318 overheating

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1970PAValiant

1970PAValiant

master of the break down
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So I just got a 1971 Dodge Dart 2 years ago and have been working on it and driving it for some time. Last week when I was driving my temp gage went dead. Ok I’ll go work on it this weekend. Today I started the car up and the temp gage was working. Ok cool. Started driving it and the needle was between the e and m on the gage. Then after a bit it climbed to the M. So I got where I was going and let it sit for 3 hours. Came out and it was reading at the T (like 1/4) I thought it was odd but whatever, went to get some food and the gage hit the line before red. So I got back (it was 1/4 mile drive and 2 mins at a drive through). It spit out prob 3oz of coolant, I went to see if I could borrow a temp gun from my coworker. Upper rad hose was 207 lower was 198, intake was 210. Rad was 200. When I got the car there was no thermostat in the vehicle so I put a 195 one in. Drove it a few times and it was all fine. So I had to drive this home but after 3 hours of sitting, the temp gage is reading 3/4 hot. So I start driving and it sits at the line before overheating, doesn’t go over it, just sits there. I turn on the heater and the heat isn’t insanely hot like I would think. So I am driving it and after about an hour it starts to go into the hot zone. Pull over. Open the radiator cap. Coolant is full, and while idling I see the coolant moving. Sit here for 30 mins and get finally home. So it’s burping a little coolant and I get a meat thermometer and put it in the coolant on top of the rad. 214. Gage is saying it’s overheating. I don’t hear anything from the engine like knocking or position slap, not even an odd misfire. Last week I put a new temp sensor in so I figured I’ll put the old one in. So I do that, fill the coolant up and. Start the car. Temp starts rising up past 3/4. I don’t see anything swirling in the radiator like no movement of coolant. The lower radiator hose is not collapsed and is cooler than the upper one. When I turn it off and put the cap on. I can feel burping in the upper rad hose. I’m at a loss to what to diag next. Could my new thermostat not open up at the right time anymore? What should I do next?
 
1970PAValiant said:
So I just got a 1971 Dodge Dart 2 years ago and have been working on it and driving it for some time. Last week when I was driving my temp gage went dead. Ok I’ll go work on it this weekend. Today I started the car up and the temp gage was working. Ok cool. Started driving it and the needle was between the e and m on the gage. Then after a bit it climbed to the M. So I got where I was going and let it sit for 3 hours. Came out and it was reading at the T (like 1/4) I thought it was odd but whatever, went to get some food and the gage hit the line before red. So I got back (it was 1/4 mile drive and 2 mins at a drive through). It spit out prob 3oz of coolant, I went to see if I could borrow a temp gun from my coworker. Upper rad hose was 207 lower was 198, intake was 210. Rad was 200. When I got the car there was no thermostat in the vehicle so I put a 195 one in. Drove it a few times and it was all fine. So I had to drive this home but after 3 hours of sitting, the temp gage is reading 3/4 hot. So I start driving and it sits at the line before overheating, doesn’t go over it, just sits there. I turn on the heater and the heat isn’t insanely hot like I would think. So I am driving it and after about an hour it starts to go into the hot zone. Pull over. Open the radiator cap. Coolant is full, and while idling I see the coolant moving. Sit here for 30 mins and get finally home. So it’s burping a little coolant and I get a meat thermometer and put it in the coolant on top of the rad. 214. Gage is saying it’s overheating. I don’t hear anything from the engine like knocking or position slap, not even an odd misfire. Last week I put a new temp sensor in so I figured I’ll put the old one in. So I do that, fill the coolant up and. Start the car. Temp starts rising up past 3/4. I don’t see anything swirling in the radiator like no movement of coolant. The lower radiator hose is not collapsed and is cooler than the upper one. When I turn it off and put the cap on. I can feel burping in the upper rad hose. I’m at a loss to what to diag next. Could my new thermostat not open up at the right time anymore? What should I do next?
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The fact that you got the car and it did not have a thermostat is telling. A 195 is a little too hot in my opinion. Most cars I've worked on like the 180, but it needs to be a high flow, not the el cheapo slant six kind you find in most auto parts stores. You said you saw flow; was it really moving, or just a little flow? Thoughts are water pump is weak/damaged, radiator partially plugged. Is the coolant nice and green, or is it rusty colored? What kind of fan does it have, clutch, shroud? Some more details may help.
 
