I think I'm close to fixing a chronic overheating problem on my '78 F-350 flatbed. The 351 blew aqnd I replaced it with the dealer's only replacement engine, a 400. It immediately developed an overheating problem, but only on days over 80 degrees, and only when it idled for more than 5 minutes. Since this is a portable toilet "tanker," it does a lot of short idles while pumping. By "hot," I mean up to 230 or 240, to the point it'd stagger and die! Even though the radiator was fairly new and had worked fine with the 351 in hot weather, we went to an oversize radiator when pulling the thermostat had no effect. The water pump & radiator cap (12 lb) are new, and we reinstalled the overflow system that had been missing for years. Still it kept climbing past 220, at which point my drivers would either get the truck moving again quickly or shut it down and wait. We never had a problem with the 351.
After searching this site, we put a new thermostat back in, and it helped (kept it at 210) until the weather began to get warm here (80's). At 80 degrees outside, at idle it quickly gets up to 220 -- it seems as if it might go higher, but we haven't allowed it to happen yet. At night, at 60 degrees, it'll idle for 4 hours at 195. We have a very high-dollar racing gauge, so I'm pretty sure it's accurate. The local Ford dealer mechanics are vague about what temperature is normal and safe for this engine. Several said that 400s are supposed to run much hotter and 230 isn't a problem. I have trouble believing this, since it began to stagger slightly above that point. I have heard that new Ford pickups commonly run at 210-215. I only have a "half shroud" that we rigged up, since none are available new or used, and I installed an electric fan in front of the new radiator (or actually half the radiator). My next plan is moving the radiator closer than the current 4", or getting a spacer for the fan....or getting "water wetter," or a fancier fan than the stock 5-blade. I have a small fortune in this truck and it's the backbone of my little business. With over $5000 in new engine, transmission, rear end & brakes, I can't afford to take chances. What temperature should I accept as the max? Is it really supposed to run this hot? In addition to posting, a quick email would also be VERY appreciated, since this poor truck is driving around as we speak, and the weather's getting warmer!

 

Well , I think its too hot at 220... Is your coolant at 50/50 mix? What temp thermostat have you settled for? I would add on a `Flex Blade` fan that is the largest you can use like 16-18 in.
Look for one rated at Low Rpm highest air flow. They are not all the same! Place the fan at the same distance to the radiator as was original...
Ive never done the swap you have. Is the Fan/pump in the same place(center of the radiator..for example) as the 351 setup?
I`ve never used the `super cooling additives` seems like they just hide a problem ,to me anyway.

maby the electric electric fan setup is just interfearing with the stock setup. I`ve never run both at the same time.


__JOHN__Õ¿ö
72 F-250
ICQ#6030753
http://clubs.excite.com/72FORD-F-250

 

>Well , I think its too
>hot at 220... Is your
>coolant at 50/50 mix? What
>temp thermostat have you settled
>for? I would add on
>a `Flex Blade` fan that
>is the largest you can
>use like 16-18 in.
>Look for one rated at Low
>Rpm highest air flow. They
>are not all the same!
> Place the fan at
>the same distance to the
>radiator as was original...
>Ive never done the swap you
>have. Is the Fan/pump in
>the same place(center of the
>radiator..for example) as the 351
>setup?
>I`ve never used the `super cooling
>additives` seems like they just
>hide a problem ,to me
>anyway.
>
>maby the electric electric fan setup
>is just interfearing with the
>stock setup. I`ve never run
>both at the same time.
>
>
>
>__JOHN__Õ¿ö
>72 F-250
>ICQ#6030753
>http://clubs.excite.com/72FORD-F-250

Thanks, John. The original fan is still centered on the radiator, and appears to be about the same distance (about 6 inches as I recall; it's on the road now so I can't check). The mix is about 50/50 -- I searched the Forum & tried to eliminate all the basic stuff, like mix, radiator cap, "reversed fan," collapsing hoses. My mechanic had a similar problem on his Bronco and fixed it with the add-on electric fan, and I did it out of desperation, and it did make a big difference a month or so ago before the outside temperatures went up to the 70's. After it went into the 80's, the problem came back, and we put a 195 thermostat, which helped noticeably, but after a bit of heavy traffic or 10-minute idling, we're hitting 220 and climbing again. I don't think the extra fan could hurt matters, like removing the thermostat, since it doesn't affect how long the water stays in the radiator -- just how cool the fins get....and it doesn't seem at this point that overcooling them could be a problem. Disconnecting the electric fan makes it worse. I've considered adding a second electric fan, since there is room on the left side. In my wilder moments, I've also thought about taking the old original radiator, mounting it somewhere and running the heater hoses to it....using it as sort of a giant "heat sink" (like an oversized heater core) to cool the mixture further and increase the capacity of the overall system. That's a last, wild-eyed resort, of course. Your info on flex fans is very helpful. I think the stock 5-blade fan is pretty narrow. I'll measure the fan area this afternoon and look for a hi-performance fan when the stores open tomorrow, with a spacer to get the new fan within an inch or so of the radiator. To make things a bit more complex, I know that my carb is running a bit lean, but I've been a bit short to get another because of throwing so much time & money into this problem. I believe it's not bad enough to be more than a minor contributor to this problem, but it's there, nonetheless. Thanks for the good advice!

Gid
'78 F-350
'78 & '82 1-ton "tanker" vans
'78 Econoline

 

Gid, I did forget ....What is the Initial advance set at??
If you are pulling vaccum on the distributor at idle and the timing is too far advanced you will tend to run hotter!!


