AL1630

Strange overheating issue

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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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Perhaps you have a hose collapsing from lack of a wire coil in it - a water pump has pretty impressive suction.

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Try pulling the bottom hose off the radar from the block and sticking your garden hose in the filler neck. Water should flow out a a good rate. 
If not , your rad is plugged or to effective for the age of your car. 

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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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Dwell should be the same at all rpms and the needle should be stable.

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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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I spent a lot of time corresponding with a friend having cooling issues with their 1931 Auburn - turned out the impeller was slipping on the shaft (I just joked about it as never really thought that could happen, but after looking at 100 other things.... - and then sure enough)

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Flowing only 26 percent.  Wow.  How did someone manage that, Ed?

 From MANY years of experience, I believe most "overheating" problems are "under cooling"  due to plugged radiators or too small radiators. Easy to check. 

 

  Ben

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On 10/14/2019 at 6:26 PM, 19tom40 said:

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.

 

I got a dwell meter and hooked it up, and when I gave the engine gas, the dwell dropped by 10-15 degrees. I think I may have finally found the culprit (Or a big one anyway). The tachometer on the dwell meter also said that the engine is idling way too fast-I think that my throttle isn't returning all the way to idle, even after I replaced the spring.

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AL1630, 

 

It sounds like you might have a problem with the distributor, maybe a worn bushing. 

 

Once you fix that, you might want to try timing the car an old fashioned way to be sure the timing is not retarded too much causing the over heating.

 

To do that, get the car up to temp, remove the vacuum hose from the distributor and connect it to a vacuum gauge, and slowly move the distributor increasing the advance until the RPMs increase.  You can also look at the vacuum gauge to see the vacuum increasing.  When the vacuum reaches a maximum and/or the RPMs stop increasing back the distributor maybe 5degrees, hook up the vacuum advance hose and check the timing with a light to see where it is.  Test drive the car and let us know how it runs.

 

 

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Thank you, I'll look into getting the distributor rebuilt. I'll also try the vacuum timing.

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This weekend I put in a thermostat, 180 degrees. Driving this morning with the ambient temperature about 25 degrees, the engine didn't even get up to temperature on my 10 minute drive. This afternoon, it's been about 60 and the temp gauge would get well above the middle especially when idling.

 

As I mentioned before, my gas pedal doesn't return all the way, and if I pulled it back to the right idle speed, the temperature would drop, but as soon as i started moving it would rise again. Turning on the heater also dropped the temperature.

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Reading this last post, it sure sounds like a lazy water pump to me.

 

Mike in Colorado

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I once had what looked like a perfect water pump on the outside. it was sitting for 50 years with coolant in it. When I opened it up the blades of the impeller had disintegrated. It wouldn't move much water.

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I would hope it's not the water pump, I've already replaced that with a NOS one.

Edited by AL1630 (see edit history)

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If you haven't solved the problem already, I'd recommend you contact the AMC Club https://www.facebook.com/AMCRambler

 

You may find it is a common problem with a well-known solution, or find a colleague who has had the problem and figured out a fix. 

 

I have a 1966 Morgan that had the same symptoms. For that car it was a design flaw: The water flow rate through the radiator was too high, so it didn't have a chance to cool adequately. The solution was to put a partial plug in the bypass hose. 

 

Please post the solution for your car, once you have it.

 

Good luck,

 

Phil

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Yes, I'll double-up on pmhowe's request. I'm a Rambler fan and want to see how everything works out. 

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