 
UPDATE
I took the Dart out for a good long drive. I changed the thermostat to a 160 the car is running a little cooler. After the long drive here are some of the numbers 174 at the thermostat housing, 182 at the top of the radiator and 126 at the bottom rad housing. The gauge responded by running at the very top of normal range not going into the extreme hot range if you know what the gauge looks like in a 65 Dart. I'm going to replace the water pump to a 8 blade impeller from the 6 impeller in there now. I have a question regarding the water pump. I'm able to grab the fan and turn the fan clockwise with little effort, however it is very difficult to turn fan counterclockwise. Is that the sign of a bad water pump? Once I have the water pump off I will back flush with a hose. Next will be recording the radiator if the water pump doesn't do the trick.

Thanks to all who reads and responds.
 
Why? Your temperatures are actually cooler than I'd like to see. 174 at the thermostat housing is about 15-20 degrees cooler than I aim for with my engines.

It seems like your gauge is reading wrong. Get the auxiliary gauge in there before you go changing more stuff.
 
I've order two gauges so far both do not have the correct fitting, what gauge do you have?
 
Re flow rate question. I know of no such spec. The radiator has a restriction to flow [Cv in engineering, gpm/sqrt(psid)]. The water pump builds up pressure to cause flow thru the radiator. I also saw an old radiator guy test for excessive restriction. by filling w/ water and seeing how fast it flowed out under gravity.

The 6 vs 8 water pump blades (first I read of 5) has been much discussed. As I recall, AC cars were the ones w/ 6 blades. The reason has more to do with the different pulley diameters on AC vs non-AC cars.

To clean the radiator and block, I flush out all coolant and fill w/ a water & 2 lb citric acid mix, and drive it several times for ~40 miles, then totally flush. Posts w/ before & after photos display a remarkable improvement - shiny & new inside radiator. I bought 5 lb of citric acid on ebay, or buy at food supply places.

67Dart273 makes the good point that even if the water pump works and the radiator flows well, if the fins are no longer bonded to the tubes, you won't get good cooling. I don't know if that is a known problem. Perhaps a heat gun could show a difference between tubes and fins.

Installing a lower temp T-stat will generally not help if you are over-heating. Both would be full-open at that point.
 
williaml said:
I've order two gauges so far both do not have the correct fitting, what gauge do you have?
Click to expand...

I just have a parts store special with a capillary tube or whatever it's called. I used a fitting at the top tank of my Aspen radiator. If you use the original location, I imagine you'll have to rig together some kind of adapter system out of a couple of fittings. It will probably be ugly, but should work. :)
 
williaml said:
UPDATE
I took the Dart out for a good long drive. I changed the thermostat to a 160 the car is running a little cooler. After the long drive here are some of the numbers 174 at the thermostat housing, 182 at the top of the radiator and 126 at the bottom rad housing. The gauge responded by running at the very top of normal range not going into the extreme hot range if you know what the gauge looks like in a 65 Dart. I'm going to replace the water pump to a 8 blade impeller from the 6 impeller in there now. I have a question regarding the water pump. I'm able to grab the fan and turn the fan clockwise with little effort, however it is very difficult to turn fan counterclockwise. Is that the sign of a bad water pump? Once I have the water pump off I will back flush with a hose. Next will be recording the radiator if the water pump doesn't do the trick.

Thanks to all who reads and responds.
Click to expand...

I could have swore you said the engine was rebuilt (assuming a new thermostat went in then)
So now I have to wonder if ALL that time that two different owners of that engine had overheating issues, but neither of you ever changed the thermostat and even put it back in after a rebuild???

Anyway,
If the belt is on while you are turning the water pump it turns a lot easier one way than the other due to the drag of the belt in the pulley and other pulleys involved.
If no belt and it's hard to turn, then yes it's a bad water pump.
 
Yes, the engine was rebuilt and a new thermostat went in then. I've changed it to a 160 just to see what would happen. I'm getting the radiator back today, the shop said it was a little dirty but isn't the issue. I'm thinking it must be the gauge. The thing that stumps me is that the gauge worked fine with the 69 engine installed.

thanks for reading and responding...
 
Are you using the same temperature sending unit between the two motors?
Resistance can differ between two sending units.
Reread post 23
 
No, I just replaced the sending unit last week to ensure an accurate working sender.
 
Did you use the exact same sender between the two engines? Senders (especially new ones) have widely varying resistance values.
 
williaml said:
One member on here gave me the exact napa number and I purchased that sensor.
Click to expand...

Yes, but did you use that sensor on the old engine? If not, your comparison between the gauge readings between the two engines is irrelevant. The two sensors likely have different resistance values, so the only true comparison is to use the exact same physical sensor you used in the old engine.
 
Aaron the sensor was changed several times after the "new" engine was installed. I changed it out to see if I had the correct sensor. I had the radiator serviced today and the tech indicated that for its age it seems great. The tech also said it wasn't clogged but it was a little dirty and now it is 100%. I installed a 8 blade waterpump and all new antifreeze so once I test it I'll report back my numbers. I'm thinking it is probably the gauge at this point. The engine rebuilder would of had to leave quite a bit of dirt in the block to have the engine overheat with all the new or updated parts.

Thank you for following the thread and giving me your advice...

Thanks all for reading and responding...
 
Ya got a shroud on that radiator, right? It may not have come with one, but they make a big difference. Just my 2C
 
Bob,

No, the car doesn't have one but either did it when the 69 engine was in it. I will look for documentation as I haven't seen a 1965 Dart with a slant 6 225 with a shroud? Thanks for the advice...
 
So I took the Dart out to a car show last night. On the way to the show the car ran well the needle didn't get to the extreme hot side of the gauge. Coming home with lights on the gauge stayed in the normal range, so now I'm thinking it is the gauge. I shot the usual spots when I arrived at the car with my temp gun and at the stat housing 164 the top of rad 194 the bottom of the rad 136 safe to say the car doesn't have a temp problem, thanks to all who read and responded....
 
williaml said:
So I took the Dart out to a car show last night. On the way to the show the car ran well the needle didn't get to the extreme hot side of the gauge. Coming home with lights on the gauge stayed in the normal range, so now I'm thinking it is the gauge. I shot the usual spots when I arrived at the car with my temp gun and at the stat housing 164 the top of rad 194 the bottom of the rad 136 safe to say the car doesn't have a temp problem, thanks to all who read and responded....
Click to expand...
Sounds like you're fixed up!
 
Well now my situation is almost like this except we were breaking the engine in yesterday and she got to 150 then spiked to over 200. We shut her down. The distributor would not advance more than 15 degrees so I had an extra distributor laying around threw that in we were able to go to 30 degrees advanced she held steady watched the thermostat open then spiked again. Shut it down. The thermostat is new its a 180. The last thermostat I had in there was a 195 I tested it and it worked fine, but decided to replace it anyways. This is the second time I have run into overheating issues during the break in. I checked the water pump while it was still on the engine I hear the blades turning. My question is.....should I have the radiator flushed by a professional? I am thinking either there is air in the cooling system or....there is a block in the radiator core. Please let me know what you guys think. Thanks.
 
Spunk,
There are enough recommendations in this thread to get you started. Report back on your results. You don't need a professional. Get some citric acid powder and clean the whole system as you drive. If that causes leaks to spring, that is good. They were fixin to fail anyway. I haven't read that our engines trap air pockets, but wouldn't hurt to drive the front end up on ramps to help purge any, or try to find a good hill in Ohio.
 
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