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Odd cooling issue. Would appreciate input

M

MikeyM

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Hi all,

69 Bee with a 383, 22" radiator, no AC. The car runs and cools fine except at idle in hot weather, it starts to creep up. I will be installing a shroud soon but my questions are:

- Why does the temp gauge go up when the engine is turned off? Is this just residual heat going into the coolant?
- Why does my standard (non-lever type) radiator cap burp coolant out of the very top? I have an overflow bottle installed but the coolant doesn't go down the hose to the bottle.. I've confirmed it's clear.

Thanks,
Mikey
 
Where does your cap burp fluid? Temperature goes up when car is shut off due to residual heat and no cooling flow. Temp goes up at idle because no airflow across the radiator and reduced coolant flow because water pump is not spinning at a higher rate.
 
RR Fan Dan said:
Temp goes up at idle because no airflow across the radiator
Click to expand...
Nor the across the engine itself. An engine radiates by itself a decent amount of heat. Another factor often overlooked, heat takes time to travel. When an engine is ioperating, there can significant internal hot spots that generate heat. When the system is operating normally, the amount of heat being removed is equal to the heat being generated and that is flowing. When engine/water/fan all stop, the heat is still present and continues to flow, so cooler surfaces that where present when everything is running normal, keep absorbing the flowing heat and their temp rises. When that temp rises enough that the temp differential is great enough (delta), the system stabilizes and starts to slowly cool at the new higher temp and rate.
 
j-c-c-62 said:
Nor the across the engine itself. An engine radiates by itself a decent amount of heat. Another factor often overlooked, heat takes time to travel. When an engine is ioperating, there can significant internal hot spots that generate heat. When the system is operating normally, the amount of heat being removed is equal to the heat being generated and that is flowing. When engine/water/fan all stop, the heat is still present and continues to flow, so cooler surfaces that where present when everything is running normal, keep absorbing the flowing heat and their temp rises. When that temp rises enough that the temp differential is great enough (delta), the system stabilizes and starts to slowly cool at the new higher temp and rate.
Click to expand...
You are correct. I was trying to keep it simple.
 
I know this doesnt answer your questions, but it is worth noting, since you said that you'll add a shroud soon, that any part removed from the cooling system in your car is going to play a part in this problem.

Ive seen dicussions over the years, especially in the C body forums regarding cooling issues from the get go, up to and including the bean counters at the corporate level trying to save a buck in the radiator department. While you may find that to be a stretch, i can assure you that if your car came with a shroud and also rubber trim designed to channel air from the bumper area to the core support, you will see a rise in temperature if these items are altered or removed.... The engineers job does include doing his best with the materials and methods alloted to him.
 
Last edited:
If your cap leaks thru the rivet it has failed, if it is a smooth top there is only 1 place coolant can go, past the gasket at the neck (failed spring) and/or a issue with the overflow. Possible a little of both.
 
Most all cars will have a rise in coolant temps when 1st shut off.
If you have a clutch fan test the clutch.
The shroud will help.
Also buy yourself a new 15# cap and when filling the radiator leave the coolant level at least 1 " to 1 1/2 "below the radiator top.
 
Thanks, everyone.

No fan clutch or shroud from the factory that I'm aware of but they will be added soon. All of what you guys said makes sense.

RR Fan Dan said:
Where does your cap burp fluid?
Click to expand...
From the top rivet. New Murray cap does the same damn thing, maybe a fluke. Probably need better parts with no rivet.
1STMP said:
69 Sleeper Bee said:
I have the same exact setup as you and no issues. I would look at a new cap first.
When you say the temp creeps up, to what ?
Click to expand...
Stock or aftermarket aluminum
radiator?
Click to expand...
Stock
69 Sleeper Bee said:
I have the same exact setup as you and no issues. I would look at a new cap first.
When you say the temp creeps up, to what ?
Click to expand...
About 1/2 way. Normally sits at 160/170 - Rallye cluster.

Thanks again,
Mikey
 
Rad cap for a recovery system is different to the standard cap. Make sure you have the correct cap.

