Still Overheating

[shortbed]

Okay, I need to back up and start again with my overheating truck problem.
Yesterday I drove through two counties looking for a fan shroud, because two mechanics said ‘that’s your problem.’ There was no fan shroud to be found and I got home tired and disgusted with my truck literally blowing steam out the wheel wells.
(For those new to this we're talking about a '78 F150 300 4X4 without airconditioning) If you're interesting in the backstory See "Overheating" for all the back and forth that went back and forth.

Here is some more information I hadn’t mentioned before. About six years ago I stopped needing the truck for about two years and it was hardly used and, Okay, I’m ready to admit it. There was only the weakest solution of coolant in the engine, maybe almost water. One day, dead of winter, I took it out and it overheated after only a few miles. I wound up getting a new radiator, but it would still overheat now and then. Last summer I was taking it on long trips and it would overheat on the highway, or going up steep grades. I changed out the radiator again during the winter and that seemed to fix the problem. Now . . . last weekend I drove across the state (daylight, hot, highway) and it rode fine. Then I drove it back the next day. Same conditions and it overheats half way back and has been overheating every day since
Now I’m thinking there must be something clogging the system. Nothing else has changed.
For those new to this:
I have changed the thermostat (run it with no thermostat, run it with a 180 degree and a 160 degree). This does not help.
I’ve changed the radiator cap: 13 pound, 7 pound, run it with the cap loose. All no help.
I’ve replaced the water pump. This has not helped.
I’ve checked coolant mixture and levels. They are right.
The fan is turning. The gauge is right (it definitely overheats, take my word for that).
There is not water on the dipstick.
There is no white smoke coming from the exhaust, or water apparent in the exhaust.
I do not see bubbles in the radiator.
At idle the water seems to be circulating in the radiator just fine.
The truck runs good otherwise. The timing seems right.
I’ve been told “fan shroud” but it has run without one for ten years and ran two hundred miles on the highway one week ago without a problem . . . without one.
What would explain the truck running fine on the highway on Sunday and overheating on Monday with the same conditions.
Yesterday I bought some Peak brand “Super Cleaner and Flush” and think I will try this. I can’t think of anything else to do.
Anybody have any other ideas.

 

[bowtiehatr]

i see where the truck was sitting for a long period. even though you replaced the radiator, i would take it back off, and have it rodded out to see if it is stopped up. i had to get one rodded out twice due to one of mine sitting so long it stopped back up. if the radiator checks ok, being all other stuff checks ok, i would go for headgasket. i know the oil and water is not mixing, niether was one on my bronco, but the seal had failed on #5 cylinder letting just enough compression to get in to cause a air pocket causing it to run hot.

 

[TexasRho83]

Checked the head gasket on that badboy?

 

[Mil1ion]

I still think you are getting a false reading of the gauge

Note: There two applications for sending units
One for warning lights one for gauges.

You say it is was fine for years.

I say it there is a signal problem to the gauge.

Do any of the other gauges like the FUEL gauge also read high when the Temp gauge goes up ?

Get a candy thermometer and insert it in the rad cap hole and run the engine just off idle to get the temp up.

Is this the truck that blows coolant out the tube ?

 

[shortbed]

Bowtiehatr: Thank you for your reply. Yesterday I got home with steam literally blowing out under the hood like an old time locomotive and enough water was gone this morning for me to see down into my radiator and dang if there aren’t little clumps of rust all along in there.
Tell me this: the radiator I put in there six months ago was from Advance Auto, about $150; NAPA sells their’s for $220. Will the cheaper radiator hold up to this ‘rodding’ you’re talking about (I’m guessing some kind of flushing). Will it cost enough in time and money for me to be as well off getting a new radiator? Do you think maybe I should get the better (if you think it will be better) radiator from NAPA?
And, should I think about getting some kind of engine flushing done? and what kind of place would you suggest for that?

I think checking out the radiator and engine is worth doing and then, well, I talked to a mechanic today who said he could pull the head for me if we run out of other choices.

Thanks Bowtie. I appreciate your time.

 

[4x4Bart]

You might can flush it out yourself and save some money. It's worth a try and can't hurt. Your radiator is not very old and it might come clean if you can just flush the rust out of the rest of the system.

