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Thermostat

Tiny
EDWARD VAHOVICK
  • MEMBER
  • 1964 CHRYSLER 300
  • 6.8L
  • V8
  • RWD
  • AUTOMATIC
  • 45,000 MILES
My car overheats when stationary and idling or when driving slowly in traffic at less that fifteen mph. I have had a very though flushing of the cooling system and have changed the original 180 degree thermostat with a 160 degree one. But it still gets very hot. Did I make things worse by going to a 160 degree thermostat? What more can I do to help keep things cool?
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Thursday, August 17th, 2017 AT 12:21 PM

14 Replies

Tiny
HARRY P
  • MECHANIC
  • 2,292 POSTS
I cannot get any specific information on the car, but would guess that one of a few things is happening here. (1) It is possible that there is a buildup of dirt and crud and stuff blocking airflow through the radiator. Simply rinse the core of the radiator until it is all gone. (2) It is also possible that your cooling fan is not pulling enough air through. This could happen if the blades were damaged/broken or, if it is a clutch fan, if the fan clutch is slipping. (3) It could be that the water pump is worn out. The blades that push coolant through the system could be bent from years of use (heating and cooling especially) and they just do not push like they should.

So (1) take a look at the radiator to see if airflow is being blocked. (2) See if it is a clutch fan. If it is, you will be able to spin the fan almost freely while the engine is off. If it is a regular mechanical fan, you should not be able to move it without some force. (3) I cannot think of a way of checking a water pump without taking it off.

It could also be that you simply got a dud for a thermostat, or possibly that it is installed backwards (easy to do, seen it a few times). You might look at that before taking the pump off. Let us know.
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Thursday, August 17th, 2017 AT 3:09 PM
Tiny
HARRY P
  • MECHANIC
  • 2,292 POSTS
Here are some guides to consider:

https://www.2carpros.com/articles/symptoms-of-a-bad-water-pump - Some pump symptoms

https://www.2carpros.com/articles/how-a-clutch-fan-works - Clutch fan information
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Thursday, August 17th, 2017 AT 3:20 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,414 POSTS
First off, beautiful car. Back when they used real iron and steel.

The 160 thermostat will not help much as it is the total capacity of the cooling system that sets the actual operating temperature limit.
What sort of temperature are you seeing?
Check the timing and the mechanical advance for proper operation.
Are you running pump gas with ethanol? If so you may want to have the carburetor jets altered as the ethanol will cause the engine to run lean and get hotter. To see if that is the case you can pull the plugs and see if they are shiny white and glassy looking.

I would also check the fan clutch, if it is not engaging it will cause it to run hot at low speeds.
Does it still have the fan shroud? They were not much but they do help.
Does it have AC? If so have you tried cleaning out between the two cores? Crud builds up and blocks the airflow.

Just a few things to look at.
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Thursday, August 17th, 2017 AT 4:13 PM
Tiny
EDWARD VAHOVICK
  • MEMBER
  • 8 POSTS
HEYMAN1104 : (1) It is possible that there is a buildup of dirt and crud and stuff blocking airflow through the radiator. A: I see no blockage of this sort, I do have a large transmission cooler in front of the radiator though.(2) It is also possible that your cooling fan is not pulling enough air through. This could happen if the blades were damaged/broken or, if it is a clutch fan, if the fan clutch is slipping. A: It has the original four blade fan with no clutch (all OEM). All original design. (3) It could be that the water pump is worn out. The blades that push coolant through the system could be bent from years of use (heating and cooling especially) and they just do not push like they should. A: I just replaced the pump one month ago so that is not it. (4) It could also be that you simply got a dud for a thermostat, or possibly that it is installed backwards (easy to do, seen it a few times) A: I will check this as a possibility but would not that cause over heating all the time? STEVE W. : (1) What sort of temperature are you seeing? A: temperature gauge goes to the upper limit of the normal range (gauge has a bar with no numbers) but needle reaches about 90% of full scale. (2) Check the timing and the mechanical advance for proper operation.
Are you running pump gas with ethanol? If so you may want to have the carburetor jets altered as the ethanol will cause the engine to run lean and get hotter. To see if that is the case you can pull the plugs and see if they are shiny white and glassy looking. A: I will check this asap. Thanks (3) I would also check the fan clutch, if it isn't engaging it will cause it to run hot at low speeds. A: Car never had a fan clutch installed. (4) Does it still have the fan shroud? They were not much but they do help.
Does it have AC? If so have you tried cleaning out between the two cores? Crud builds up and blocks the airflow. A: Car never had a shroud and does not have AC. Thanks for all the ideas I will check them and see if that helps. The engine is a 413 CI (6.8L) stamped (HP) on the engine block denoting "high performance". It has 10.1:1 CR does that factor in? I run Premium 93 octane gas with an octane boost and lead substitute additive at each fill up. Attached are some photos I took. Thanks for all the help guys!
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Friday, August 18th, 2017 AT 9:38 AM
Tiny
EDWARD VAHOVICK
  • MEMBER
  • 8 POSTS
Here is the temperature gauge. Pen shows where it reaches when hot.
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Friday, August 18th, 2017 AT 9:52 AM
Tiny
STEVE W.
  • MECHANIC
  • 13,414 POSTS
Hmm, the AC cars must be the ones that had the fan shroud. They do help. On my 1966 Impala the shroud dropped water temperatures by 14 degrees.

