My 56 tbird temp gauge shows that the engine is running about 212 degrees but the engine never seems to steam out the radiator. I have replaced the gauge and sending unit with a new one that is made for the tbird. I also have a hand held infared temp sensor gun that I have tested the engine with. Here are the results: When the gauge is reading 205-212, the hand gun picks up the following temps: at the thermostat housing 188; on the head where the heat sensor is screwed into the head 170: on the surface of one of the expanision plugs on the side of the engine block 190; on the side of the block about half way down in the rear 200. Any suggestion?
312 overheating?
- Thread starter cjc56
- Start date
dmsfrr
Well-known member
cjc56,
What temp rating is your thermostat? Other than the dash gauge reading a bit high (which is a cheap safety feature, haha) and never having checked one with a heat gun, at first guess it seems pretty normal.
I found this on another car make/model website (from the 70's & not Ford) so it isn't specifically about older y-blocks but I thought it very clearly & thoroughly explains engine cooling.
Given the explanation below, and your heat gun readings, I think your engine temp is fine.
excerpt from -> http://www.bricklin.org/TechCentral/TCArticleV6n2p5.htm
" I'd like to explain the theory of overheating. A car with a 15 pound radiator cap will not boil the water in the radiator until the coolant reaches approximately 250 degrees temperature. With anti-freeze, the boiling point is 250 to 260 degrees. You can run your car at 240 or 250 degrees without hurting anything, as long as the water in the radiator doesn't boil. Once the water boils, it will immediately push water out the overflow, lower the coolant level in the radiator, and give you air bubbles circulating through the cooling system. Air bubbles do not cool an engine, so the engine temperature will immediately skyrocket. Your main concern should be to keep your engine below the boiling point of your coolant. If your radiator cap is no good, it will lower the boiling point of your coolant to 212 dgrees. A leak of any type anywhere in your cooling system will have the same effect. That is why you must have a good radiator cap on your car.
Many people get worried if their car gets up to 220 degrees. On a hot day, going up a hill with your air conditioner on, that is a normal temperature, and is nothing to worry about, as long as you aren't losing coolant. You can safely operate to 240. Above 240 you are nearing the boiling point of your coolant, so start being concerned. If you reach a point that your coolant boils, the radiator cap will immediately release the pressure on the radiator, and the coolant will immediately boil out the overflow. Now get worried!! stop the car and cool it off. If you continue to drive past this point, the engine temperature will skyrocket. The gauge will not show how hot it really gets, because the gauge will only read water temperature. Once the water boils, there is steam in the cooling system, and the gauge doesn't read steam pressure. The gauge can read 220 after overheating and boiling, but in actuality, it is closer to 300. Once the water boils, the gauge is useless. If you don't stop the car and cool it off at this point, you will cause engine damage, such as blown head gaskets, cracked heads and blocks, etc. "
What temp rating is your thermostat? Other than the dash gauge reading a bit high (which is a cheap safety feature, haha) and never having checked one with a heat gun, at first guess it seems pretty normal.
I found this on another car make/model website (from the 70's & not Ford) so it isn't specifically about older y-blocks but I thought it very clearly & thoroughly explains engine cooling.
Given the explanation below, and your heat gun readings, I think your engine temp is fine.
excerpt from -> http://www.bricklin.org/TechCentral/TCArticleV6n2p5.htm
" I'd like to explain the theory of overheating. A car with a 15 pound radiator cap will not boil the water in the radiator until the coolant reaches approximately 250 degrees temperature. With anti-freeze, the boiling point is 250 to 260 degrees. You can run your car at 240 or 250 degrees without hurting anything, as long as the water in the radiator doesn't boil. Once the water boils, it will immediately push water out the overflow, lower the coolant level in the radiator, and give you air bubbles circulating through the cooling system. Air bubbles do not cool an engine, so the engine temperature will immediately skyrocket. Your main concern should be to keep your engine below the boiling point of your coolant. If your radiator cap is no good, it will lower the boiling point of your coolant to 212 dgrees. A leak of any type anywhere in your cooling system will have the same effect. That is why you must have a good radiator cap on your car.
