1972 Grande 302 w new thermostat overheating. With smoke coming out of my cool air intake.

iTzPayDay3x · Nov 5, 2024

What’s up mustang fam,

I just installed a new thermostat as well as the housing in my ‘72 Grande. I had a pretty bad coolant leak so figured it could be the thermostat. My brother and I were working on the new thermostat installation when we noticed the housing unit we were replacing didn’t even have a thermostat, which we found strange.

After the install, we ran the car for a few minutes to get the new coolant running through after we flushed the radiator with water. While running the car, the upper hose got very hot, the lower hose was warm but definitely not as bad as the upper.

We ofc turned the car off then tried to start it a couple minutes later, then smoked started coming out of the cool air intake by the carburetor.

We figured since the car didn’t have a thermostat, we could remove the new one since that may have caused the car similar problems in the past. But then what about my coolant leak? Do I need a new radiator and scratch the thermostat?

Any ideas and suggestions would be very appreciated.

will e · Nov 5, 2024

Greetings and welcome to the forum

First, by leak I assume you mean you could see coolant leaking out of the engine/cooling system. The thermostat is inside the closed coolant system and once correctly installed cannot cause an external leak. They can 'fail' but a failure not 'cause' a leak.

It's pretty easy to install them a bit 'off' of the seat and so when you put the housing on it doesn't seal correctly but this is quickly discovered.

The coolant comes out of the top of the engine pretty darn hot, as hot if not hotter than the thermostat rating. If you were 'flushing' at the same time it would explain the cooler water and cooler bottom radiator hose. Although the lower radiator hose should always be cooler than the top after the engine has been running for a few minutes.

A cheap IR gun can be very helpful to see the temps at the housings and hoses.

It's also possible to install the thermostat backwards. Some water will still flow (causing the upper radiator hose to get hot).

The smoke coming out of the 'cool air intake' is a bit concerning. Was it smoke or steam? Did it keep coming out or did it stop? Did it occur while the engine was running or while you were trying to start it. More details and a picture of your engine will be helpful.

But back to the cooling problem and leak.

Is, or was, there a cooling problem or just a leak? I will focus on the leak because we know it existed. Did it leak A; All of the time, even parked.. B: Any time the engine is running C: A few minutes after the engine is started D: Only after it is turned off. (Or a combination of those).

Can you tell us the approximate location of the leak?

iTzPayDay3x · Nov 5, 2024

will e said:
Greetings and welcome to the forum

First, by leak I assume you mean you could see coolant leaking out of the engine/cooling system. The thermostat is inside the closed coolant system and once correctly installed cannot cause an external leak. They can 'fail' but a failure not 'cause' a leak.

It's pretty easy to install them a bit 'off' of the seat and so when you put the housing on it doesn't seal correctly but this is quickly discovered.

The coolant comes out of the top of the engine pretty darn hot, as hot if not hotter than the thermostat rating. If you were 'flushing' at the same time it would explain the cooler water and cooler bottom radiator hose. Although the lower radiator hose should always be cooler than the top after the engine has been running for a few minutes.

A cheap IR gun can be very helpful to see the temps at the housings and hoses.

It's also possible to install the thermostat backwards. Some water will still flow (causing the upper radiator hose to get hot).

The smoke coming out of the 'cool air intake' is a bit concerning. Was it smoke or steam? Did it keep coming out or did it stop? Did it occur while the engine was running or while you were trying to start it. More details and a picture of your engine will be helpful.

But back to the cooling problem and leak.

Is, or was, there a cooling problem or just a leak? I will focus on the leak because we know it existed. Did it leak A; All of the time, even parked.. B: Any time the engine is running C: A few minutes after the engine is started D: Only after it is turned off. (Or a combination of those).

Can you tell us the approximate location of the leak?

Thanks for the welcome!

The air intake was most likely steam as it didn't start until I had turned the car off and wasn't black nor had any kind of burning smell....
And it was seated properly as there wasn't any leaks or squirting in that area...

But I also need to mention that the car has a lot of what looks like vacuum hoses that aren't connected to anything, also the intake manifold has a hole on the side that seems like a hose should be connecting it to the valve cover which has a male hose attachment but no hose....and to make things more interesting there is a second radiator in front of the main radiator the has threaded out put, but again no hoses connected to it.

Oh and also there was significant rust in both the radiator and the engine.

I left the car sitting overnight and there were no leaks anywhere. It only leaked coolant once which made me believe it was the thermostat which is where the big leak was under the car. The leak happened after the car was turned off.