If the rad is old, it may be blocked with sludge. Flushing it out does NOT guarantee that all the sludge will be removed. The PROPER way is to take the rad to a rad shop. They will remove the tanks & pass rods down the tubes to push out any sludge. This procedure may cost more than a new alum rad, which is more efficient than copper/brass.
 
What Pressure Radiator Cap Rating Should I Use?

Caps are #1 thing to test. Std vs, Recovery system are 2 different types of caps.
The recovery cap has a 2 way valve that allows hot coolant to escape into the recovery bottle and when the coolant cools it causes a vacuum that pulls the coolant from the bottle and returns it into the radiator.
All cars have used recovery systems since the mid 70's and you can buy universal kits to retrofit your system.
The Radiator should idealing never have air in the system, only coolant.
If you have ever done any cooking you would know that food continues to cook even after it is removed from the heat source.
Radiator is exactly what it does. It Radiates the heat to remove it from the coolant.
Hot and cold are accomplished the opposite of what most people think.
The a/c does not cool down the air in the car, refrigerator or house hvac system.
The system removes the heat from the air.
To better understand this, look up how an a/c system works on line.
 
Last edited:
MikeyM said:
No fan clutch or shroud from the factory that I'm aware of
Click to expand...

MikeyM said:
Stock
Click to expand...


Possibly a learning moment for some of us, and a teaching moment for others here...... I thought that 66-67 were that inaugeral years for putting plastic or Bakelite shrouds on about everything, where as '65 and back they were tin and rarely used. Was it much later than I thought???....I'm not sure hitting the parts book will give me a definative answer.

Which B bodies got fan shrouds in 1970
 
MikeyM said:
Hi all,

69 Bee with a 383, 22" radiator, no AC. The car runs and cools fine except at idle in hot weather, it starts to creep up. I will be installing a shroud soon but my questions are:

- Why does the temp gauge go up when the engine is turned off? Is this just residual heat going into the coolant?
- Why does my standard (non-lever type) radiator cap burp coolant out of the very top? I have an overflow bottle installed but the coolant doesn't go down the hose to the bottle.. I've confirmed it's clear.

Thanks,
Mikey
Click to expand...
A guideline...as nothing is Black & White.
1. Overheating at idle...typically means slow coolant flow due to numerous reasons such as Radiator need "Rodded" as corrosion and sediment has slowed flow due to clogging of tubes or thermostat is not functioning properly or water pump isn't functioning 100 percent.
2. Overheating at speed ...can be be clogged radiator
Remember:
A) At speed air flow is not important as the air rushing in over the radiator should be sufficient to cool
B) At idle: A few options...Fan Clutch no op, thermostat, coolant restrictions, thermostat slow to open...
Good luck and the Guys have all given you great tips
One thing to remember, Muscle Cars and older cars were built to run at 205-210 degrees back in the day.
 
Hey all,

A little update on this - turns out my t-stat was stuck open. So I replaced it with a 180* and it cools fine but still creeps up in traffic. Since the old radiator in the car had a pinhole leak I ordered an ACC 22" unit. It cools fine but when I was running the old stat, the temp barely registered.

Now, with a 180* stat, it warms up super quick, runs right about 180* but still creeps up. So I need a shroud and have to figure out a way to mount it since the ACC radiator did not come with that "rear" flange that the shroud would mount to... I think.

But my main question is when I shut off the engine and return 10 or so mins later, I turn the key on and notice the temp has risen to just about the end of the "safe" zone, maybe a hair past it. Do any of you experience this same level of temp rise after shutdown?

Thanks,
Mikey
 
The better question should be, how fast or does it return to a normal range after start?
 
If you’re not worried about stock appearance, you could get some electric cooling fans that will stay on when the car is shut off until the car cools down.
 
Fan Dan - not too worried about that, just not sure I need it yet. Might go with a 160 stat depending. Good idea, though.

Jee 62 - right when I fire the engine, the temps immediately start dropping into the high end of the safe zone. Once air is moving through the radiator at street speed, it takes a few mins to drop back to 180 or so. At freeway speed, it drops more quickly.

Mikey
 
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