How long have you owned it and is the temperature rise a recent thing or has it been getting worse over the years?
You might want to add a test gauge just to see where the temperature really is. That OEM gauge might be showing its age.

High compression is going to drive the temperatures up but the higher octane and backing down the timing could help as well but you have to be careful there.

You say a thorough flush? Did that involve removing the radiator and having it rodded out? If not there may be enough scale and build up inside the tubes that it is not transferring the heat very well.

What are you running for coolant 50/50?
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Friday, August 18th, 2017 AT 11:46 AM
Tiny
HARRY P
  • MECHANIC
  • 2,292 POSTS
As Steve suggested, if the timing is slightly advanced, it could cause your car to overheat. I did not think of it because it has been a while since I have dealt with a car with a regular old school adjustable distributor.

I was also thinking about the internals of the radiator. There are a couple dozen little lines running from one side to the other and straight through the core so the coolant can be cooled by the air. If several of them have gunk built up and clogging them, that will cause an overheating issue like yours. If you take the radiator out and take it to a radiator shop, they can pull the tanks off and shove a small rod down the lines through the core and clear out the junk. This is a much more common issue than you might think.
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Friday, August 18th, 2017 AT 2:05 PM
Tiny
EDWARD VAHOVICK
  • MEMBER
  • 8 POSTS
Thanks for the suggestions. I suspected the radiator. Also could it be there is a lot of sediment in the bottom of the block causing this? This car had sat for over thirty years in a dealership. When I got it I had to have the gas tank pulled and cleaned along with the fuel lines. The overheating issue has been a problem the last six years I owned it. About a year ago one of the freeze plugs started to leak and when the mechanic removed the old plug there was a lot of sludge present. He suggested a though flush which I had done three times since. I found an interesting "reverse flush" procedure in a 1964 Chrysler service manual Chrysler recommended. Have you heard of such a thing now a days? See attached photos.
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Friday, August 18th, 2017 AT 2:42 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,414 POSTS
Reverse flush is the old school way. Still do it myself on my vehicles. Along with running acid flushes, pulling the block drains and running air in them.
Flush guns are fun. I have an Eveready unit that was new when your car was built. Have a newer OTC one that is much lighter to use.

If it was me, I would wait until you park it, drain it out, pull the freeze plugs and clean out what you can. See about having the radiator pulled apart and cleaned out. Then do not put "normal" coolant in it, put in some Evans waterless coolant. The stuff is great and does not corrode the system.
You may also want to see if you can move the transmission cooler out some. As large as it is I am betting it blocks a lot of air. As a test you could pull it out and bypass it, then see if it still gets as hot. I hid a transmission cooler and oil cooler on my 1966. One is in each front fender with a fan on each one if things get hot.
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Saturday, August 19th, 2017 AT 12:01 AM
Tiny
EDWARD VAHOVICK
  • MEMBER
  • 8 POSTS
Sounds great. I think this winter I will check these options out. Thanks everyone!
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Monday, August 21st, 2017 AT 7:35 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,256 POSTS
Nice work team. ;)
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Monday, August 21st, 2017 AT 6:11 PM
Tiny
EDWARD VAHOVICK
  • MEMBER
  • 8 POSTS
Just a follow up on this issue. I solved the problem by removing the Trans cooler and just using the cooler in the radiator. This seems to have solved the problem. Once again Thanks for all the help!
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Wednesday, September 20th, 2017 AT 9:38 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,256 POSTS
Nice work and sweet rides, we are here to help, please use 2CarPros anytime.

Cheers, Ken
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Wednesday, September 20th, 2017 AT 11:30 AM
Tiny
STEVE W.
  • MECHANIC
  • 13,414 POSTS
Great to hear you got it sorted out.

Was afraid that big cooler was blocking air. I have two of these on mine. They are Derale units. One for trans one for oil. Both have thermostatic and manual switching.
They make a much smaller plate type now. You can "hide" them easy enough.
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Wednesday, September 20th, 2017 AT 1:20 PM

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