I really appreciate the response, this is a very interesting project !

midlife · Nov 5, 2024

Are you filling up the radiator to the very top? It should be just above the upper cross-plate when looking with the cap off. Water expands when it gets hot, and you may be seeing overflow. Normally, there's an coolant overflow bottle somewhere to catch it. Do you have it and is a hose attached?

Spaceman · Nov 5, 2024

Could you post some engine pics? That vacuum hose from the valve cover should be your PCV and connect to a port on the back of the carb.

The second radiator not connected to anything is likely leftover from AC that was removed - mine has the same thing. It's the old condenser.

Is this steam coming from your carb?

iTzPayDay3x · Nov 6, 2024

Spaceman said:
Could you post some engine pics? That vacuum hose from the valve cover should be your PCV and connect to a port on the back of the carb.

The second radiator not connected to anything is likely leftover from AC that was removed - mine has the same thing. It's the old condenser.

Is this steam coming from your carb?

Thanks for the reply @Spaceman, steam was coming out of the air intake manifold to be specific.

It’s definitely not stock under the hood. It’s a hodgepodge of sorts that I’m working with.

I’ve been looking for a shop repair manual for these models online to really get an understanding of what under the hood should actually look like. I added a few pics below. The filter inside the carb also doesn’t seem to be the right size so I’m curious if that should be replaces as well and its missing the ac unit which I have in my trunk.

iTzPayDay3x · Nov 6, 2024

midlife said:
Are you filling up the radiator to the very top? It should be just above the upper cross-plate when looking with the cap off. Water expands when it gets hot, and you may be seeing overflow. Normally, there's an coolant overflow bottle somewhere to catch it. Do you have it and is a hose attached?

We filled the radiator to the top, the top tube had water boiling but there was nothing coming out if the overflow spout. The car doesn’t have that overflow bottle you’re referring to unfortunately.

giantpune · Nov 6, 2024

I dont see a cold air intake. Can you circle on the picture where the smoke/steam was coming from?

I do see a couple missing things like the passenger side PCV line and the vacuum line coming off your breather snorkle.

And its hard to see in the pictures. Do you still have the metal tube in place that runs from the passenger exhaust manifold to the snorkle on the air intake?

iTzPayDay3x · Nov 6, 2024

giantpune said:
I dont see a cold air intake. Can you circle on the picture where the smoke/steam was coming from?

I do see a couple missing things like the passenger side PCV line and the vacuum line coming off your breather snorkle.

And its hard to see in the pictures. Do you still have the metal tube in place that runs from the passenger exhaust manifold to the snorkle on the air intake?

Could the missing PCV line be one of the causes for this steam? Or the breather snorkel like you mentioned? Just curious on what my next steps should be. I’m going to remove the thermostat because there wasn’t one in there when I got the car, but then I figured it probably should have the thermostat so I’m a bit torn.

giantpune · Nov 6, 2024

No, there should not be any water anywhere near that red circled area. It would need to either be condensation from morning dew or something, it the steam would have to come from inside the motor, back up through the intake manifold, through the carb (backwards, against the direction it is sucking air), through your air filter, and out to that spot your circled.

will e · Nov 6, 2024

Let's step back to make sure we are on the same page.

1. Is it still leaking fluid? That's one of the first things to get fixed. If it is leaking where is it leaking from (as detailed as you can provide)
2. Is it running hot? What temp is it running at? How are you measuring it? If it is not running hot there is no need to mess with the thermostat again.
3. The hodgepodge. Frankly, I've seen worse! The only thing I would do at this point regarding the hoses is get a hose attached from the valve cover (passenger rear) to the air cleaner. There is a good picture of what you are looking for in this thread: https://7173mustangs.com/threads/hose-from-pcv-valve-to-air-cleaner.36557/ The car will run without that connection but it will 'smoke' out of the valve cover opening when you are at low vacuum conditions. At idle/cruise and other high vacuum the PCV system (fitting on other valve cover and the larger hose to carb connection) on the other cover draws air through the crank case. It comes in the passenger side valve cover hole. When there is no vacuum the crank case air gets drawn through the passenger side valve cover hole into the air cleaner through the hose you are missing.

Keep in mind that most of the hoses are for emissions purposes and mostly effective at idle and when the engine is cold. Most are good to 'have' since they trap fumes or help the engine warm up more quickly but to get the car 'running and driving' you don't need them. Focus on those last.

