73 Duster 318 seems to be running pretty hot

[Trevor B]

Hi All,

I have replaced the water outlet and thermostat (boiled it to make sure it works, first), burped the system, and still the dashboard gauge is indicating really hot: see picture. This is after I idled for a while, then took her down the road a few miles, up to about 50 mph but mostly cruising between 30 and 40...

The pictures shows the idling temperature after my little drive.

After I shut the engine off, the reservoir overflows a bit (not like crazy but there's certainly some coolant/water boiling over).

Should I install a fan shroud?
What size - it's pretty hard to get a good measurement on the fan itself but the radiator measures about 26" corner to corner.
Where would I find one?

 

[AJ/FormS]

Trevor; Stock 318s, in A-bodies, with 26 inch rads,are nearly over-heat proof, even without a shroud. They most certainly shouldnt overheat at idle or low speeds.
-If your overflow tank is puking, might it have been overfilled?
-Do you trust your guage?Infrared heat guns are cheap.
-For you; check out items C to F
-So heres the list of possible problems;
-A) faulty stat, or too high a rating,or faulty gauge
-B) loose belt tension,
-C) restricted air-flow through the rad fins,Or faulty fan-clutch, or non-stock fan
-D) poor Coolant circulation(pop the cap,and while looking inside the rad,blip the throttle.On a warm engine with open stat, you should see the coolant flowing.) For you, start this test on a cool engine, with the cap off. Wouldnt want you to scald your face.
-E) Lower hose collapse; Try to feel the wire support-coil inside it. Its quite possible for a soft hose to become collapsed as the water pump rpm increases.
-F) Pressure test; I urge you to do a cooling system pressure-test, or a compression test.If the engine is blowing combustion pressure into the cooling system, even the mighty 318 cant fight that.
-G) missing Under-hood seals, and shroud.
-H) Faulty waterpump,
-J) very late ig timing
-K) Other; Fluid other than water or anti-freeze. Foreign objects in coolant hoses,goes back to D. Chassis problems.

-I think I got it all.

 

[Trevor B]

Thanks for the great list. I picked up a temp gun and was all ready to check out the radiator and engine and now she won't start. Awesome!

 

[Bad Sport]

T stat in the correct way? Check the bottom hose as mentioned to see if it's collapsing, when you get it running, operate the throttle by hand under the hood and watch the bottom hose.

 

[krazykuda]

If it's running hot, get a garden hose and spray the radiator and see if that helps it cool down.

then you will know that the "bottleneck" is in the ability of the radiator to transfer enough heat.

 

[Trevor B]

The bottom hose does, indeed, collapse when I rev the engine. That probably means I need new hoses.

But it doesn't happen at idle.

I let it get good and warmed up and took the following temperatures with the temp gun:
1) Block: 255
2) Radiator: 215
3) Top hose: 160
4) Bottom return hose: 130.

Seems pretty clear that there is bad circulation.

 

[Bad Sport]

The bottom hose does, indeed, collapse when I rev the engine. That probably means I need new hoses.

But it doesn't happen at idle.

I let it get good and warmed up and took the following temperatures with the temp gun:
1) Block: 255
2) Radiator: 215
3) Top hose: 160
4) Bottom return hose: 130.

Seems pretty clear that there is bad circulation.

Hold on, you said it overheats after a drive.

Does it overheat when you start it and just let it sit and idle?

Seems pretty clear that there is bad circulation.

Well there would be poor circulation when you're driving it, because the bottom hose is collapsing.

Get a wire coat hanger and a piece of pipe about the same as the inside diameter of the bottom hose.

Coil the coat hanger around the pipe forming a coil, stretch it out and install it in the lower hose.

Take it for a drive and see if it overheats.

 

[Trevor B]

To be clear, I have not allowed the car to "overheat" (at least in the sense that I understand where it shuts off). I just think it's running too hot and my temp gun reading of 250+ on the block and still climbing suggests that overheating might not be too far off.

It will continue to get hotter and hotter at idle. This morning, it was only idling when I took the temperatures (idle is fairly high as I haven't gotten around to lowering it after we advanced the timing)

When driving, it has hovered around the high mark as seen in my picture. I have not ventured any farther as I don't want to reach the point of actual overheating.

I just bought some new hoses and will install them as soon as the engine is cool enough.

Also borrowed a radiator pressure testing kit from the auto parts store and will take a shot with that after I replace the hoses.

 

[Bad Sport]

Do you have a candy thermometer? If so, let it get to where it was and check the actual water/coolant temp.

Also, when running it after it's warmed up, with the cap off, do you see movement in the water?

AND are you sure the T stat is in correctly? You wouldn't be the first to get it in backards, lol.

 

[Trevor B]

T-stat is in correctly. Spring-side is down.

Pressure testing the system showed a very small leak from the radiator end of the top hose.

I do see what I would consider to be a little bit of movement but not like a rushing current or anything. More like vibration on the small surface area of the water.

I've just flushed out the the whole works and replaced the top and bottom hoses.

I will re-fill and pressure test the system once more.

Yes, I certainly can stick a thermometer in the radiator water - will the system do anything with the radiator cap off? I thought the entire thing needed to be under pressure (please excuse the stupid questions!).

Thanks!

 

[Bad Sport]

Yes, I certainly can stick a thermometer in the radiator water - will the system do anything with the radiator cap off? I thought the entire thing needed to be under pressure (please excuse the stupid questions!).

Thanks!

Just put the cap on loosely, and let it run until warm (T stat opens), remove the cap and throttle it up a little by hand and watch for flow, yes, it will flow while not under pressure as long as the stat is opening.

That brings to mind another question, are you sure the stat is opening? You can check it in a pot of water on the stove with the candy thermometer.

Bring it up towards a boil and see at what temp the stat starts to open.

