1976 Dart Overheating and other issues

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Mako21

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Hello,
This is my second post on the forum. I just purchased a nice 1976 dart with the 225 slant six. I'm located in Miami and it's always hot here. I can drive 20 miles before the temperature gauge goes to the 2 o'clock position just prior to the max approaching 250. I spoke to the previous owner who rarely drove the car and simply sold it as he is approaching his mid 70's in age. He took great car of it (original Florida car with no rust), however strongly recommended to have all fluids gone over. I changed the oil to what he was using Castrol 10w30 high mileage).

What can I do to get the car running cool so I can drive it? Amongst my research on here would be:
1. Flush the radiator
2. Replace the thermostat with a 180 (minimum)
3. Replace the radiator cap (I currently have a 13# pressure)
4. Ill probably change out all the hoses (although they look ok- they're soft)
5. Change plugs for good measure
6. Check the timing (I've read 6 degrees is good)
 
I think your plan is valid.

Do #1
Do #2 but use the proper temp.
Do #3 with correct pressure.
Do #4 with hoses off you can see if the impellers on the water pump are intact and turning.
Dont do #5 at this time if engine is running well otherwise.
Do #6 refer to factory service manual

Additionally I would:
do a pressure test on the cooling system.

look for signs of combustion gasses in the coolant.
 
Also, I am thinking of changing the three belts. When i accelerate the car in park or neutral, i do here a belt screech. No leaks from the water pump area or coolant leaks in general, so I'm thinking the water pump may not be spinning as efficiently, although the belts do seem nice and tight.
 
Also, I am thinking of changing the three belts. When i accelerate the car in park or neutral, i do here a belt screech. No leaks from the water pump area or coolant leaks in general, so I'm thinking the water pump may not be spinning as efficiently, although the belts do seem nice and tight

With belts off see if water pump is able to turn and you should be able to hear some fluid movement.
 
Soft hoses are a bad thing. They should be firm. But not hard. Soft hoses can collapse and interfere with proper circulation.
 
Ok I will definitely be changing the belts. The belts are three different brands embossed ( Goodyear, Dayco, and some other I can't make out). This is a 3 pulley car. I have factory AC and Powersteering. Trying to research online all 3 sizes to get.

Also, when flushing the radiator, I see three outlets at the bottom of the radiator. A plug at the drivers side, then moving to the passenger side a pipe that I assume runs to the heater core? and then next to it the rubber hose running to the water pump. Do I pull all 3 to flush the radiator?
 
Also, when flushing the radiator, I see three outlets at the bottom of the radiator. A plug at the drivers side, then moving to the passenger side a pipe that I assume runs to the heater core? and then next to it the rubber hose running to the water pump. Do I pull all 3 to flush the radiator?

Really could use more information here. A few pictures of the engine and radiator area would help out a LOT! It would be nice to see what fan is there and if it has a shroud or not. 20 miles at what speed? Was the A/C on?
Buying an old car is like a box of candy, you dont know what you have until you bite into it. Assume nothing as far as maintenance issues go. Until you verify everything, you dont know where the problems are. Do not fix things that aren't broke or do too many things at once.

Look on the firewall above the engine on the passenger side and you should see 2 rubber hoses approximately 1-1/8" O.D. Those are the heater hoses leading to the front of the engine. They do NOT go to the radiator.

There is a petcock on the bottom of the radiator that drains the radiator. If you have an automatic transmission, there will be 2 hard lines that lead in and out of the transmission to the lower radiator. Do not mess with those as the radiator also is used to cool the transmission fluid. If you drain some of the coolant, look at the color. It most likely should be green if the right coolant was used. If it looks brown, you should change it. A 50/50 mix of coolant and water raises the boiling point of the fluid. Look for blockage at the front of the radiator. The fins should be clear without blockage. You can squirt a hose from the engine side towards the bumper to dislodge the junk. Hell, If it was me I'd drain it and remove it to get a good look at it.
Factory gauges are kind of approximate indicators. Running at 220 is nothing to get upset about if the cooling system had been verified to be in good shape.
 
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For the belts... I recently redid all three on my ‘75 Dart Sport (with /6 and power steering + factory AC). I had a hard time finding the right belts online and recommend Rock Auto for this. Reason: They had such killer cheap deals that I ultimately bought multiples of sizes. <- This way I was covered for any scenario. It was around $24 for 3 belts for each location. I might be able to email my cart with part#’s. In the end I kept the extra belts for other project cars..

Also, this is one of those few jobs where I really had to rely on help from a retired mechanic (that knew precisely where to look for the swinging mounting brackets). Mine were all covered with grime and I never would have figured out where the PS pump bracket swings/rotated without someone to help me located it.

