jacob94

I have a 1970 442 and I’m having an over heating issue. I think it has to do when I have the a/c on. Is that possible and if so, what would be causing the issue?

Vintage Chief

What makes you think it's an over heating issue? Is coolant puking from the radiator? What is the engine temperature @ idle and during cruise? Are you using a 180° thermostat?

jacob94

When idling and running the a/c for 30 or so minutes The mechanic put the radiator cap on and it started to overheat. My mechanic put a new radiator cap on and a thermostat but we still had the same issue. I drove the car back home (maybe 3 miles) without the a/c on and it did not overheat. My mechanic is puzzled.

Vintage Chief

Once again WHAT does OVERHEAT mean? See, Post #2.

jacob94

Sorry... I’m new to this and the car. When it first overheated the coolant came out of the discharge tube. My car does not have the overflow container.

cjsdad

Your A/C condenser generates a lot of heat in front of your radiator. There are a few things you can do to help minimize the effects though. Use some weather stripping foam tape (the thick stuff) to seal the condenser to the radiator so that the air cannot escape out the sides of the condenser. Next, make sure the radiator is sealed to the core support. Use more foam tape, the thick stuff to seal all the way around it. Make sure your fan shroud is secure and intact all the way around the fan and make sure the fan is at least slightly inside the shroud. Lastly, make sure your fan clutch is still good. Spin the fan on the clutch while the engine is cold and get a good feel for it, then warm the engine up to the point it begins to overheat, then shut it off and feel the tension in the clutch again. It should be harder to turn when hot. You want the fan to put all of the air it can through the condenser and the radiator.

cjsdad

Dood! It usually means the engine is running hotter than normal. What does it mean to you?

cjsdad

Were you driving around when it overheated or were you sitting still? Is the A/C new? Anything else new?

rocketraider

Is the fan clutch working? You should hear a pronounced roar when it engages.

Next- how full are you filling that radiator? There's a "fill cold" mark on the tank below the radiator cap. If you're filling it all the way to bottom of the filler neck and don't have a recovery system, IT IS GOING TO PUKE OUT COOLANT UNTIL IT FINDS THE LEVEL IT WANTS. Which coincidentally is usually where that "fill cold" mark is.

jacob94

the car was sitting still and yes, the compressor is new.

jacob94

good suggestion. I will try that tomorrow and report back.

jacob94

should the hood be open in order to hear the fan clutch?

I will have to open the cap to see where the coolant is filled up to.

rocketraider

Re #6. You're confusing this kid with all that. I've been fooling with cars nearly 50 yrs and I had to read it a couple times. If he don't know all the terminology his eyes are probably glazed over by now.

I'm guessing he's mid 20s and has never dealt with older cars. Jacob, never be afraid to ask a question here. We'll get you through it. And if you are driving a car twice your age, my respect.

Vintage Chief

I'll tell you what it means. It means it's overheating. You got that? It means it's overheating. How do you determine an engine is overheating - Dude! I'm waiting anxiously for you to state how you determine the engine is overheating. I asked the OP if the engine was puking. The OP did not answer. I asked what the temperature was at idle and cruise. Since you seem to already KNOW what the issue is, why not tell us what overheating means to you without asking the appropriate questions to determine what an overheating condition is - Dude!

jacob94

Ha... I wish I was in my 20s, but I am not. This is my first classic car and I am not mechanically inclined. So any help is much appreciated.

Vintage Chief

Agree, Jacob will get through this. And, knowing whether the engine puked coolant out of the radiator is the first question ANY mechanic would ask anyone. Now, we have an answer to move forward.

rocketraider

You should be able to hear the fan clutch engage with hood shut. What they often do is roar a few seconds when the engine is first started and then disengage and quieten down until temp is high enough it's needed again. Once engine is up to temperature you should hear it cycle; roar and quieten down. Does this car still have its fan shroud? Plastic piece between radiator and engine, that covers the radiator and has a circular opening surrounding the engine fan.

Very important. You have to check coolant level with engine COLD.

oldcutlass

No where in this thread do I see a temperature posted that verifies the engine overheated. It could be as simple as an over filled radiator.