Many people get worried if their car gets up to 220 degrees. On a hot day, going up a hill with your air conditioner on, that is a normal temperature, and is nothing to worry about, as long as you aren't losing coolant. You can safely operate to 240. Above 240 you are nearing the boiling point of your coolant, so start being concerned. If you reach a point that your coolant boils, the radiator cap will immediately release the pressure on the radiator, and the coolant will immediately boil out the overflow. Now get worried!! stop the car and cool it off. If you continue to drive past this point, the engine temperature will skyrocket. The gauge will not show how hot it really gets, because the gauge will only read water temperature. Once the water boils, there is steam in the cooling system, and the gauge doesn't read steam pressure. The gauge can read 220 after overheating and boiling, but in actuality, it is closer to 300. Once the water boils, the gauge is useless. If you don't stop the car and cool it off at this point, you will cause engine damage, such as blown head gaskets, cracked heads and blocks, etc. "
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Thanks. That all makes sense but I sure would like to have a gauge that works. My original one stopped working so I decided to bite the bullet and get a combo gauge/sending unit from CASCO. You would think the new gauge would give a more accurate temp. Surely the gauge is meant to warn you of a increase in engine temp. Otherwise why have one. Just wait for the steam to appear. Yes I will call CASCO!!
miker98038
Well-known member
Well. FWIW, that's pretty common. My 55 bird runs 56 gauges and senders, since I converted it to 12volts. I think both years used King-Seely gauges, which are a more complicated device. There was a long article at Y blocks forever some years back about adjusting them. I don't know if it survived the latest software change.
Dmsfrr's comments are right on. You don't seem to have an overheating problem, just a gauge problem. I knew mine was hot just as the gauge pegged. Home in the garage, hot day, idling. The infrared gun is really your friend at that point.
In my case, it really was overheating, even though I didn't lose fluid. A really good fan shroud, better fan, and clean cooling system are the answer to that. Greenbird56 has posted some good articles on clutch fans, cooling restrictions, and larger fans. Here and at y-blocksforever. He's in Tucson, and 115 degrees happens almost every summer.
One last thought, if you're going to raise the cap pressure. It's not just the radiator and hoses, you want to have the heater core checked too. Nothing worse than blowing the heater core into the footwell on a hot day. Guess how I know.
Dmsfrr's comments are right on. You don't seem to have an overheating problem, just a gauge problem. I knew mine was hot just as the gauge pegged. Home in the garage, hot day, idling. The infrared gun is really your friend at that point.
In my case, it really was overheating, even though I didn't lose fluid. A really good fan shroud, better fan, and clean cooling system are the answer to that. Greenbird56 has posted some good articles on clutch fans, cooling restrictions, and larger fans. Here and at y-blocksforever. He's in Tucson, and 115 degrees happens almost every summer.
One last thought, if you're going to raise the cap pressure. It's not just the radiator and hoses, you want to have the heater core checked too. Nothing worse than blowing the heater core into the footwell on a hot day. Guess how I know.
I don't mean to hijack the thread, but what size should the radiator cap be? I have some old documentation with the car about it over heating but it has been fine for me. It has a 5 pound cap on it. It is a former Texas car that moved to Minnesota for a couple of years before migrating here to northern NY. The temps run about 180-190 in cool weather. Haven't had a chance to run it in hot weather.
dmsfrr
Well-known member
I've never tried it but there might be a resistor that could be put inline with the sender and gauge that will correct the high reading. A variable resistor (like the volume control for a radio), with the right 'current' capacity, could be used to set/adjust your existing gauge to perfectly match your heat gun.
I'll bet the electrics person at Casco has done it before & could probably give you a good clue for that resistors value. It might be as close as the nearest Radioshack.
I have an NPD 2015 parts catalog for '55-'57 T-Birds and at the top of pg 43 it shows a 7# cap for 55's and 13# caps for '56 & '57.
I looked in a few other catalogs but didn't see pressure ratings.
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Dobie Gillis
Well-known member
You may not want to tackle this but if you look at the back of the gauge you'll see some "teeth", for lack of a better term, through a hole in the case that King-Seeley, the manufacturer, used to calibrate it during assembly. There isn't much adjustment there but maybe enough to get you in the ball park. It will take some fiddling to figger out which way to move the adjustment.
miker98038
Well-known member
Putting a variable resistor in a King Seely lets you get one reading right, wherever you set it, and everything else wrong. That's what I did. I think the article (by bergmanj, jbergman ?) went thru the reason for that. It's some kind of a feedback loop, and setting the gauge was (according to him) on the bench, a battery, pot of hot water, and time to let it cycle and work.
My caution about the heater core was due to the mention in the article of a 15lb cap. The factory was much less. Everything has to be like new to go to 15lbs.
My caution about the heater core was due to the mention in the article of a 15lb cap. The factory was much less. Everything has to be like new to go to 15lbs.
scicala
Well-known member
I think you're dash temp gage is more accurate than you think. When using the temp sensor gun you are measuring skin (outside) temps which are always lower, especially by the factory temp sender which is mounted in thick cast iron. I would expect the outside temps to be slightly lower.
dmsfrr
Well-known member
The 15lb cap was just an example mentioned in the article I copied/pasted that's about another make/model of car that was made in the 70's, not for an early y-block. I didn't mean to confuse anyone.
Thanks Dobie Gillis, I'll eventually have to look at mine. It only shows cold or hot, nothing in-between. But I won't have to worry about it until I get the engine back in.
That sounds right to me.
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