Good luck!
 
Thanks for the great fredback. I didn’t get as much time as I was hoping for today, due to the kids going back to school tomorrow and having to get things in order.

I can drive about 20 miles and through the drive the temp needle never really settles. It’ll steadily climb its way up to the mark just prior to the 250. Speeds are usually at 45-50 mph, minimal stoplights.
The car is completely original. I did take some quick photos of the engine bay. My Dart is a factory AC car, however I leave it off as the system is r12 and not charged. I do have a shroud. I also tried tugging on the cooling fan in front the radiator and it doesn’t wiggle an inch, so I think it’s ok.
Regardless, since it’s a new purchase for me, I’m changing out l the fluids to get a baseline for my maintenance logbook.

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The orange hose from firewall to front of engine is one of your heater hoses. The black one next to it is the other heater hose.

Just have to ask... Do you have radiator fluid in the engine?

A quick check to see if the thermostat is opening. Cold engine, remove rad cap. Start engine, idle till hot, look for water movement in the radiator
 
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I checked to see if thermostat is opening. Fired up the car with the radiator cap open and eventually watched water flow. Let the car idle for 45 minutes with cap off and had consistent flow with the fluid.
The car stayed at the first indicator just above 120. I deduce from this that she’ll idle all day and never run hot. But the moment I go drive within 20 miles at 50mph she slowly makes her way to the upper peg, prior to 250. I have to shut it down at that point and wait about an hour for things to cool . Drive back home.

So if the radiator has fluid, thermostat confirms it’s opening, could I have a water pump issue? I have no coolant leaks under the car. No blockage in front of the radiator. Fan appears to be turning and pushing air well (it’s not backwards). Fan has no play in it with engine off. Here’s a picture of the radiator. It’s discolored by I don’t see any fins being very bent.

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To be honest, that radiator top tank looks terrible. But looks can be decieving. Clean off all of the copper and iron corrosion residue. Then if there are any leaks when the system is hot (under pressure) you will see them, or at least the fresh evidence. It could be pinhole leaks, could be a cap or hose, could be a solder joint. Any loss of pressure holding ability will result in the temperature climbing above the normal range under extended use.
 
I would first take the radiator out, and take it to a radiator shop, get it flushed out properly, possible it even needs re-cored, it looks really rough on the outside, the inside cannot be any better.

Second, the factory gauges are not too accurate I would add an aftermarket gauge, on my 76 duster, it was a simple as pulling a plug above the thermostat housing, and adding a mechanical gauge.
 
Timing. If everything is factory, then follow the factory guidance. The advance curve in a '76 distributor very well may be difference than a '75 and most certainly different than a '67.
The best source of information will be the sticker(s) in the engine bay. Clean them gently. Hopefully they are there and readable. One should have the timing. It will also show what rpm the timing should be measured. Use a golf tee to plug the vacuum hose that normally connects to the distributor.

While there, make sure the vacuum hose from the distributor to the timing port on the carb is not cracked or leaking. They generally last a long time but good to check.

lemme also mention that 1976 has a fair number of differeces from other years. Generalizations that may be often true do not always apply. Be careful when reading/hearing any sweeping statements about parts or systems.
 
I just shut it down and there is an ever so slight bubbling at the upper outlet in the metal just before the rubber hose. Barley noticeable, but probably a pinhole. Also, when I turn the key to ACC position to look at the gauge, the temp went from the lower tick to the middle after shutdown, but I assume that’s normal due to the reduced airflow from the fan since I shut it down.
 
I just shut it down and there is an ever so slight bubbling at the upper outlet in the metal just before the rubber hose. Barley noticeable, but probably a pinhole. Also, when I turn the key to ACC position to look at the gauge, the temp went from the lower tick to the middle after shutdown, but I assume that’s normal due to the reduced airflow from the fan since I shut it down.


Yes its normal for the temperature to rise after shutdown.
I'd say the temperature gage is providing exactly the information it should, and you are interpreting correctly.

Upper large hose connection is the radiator's inlet.
let it cool, drain off some coolant and check out that leak.
If its a solder joint, repair should be easy.
Core doesn't look terrible in the photos through the fan.
But again looks, esp in a photo, can be decieving.
See what it looks like on the inside once you drain it (and maybe run some clean water through it).

Or if you can find an old school radiator shop, have them check it out.
Good recore of an original radiator is a couple hundred easy. If neccessary, it is worth it assuming the tanks aren't too thin. Solder repairs and patches are less expensive.
New radiators are often made thinner and with less quality control.
 
