Headed from Columbus to Louisville for the NSRA event this past weekend. On the way down the ole slant ran great averaging 65 to 70 the whole way at a lovely 18 miles per gallon then ran as it should all weekend. On the way home there were some issues.

First was the noise. Looks like she burned through the exhaust gasket at the tail pipe connection. May or may not be related to the next issue. If there is a more durable gasket than the felpro I'd welcome suggestions.

Second, about 40 minutes north of Louisville in the Kentucky hills she started to overheat. Had been running at 180-195 religiously. When I finally was able to get to an exit it was up to 220 and climbing. Radiator was full, no leaks. Fan working with no slippage. Pulled thermostat. Flushed radiator. Could see good flow through top of radiator. With the temp down and thermostat out we headed back on the road. Still overheated.

Interesting find that actually got us back to Columbus. We noticed that after stopping and turning the motor off then quickly back on, within seconds the temp would drop 10-15 degrees. Any time I was able to coast downhill I turned the car off then back on in neutral. Quite annoying but it worked and saved the wrecker cost.

Any thoughts on where to start?



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Current Project: 1967 Dodge Dart GT, 2dr Hardtop California Car with 225 Super Six, Automatic 904 Transmission, and Factory A/C

did you do any actual temp measuring or just the stock gauge?

i am wondering if the perceived temp drop was not a temperature change, but actually a voltage drop from the restarting.

another possibility is that there is something acting like a check valve in the system, it works fine until coolant flow pushes it in the way and then the coolant cant flow properly.

Using aftermarket gauge. I've got the power wire gator clipped into the lighter plug so it's always hot even when the ignition is off so I don't think it's a voltage issue.

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Current Project: 1967 Dodge Dart GT, 2dr Hardtop California Car with 225 Super Six, Automatic 904 Transmission, and Factory A/C

A partially clogged radiator will flow, but not enough to keep up with high btu load in hot weather. When radiator becomes plugged up the low pressure side of the water pump can be strong enough to collapse lower radiator hose further limiting flow.

Where after shutting down the engine, and restarting resulting is a quick cool down, I suspect lower hose collapse, a symptom of partially plugged radiator. So what I'm saying is it's not a hose problem, but most likely a flow problem through the radiator.

I know you flushed the radiator, but flushing won't always dislodge all the crap stuck in its tubes, and not all tubes are blocked as some coolant is flowing, just not enough. In other words because of blockage, your engine sees a much smaller radiator unable to shed enough heat when stressed in hot weather.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

with ignition off, you get ~12.5v, with the motor running you get ~14.7. the gauge might not react instantly to this change.

I plan to actually pull the radiator tonight and flush. Any good tips or suggestions on what to use to get any lodged material out of the tubes? I know to flush from the bottom.

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Current Project: 1967 Dodge Dart GT, 2dr Hardtop California Car with 225 Super Six, Automatic 904 Transmission, and Factory A/C

Update: Got everything apart and the radiator pulled tonight.

First thing I noticed is the inlet and outlet heater core hoses were installed backwards. Don't know if that would cause any issues.

Second thing I noticed when taking the radiator out is the fan would turn without moving the belt. Got the petcock hung up on a blade. Maybe belt is too loose?

Turned radiator upside down and put the hose in the bottom radiator outlet and ran it till water came clear. Got a few little particals and a little bit of slime to come out. Took the hose to the thermostat inlet and ran till it was clear. I bypassed the heater core for all of that so I took the hose to the outlet side and ran till clear. I plan to get radiator flush to run through it and run the car for 20 minutes then flush again. I wish I had more pressure with my hose. Thought about driving it to the shop while the radiator flush does its thing and get it professionally done.