Vacuum lines you should have to get the car running and driving:
PCV from carb to PCV valve. (must have) and from air cleaner to valve cover (good to have)
Large Vacuum to Brake Booster
Vacuum from distributor to carb or manifold. Depends on if you use ported or manifold vacuum for the distributor but that is for another discussion
Vacuum from manifold to transmission (for the modulator)
Vacuum from manifold to vacuum canister which then goes into the cab and controls vent positions and such. This one is not necessary to get the car running and driving.

There are other lines which if they are connected are fine like the charcoal cannister or the one that controls the flaps on the cold air inlet. These are 'nice to have' but not necessary to get the car driving. I can't tell if your aftermarket manifold came with an EGR, if it does, that is another great emissions system that doesn't impact performance but isn't required to 'get the car running and driving'. My point is to focus on the basics first, get it running and then work out the rest of the hodgepodge.

iTzPayDay3x · Nov 6, 2024

will e said:
Let's step back to make sure we are on the same page.

1. Is it still leaking fluid? That's one of the first things to get fixed. If it is leaking where is it leaking from (as detailed as you can provide)
2. Is it running hot? What temp is it running at? How are you measuring it? If it is not running hot there is no need to mess with the thermostat again.
3. The hodgepodge. Frankly, I've seen worse! The only thing I would do at this point regarding the hoses is get a hose attached from the valve cover (passenger rear) to the air cleaner. There is a good picture of what you are looking for in this thread: https://7173mustangs.com/threads/hose-from-pcv-valve-to-air-cleaner.36557/ The car will run without that connection but it will 'smoke' out of the valve cover opening when you are at low vacuum conditions. At idle/cruise and other high vacuum the PCV system (fitting on other valve cover and the larger hose to carb connection) on the other cover draws air through the crank case. It comes in the passenger side valve cover hole. When there is no vacuum the crank case air gets drawn through the passenger side valve cover hole into the air cleaner through the hose you are missing.

Keep in mind that most of the hoses are for emissions purposes and mostly effective at idle and when the engine is cold. Most are good to 'have' since they trap fumes or help the engine warm up more quickly but to get the car 'running and driving' you don't need them. Focus on those last.

Vacuum lines you should have to get the car running and driving:
PCV from carb to PCV valve. (must have) and from air cleaner to valve cover (good to have)
Large Vacuum to Brake Booster
Vacuum from distributor to carb or manifold. Depends on if you use ported or manifold vacuum for the distributor but that is for another discussion
Vacuum from manifold to transmission (for the modulator)
Vacuum from manifold to vacuum canister which then goes into the cab and controls vent positions and such. This one is not necessary to get the car running and driving.

There are other lines which if they are connected are fine like the charcoal cannister or the one that controls the flaps on the cold air inlet. These are 'nice to have' but not necessary to get the car driving. I can't tell if your aftermarket manifold came with an EGR, if it does, that is another great emissions system that doesn't impact performance but isn't required to 'get the car running and driving'. My point is to focus on the basics first, get it running and then work out the rest of the hodgepodge.

1. Is it still leaking fluid? That's one of the first things to get fixed. If it is leaking where is it leaking from (as detailed as you can provide)

No it’s not leaking any fluid fortunately. While the car was running, the upper hose was boiling water which I figured meant there was no fluid pumping into the engine.

2. Is it running hot? What temp is it running at? How are you measuring it? If it is not running hot there is no need to mess with the thermostat again.

The car was hot then turned off on its own. When trying to get to a tricky bolt on the bottom of the thermostat housing, we removed the distributor which may be the reason the car turned off as the timing is disrupted. The distributor also doesn’t sit in it’s hole as snug as it should. That might be one of the problems I’m running into. I’m thinking about turning the crank shaft manually while my brother drops the distributor aligns as it should.

will e · Nov 6, 2024

I'd get an IR gun or a temp gauge. You could pick up a fairly cheap one and screw it into where the CTO is on the upper hose housing as a temporary use gauge.

So it was running and turned off on it's own. The distributor isn't 'tight' with the hold down so it's easy to move. Is this accurate?

Your next step, before replacing the thermostat, is to get it running again. Note where the #1 cyl is on the cap and then bump the engine or hand turn to TDC. The rotor should be pointing at where the #1 position is on the cap, if it is pointing in the opposite direction you are on the exhaust stroke, rotate the crank a full turn to get the rotor pointing close to where #1 is on the cap. Do you have a timing light?

1972 Grande 302 w new thermostat overheating. With smoke coming out of my cool air intake.

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