a few weeks ago I put a new water pump in my 86 F250 with a carb'd, feedback system 300 six. it was fine heatwise after that until last week, while out wheeling, the truck started running really hot, the gauge was pegged. I figured at the time that the radiator was just clogged up with mud, which it was, which was causing the engine to overheat. I ended up running it like that for about an hour, shutting it off from time to time. (I know, bad.) Well, I finally got to a hose where I could wash the radiator out, and after that, it cooled off a bit, and then, it got hot again, so I put the heater on full blast, and drove home. later, I found out that I was down about 3 quarts of oil the whole time the truck was hot (yes I know ) I figured maybe that was why the truck was overheating. so, after putting oil in it, I went through a couple days of the truck sometimes getting a little hot, and sometimes not. then, when it finally popped a hole in a hose, I figured it would be a good time to throw a thermostat in it. I did that, and a couple hours later, drove it. it started to get hot again. What else could possibly be causing it to overheat? could I have blown the head gasket or something when it got really hot the one day??? I am going to pull the spark plugs soon and do a compression test if I can get a compression tester. I hope I didn't really screw something up. I've noticed a slight loss in power since the day it got really hot. I feel really bad for doing that to my truck.

so any help is apprecieated....

 

I'm sorry to hear about your problems. You said the rad. was full of crud. I'm wondering if the w. pump impellers are gone/going. If you aren't getting coolant in the oil, then I don't think it's a h.gasket, but a compression test will not hurt. I would get one of those cheapo fittings and hook the hose to it so you can flush the engine. My guess is the w. pump. How old is it? I have heard the older model pumps with the cast impellers last longest. Check in rad. to see if the pump is circulating wtr.

Good luck.

 

Best of luck with this. I was plagued with overheating problems with my last 300, and lately been dealing with the same BS on my current one. About 2 mos. ago I had a water pump go out. Ended up when I pulled it the impeller was gone (had one small piece of one blade, all others completely missing. Anyway, still been running hot from time to time since and getting worse. Lost power and gauge pegged quickly on the way to work Friday. Pulled the head yesterday and it's cracked right across the chamber of number 4. The previous truck cracked two heads in the time I was driving it. Thank God I had two spares sitting in my junk parts. Just dropped one at the machine shop today. Decided to go ahead and rebuild the whole engine while going this far. Can't really afford it, but don't have much choice. I hate to say these heads crack easy when overheated and so far always in the chamber. Good luck.

 

Definitely hope you didn't hurt anything. A compression tester is cheap. I think I got a nice one at Walmart for around $20 and it's been very reliable and useful.

If your radiator, thermostat, and water pump are new, have you ever replaced your heater core? That'd be the only last place I can think of where junk could be hiding.

Other than that, if everything checks out fine, and your cooling system is in top order, don't disregard the idea that your gauges just may be faulty. I've had that issue before.

 

As a mechanic for Ford I remember the 300 having casting issues on the number 1 jug. This in some cases would cause a new pumps impellers to come in contact with the number 1 cyl. We would have to put in a couple of gaskets and in some cases make a shim to set the pump out more. Prolly not your issue but thought I would post it anyway. Good luck

 

what is a good way to tell if I'm circulating water??? the upper rad hose and the hoses running to the heater are definately full of water. The water pump should be fine as I hear no noises and something has to be giving me the water pressure I have. What I'm wondering is maybe my thermostat that I got from o'reily's is too cheap or has gone out again or whatever and is not opening???? how can I tell for sure whether or not it's opening??? btw I just drove it for a while. it starts to heat up when I put more of a load on the engine, like going up a hill or whatever, and then I can cool it off with the heater, but once it starts to get hot and I don't use the heater, it stays hot. It seems to get even hotter after I shut the engine off. wtf?????

 

and like I said I really hope I didn't screw it up bad. I know that these engines are tough, and I've heard stories of 300's in dump trucks running with the exhaust manifolds glowing red hot and stuff like that, but I wish I knew what to do right now!

 

A few things you could try:

Have a shop pressure test the cooling system and/or a professional reverse flush to be sure there's no more junk in the system.

If, while driving, the thermostat stays open, your engine would have a hard time warming up. If it was stuck closed, it'd probably heat up just sitting there idling and wouldn't cool back down for anything.
You can test a thermostat by removing it and putting it in a pot of boiling water to see if it opens.

If it continues to heat up after you turn it off, it's probably heat-soak. It's where the residual heat of the combustion chambers spreads through the block because there's no moving coolant to cool it back down. Pretty normal I believe.

 

Don't eliminate the fan clutch (like I did for so long, DOH !) mine was bad and for $30 it fixed the problem. The old one I guess just could not keep up with the heat wave we have right now.

 

Forgot about the fan clutch as mine doesn't have one. Definitely a good thing to check.

 

my fan spins at idle. when is it supposed to disengage??? also, I don't think there is any junk in the cooling system. like I said, the mud was in the fins of the rad, not inside of it. There is no coolant in the oil, and if the head was cracked, wouldn't there probably be coolant in the oil? and if I warped the head, wouldn't I also have blown the head gasket? I don't really seem to be showing signs of any major problems......so I guess I will just check the thermostat again.

 

An old general rule of thumb is it tends to disengage over 40 mph when the air going through the radiator takes over & cools it. But, unless it's super hot and the air going through your grille is not getting it cool enough it should remain on ! Yes , it should remain on when started.
When they age sometimes they slip more and usually can't keep up with the rpms/demands needed to do the cooling.
Don't know where you live, but here in KY (as if my **** poor grammar isn't a dead give away !) we have what the news is calling a "Heat Wave" it's humid as all hell with all the rain, so it's working engines hot right now !

 

okay both my old thermostat and my new one I just put in work fine. they opened right up in boiling water. so I don't know. I guess a compression test. and pull the spark plugs and check em out. but first I have to wash all the dirt and oil off that the engine is covered in.

 

Didn't think it was the thermostat since it increases drastically in heat under hard load, but cools back down. Are you sure you don't have a bunch of air in the cooling system?

 

that happened before, after I overhauled this engine just over a year ago. what is a good way to bleed the air out? last time I force fed water into the rad with a hose, and a bunch of air and coolant sprayed back out.