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Strange overheating issue


AL1630
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Hi all, I've been fighting a somewhat strange overheating issue on my 1963 Rambler American, OHV inline 6. When sitting in traffic, the temp gauge begins to climb. Once I get up to 35-45MPH, the temp drops back down into the middle again and seems to stay there, but if I go faster, say 55-60, the gauge begins to climb again, and will go all the way to the top. These issues seem to happen with any outside temperature, but happen much faster if it's hot outside.

  • The car has a brand new 2 row aluminum radiator
  • New water pump
  • flushed the system with Evapo-Rust, it now seems clean inside.
  • I've tried using a thermostat vs no thermostat vs just the restrictor plate, none seem to make much difference

So, has anyone seen something like this before or have any ideas to fix this?

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I tested it in a pot on the stove before installing it, and it opened at 195 degrees (Stock temperature). I had it in with the pointed end facing toward the radiator, which i assume is correct? What's strange to me is that this issue persists even with no thermostat when it's relatively cool outside.

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That depends on how much you need to test it. If you need to know how far it pulls and at what vacuum, then yes you need a vacuum pump and probably a dialback timing light.

 

If you just need to know whether it has failed or not, and if it connects with a hose, you can just put on a piece of clean, new, tight-fitting vacuum hose and suck on it, while watching for movement inside the distributor (with the distributor cap off). Move it as far as it will go and plug the end of the hose with your tongue. It should hold vacuum and stay in the advanced position (until you release it). If it does not hold vacuum, there is a hole in the diaphragm and it is bad.

 

Slightly more expensive suggestion: Got a Harbor Freight nearby? The pump does not cost much if you get a cheapie.

 

If it is hooked up with steel tubing, you would have to find a hose barb (and some thread sealer) to fit it in order to test.

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4 hours ago, AL1630 said:

The car has a brand new 2 row aluminum radiator

Is this an engineered replacement radiator or just a generic rad?  Did the engine overheat with the old rad?

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And if those suggestions don't get you anywhere, see if that parts store that rents things has a "block check" kit, a device you pour a blue liquid into and put over the radiator neck with the engine warm. The point is to find out if combustion pressure/fire is leaking into the cooling system. The most common cause of that would be a bad head gasket, followed by a cracked head or block. If you find combustion in the cooling system, you will need to pull the head off and have a look. I am getting ahead of myself here though, always try the simple and cheap things first.

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I was able to borrow a vacuum pump from a neighbor, and the vac advance seems to be working.

2 hours ago, Tinindian said:

Is this an engineered replacement radiator or just a generic rad?  Did the engine overheat with the old rad?

It's just a generic aluminum one. It didn't have a radiator when I got it as it had been sitting for a long time. I replaced the head gasket already, hopefully that's not the issue.

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I've owned a 1966 and a 1970 Rambler (actually, AMC). Daily drivers (before they became collectible). I've had something similar happen twice. Each time it was a bad head gasket. 

 

I hope that's not your problem, but check your water consumption. 

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I agree the original thermostat was probably a 160 or 180, changing the thermostat probably won't fix it.  Thermostats only control minimum temperature, not maximum temperature.  The rest of the cooling system and engine condition such as cooling capacity of the radiator(is the new radiator thermal capacity equal to or greater than original?),  water pump condition, cleanliness of the water jacket and exhaust leaks into the cooling system via the head gasket or a cracked head or even cylinder block are the items that will affect maximum temperature.  If the car spark-knocks on acceleration the timing could be too far advanced or if this were a high compression engine the fuel octane level could be too low.  If it pops out the exhaust the timing could be too retarded or the fuel octane could be too high.  If you are getting a normal temp reading at 35mph and the gauge is accurate and the rest of the system is healthy the 195 thermostat probably would not make the car overheat at idle or higher speeds.  Something else is wrong.   Is there foam in the radiator or are you getting heavy white deposits on plugs?  Is anti-freeze coolant getting into the oil making it milky?  If running straight water do you get water beads by wiping the dipstick with clear cellophane?  These are all signs of exhaust leaking into cooling system.  If it is losing coolant out of the radiator, I.E. radiator boil over, is the radiator cap the correct pressure rating and is it working?  The boiling point of water goes up about 3 degrees per PSI of pressure in the cooling system so straight water wouldn't boil until 242 degrees with a 10 psi pressure cap.

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195 is in the middle, the factory service manual says that's the stock thermostat temperature. I'm fairly certain the gauge works, on a cold morning it warms up more slowly than a hot day, but i haven't tested with a thermometer. The radiator doesn't seem to have foam in it and the oil isn't milky. Rad cap is working ok, it was new with the radiator and holds pressure.

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I'm inclined to go with those suggesting exhaust getting into the cooling...

Had a Chev Cavalier the same---regular running around town or in semi-country/suburban area was fine; get stuck in heavy traffic it heated and would go into the red if couldn't get going or park to cool. Uphill, any load, same thing: watch it slowly heat....Running fan on defrost slowed heating but couldn't prevent it.

Don't recall ever adding any coolant, ran ir like that for a year or so, and no visible exhaust when starting or running.

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On ‎9‎/‎22‎/‎2019 at 7:33 AM, AL1630 said:

flushed the system with Evapo-Rust, it now seems clean inside.

 

'Seems' may be the clue. How can you tell?

Do you have one of those infrared temperature gizmos? Maybe take its temperature front, middle and rear.

Also use it to look for hot and cold spots on the radiator.

Another thing to look at are the hoses, they can deteriorate on the insides.

