# Thanksgiving Day blues....



## blondie67 (Jan 28, 2008)

Hey guys,
So I took my car out for a drive on Thanksgiving and went to the gas station down the street. When I got there, all of a sudden my heater core exploded (not really exploded, but you get the idea). It built up so much pressure that it started leaking. It was new with new hoses. My question is...could a rise in pressure/heat be caused by a stuck thermostat?
Thanks,
Linda


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## Too Many Projects (Nov 15, 2008)

Definitely. Any other symptoms ? Did coolant come out the overflow hose ?
That sux. Think you're gonna take it for a ride and it has issues.


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## geeteeohguy (Feb 2, 2008)

Ditto. Yes. When I overhauled my engine in the '67, I was breaking in the cam on initial start up, and the BRAND NEW thermostat was defective. Almost destroyed the motor. And you put in a new core. When you get the new stat, tie a string to it, and put it in hot water with a meat thermometer. You can verify it's operation. I recommend a 160 degree Stant or Robertshaw USA 'stat. Also, you can wedge it partially open with an aspirin tablet, install it, and when you add coolant, it will fill up without air bubbles. The aspirin will dissolve with no harm. An old trick. I did the brakes on my '65 yesterday, and put in a brand new, defective wheel cylinder: it had no seat cut for the brake line!!! Made in USA, supposedly, but what CRAP. Now I have to do the job twice, the parts place has to order a new one, etc. etc. So, take heart......we all have setbacks. Really glad it's ONLY a heater core: when I saw your post, I was afraid to open it: I thought you'd wrecked it or scratched it!!!! Whew! It's nothing, really, compared to all you've been to!


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## Rukee (Feb 8, 2007)

A heater core is bad enough as you have to take the front clip back off to get to it. 
Being a mechanic I see bad parts out of the box all the time, you may be able to recoup some of the labor through the company or parts house you got the heater core from. I know when NAPA sells me a bad part, I charge them the labor to replace it. GLHF.


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## geeteeohguy (Feb 2, 2008)

I've done heater cores in both of mine without removing the front clips. Both are non AC cars, though. The only problem was the ONE stud on the outside (fender side) of the housing assembly. It would be a heck of a lot easier with the sheet metal off, though!!
Jeff


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## blondie67 (Jan 28, 2008)

So yesterday we checked out the motor and replaced the thermostat. Not the problem. It looks like there's no circulation! I guess either a water pump issue or the radiator. It was running awesome the week before. Does a water pump just go bad all of a sudden? 
Linda


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## Too Many Projects (Nov 15, 2008)

If the impeller comes loose and doesn't turn, yes, not common, but anythings possible. 
No one left a shop rag stuffed up the lower hose during the build and then put the hose on the rad did they ? Don't ask how I come up with this crap.........


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## geeteeohguy (Feb 2, 2008)

I agree with Too Many. Impellor failures are pretty rare. Was a rag stuffed into the lower hose to prevent leakage? You can disconnect the lower hose, and run water thru the core to see if it's blocked. I doubt it is, though. Yu would have had all kinds of problems. You can alos bypass the heater core for now and drive the car until yu figure out the problem so you don't blow the next core.


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## blondie67 (Jan 28, 2008)

Jeff,
We bypassed the heater core the day it happened. It's funny how three guys are waiting there to help a blonde chick with a beautiful car at a gas station. I don't think a rag was in there. It was rebuilt 600 miles ago and ran beautifully. Just happened all of a sudden. We're flushing the system today and checking the water pump. How can you tell if a radiator is bad? When the thermostat opens, is that when you can see the water circulating through the radiator? I'm new at this stuff and even though there is a person knowledgeable looking at it, I'd like to get some feedback. Thanks so much.
Linda


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## Too Many Projects (Nov 15, 2008)

There is always a minimal amount of circulation even with the thermostat closed. You will see much more when it opens. As you bring the rpm's up the coolant level should drop in the radiator and the flow will be significant.


