Ok. I have a 1970 f100, with a rebuilt 351w. Everything under the hood is new including the radiator and hoses. Over the last two weeks of driving it gradually got hotter until it got to the point of overheating. I did change out the thermostat and I put a temperature gage in that I bought from the part store. Although, the temperature gage on my dash worked, I went ahead and put another one in, just to make sure, and it still overheated. I checked the radiator hoses and they are not being sucked shut. I am not loosing water anywhere. The waterpump is new and works good. The belts are tight and not slipping either. Not having anyother options, I took the heads off and had them magnafluxed, no cracks. I put the heads back on after having them redone. They did happen to find a couple of cracked valve seats. I have not got my engine completely back together yet. Still need to put on the carburetor, powerstearing pump, and alternator. Like I said, I have been driving it for about a year, with no heating issues. I also have new exhaust with headers.[ So there is no heating valve/coil in the exhaust manifold. So, why now? Any suggestions?

 

70, You said that you are not loosing water, correct??

From my experence, if it is not boiling water out, it is not overheating. These ol trucks will puke coolant pretty quick when they get too hot.

Is your coolant green, muddy or what?

John

 

It was kind of brown. So I added some new coolant-made it green again. My radiator cap is rated at 13lbs. maybe thats why it hasnt boiled out.

 

Come to think about it there was this kind of mucky silver stuff on the sending unit. I passed it off as the stuff in the coolant.

 

if your water is muddy looking then you are getting oil in the cooling system somewhere. since you had the heads magniflux it could be a head gasket or cracked block. when the engine was rebuilt did you have it bored any?

 

Nope the engine did not need bored. The brownish color (not muddy) I say would have most likely come from the block, as some oxidation or rust color. Thus I would most likely have water in my oil....Which I do not. It very well may have been a head gasket but I wont know until I start it and let it run. I did look at the gaskets when I took the heads off, they did not seem to be damaged. I did notice though how three of the head bolts on one head seem to be not as tight as the others. Thanks

 

I suggest that you put it back together, flush the system really good, if you didn't already. Use a mix of coolant and distilled water to refill the system. Keep about 2" down from the top with the coolant for expantion, and watch it for a week or so. If the fluid level stays constant or if it pukes a little the first time out, just keep an eye on it checking it only after it is in a cold condition. Warm or hot coolant is expanded and will not give you a true reading. IMHO

John

 

Could it be maybe that I had to much of one or the other-coolant or water? When I first put my new motor in I ran about half & half.
Thanks Tony

 

that is the correct mixture 50/50

 

Tony, 50/50 is the recommended mix of most comercial antifreeze coolants. After growing up in North Carolina, having minerals in the water, and seeing the mix turn to mudy looking yuk, I was advised to use distilled water in the mix (less than a buck a gallon at the grocery) and have been as happy as a fat baby with a big nipple in his mouth ever since.

I went back and reread your original post. Can you provide us with a little more info (Over the last two weeks of driving it gradually got hotter until it got to the point of overheating.)
Did the truck start boiling over? What caused you to come to that conclusion.

thanks
John

 

Yea John, It always ran cool according to the factory temp gauge for a good year or more. Over a period of two weeks or more it continued to get hotter until it pegged out on the temp gauge. I knew the gauge or sending unit might be bad so I went to orielly's and bought a sun-pro gauge. After installing that-and letting my truck run for a good 10 minutes the temp started to reach the 212 point after the thermostate already opened. I thought it might have something to do with my tranny cooler but I really dont think that would be causing this. It never boiled out or puked coolant.

 

It sounds to me like you need to do a very thorough flush and refill before you can make any real headway on solving the problem.

If there is a sticky goo in the radiator, then you have an oil leak, and that is not good at all, but a mere muddy silted appearance is just dirt and rust. If you do not have goo, then try cleaning the system first. Drain the radiator by removing the lower hose - it will give you a better idea of the crud that may be in there. Stick a finger in the lower part of the radiator through the hose nipple, and see what you get on the bottom. If you get a layer of slime, you need to clean the system.

Clean it out, run some plain water in it for a day or so - but no more - then clean it again. Do it again if necessary, until you get the filth out of there. Once you are getting clear water to run through it, refil it with 50/50 mix to protect the system.

If it still overheats, you need to check the coolant flow. With the description you have given, it is possible the fine rust silt or hard water deposits have clogged the radiator. (If the radiator is clogged, then the heater core is too.)

When the engine if properly warmed up, the upper radiator hose should be HOT, and the lower one should be very warm. If the lower one is cool instead, then you may have a clogged radiator.

If all this doesn't work, and you still suspect a clogged radiator, take it to a good radiator shop and they can boil it out for you.

Good luck, and post back what you find.

 

Tony, Design has changed a lot in 30 years. If you look in my Taurus engine bay, you can not see a radiator because of shrouding and fans. I sat out in my car for 90 minutes in 97º heat ideling and the AC running waiting for someone that didn't show up. The temp guage never moved up at all.

My pickup will run all day long in heat and as long as it is moving the needle holds steady, but it will not sit still very long at idle without overheating. While it has a huge new radiator there is no air flow regulator on it to direct air through it. I have a shroud and will install it one day, I know I will. I get around the issue by not letting it sit and idle in warm weather.


I have a feeling that by getting you truck moving, your concern will go away on it's own.

John