Vintage Chief

And, that^^ in fact may be the only issue Jacob is having. Which would NOT be an overheating condition if the radiator was filled to the very top without the appropriate air space (headroom) above the radiator coolant level when the engine is cold to allow the fluid to expand while hot.
Since you have no radiator overflow container (which did not come as original equipment on your car) it's important to maintain the appropriate air space above the coolant as rocketraider perfectly stated.

Even a new mechanic not familiar with these older cars may not know there is a requirement for free air space above the cold coolant level in the radiator and as rocketraider stated - it will continue to puke until it finds equilibrium.

Vintage Chief

Agree

cjsdad

The things I suggested were learned while repairing and installing air conditioning systems in Phoenix, Az. Heat dissipation is extremely relevant to A/C systems and foam weather stripping can resolve a great many problems. It is not expensive or complicated. Overheating issues were often magnified after an A/C system was repaired or installed so having the compressor newly installed means it wasn't working, or wasn't working right. One of the first steps in troubleshooting an overheating problem, or any problem for that matter is "what is wrong is what is new". The A/C system working is apparently new. The car is a '70 Cutlass so it is not terribly complex. The thermostat has been replaced so there are only a few other things that can cause the problem when the A/C is turned on. Poor airflow through the radiator is a big one, and I did mention the fan clutch did I not? We're working in the same direction.

cjsdad

Calm down, we're both trying to offer experienced answers for a car enthusiast with a problem. He mentioned that it began overheating recently. It only overheats with the A/C on. So what I KNOW is that means the A/C system is introducing more heat into the cooling system than it can dissipate in it's current form. Whether it pukes or not, overheating means the engine is running hotter than it did before. The system is not complicated. Airflow, radiator flow, water pump flow, thermostat flow. Sorry if you took offense.

cjsdad

Eric, you keep saying that, but keep in mind, the factory dash gauges in a 1970 Cutlass do not have numbers on them. Factory gauges are also notoriously accurate as a Ouija board. But if the temp gauge suddenly reads much higher than normal, it can be described as overheating. The actual temperature is irrelevant it is the temperature difference that matters.

oldcutlass

I have to respectfully disagree, even a factory mechanic would put a temp gauge on it to monitor actual temp. However with that said no where in the thread is a gauge reading even mentioned.

jacob94

I did not have a temperature gauge to tell me what the temp was at the time of overheating. I plan on gong to a parts store and purchase one.

I do have another off the wall question. The temperature gauge when not running, should the needle be in the middle or should it be at the “C” position?

oldcutlass

A stock in dash temp gauge will have an arbitrary reading when the key is off as with probably an electric aftermarket. An aftermarket mechanical gauge will read exact temp as power in not required, it uses a bourdon tube, a bulb and capillary system to read temp.

matt69olds

With the key on, engine not running, the temp gauge will read whatever the engine temp is.

Keep in mind, leaving key on for more than a few minutes with the engine not running is a good way to burn up ignition points, so don’t do it anymore than needed, and for as short a period of time as possible

As long as temp gauge stays around the halfway point idling, I think you would ok. The factory hot light is designed to come on around 240ish. I would imagine the gauge would be calibrated to go to the high side of the scale about the same temperature. That’s also assuming the sending unit installed is accurate.

Your best option is to install a mechanical temp gauge. If there is a unused pipe fitting in the intake manifold, it would be ideal to leave the factory gauge functional, and install the mechanical gauge thermal probe in the unused port. Then you can compare the actual temperature to what the factory gauge indicates.

You can install a coolant recovery system to eliminate the puking coolant. It will consist of a new radiator cap, and a tank to catch coolant. If you can use a drill and screwdriver, you can install it without paying you mechanic to install it.

Vintage Chief

The very first thing you need to do is ensure the coolant level is established CORRECTLY when the engine is COLD. There should be a fill line mark on the radiator below the neck where you add coolant. Make absolutely certain you have NOT overfilled the radiator with coolant - it REQUIRES air space above that coolant line, generally ~1 3/4” below the lowest level of the radiator cap.

Vintage Chief

I understand you aren’t completely mechanically inclined, no worries. Your vehicle with AC also requires a higher low idle RPM than a vehicle without AC. The purpose of which is to reduce load on the engine (which increases engine heat) during AC compressor cycling when at a low idle. Generally/Roughly ~150 RPM - 200 RPM higher. FWIW