Finally found the cause of my overheating

-
S

Smcomanche

Well-Known Member
Joined
Nov 11, 2017
Messages
66
Reaction score
28
Location
Denver
Two weeks ago I was headed home in my 1964 Dodge Dart Convertible from the local dart game night at the brewery near my office. To my surprise I see the temperature gauge flirting with the end of the "OK" temperature range. I nurse the car home with the heater on making sure I don't exceed the high temperature level.
Last weekend I check the thermostat in boiling water, flush the system, add fresh coolant, and viola everything looks great. Drive to work yesterday morning and all is good in the world.
Last night, I am again heading home from darts, and guess what, over heating again! I pull into a gas station to fill up, and let the engine cool down. As I pull out something occurs to me, turn the headlights off. Sure enough, head lights off, engine cools down. Turn them on, and needle starts to climb.
So do I need a heat shield for my headlights!? :lol:
 
J Glenn said:
Is it overheating or is the gauge wrong when the headlights are on?
Click to expand...
It acts like it is overheating more than incorrect gauge, based on how the gauge moves. I plan to measure the current draw with the fan's and headlights on, I may be exceeding the ampacity of the alternator.
 
Smcomanche said:
It acts like it is overheating more than incorrect gauge, based on how the gauge moves. I plan to measure the current draw with the fan's and headlights on, I may be exceeding the ampacity of the alternator.
Click to expand...

Even if you are, the engine temp shouldn't change because of it.
I vote for an electrical issue causing the gauge to read wrong.
 
Smcomanche said:
It acts like it is overheating more than incorrect gauge, based on how the gauge moves. I plan to measure the current draw with the fan's and headlights on, I may be exceeding the ampacity of the alternator.
Click to expand...

Maybe put a volt meter on your temp gauge and see if it climbs when you turn your lights on.
And if you have an instruments fuse pull it and see if the gauge still climbs.

You may be getting extra voltage from the headlights circuit, or park lights circuit either one, and this could verify the possible causes.
 
Thanks! Checking the circuits did not occur to me. Given the number of electrical gremlins I am finding, it is a good possible cause. I have been planning to pull the dash this winter to do a full rewire. I did the engine last winter.
 
Buy yourself a laser temp gun from Harbor freight & check the temp at the stat housing. Just my.02.
 
TrailBeast said:
Even if you are, the engine temp shouldn't change because of it.
I vote for an electrical issue causing the gauge to read wrong.
Click to expand...

If the fans are turning at 1/4 speed because of lack of current availability, engine temp would/could be affected.
 
65wgn440 said:
If the fans are turning at 1/4 speed because of lack of current availability, engine temp would/could be affected.
Click to expand...
Fans? It's a 64 Dart with a slant 6. Unless it's a a/c car it has a belt driven 4 blade fan. And as a side note, unless it's puking coolant out all over it's not overheating, regardless of what the gauge says.
 
toolmanmike said:
Fans? It's a 64 Dart with a slant 6. Unless it's a a/c car it has a belt driven 4 blade fan. And as a side note, unless it's puking coolant out all over it's not overheating, regardless of what the gauge says.
Click to expand...
I swapped over to electric fans. So over taxing the alternator and slowing the fans, or current bleed to the gauge are both possible causes. I grabbed a water temp gauge and sensor from work today, so bisecting the issue should be easy. Finding and fixing the possible circuit problem will be more difficult, but I am sure it would be in the dash as it is years of band aids and splices in that rat's nest.
 
Smcomanche said:
I swapped over to electric fans. So over taxing the alternator and slowing the fans, or current bleed to the gauge are both possible causes. I grabbed a water temp gauge and sensor from work today, so bisecting the issue should be easy. Finding and fixing the possible circuit problem will be more difficult, but I am sure it would be in the dash as it is years of band aids and splices in that rat's nest.
Click to expand...
Ah, Now I see "fans" in post #3. @65wgn440 Sorry for the confusion.
 
Smcomanche said:
I swapped over to electric fans. So over taxing the alternator and slowing the fans, or current bleed to the gauge are both possible causes. I grabbed a water temp gauge and sensor from work today, so bisecting the issue should be easy. Finding and fixing the possible circuit problem will be more difficult, but I am sure it would be in the dash as it is years of band aids and splices in that rat's nest.
Click to expand...
Why did you change to electric fans? Have you been chasing the "overheating" problem?
 
65wgn440 said:
If the fans are turning at 1/4 speed because of lack of current availability, engine temp would/could be affected.
Click to expand...

If this were the case it would end up draining the battery while driving and end up stalling the engine.
 
Bone stock 64 alternator may be 40 Amps at best. I looked in a 65 service manual and it shows 3 different ones. 26, 34.5, and the heavy duty and/or A/C rated at 39 plus or minus 3 amperes measured at 1250 engine RPM.
 
toolmanmike said:
Why did you change to electric fans? Have you been chasing the "overheating" problem?
Click to expand...
Nah, I had the engine rebuilt this winter I decided to install electric fans at the same time. Mainly a preference, and I did not like the fan with out a shroud.
 
Thanks for the responses. This morning I started her up, turned on the headlights, and sure enough temp started climbing, turn off, back down again. Combined with a new problem of intermittent gauge lighting, I think the cluster ground is the winner. Hopefully I will have time to fully diagnose this weekend.
 
I think when you are loading the slant 6 engine to the max. - Alternator full load, and mech fan load, the engine takes more gas for the increased load, but the fan speed does not go up. A larger alternator or electric fans should solve the overheating.
 
Find the gremlin and then get yourself a 1970 alternator, double the rating and then upgrade the wire to the starter relay to 10G. All the juice passes through the bulkhead connector via some weak *** cable so you may want to upgrade that conduit too.
 
You must log in or register to reply here.
-

Back
Top