It's quite possible you have a defective one, new or not.

 

[Trevor B]

Tested the t-stat before installing it. It definitely opens and closes.

 

[Bad Sport]

Tested the t-stat before installing it. It definitely opens and closes.

At the proper temp? If, for some strange reason, it's not opening until 220*, for example, that could be an issue.

I dunno, I'm just thinking out loud.

 

[mguner]

If the bottom hose is collapsing the spring inside will help but the radiator may also be restricted and need to be rodded out and cleaned a bit. I have found that a 195 T-stat will usually make one run cooler than a 165 simply because it slows the water down enough to transfer heat better. My $0.02

 

[Trevor B]

Update:
With new upper and lower hoses and after bypassing the heater core, I can say that the fluid is not circulating much, if at all. The t-stat opens at about 180 and closes, as confirmed by the pot of water test.

At this point either the radiator is really clogged up or the water pump isn't working. Either way I'm not thrilled.

 

[Inertia]

While its hot ,, take temp readings across the rad about mid-way down,, you're looking for cool areas,, they are plugged tubes not allowing water to pass,,the larger the cool area,, the larger your problem..

Before the guns,, I used to use the back of my knuckles to test for cool areas..

I found if you shoot the actual rad hose fittings,, top and bottom,, there is generally over 40*- 50* difference, on a good rad..,

 

[AJ/FormS]

Here are some more tests;
-With cold engine, remove radcap. Drain the coolant into a large pan by removing the lower hose.Witness the rate of draining. After the initial gush,it should continue out at about the same rate from start to finish. You can stick a garden hose in the top to extend the diagnoses time. It should come out at nearly the same rate as you could pour it in, from an anti-freeze jug.
-Take an old stat apart and put just the washer part back in the motor.Fill up the system. then with cap off inspect the coolant flow while blipping the throttle.Coolant flow should be clearly evident, or not.
-Here is a pump test.With engine cold, disconnect the heaterhoses from the heater core. Route the one still on the pump into a drainpan. The one that goes to the intake, you will need to clamp off. Remove the radcap, and stick a garden hose into the top, and a drain pan underneath to catch overflow.Turn on the water, and start the car.Check the waterpump output from the discharge hose in the pan. Adjust the waterflow to match the output, so you dont make too big a mess. Blip the throttle and the output should increase proportionally.If the stat is not still in the motor , you may have to clamp the bypass hose off and maybe restrict the top hose as well.The pump can move quite a bit of water, so take it easy on the rpms.

 

[Bad Sport]

Update:
With new upper and lower hoses and after bypassing the heater core, I can say that the fluid is not circulating much, if at all. The t-stat opens at about 180 and closes, as confirmed by the pot of water test.

At this point either the radiator is really clogged up or the water pump isn't working. Either way I'm not thrilled.

Well, at least you are narrowing it down.

I remember a thread on here a while back where someone was pulling their hair out over a similar situation.

What he finally discovered was the impeller was spinning on the shaft in the water pump and wasn't moving water as it should.

Pumps are cheap and easy, just keep track of which bolt came out of which hole.

 

[Inertia]

Easy enuff to check the impeller,, form a tool similar to pic,, and push it down the bypass hose fitting,, you can hook the impeller, and turn the fan to check if the impeller is secure..

 

[Trevor B]

Radiator did, in fact, have a bunch of cool spots.

Water poured into the top of the radiator didn't come out the bottom at same rate.

Removed t-stat, reconnected water outlet, and observed no current/circulation by looking into the radiator.

Disconnected bottom hose and ran a hose into the hole where the t-stat sits/water outlet while running engine, it dribbled through at idle. When I revved the engine, water came back out of the water outlet - it was not being spat out the lower hose like I expected.

Did not put any hook tools to check the impeller.

I pulled the radiator and am going to take it to a local shop tomorrow to be tested/inspected.

Part of problem is that I can't quite visualize the path the coolant takes. I'm new at this!
This is frustrating but hopefully the radiator is the culprit.

 

[Trevor B]

Okay, wow... I have had this whole thing upside down and backwards. I just watched a video on YouTube and I had totally misunderstood the direction the water flows. To my credit, I was TOLD, by someone who seemed to know what he was talking about, that the water flowed out of the top hose into the engine, which seemed counter-intuitive, to say the least. Wow again.

Please excuse how exceedingly stupid my last post must have appeared, what with putting a hose on the outlet! I am waaaay less baffled about the problems and now can clearly visualize the water's path. It also makes way more sense about the bottom hose compressing when revving - it is trying to suck liquid through the clogged radiator.

Amazing how baffling things can be when you are missing a piece of information.

 

[Inertia]

Right On ! !..

Hopefully the rad can be rodded out..

Get an estimate, cuz you may find getting an after-market aluminum rad less than a re-core..

cheers

 

[AJ/FormS]

Yeah, if its that bad, Id replace it. More security down the line.
-Rads may not be cheap, but cheaper than heads or long-blocks. And almost nothing is scarier than sitting in traffic watching the temp gauge climb.
-Except maybe seeing steam billowing out from under the hood at speed.

 

[Trevor B]

Just dropped off the radiator to get a new core this morning. Hopefully I'll have it re-installed by tomorrow afternoon.

Interestingly enough, the radiator guy pointed out that it was probably not the original unit as it was only 18" and didn't have the Chrysler stamp on the top. He had another one in the shop that was 22", from another Duster. He was pretty old-school and quoted me slightly less than a new aluminum one, which he dismissed immediately (being made of aluminum).

Man, I sure hope this is it. My wife gets back in town tomorrow night and she hasn't seen this car yet... If we can go for a spin it'll be great. If it's just sitting there in front of the house not working, it won't be great.

 

[TF360]

AJ/Forms-great advice!