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Discussion Starter #1
Hi all. My name is Rocky, I've been directed here for many inquiries, so I'm definitely happy step up and join the site.
My question is regarding my 73 Nova with an inline 6 250 and PowerGlide. A few days ago it got hot on the way from work. It used about a quart of water a week. Anyway after I added water, it got hot again. I find water leaking out of the cover for the torque converter. The only thing I could think of is maybe a leaky freeze plug in the back of the motor. I'm not even sure there is a freeze plug back there but I don't see any hoses going back there. Is there anything else it could be? What the best way to fix it? Pull the tranny or the motor, or both? Thanks in advance guys, I appreciate it.
 

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I have never messed around with the 250 before but....

Dropping just the tranny would be less work to me to check it out.

Was it leaking before it got hot? Typically, getting hot wouldn't cause a core plug to blow out.

Do you have a functioning overflow setup?

It looks like the back of the cylinder head has a core plug you can check out with an inspection mirror.

Looking a photos of those cylinder heads, it looks like there are 2 water jackets on the back of the block. Does your coolant smell like exhaust by chance? I think you can rent a leak down tester from Oreilly's/Autozone and check that cylinder for leakage. Also compare that #6 spark plug to the rest to see if it looks like it's been steam cleaned.

I would certainly unhook the trans and look at the back of the block before removing the head.

Maybe someone that knows the 250 a little more will chime in.
 

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Thank you @amatojm . It wasn't leaking before, but it was using about a quart of water a week. I noticed any smell when adding water. But I should try to take a better look, especially at rear of the cylinder head.
 

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Thank you @amatojm . It wasn't leaking before, but it was using about a quart of water a week. I noticed any smell when adding water. But I should try to take a better look, especially at rear of the cylinder head.
Should read, I didn't notice any exhaust smell.
 

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What you can also do is if you have an air compressor that can be regulated down to 10 psi or so, you can drain the coolant and hook your air hose up to wherever your temp sender threads into the block.

Then use the old soapy water in a spray bottle method to find the leak. Or you may just be able to hear it.
 

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Have you seen water puddling under the car or obvious water leaking out from anywhere..?
How much fluid is in your transmission currently..?
Is you trans cooler integrated in the radiator..?
 

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Mike - 74 Nova Baltimore, MD
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The 73 Nova should have a radiator overflow/recovery tank... connected by a tube that runs from a port under the radiator cap to the overflow tank.
- Does your Nova have this overflow/recovery tank?

If not... each time your engine heats up. water/coolant expands within the engine's cooling system. When the coolant reaches a certain pressure, some coolant will flow out of the port located under the radiator cap. If this port is not connected to an overflow tank, you will loose this coolant. When you check the radiator level after this occurs, it will seem low. If you refill the radiator to the FULL level, you will just repeat the process shown above until you install a coolant overflow/recovery tank.

Regarding your coolant leak. Just because you notice some water/coolant on the torque convertor cover does not mean the leak is coming from that area. As you drive your car, the movement of air around the engine will cause leaks to move around as the fluid is descending.
There are dyes and UV light kits that are helpful with finding coolant leaks.
 
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Hey Rocky . . . .

I have a 'spare 250 motor' sitting in the shop - - - I can take a picture of the 'rear side of the engine block '
and freeze plug area. give me a day …….
But, I'd also Check things out 'real close' before "pulling things apart" . . . . . as Mike says above ^^^^^^^^^^ .

Then just for "grins" …………….. if you do / find a bad 'freeze plug' ……………. I'd plan on doing them all ..
to be good , going forward (if you have a good running engine) .

do 'em all , if needed ……………….. let me get that picture …. jim

and, WELCOME to SNS , glad to have you here .
 
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Discussion Starter #9
  1. Wow thank you guys for the responses! I am going to take a closer look at it tomorrow. Seems now I have time to work on it. It doesn't have a functional overflow so that's kind of what I attributed the water loss to. I'll look at it in the morning. I know it seemed like the water poured out of it, as fast as I poured it in. I could hear the water trickle through the motor.
 

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Hi Nova thug. No I didn't notice any pudding. I don't recall seeing a transmission cooler. I'll look tomorrow.
Hi Twinshadows thanks I appreciate the welcome also!
 

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Alright guys. So it seems the first thing I need to do is find out exactly where the leak is right? I will go back and inspect. I don't think I'll see anything, but will double check. If I don't see anything, I should get some pressure into the cooling system to try and see where the water is coming out. I think I've seen my dad use this radiator cap with a pump on it. I'll try to use that. Does this sound right so far? Thanks guys.
 

