Over heating Help

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Cmaugel

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Let's try this again under the correct forum section...:eek:ops:

Heya all. I'm having an issue with my motor running really hot when at idle after running for a bit.
It's a '66 383/4spd. Last week on a hot & humid day I had it on the road and all was well and it stayed between 160-180 degrees. It ran great and stayed cool...until I got home. When it was parked and idling, it got hot really fast, (well past 210) and spit out almost half a gallon of coolant through the overflow hose.
I know that it wasn't overfilled because I had just checked it, and prior to this happening I didn't notice anything out of the ordinary and hadn't ever had a coolant leak or overflow. It does have an aftermarket radiator from Summit, but it appears to be fine. No leaks or anything else I can see. The engine is in excellent mechanical shape and has under 5k miles after being completely rebuilt/machined.

The only thing I have noticed out of the ordinary is that the radiator cap on it is rated for 7lbs, but the oem cap for this engine without A/C is supposed to be 13lbs. I also know that the cap on it did not come with the radiator and is probably just a universal aftermarket part. I know that the fan and water pump are also fine. My only other thought is that it could be a bad thermostat. I'm far from an expert with this so I realize there's probably stuff I'm not looking at that I should.

Anyone had this happen in the past, or have any ideas? Thanks much in advance for any help!
 
The fastest and cheapest way to start trouble shooting is first a new cap and thermostat with a thorough flush.
Then go from there.
Don't listen to all the replies that throw jello on a wall and we end up with seeing what finally sticks.
Thermostat, cap, flush. Just do it.
After you grab hold of the fan and jiggle it hard to check for loose play.
 
Ok good to know, thanks. I did the fan jiggle earlier and it was all good. Thanks again!
 
Yea... what Commando said....

One other thing... I would check the dipstick for water in the oil. No cost.. no real effort, but it could tip you off if there is a bigger problem.
 
Get one of those IR temperature guns from Harbor Freight and check and see what it actually running at, you might be surprised.


Alan
 
Thanks guys. I know the oil is good, (water free) and was just changed. I did re-check it to verify today. I am 99% sure the water pump is good, there's no noise at all and no play in it at all. I'll have to try the IR temp gun, hadn't thought of that and I've never used one for that before. Any particular spot you should hit it at that is most accurate?
It does have an aftermarket gauge cluster which includes the temp, but it wouldn't shock me if they were off.

Do you guys think the 7lb cap would cause the overflow issue in particular when hot? I've never dealt with that particular issue before. I also never knew until now that they had different pressure caps for A/C vs. non-A/C equipped motors.

Any particular reason why you'd say it is definitely not the thermostat? Just curious.

Thanks again all.
 
When I was working through my issue I hit different parts of the radiator, water neck, heads, and water passages for temp. Water neck was always warmest. An IR thermometer gives you a very good idea where it's hot.
 
Small update for this issue:
I put the new/correct radiator cap on and drove the car for about half an hour. On the highway going 65mph @ 2800 rpm it never got above 170 degrees. It'll do that all day without any temp rise whatsoever. When I got off of the highway and went through a drive-thru for coffee it got up to 200 by the time I left, (less than 3 minutes). Got back on the road and it went right back to 165 degrees within a minute.
So it's still heating right up but when idling, but with the new cap it hasn't spit anything back out through the overflow hose. I have also noticed that when idling and heating up, I can put the clutch in and give it gas, but the temp doesn't go down at all. I've had other big-blocks that would cool right off when I did that.

Next is going to be a flush as soon as I am able. I have a simple float type anti-freeze tester and it is reading perfect as far as temp protection but I have no idea how long the coolant has been in the car and it's probably due anyways. I suspect that the car had sat for a bit before I bought it, and I've only put under 250 miles on the car to date.

Thanks again to everyone who's offered their thoughts on the issue.
 
That tells me it is speed related which means airflow which means did you leave off the shroud?
 
Does your car have or has it ever had a/c? If not, you probably have the narrow radiator (22") as opposed to the wider radiator for the a/c cars (26"). For low speed operation on hot days, the factory 22" radiator was already borderline on being able to keep a car cool . If you got a replacement radiator from Summit, I would guess it will have much less fin density than the factory unit, especially if the price was low for it. I would never have a 22" radiator in California even on a non-a/c car, as on days over 90F, they won't keep an engine below 210 and will likely gradually keep heating up even over 210 in slow moving traffic. For good cooling in slow traffic, radiator width is the most critical dimension, while keeping an engine cool at speed will depend more on number of rows of fins. I usually get high fin density cores and always get 26" radiators with 3 rows of tubes/fins, even if I have to replace the radiator support to get the larger opening (which you can get from any a/c equipped car). Been down this road many times now.........................
 
My car never had A/C, but the current radiator is in fact under 22". This is the radiator that was put into the car by the previous owner after the drive train was rebuilt: http://www.summitracing.com/parts/sum-380501
It is narrower than the factory unit but isn't a cheap one from what I can tell. I am starting to think it's definitely a part of the problem though, especially after reading your post Saforwardlook. I hadn't noticed until now that the Summit description says it's for "small to midsize cars" as well. I was kinda on the fence about it being so much narrower than the factory unit, but what you're saying makes a lot of sense. Thanks for the info.
 
Make sure you have a shroud on the radiator no matter if you stick with the one you have in it or not. The shroud is a must have item.
 
Thanks Wollfen, my father had said the same thing about the shroud, I'm looking at which one will work best. Not sure if I'm going to try it w/this radiator or get a different one just yet.
 
A shroud will help, but not enough to enable a 440 to run cool on a warm - hot day. If it were me, I would do a real upgrade and replace the radiator support with one from an air conditioned car, that would have a 26" wide radiator opening and then get at least a 2 row or better yet a 3 row 26" wide radiator with very high fin density and the requisite shroud. It will be expensive but well worth it when your car always runs cool thereafter.

Steve

p.s., I don't know why the word "radiator" is highlighted in my post linking you to a site that sells radiators - very annoying.
 
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