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## geeteeohguy (Feb 2, 2008)

Linda: with the engine stone cold, remove the radiator cap. Start it up. Let it idle, and look into the radiator filler neck. When the Thermostat opens, the water will start to really circulate. IMPORTANT: The uupper radiator hose will be cold when the stat is closed. As soon as it opens, the upper radiator hose will be HOT. That's a sure way to check it's opening. Radiator plugged: Look visually at the "rods', which are the tubes inside the radiator. Are they clear, or scummed up? Borrow a pyrometer, or use your hand (be careful!!!) and check different areas of the radiator core on the front side (away from the fan...bumper side!!!) for cold spots. The coolant will be cooler at the bottom than at the top, that's normal. But, if you have cold spots in the middle, it means blockage. I think you might have run into a defective core. Another thing, you will want to pressure test your system. It may be you had a high pressure surge due to a leaking head gasket: That's when combustion pressure enters the cooling system. Quick check for leaking head gasket: Stone cold engine, radiator cap on. Start engine. Grab on to the upper hose. It should get hard when the engine is fully warm, after the Thermostat opens. If it gets hard right at start up, you have a leak. Good luck, keep us in the loop.
Jeff


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## geeteeohguy (Feb 2, 2008)

PS....I meant you may have gotten a defective HEATER core. Sometimes happens.
Jeff


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## blondie67 (Jan 28, 2008)

*Ghost in the machine.....*

So, after replacing the thermostat and running it for a while, two days later, it is fine. the water is flowing, and there is no overheating. Could it be from a fresh rebuild? Very strange. Hopefully it won't happen again when we install a new heater core....
Linda


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## Too Many Projects (Nov 15, 2008)

Did you ever determine if it really overheated or did the heater core just start leaking ??? If there were no other symptoms of overheating, I would vote with the rest that you just got a defective heater core. In my first post I asked if coolant came out the overflow hose. If it didn't, I doubt it overheated.


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## blondie67 (Jan 28, 2008)

I thought it might just be the heater core also, but it still ran hot after bypassing it. We changed out the thermostat the next day, and it still would run hot and the water wasn't flowing at all. It would shut down all funky like. Now, the water is flowing and it shuts down fine and isn't idling funny. Maybe it just took the thermostat to open once and all is fine.??? I did have to refill the overflow container when it first happened. After that, no water was flowing at all. Oh well, I'm not going to complain. I just hope it doesn't happen again....what a pain in the *&&^ to replace.


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## Too Many Projects (Nov 15, 2008)

That does seem, odd, but if the heater core didn't purge on initial fill it could be the cause too. All that air would've finally made its way to the engine and caused it to be low and overheat. Then the increased pressure caused the core leak. Still strange that it ran hot after bypassing the core, but maybe there was still air in the block that wouldn't purge out. It and sh!t happens. I'm hoping it's all good for you now, but check the coolant level frequently for a 1/2 dozen times after cooling down to make sure it is still full.

Jeff's suggestion to watch/check for a head gasket problem causing over pressurization is still a valid cause too. Stay mindful of that.


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## blondie67 (Jan 28, 2008)

Thanks for the great advice....I've been watching like Jeff said, but wouldn't there be bubbles in the radiator if there was a head gasket problem?


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## Too Many Projects (Nov 15, 2008)

blondie67 said:


> Thanks for the great advice....I've been watching like Jeff said, but wouldn't there be bubbles in the radiator if there was a head gasket problem?


If it's small, probably not. They would just keep adding up till they caused a hot spot and overheating. You could get the coolant system pressure tested for leaks too. The tester goes on the rad in place of the cap and has a pump built in to pressurize the system to normal pressure and then wait to see if it goes down.


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## Rukee (Feb 8, 2007)

blondie67 said:


> Thanks for the great advice....I've been watching like Jeff said, but wouldn't there be bubbles in the radiator if there was a head gasket problem?


Yes and no. A head gasket can fail in many different ways depending on were exactly the gasket fails. It can leak coolant into the oil, it could leak oil into the coolant, or it could leak coolant to the outside, it could leak compression into the coolant, it could leak coolant into the cylinder, it could leak compression between two cylinders.


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## geeteeohguy (Feb 2, 2008)

I agree with all of the above! Keep a vigilant eye on it, you may have some air in the system, etc. I'd like to think it was a giant air pocket, it does happen. Start using the car, and keep checking the coolant level each morning when it's cold, before you drive it. It should be about an inch below the filler neck in the tank. If you fill it too full, with no overflow tank, it will expand, start a syphon effect, and you'll lose coolant. NEVER open the rad cap on a warm or hot engine!!! My $$$ is on a defective heater core. If there were other huge pressure issues (like a blown head gasket would cause), there would more likely be other components failing, as well. Keep an eye on it, and you'll be ok. You certainly don't want to be "all funky like".....


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