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When I pulled off the water pump, it looked clean and I couldn't feel any rust or gunk buildup when i poked around again. Of course, there could be more hiding in the block. I might have to try the temperature gun if I can find one. All my hoses are just a few months old, I would hope they aren't the problem.

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I might have to pull out a core plug sometime. What makes me worried it's a bigger issue than dirty cooling passages is that the engine runs ok, not great, and only gets about half the MPGs it's supposed to. I tried tuning some stuff and got it from 10 to 13 mpg, but last time i filled up it dropped back to 10. The car is supposed to get at least high teens/low 20s for mileage. Could these 2 problems be related or caused by the same issue?

 

Edited by AL1630 (see edit history)
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How are you measuring your mileage??

Granted 10 is low, but remember these cars only got their "customary" mileage running at normal speeds on generally smooth level highway in clear weather conditions...

Anytime you ran in short trips, or in-town traffic, your mileage fell , sometimes drastically, if you spent time in going thru the gears to the next stoplight, and if the  engine's been idling/running while you tinkered, that consumes gas too.....

Do lpok at the plugs, as mentioned above...

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Unfortunately, even after driving on the highway, mileage doesn't seem to change much.

I pulled the plugs - they're in order from #6 on the left to #1 on the right. They are the same plugs that were in the engine before I changed the rings, which may explain some of the blackening.

2019-09-25 19.54.31.jpg

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#6 looks to be somewhat cleaner than the rest.

A cleaner plug could be a sign of ingesting water. Which could lead to pressurizing the cooling system.

Someone here can tell you about sniffing the coolant for exhaust in the radiator. I have never done that.

Odd that the spark plugs are mismatched and didn't get replaced with a ring job.

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With the engine fully warm, you can wave the probe of an exhaust analyzer in the air right over the water neck. If you see HC in there, you most likely have a combustion leak, and if you see CO, you definitely do.

 

Another method involves a clear plastic tube that you pour a blue liquid into. The tube goes on the radiator neck of a warm engine, and it looks for CO2. The liquid turns yellow or at least green if you have a combustion leak. You can usually find this thing at al auto parts store that rents tools (Oreilly, Autozone, etc.). They will have blue liquid for you to buy to use with the tool.

 

Neither method is perfect or completely perfect of foolproof, but you generally won't get false positives. If one of these tests says it's bad, it is. If the test says it's ok, it might still be bad.

 

Another thing that sometimes works is to do a leakdown test, and watch for bubbling in the radiator.

 

 

Edited by Bloo (see edit history)
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I was able to borrow a blue liquid tester from the parts store, and it stayed blue, so hopefully there's no combustion leakage. I also did a compression test and got 130 PSI or above on all cylinders. I also got all new plugs to put in. I guess at this point the most likely cause is probably rust in the water jackets, unless someone thinks of something  else.

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Al,  what is happening here is the COOLANT is running hot. For it to get hot, it has to be soaking up the heat from the engine.  Seems to me even if the block water jacket is partially plugged,  the coolant should still cool down in the radiator.  There would just be a hot spot at the back of the engine. It has been suggested that you get an infrared thermometer. Please do so. Run the engine until the temp goes above the 190 so you know the thermostat is open . With the thermometer, check temps at the thermostat outlet and record.  Check the front of the radiator, left to right about three places. Do this top to bottom at three places and record . Check the radiator inlet and outlet.. Lets see what you find. 

  There was a thread awhile back on the HAMB like this. The NEW radiator was plugged.

 

  Ben

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  • 2 weeks later...

Not trying to be difficult, but I have never seen a car with an overheating issue that I couldn’t identify the cause in less than a few hours. I recommend taking it to a shop with experienced people......yup, it will cost money.

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I have coils in both upper and lower hoses. Water seems to flow pretty well with the garden hose. It's been a lot cooler outside recently and the engine is staying cooler now. I should probably go to a shop, it seems like I've crossed out pretty much everything.

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Incorrect spark timing can cause poor mileage and overheating.

 

Have you checked your point dwell at various speeds? Worn distributor bushings can cause the dwell to vary and change the timing. Worn timing gears or a stretched timing chain will also cause the timing to vary.

 

If your timing marks are on the vibration damper, it is a good idea to check that the TDC marker is correct. Some vibration dampers can slip on the pulley and give you an incorrect indication of TDC.

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I'll try to track down a dwell meter to test. Should the dwell stay the same at any RPM or should it change as it increases? The engine also seems to shake a bit if revved up in neutral, and sometimes when it's cold and idling. Those symptoms seem to have developed fairly recently. Could those also be a timing issue?

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use a timing light and check the mechanical advance and the vacuum advance separately. The Timing should be set with the vacuum disconnected at the proper idle speed. then hook the vacuum back to the distributor. If the vacuum line comes from manifold vacuum the timing light will show the mark (Timing marks on crankshaft) advanced when the vacuum is connected. If the vacuum comes from a ported location on the carburetor (vacuum line connected above the throttle plate) it will only get advance from vacuum when the throttle is opened. You can substitute manifold vacuum temporarily to check for proper advance with the timing light and if OK put the correct ported vacuum line back in place for operation. To check the centrifugal advance leave the vacuum disconnected and with the timing light raise the engine speed while watching the timing marks. As the speed increases you should see a timing increase if the weight system is working.

 

One of the biggest mistakes people make is to put points into a distributor and set the ignition timing with a timing light without disconnecting the vacuum to the advance diaphragm at the distributor. This has the timing set on the retarded side which will lower power and fuel mileage.

 

I hope this will help you.

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