It sounds like you are fairly inexperienced at this.
So....DO NOT remove the radiator cap while everything is hot! I've seen 2 guys get badly scalded doing that. Imagine Old Faithful geyser right in your face. Even just warm, cover the cap with a doubled up towel before removing.

Overheating at cruising speeds sounds like a radiator problem. As mentioned already, I'd take it to a raduator shop and get it checked out.
 
Yes, this is my first vintage car so I am I new to it. I’ve been reading a lot on the forum for how to get things done.

I found a shop local that specializes in radiators. I’ll make an appointment.

To the poster who mentioned to check the timing, My sticker on the fender says timing is to be at 2 degrees BTC.

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My first suggestion would be to flush the cooling system with what you can find at your local parts store, then get he radiator cleaned properly. My final suggestion would be to go to "mymopar" & download a factory service manual (FSM). Read up on the cooling system & tuneup, including timing. I think if you follow these suggestions, you maybe able to solve a lot of your problems. Along the same vein, get an infrared temperature gun (Harbor Freight) & check the temp at the radiator & stat housing to see if your gauge is close to accurate.
 
Yes, this is my first vintage car so I am I new to it. I’ve been reading a lot on the forum for how to get things done.
The advice to relay on the shop manual and Chrysler's Tech Bulletins is a sound one.
A lot of keyboard mechanics on the internet. Starting with a good foundation will go a long way in seperating the chaff from the wheat.

I found a shop local that specializes in radiators. I’ll make an appointment.
That sounds bad.
A radiator shop doesn't specialize in radiators.
Shops that say they specialize in radiators are usually general repair shops.
Call the shop and ask if they rod and clean radiators. Ask if they solder. If the answers are yes, then bring them the radiator. Some will let you bring the car and do the removal and install. if they answer yes to the first two, you could ask them about that if you really want.

To the poster who mentioned to check the timing, My sticker on the fender says timing is to be at 2 degrees BTC.

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if you turn the photo horizontal before posting it will appear larger in the post.
The forum software resizing feature seems to allow about 800 pixels horiz but maybe less vertical.

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Note the other information with respect to timing. In particular, 2*BTC plus minus? 2* at 750 RPM plus or minus 100 rpm.
Also further down, to disconnect the vacuum advance canister. On the slant six, its often easier disconnecting the hose on the other end and capping the manifold source. Reconnect after setting the timing.

However since you've found a leak, and the system wasn't even hot yet, its pretty clear this is the first thing to address.
Any leak means the system can't hold pressure. Fix that.
The engine bay looks clean and that may be the only big issue.
Since the car has A/C, there will be a condenser in front of the radiator.
If you remove the radiator yourself, just take your time and keep track of all the parts. Its not hard. Be prepared for ATF to drain out when removing the transmission lines. Use a pair of 'line wrenches' when breaking the nuts free.

www.Mymopar.com has many of the Chrysler Tech bulletins and films, along with scans of some factory shop manuals.
www.imperialclub.com also has many Chrysler tech bulletins and films, but less so for mid and late 70s.

Hopefully you have the owners manual. Not many, if any, are available digitized. For paper copies of manuals, originals and reproductions are available from various sources. Bishko is a big vender with good rep.
 
I agree with Mattax on the radiator, it needs the tanks taken off & the core cleaned & inspected completely before resoldering the tanks back on. A true radiator shop can do ALL of this, if they just want to flush it, you can do that on your own.
 
Something I noted is with all the green on the fins your rad might be clogged on the outside. Meaning the fins have so much corrosion in them that air cannot efficiently pass to pull heat away.

Also with an a car as mattax mentioned the ac condenser is infront of the rad and it might be clogged up too.

I have seen folks pull an ac condenser and the fins just fall apart into dust just be prepared.
 
Ignore the 2* BTC and try 6-10*. It's pretty much SOP for slant owners.
 
Ignore the 2* BTC and try 6-10*. It's pretty much SOP for slant owners.
That may work well for a non-smogged 60s 225 slant six. And it might be a good starting point for a mystery distributor on a mucked with car.
When using the original distributor on the original engine, its setup to advance off idle to the correct timing for the engine.
Without any further information, 2* plus minus 2* at 750 rpm (plus minus 100 rpm) is a good starting point.
I think OSAC is gone in '76. If not, and the owner is wishes to experiment, that would be the first timing change to make.

Before making any change, it is critical to measure what the timing and rpm are at slowest idle it will run, and at 750 rpm.
Making changes without a baseline too often reuslts in chasing your tail. Been there, done that. Hate to see a new guys make the same mistake.
 
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