Help! Overheating!

[gbarber]

I just rebuilt my 289 (.040 over) and now have it running (12 degrees BTD). Everything is new (radiator, waterpump, thermostat, heater core, hoses). My problem is overheating. I'm blowing coolant out the overflow at about 210 degrees. I installed a 260 degree thermostat. (I thought this would reduce heat, but I have now been told this may be a problem). Like I said, I just put this engine in the car. Is there a normal process for getting the air out of the system? Left alone, the temp. will easily get to 230 degrees at idle (900 rpm). Is there something obvious I'm overlooking? If I need to include additional information let me know. Thanks in advance!

 

[65shlbycln]

2 simple things to look at. I was overheating a while back, and the problem was that i had almost no coolant in my radiator. Instead it was mostly water. So after a few minutes at idle, the water started to boil, and i was spitting out water through the over flow just as you are.

Another thing, if you connected the wires to the temp gauge backwards, you will get a faulty reading that will make you look like you are overheating when you actually arent.

 

[paintballtommy]

a 260 degree thermostat will not open to allow coolant flow untill 260 degrees. buy yourslef a 160 degree thermostat and that should help.

 

[gbarber]

65 shlbycln, thanks for your info! Just so you know, I put an aftermarket guage in that pretty much showed that the factory guage was reading correctly.
paintballtommy, You're right I'm basically an idiot. I meant 160 degrees. That's probally why I have so many problems. Thanks

 

[Ozsum67]

Your overboring is typicall of heat related problems. Try a lesser mix of coolant like 70-30. You may have to modify to fan to acheive more cooling. Have you checked the radiator to see if circulation is happening?

 

[6t6stang]

Overheating

Are you sure your head gaskets are on properly.

If they are backward it will overheat because the coolant holes are in wrong place.



Just a thought

 

[Ozsum67]

That's why the need to check for circulation.

 

[10secgoal]

Try a 180.... If you thermastat is too small, you water won't stay in your rad. long enough to be cooled. This is way people get pissed of when they overheat and they don't have a thermastat installed. Also, your coolant is your best friend. It protects but it also raises the boiling point of water. That way it won't shoot out of your rad if it's not boiling. Get a 16 lbs cap for your rad. If your water boils, and comes out of your rad. then you lose water and now you only have lets say 4 1/2 gallons rather than 5 to cool you motor. It's a snow ball effect.

 

[Lswhat]

also a fan shroud will help a bunch. and maybe a 3 row big core rad i barely get over 160 at idle for 10 mins in the summer heat of fl.

 

[Ozsum67]

Try a 180.... If you thermastat is too small, you water won't stay in your rad. long enough to be cooled. This is way people get pissed of when they overheat and they don't have a thermastat installed. Also, your coolant is your best friend. It protects but it also raises the boiling point of water. That way it won't shoot out of your rad if it's not boiling. Get a 16 lbs cap for your rad. If your water boils, and comes out of your rad. then you lose water and now you only have lets say 4 1/2 gallons rather than 5 to cool you motor. It's a snow ball effect.

You got it bassacward. The coolant needs to stay in the engine long enough to absorb heat and disipate it away via the radiator. Too much coolant is a BAD, BAD thing in the way of overheating.

 

[6Stang7]

That's why the need to check for circulation.

How should one check?

-Shaun

 

[Lswhat]

leave the cap of the rad then let it worm up u should be able to see the water flow after the thermo opens up the water will look like a river

 

[10secgoal]

I don't think that's a$$backwards.. If it were true, it wouldn't take 25 minutes for a car with no thermastat to warm-up. When the water comes out, you talking about 180-200 deg going into a rad. that is being cooled by air temp that is60-100 deg. That's a difference of 80-140 deg. difference. Now compare that to a motor where the plug gets 700 deg and the cumbustion that takes place is around 1000-1400 deg. I don't think the water has to be in the motor before it starts to get hot.
And if coolant was a bad thing, they wouldn't use it. They would just use tranny fluid for the protection. The coolant raises the boiling piont of water keeping more of the fluid you need to cool the motor in the rad. That's why I have a 25 lbs cap on my rad.(no my rad. won't split.)

 

[12sec67]

You got it bassacward. The coolant needs to stay in the engine long enough to absorb heat and disipate it away via the rad.

nope... you got it bassacwards....


10 sec goal is correct

 

[ddonaca351]

-Make sure you have a fan shroud, that fits properly, and that the fan fits nicely in the shroud. (no huge gaps, not all chewed up)

-With the motor just up to temp (thermostat JUST opened) hold your hand in front of the radiator, and feel for a nice even warmth from all areas. If you have any cold spots that means that there is an abstruction in that area of the radiator killing the flow. If this is true you should get a new one, or get the old one rebuilt.

-Are you sure the thermostat is working properly and is the proper heat range? people build a 5000 dollar motor and put in a 97 cent thermostat.... buy the 10 dollar hi-flow modle from Mr G or whoever that reads the right temps, etc... it is cheap insurance. It is my own personal opinion to not go more than 2 heat ranges colder than stock with a STOCK radiator. Reason being the thermostat does two jobs, it opens to allow the motor to cool, it also restricts some of the flow so that the coolant has time to "give off" its heat to the radiator. A stock radiator is not real good, aluminum ones or aftermarket ones with larger surface area or larger tubes can absorb more heat in a shorter amount of time. If your radiator is on the limit of what it can do, installing a colder thermostat can hurt as much as it helps.