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Current Project: 1967 Dodge Dart GT, 2dr Hardtop California Car with 225 Super Six, Automatic 904 Transmission, and Factory A/C

For what I know the fan in a slant has a solid connection to the water pump pulley, and they're moved via belt by the harmonic damper (belt includes also the alternator, which acts as the belt tensioner. The fan does not have a clutch like the 318 V8. So, unless somebody modified your engine, yes the belt is too loose. I can move the engine using the fan if it has no plugs in one direction. It can slip in the other, but still its hard to move. Stuff that can clog the rad might be hard to move, probably having it flushed helps (if the price is reasonable).
Could you also check hoses (mine have a spring inside that keep them from collapse, don't know who installed it and what p/n is), and the radiator cap? (maybe replacing it too)

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/6 Dodge Charger 69
...there's nothing like using the "Search" link above to solve most of your problems...

A loose fan belt isn't causing your problem -- at speed, the fan's not pulling air through the radiator; the car's forward motion is pushing air through it. The only way the fan can cause a problem at speed is if it's installed backwards.

Radiators can reach the end of their useful life even if the tubes are clear; when enough of the solder holding the fins to the tubes corrodes, there's not enough heat transfer from tubes to fins. Then it's time to re-core or replace the radiator.

A radiator cap can mean the difference between overboiling and not overboiling, but not the difference beween overheating and not overheating.

Built-up crud (mud) in the block and trash in the head can cause overheating. So can exhaust restriction.

The thing about needing a spring to prevent the radiator hose from collapsing is a myth.

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

It has a new aluminum radiator but no shroud. The hoses are the universal flexible style with the metal rings in them. The cap of course has Chinese writing on it and no indication of how many lbs of pressure it is designed for. I've driven the car long distances before with no issues. 6 hour trip but 10 degrees and the 3 hour trip to Louisville but it was at night and 58. Sunday would have been the hottest ambient temp trip to date. Just trying to think which variable would have changed between past trips and now. Thought maybe head gasket but not seeing water in the oil at least at the dipstick

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Current Project: 1967 Dodge Dart GT, 2dr Hardtop California Car with 225 Super Six, Automatic 904 Transmission, and Factory A/C

Many of the off-the-shelf universal aluminum radiators are junk from China. Getting more than one pays for is a rare treat, not the usual way things work.

The lack of a fan shroud isn't causing your problem, either -- that would come into play at low road speeds/stuck in traffic, especially if you have A/C.
Radiator probably of similar "quality". It might not be your problem now, but it stands a pretty good chance of being a problem eventually.
Water-in-oil is only one way head gaskets can fail. Can also get water-into-cylinder, combustion-gas-into-water, etc.

What's your fuel economy been doing? If the muffler or other exhaust component developed a blockage, fuel economy would suffer along with an overheat condition developing.

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

On the trip down I ran 17 mpg running 65-70 mph. I haven't filled up since making it home to see what I used on the way back. Only difference from the way down to the way back was the gasket that failed between the exhaust manifold flange and tailpipe flange.

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Current Project: 1967 Dodge Dart GT, 2dr Hardtop California Car with 225 Super Six, Automatic 904 Transmission, and Factory A/C

Headpipe flange. The tailpipe runs from the rear of the muffler to the rear of the car. And while excessive backpressure isn't the only cause of a failed headpipe flange gasket, it's one cause of it.

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

The exhaust is new from the firewall to the rear. They basically welded a splice about 2' from the head pipe flange. That is not something I thought to look at after the overheating issue. There were a lot of things done before I bought the car. Whether correct or not time will tell, or has told.

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Current Project: 1967 Dodge Dart GT, 2dr Hardtop California Car with 225 Super Six, Automatic 904 Transmission, and Factory A/C

another new finding..... I have a dead cylinder. Looks like #5 (second from firewall) is not firing. I have spark to the plug but nothing when installed. We just recently did a valve adjustment, but that wouldn't have anything to do with that would it?

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Current Project: 1967 Dodge Dart GT, 2dr Hardtop California Car with 225 Super Six, Automatic 904 Transmission, and Factory A/C