There is a test kit for combustion gases. Thats where i start. No gases, then water pump. Then rad. If you can see inside rad with a good light, look for blockage.
A good telltale is the air passing through rad should be hot, like a furnace if rad is doing its job.

poor heat from heater, in warm weather, the heater should be unbearably hot. Heater fan on high, if core is working properly hoses should be near the same temp. Plugged core, big difference in temp.
If core is plugged, good chance rad is too.
 
Sounds like the radiator is stopped up.
 
The coolant is a nice green. When I got the car the fan shroud was cracked and they had an external cooler for the trans ( the trans cooler lines were 80% cut up rubber tubes which the return one was pinched and overheating the trans. I put new lines on and fixed that) after taking that cooler off found a baseball size hole in the radiator so I got an aftermarket radiator, removed the old one. Flushed the block with a garden hose both directions until I got clear water. Put a new one in and ran it all last year, even to Carlisle and back no problems. The fan is just a bolt on to the water pump. No clutch, no fan shroud.
 
My amateur video with plugged heater core.
 
1970PAValiant said:
The coolant is a nice green. When I got the car the fan shroud was cracked and they had an external cooler for the trans ( the trans cooler lines were 80% cut up rubber tubes which the return one was pinched and overheating the trans. I put new lines on and fixed that) after taking that cooler off found a baseball size hole in the radiator so I got an aftermarket radiator, removed the old one. Flushed the block with a garden hose both directions until I got clear water. Put a new one in and ran it all last year, even to Carlisle and back no problems. The fan is just a bolt on to the water pump. No clutch, no fan shroud.
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So after all that work, did you check the coolant level after the air worked out? After see the gauge move around it could be passing air. Tuning might be causing some of your issues too.
 
Test the cap. Fond someone that has a tester.
 
1970PAValiant said:
So I am driving it and after about an hour it starts to go into the hot zone. Pull over. Open the radiator cap
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Was the system pressurized when you took the cap off, it should have sprayed coolant all over the place if it was pressurized.

What pressure cap do you have?

The temps you saw don't seem too far off to me.

You mentioned you replaced the rad. What part number is it?

Regarding the temp guages... You could have an IVR issue. What does your fuel gauge show?

I can't imagine the engine being very warm after 3 hours.
 
Dana67Dart said:
Was the system pressurized when you took the cap off, it should have sprayed coolant all over the place if it was pressurized.

What pressure cap do you have?

The temps you saw don't seem too far off to me.

You mentioned you replaced the rad. What part number is it?

Regarding the temp guages... You could have an IVR issue. What does your fuel gauge show?

I can't imagine the engine being very warm after 3 hours.
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When I took the cap off it didn’t spray anywhere. Pressure cap is pretty old so I can’t see what it is rated at. The Rad was just a generic one I found on Amazon. It’s been good for over 3000 miles so far. When it started going a little high the fuel gage was working, then when going to lunch the fuel gage stopped working. It’s done that before but never overheated. After having it home for 3 hrs the engine was still pretty warm and was at an ok temp when I rolled the key. I started it and it idled fine in park but drive it started to idle very rough. Got it to idle after adjusting the idler screw 1/8 turn. I’ll look at it again on Monday when I get home
 
1970PAValiant said:
When I took the cap off it didn’t spray anywhere. Pressure cap is pretty old so I can’t see what it is rated at. The Rad was just a generic one I found on Amazon. It’s been good for over 3000 miles so far. When it started going a little high the fuel gage was working, then when going to lunch the fuel gage stopped working. It’s done that before but never overheated. After having it home for 3 hrs the engine was still pretty warm and was at an ok temp when I rolled the key. I started it and it idled fine in park but drive it started to idle very rough. Got it to idle after adjusting the idler screw 1/8 turn. I’ll look at it again on Monday when I get home
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That tells me the cap is not holding pressure. Every pound of pressure raises the boiling point 3°. A 15# cap get's you 45° and raises your boiling point from around 212° (depending on your altitude and antifreeze concentration) to around 257° and it will help prevent it from puking when you shut it off. Don't be concerned about how warm it is after it sets 3 hours. It is what it is and really has nothing to do with overheating. Now all that said, you may have other issues but don't overlook the obvious.
 
