Overheating

#1

I am writing this request for my Dad, owner of a 1974 Sedan Deville 472 C.I.D. V8Eng, approx 111,000 miles

Problem:

90 degree day, car driven about 25 miles at speed of about 50 mph. Parked the car and there was a huge amount of leaked anti-freeze, it appears to have come from the overflow/return as it was full. Dad suspects it is the intake gasket or has something to do with A.I.R. (Air internal recirculation?). He has checked numerous things, all seems O.K. but afraid of it overheating again, would like to repair all that is needed for caution. Dad saw a clip or a portion of one of your former articles dated 7/2007, it was part of an advertisement in 5/2008 in the Greensboro News and Record. I would like to retrieve the article in it’s entirety, starts…“My car is ovrheating…”

If you cannot find the article, can you help me with the real problem, which is the overheating cadillac and the lose of antifreeze? What all SHOULD be checked, what do you recommend? Thanks, 1974 Caddy

#2

I’ll buy it LOL. Start simple. Thermostat, coolant mix, radiator flow, water pump, belts that drive fan and pump, radiator cap and hoses. You mention he checked things but what things? Is the front of rad. clogged with 30+ years of bugs and not cooling the coolant?

#3

O.K. hears the scoop…1st thanks in advance for your reply…
Replaced hoses and reduced radiator cap to 3 lbs
(pressure built up)
removed antifreeze and flushed with a chemical 5 times
(still hot)
Removed the themostat and flushed again
Installed a temperature gauge
Did not add antifreeze but installed a no pressure cap
Eng runs seemingly ok until stopped and turned off, appears hot
Blew out the radiator core (free from bugs and debris)
Decreased air jet in carburator
timing from 8 to 10 degrees, top dead center
compress. check averages 146 lbs
Brakes not dragging, proper tire inflation
Only burns 93 Octane
Fan belts stable
Exhaust is clear
cleaned and recapped plugs
(has a manual cloke)
Can you tell my Dad how to check the A.I.R. system…What do you suggest?
Thank you, 74 Caddy

#4

Is there still a belt on the smog pump? If not is it frozen. A.I.R (Air injection reaction) will not cause overheating,most cars of that age don’t even have functioning pumps on them.

Why do you keep saying “appears hot” you must verify if it is running hot

#5

Replaced hoses and reduced radiator cap to 3 lbs (pressure built up).
That’s a mistake. Put the CORRECT radiator cap on it. The increased pressure keeps the coolant from boiling at normal operating temps.

removed antifreeze and flushed with a chemical 5 times (still hot)
That’s nice, but if the radiator was CLOGGED it’s still clogged. Flushing a chemical will clear restricted passages, but won’t remove a jam from a radiator.

Removed the themostat and flushed again
A waste of time.

Installed a temperature gauge
Explain that please. What TEMPERATURE are you reading?

Did not add antifreeze but installed a no pressure cap
VERY bad idea. See above.

Eng runs seemingly ok until stopped and turned off, appears hot
Explain this too please.

Blew out the radiator core (free from bugs and debris)
Helpful, but not your problem.

Decreased air jet in carburator
Not relevant (whatever you mean by this statement).

timing from 8 to 10 degrees, top dead center
Set the timing to factory spec.

compress. check averages 146 lbs
Average is not important. Each individual cylinder’s reading is important. They should all be within about 10% of each other, and should be substantially higher than the numbers you post. But this isn’t causing overheating either.

Brakes not dragging, proper tire inflation
Not relevant.

Only burns 93 Octane
Not relevant

Fan belts stable
As long as they’re turning the fan and water pump they’re doing their job.

Exhaust is clear
Good.

cleaned and recapped plugs
What does that mean?

(has a manual cloke)
Choke is not the problem.

Can you tell my Dad how to check the A.I.R. system…What do you suggest?
The A.I.R. (Air Injector Reactor) pump pushes air into the exhaust to allow whatever is left unburned in the exhaust gases to finish burning. If there’s anything on the car that isn’t causing the engine to overheat, it’s this pump.

I think you’ve got a plugged radiator, if you in fact have any problem at all. Chemical washes are not going to fix that. Replacing it (or rodding it, if you can find anyone to do that) will fix it.

#6

For all you know, it could just be a radiator cap. If you put a radiator cap of 3 psi, you are guaranteeing that the coolant will boil out. It requires at least a 13 psi radiator cap.
What a lot of people don’t understand is what the coolants normal operating temperature is. What do you think it is? Ok, short answer: 220F to 240F degrees. The thermostat will open coolant flow to the radiator, from the engine, through the thermostat, at a coolant temperature of about 190F degrees.
Fill the radiator, put the correct radiator cap on, then see if, or where, coolant comes out.