WHEN does it overheat? In town, but not on the highway would indicate not enough flow or not enough capacity, On the highway, but not in town would indicate too much flow and the radiator cant get rid of the heat fast enough.

-Do not run too much water, OR too much anti-freeze. Too much of either is no good. Water cools better, but boils at 212 and has no anti rust / anti freeze properties or lubrication for the water pump. You have to remember that "coolant" doesnt cool worth squat (some but not very good), it stops boiling, and it stops rust, and it provides some lubrication, but it doesn't cool very well at all. About a 50/50 mix is your best all around bet, BUT if you have heating problems try a 70 water / 30 coolant mix (it will transfer heat more efficiently), BUT BE AWARE the water will evaporate away more easily and you will have to check the level OFTEN!!!
I do mine minimum once a week, usually two or three times a week in the summer. You can also add "Redline : Water Wetter" it drops the temps about 5-10 degrees for me.


- If all else fails start on the hard stuff:
- Are your head gaskets installed backwards?
- Did you make sure the ports for the waterpump to the block line up, and arent covered by part of the gasket?
- Is your radiator just too dang small to work with the motors new power level?

Hope this helps...

Dave-

 

[Ozsum67]

nope... you got it bassacwards....


10 sec goal is correct

My GOD son, the radiator is there to cool the coolant AFTER it has absorbed heat from the engine. Better hit the books some more.

 

[Ozsum67]

I don't think that's a$$backwards.. If it were true, it wouldn't take 25 minutes for a car with no thermastat to warm-up. When the water comes out, you talking about 180-200 deg going into a rad. that is being cooled by air temp that is60-100 deg. That's a difference of 80-140 deg. difference. Now compare that to a motor where the plug gets 700 deg and the cumbustion that takes place is around 1000-1400 deg. I don't think the water has to be in the motor before it starts to get hot.
And if coolant was a bad thing, they wouldn't use it. They would just use tranny fluid for the protection. The coolant raises the boiling piont of water keeping more of the fluid you need to cool the motor in the rad. That's why I have a 25 lbs cap on my rad.(no my rad. won't split.)

It will in fact, take an engine with no stat longer to warm up than one with. By more coolant being a problem, I meant more of a coolant ratio, like instead of 50/50, you can get into trouble if you use MORE antifreeze in the mix like 70 anti/30 water. The higher coolant actually holds more heat than straight water. Water doesn't do much for rust proofing or boilover, but it does disappate heat better. Can't argue with physics......well.....I guess some folks can.

 

[gbarber]

I put in a $5.00 NAPA 180* thermostat yesterday to replace the Mr. Gasket 160* stat I had installed at the time of the rebuild. (250 miles ago) I also drilled a 1/8" hole in the rim of the stat to allow air to escape. (My machine shop guy said it may help bleed air) The Mr. Gasket stat had a much smaller opening. I also allowed the engine to run for about 30 min. with the rad. cap off the try to purge the cooling system of air.
The end result- At highway speed, the engine runs at 180* or less. In the city, it runs hotter. I didn't do too much city driving, but while idling in the garage, it climbed to nearly 210* within about 10 min. before I shut it off. I guess I was happy with this result. I didn't lose any coolant in the process. I'm not sure the 160* stat was working properly, but I'm sure excess air in the system didn't help.
Before I changed the thermostat, I tried letting it run without the rad. cap. After 20 min., the coolant began to shoot out of the rad. in short bursts about 15 seconds apart. With the new stat, the coolant flowed normally.
I guess the next thing is to take some additional steps to correct cooling problem. I'm shopping for a fan shroud and probably a more modern radiator. The one in it now is about one year old, but it is the original style. The air conditioning condenser probably isn't helping things either.
Anyway, thanks for all your advice. I'm sure I'll get it under control eventually.

 

[Ozsum67]

I put in a $5.00 NAPA 180* thermostat yesterday to replace the Mr. Gasket 160* stat I had installed at the time of the rebuild. (250 miles ago) I also drilled a 1/8" hole in the rim of the stat to allow air to escape. (My machine shop guy said it may help bleed air) The Mr. Gasket stat had a much smaller opening. I also allowed the engine to run for about 30 min. with the rad. cap off the try to purge the cooling system of air.
The end result- At highway speed, the engine runs at 180* or less. In the city, it runs hotter. I didn't do too much city driving, but while idling in the garage, it climbed to nearly 210* within about 10 min. before I shut it off. I guess I was happy with this result. I didn't lose any coolant in the process. I'm not sure the 160* stat was working properly, but I'm sure excess air in the system didn't help.
Before I changed the thermostat, I tried letting it run without the rad. cap. After 20 min., the coolant began to shoot out of the rad. in short bursts about 15 seconds apart. With the new stat, the coolant flowed normally.
I guess the next thing is to take some additional steps to correct cooling problem. I'm shopping for a fan shroud and probably a more modern radiator. The one in it now is about one year old, but it is the original style. The air conditioning condenser probably isn't helping things either.
Anyway, thanks for all your advice. I'm sure I'll get it under control eventually.

You can verify if the old stat was the issue by placing it in some water on the cook stove, and with a candy thermometer, see if it opens up at the prescibed temp.