1970PAValiant said:
spray anywhere. Pressure cap is pretty old so I can’t see what it is rated at
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As mike mentioned about the cap needing to hold pressure, you need a new cap. (BTW the new cap might uncover all kinds of issues. Like leaks etc. When the cap doesn't hold pressure you can have a gaping hole somewhere and not have a leak but once you apply pressure it will leak for sure. Not saying it will happen, Just be ready)

1970PAValiant said:
When it started going a little high the fuel gage was working, then when going to lunch the fuel gage stopped working. It’s done that before but never overheated
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My point is that the reliability of your dash temp guages is suspect. I would at least temporarily invest in a aftermarket under dash temp guage to know what is really going on. Then after you have sorted out the engine and if it is indeed overheating, work on the gauge cluster.


1970PAValiant said:
After having it home for 3 hrs the engine was still pretty warm and was at an ok temp when I rolled the key
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General rule of thumb... If you can hold your bare hand on a surface it is generally less than 120 deg F. After 3 hours I doubt that there is a surface, or coolant that is greater than 120. After 3 hours and the dash temp guages goes up to anything more than the right most normal line ( I would expect it to be way less than that) you guages or sender or wiring or ivr or printed cir board in the cluster is failing.

I drive my dart for about 30 minutes 1 hour and 45 minutes ago. I just went out and with a thermal temp guages measured the hotest to be 145F, I could touch every part of the engine.
 
Secret tip #1; if the coolant temperature sensor is inside an air pocket, it will lie like a dead dog. The sensor needs to be in a liquid.
Secret tip #2; If the liquid level in the rad gets to be too low, the coolant will not get into the heater core, and the fan will NOT blow hot air.
Tip #3; if the rad fins are plugged with dirt, or the condenser in front of it is, then the rad temp will march towards the same from top to bottom.
#4; a slipping belt is not always vocal about it.
#5: As for the temp spread from top to bottom, I look for about 25/30 degrees.
 
Your fuel gauge and temp gauge are on the same circuitry, but all of the above is worth looking into.
 
CRUZE 418 said:
Your fuel gauge and temp gauge are on the same circuitry, but all of the above is worth looking into.
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Meaning that if the DVR is acting up, it will affect BOTH gauges. But if only one gauge is acting up, then it may be telling the truth.
The DVR is supposed to put out a 50% duty-cycle pulsed 12 volts. Which is supposed to generate an average 6 or 7 volts power supply to those two gauges. But the gauges are so slow to react that yo never see the pulsing.
The gauges work by grounding the other side thru the senders. With calibrated points that correspond to the markings on the gauge faces.
But the temp sensor HAS to be in the moving coolant to have a half a chance at being accurate. If the sender is in air, or in a stagnant pool, it will read low. If both gauges read high, then the VR is outputting too high. If ONLY the temp gauge is high, then either it is telling the truth or close to it; or the sender is fubarred. The sender can be ohmed out and compared to specs, or simply replaced. But they very rarely go bad.

If the DVR is intermittently showing erroneous readings, you can bet it's because the supply voltage throughout the run circuit is fluctuating. It could be the charging system, or the fusible link, the bulkhead connector, the ignition switch, or even the amp-gauge.
 
Yes to all of the above, bad circuit boards, 50 year old wiring and oxidation. I guess what I am saying is that you may have to go in and start looking for something visually bad or bad connections. My car had really awful wiring, bad circuit boards, I replaced all of it, but it's expensive. Start looking.
 
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Ok sorry for the late responses but I got a little looking at Sunday. So I got a new radiator cap and let it idle for 30 mins. Stayed in the middle temp and my fuel gage started working. Once up to temp and the thermostat opened, saw the upper rad hose leaking due to the clamp needed to be tightened. ( the radiator and hose I put on last year new). So with a temp gun and reading 201 at top and 180 on the bottom the gage started to climb just a tad. Turned off the vehicle and put 2 test lamps on the feeds to my temp gage and my fuel gage. So my fuel gage stopped working again when I turned it back on and my temp gage started to rise and the test lamp for that was on a lot more. I ordered a voltage limiter and am gonna pull the dash this weekend and clean up the board and whatever else I may find.
 
I believe the new VR's are solid state. If you have a bad circuit board or boards, I have heard of people repairing or trying to. New are available and may come with a new VR.
It's been a couple of years ago since doing mine, don't remember.
Good luck!
 
I’ve gotten an OEM since I work at a dealership and I’ve been reading all the threads here on people repairing. If not I have a friend that makes circuit boards for the milatary so he might be able to make one for me
 
Well, which ever way you go. My boards were made by charger specialties. Checked Mega Parts, they only carried one a body board, my Dart dash has 2 boards. Don't know if charger is still in business or not, here is the phone number that I had for them. 775-751-3849.
My boards came with a solid state VR and radio noise suppressor.
 
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