 

[gsxr1238]

Are you satisfied that the lower radiator hose is not collapsing?Can you get your hands on an infared heat gun?Install the 190 degree thermostat,and bring the engine to operating temperature.Take the infared gun and measure the temperature of the top radiator tank,and then the temperature of the lower tank.The top tank should run a minimum of 10deg hotter than the lower tank,and a maximum of 14 degrees.13degrees would be ideal.This differential test will show that the heat is being rejected from the coolant,or not.I suspect that since this is an intermittent problem,there is some trash/debris somewhere in that cooling system.Also install a mechanical temperature gauge,and then you will have concrete numbers to work with.Also check the oil fill/breather for signs of condensation.Let us know what you find.

 

[money_pit]

I would knock the rear freeze plugs out and see if the block is full of crap.

 

[shortbed]

Thanks for the replies:
4X4Bart . . . I bought some Peak brand radiator flush and that plastic back flush kit. You’re suppose to put this stuff in and run the vehicle for 3 to 6 hours before flushing it. I bought it because I didn’t know what else to do and wanted to do something, but most guys I’ve talked to over the years don’t hold much with these products. What do you think and do you know of a better product or better way to flush the system. And is there some technique to flushing an engine you could tell me about . . . or should I go to one of the shops that specialize in this.
GSXR1238 . . . I don’t think the bottom hose is collapsing. Of course I’ve never seen it while the truck is rolling, but every time I’ve checked it. And I’ve checked it a bunch of times when the truck was HOT, it’s never been shut down. I’ve put my hand on the radiator when it was warming and there is definitely a difference in temperature between the top and bottom, and ten to 15 degrees (as a guess, by hand) seems about what I would think it felt like. As to that infrared gun, uh, not one of those in my tool box, but I will check the breather for signs of water, though none of the dipstick.
Money_pit . . . You’re scaring me, man.

 

[fordrka1975]

If your coolant is muck brown and smells burnt, you definately are getting combustion in the coolant. You may have a cracked head or block from freezing water that one time. Cracks tend to worsen over time with thermal cycling. Randy.

 

[bowtiehatr]

any radiator will hold up to being rodded out, and this will work better than any chemical flush out there. with the chemicals, you never know if one or more flus are stopped up which can be a possibility.

 

[TexasRho83]

Not too often you see a newer radiator causing problems like that...

I don't really think it's the rad

 

[bowtiehatr]

i felt the same way untill i had one of my personal radiators do that to me. it was flushed twice in 2 weeks, stopped up both times due to so much stuff in the block

 

[Mil1ion]

perhaps there is an air lock going on ?


i had seen a truck where we had to have the front end up high to get the air out of the system.

 

[shortbed]

Well, guys, today I'm packing half a dozen water containers in the truck and going off to find another radiator or get this one cleaned out. That's the mission for the day (and a fan shroud if I can find one). Thanks again for holding my hand through all of this.

Jim

 

[TexasRho83]

Jim let us know how it goes...

Dennis had a good possible culprit...air in the system. I've personally never had that problem but I hear it's been the reason behind overheating several times.

 

[MikeWire]

I have a little input: I did have exactly the same issue after a rebuild - it was blowing steam and everything. I found that the thermo I bought was bad (did not open in boiling water) and I had accidentally installed it in reverse. I bought the cheap thermo from Napa, and returned/exchanged it for the "lifetime" version, put it in correctly, and I have had no problems since. Maybe something to pull and check since it is right in the top of the motor. I also picked up a new rad cap, which helped as well.

 

[jsutton]

I haven't read all of the replies on here so someone may have already suggested it, but you may can check for a fan shroud on 80's vans. That's what I got mine off of.

Also drilling a small hole in the thermostat to let the air out I've found is a cool trick. That way no air gets trapped behind it when you're filling it up.

 

[Mil1ion]

this is the main problem with starting another thread on the same topic by the same person

the op has tried 3 different t-stats and even ran the engine without one.

please people..keep everything on one thread

 

[m78]

Eliminate the mechanical thermostat. Find a restrictor cone like they use in race cars.