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Ok. So I just went to try and track down this leak. I filled the radiator with water (noticed the trans cooler is integrated into the radiator btw) and started it. It needs a tune-up so it really didn't even want to start. But it did start. So after running literally just a few minutes the temperature light came on. And the water in the radiator seemed cool. Originally I thought my thermostat was sticking, so right before I parked it, it was changed. I guess the new one could be sticking? Since it seemed to be not running so great I pulled the #6 plug. (closest to the firewall) It didn't look steamed cleaned, looked normal to me. I looked behind the cylinder head as best I could, but didn't see anything. Any thoughts or suggestions guys? I'd appreciate it, thanks guys.
 

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If you are loosing water it has to go somewhere. It’s either external or internal. If you don’t see any evidence of water leaking externally then it’s probab an internal leak. Check your engine oil and transmission fluid levels to see if water is escaping the cooling system and migrating these two areas. If nothing is showing up there then possibly a head gasket issue.
 

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Discussion Starter #14
If you are loosing water it has to go somewhere. It’s either external or internal. If you don’t see any evidence of water leaking externally then it’s probab an internal leak. Check your engine oil and transmission fluid levels to see if water is escaping the cooling system and migrating these two areas. If nothing is showing up there then possibly a head gasket issue.
Well. As soon as I pour water in, it dribbles right out of the converter cover. There's actually a hole there. Makes me think it's leaking on the inside, almost like the hole is there for that reason. It's raining here, so I'm kinda looking at it during breaks in the rain. I still don't see anything..
 

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Well if you can't see any water dribbling down the back of the block at the head gasket and the plug looks good, and you don't have any milkshake looking oil, you're in pretty good shape and whatever it is shouldn't be too hard to fix.

I completely forgot about those kind of radiator caps. Just be sure to not pressurize it too much. Most of these engines typically have a cap that bleeds pressure between 12-16psi. Much more than that can cause issues, if you didn't have a head gasket leak before, you will.

The temp light coming on after only a minute or so of run time sounds like a bad temp sender. Do you happen to have a gauge hooked up to read temp.
Was the block hot to the touch or was it relatively cool? You most people can handle touching something for a moment up to about 140*. At 160* it feels "HOT" pretty quick.

How did you conclude that you had overheated previously? I'm wondering if maybe that light is faulty and just made you examine the cooling system more closely.

I would use that pressure cap and see if you can hear it hissing
 

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You can just pull the convertor cover off and look between the flywheel/flex plate and look for the leak. They make a black light die you can add to your water it will leave a trail and the black light will show it up.
 

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Rocky . . . . . . here's your pictures :

# 1 - - drivers side "block freeze plugs" - - 250 ci motor ;

402723


3 each in the block - - - 3 each in the head

# 2 - - rear picture of the same motor :

1 each water 'freeze plug' (top plug) ; lower plug is "oil galley / cam plug".

402724


# 3 - - engine code @ dist pad :
"SouthBay2s" - - Adam , found this 'code' as a : 67 C-10 , C-20 . . 250
6cyl , 4 speed.
(interesting - - " S X " marking at rear of block ) . (that is the engine code) .


402725


..…///. later, jim
 
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Discussion Starter #19
Well if you can't see any water dribbling down the back of the block at the head gasket and the plug looks good, and you don't have any milkshake looking oil, you're in pretty good shape and whatever it is shouldn't be too hard to fix.

I completely forgot about those kind of radiator caps. Just be sure to not pressurize it too much. Most of these engines typically have a cap that bleeds pressure between 12-16psi. Much more than that can cause issues, if you didn't have a head gasket leak before, you will.

The temp light coming on after only a minute or so of run time sounds like a bad temp sender. Do you happen to have a gauge hooked up to read temp.
Was the block hot to the touch or was it relatively cool? You most people can handle touching something for a moment up to about 140*. At 160* it feels "HOT" pretty quick.

How did you conclude that you had overheated previously? I'm wondering if maybe that light is faulty and just made you examine the cooling system more closely.

I would use that pressure cap and see if you can hear it hissing
Thanks amatojm. Yeah I need to put a gauge on it. That temperature sender seems suspicious. I know it got hot the first time though. It actually was in the drive thru. It was dieseling and running really bad before I shut it off.
 

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Discussion Starter #20
Rocky . . . . . . here's your pictures :

# 1 - - drivers side "block freeze plugs" - - 250 ci motor ;

View attachment 402723

3 each in the block - - - 3 each in the head

# 2 - - rear picture of the same motor :

1 each water 'freeze plug' (top plug) ; lower plug is "oil galley / cam plug".

View attachment 402724

# 3 - - engine code @ dist pad :
"SouthBay2s" - - Adam , found this 'code' as a : 67 C-10 , C-20 . . 250
6cyl , 4 speed.
(interesting - - " S X " marking at rear of block ) . (that is the engine code) .


View attachment 402725

..…///. later, jim
Thank you Ts! The top plug in rear looks ominous.. 🙁
 
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