__JOHN__Õ¿ö
72 F-250
ICQ#6030753
http://clubs.excite.com/72FORD-F-250

 

John, I'm not sure where they've got it timed, to tell the truth, but both mechanics who've worked on it are very sensitive to the timing & lean-out aspects of overheating. I'll check with my guy in the morning. I used to do a lot of my own basic mechanical work, but my back & bifocals now make me rely on a couple of good local mechanics and one driver who is good at basic stuff. This truck tends to spook some mechanics (especially the dealers), since instead of using a thousand-dollar vacuum pump I use the brake booster to draw constant vacuum on the 500-gallon tank that pumps out the toilets. It only affects the engine vacuum for a few minutes in the morning and for 5 seconds at each toilet, but I have a cutout valve to make tune-ups & diagnosis simpler. Still, I've had mechanics swear that this will cause lean-out, burn cylinders, etc. However, I wore out two old Dodge 318 vans doing this, with never an engine problem. I went to Fords because of parts availability and because my wife is a hard-core "Ford man," and we have a one-ton Ford van (351) with this same set-up, doing fine for 3 yrs., hauling up to 400 gallons (3500 lbs) every day. I just got another '78 van w/a 460 and am making a tank system for that now. This is a slight wrinkle in the vacuum & timing, but it's a non-problem, no matter what the dealer thinks. I'll post again after I check the timing & search for a flex-fan in the morning. Thanks!

Gid

 

if you have a chance ride with the guy for a morning or something and at one stop just take over the drivers position and "idle" the engine at around 2000+ rpm instead of the standard idle, maybe the water pump isn't flowing enough fluid, I cant guarantee this will work, but I've noticed on my truck if you rev the engine up some it pulls more air through the radiator and makes the engine temperature drop

 

oh yeah, and if the engine temperature keeps rising above what it stays at DONT KEEP DOING IT, it's just something to try and see if your water pump is up to snuff, dont let it get too hot

 

If you've got a 195 thermostat in there now, buy a 180 thermostat and try it. My 390 was doing the same thing with a 195. I put a 180 in it, and the hottest it's gotten is about 190 degrees.

390fe

> After it went into
>the 80's, the problem came
>back, and we put a
>195 thermostat, which helped noticeably,
>but after a bit of
>heavy traffic or 10-minute idling,
>we're hitting 220 and climbing
>again.

>Gid
>'78 F-350
>'78 & '82 1-ton "tanker" vans
>
>'78 Econoline

 

It would me.

After reading all these good posts there are a couple questions thatI have.
First is the fan shroud is it in place.
Second does the 400 require a different radiator than the 351. Have you checked into a 4 row rad.?

John
jowilker

66 F100s
In the still cool hours of the night, you can hear chevys rusting away.

 

Thanks -- good idea! I can try that in the morning, since the linkage sticks (or the spring is getting weak). He has to tap the throttle at each stop to idle it down, so I'll have him leave it up & see how it does, or stay in for a few minutes and watch the gauge. Fortunately, he's real alert & very conscientious with the truck. Haven't checked to see how hot it will be tomorrow; even a ten-degree difference seems to make a lot of difference. I hope to pick up a new flex-fan and a spacer by the time he finishes his route. I also heard today about another truck junkyard, so I'll make another (probably useless) attempt to locate a fan shroud. I'll probably have an update tomorrow. Thanks!
Gid

 

Just noticed a few posts I missed (I'm kind of new at this, so bear with me). The fan shroud is NOT there; it was mostly in shreds when the 351 was running, and went completely when a motor mount broke. We patched and pop-riveted, but it was too brittle & far gone. The 351 didn't seem to care much. We made a half-shroud over the top of the fan out of scrap plastic, and have had no luck in finding a real one. I suspected that going to a lower-temp thermostat might let the fluid flow too fast, so I opted for the "stock" 195. When we change fans tomorrow (I hope) I'll stick in a 180 instead. Do you think going down to a 160 might make matters worse by letting the fluid go through the radiator too quickly? I already have a four-core, I believe. I'll check, but I think I had a three-core when this started, and I told the mechanic to get the biggest, hairiest, oversized radiator he could get his hands on -- which I think was a four-core. I'll find out in the morning. I'll also check with the dealer on whether the 400 (which I think they now call a 350/400) needs more radiator than a 351. They were pretty vague about even what temperatures I should expect, though, so I'm not sure what their advice is worth. I appreciate all the posts!
- Gid

 

I have a 351M in one of my trucks that runs about 230 deg when it is hot out. I have had no problems so far, and the motor has 253,000 miles on it with a complete rebuild at about 150,000. I would suggest getting a new shroud (no matter what the cost $), and just keep a good eye on the temp. for a while. Try www.autokrafters for a new shroud. These motors do run hot. I would stick with the stock thermostat, though. Good luck!!!

Nathan

 

Thanks, Nathan. I know a couple of guys with newer Chevy trucks (ugh!) who say that they naturaly run at 215 or 220 with no problems. However, somewhere over 230 (and my driver was so panicked that he wasn't sure where exactly), the engine staggered and died....which seems to indicate that whatever it was, that WAS overheated. He thinks it was somewhere between 230 and 240. He let it cool down, came back and changed the oil right away. My old 351 was actually a 351M, now that you mention it. It never had an overheating problem, even with the smaller radiator. Back then it had the factory gauge, with no temp numbers on it, so I wasn't sure where it was reading, and the gauge was pretty flaky so we went to a fancy new gauge from the speed shop when we got the new 400 engine. It's encouraging that yours seems to do fine at 230, but numbers like that just make me nervous and I'm going to try to drop them if at all possible. I'll try the autokrafters site tonight. If they have a shroud that'll fit I'll take it, though if I get a large flex-fan tomorrow I could have a fit problem with a stock shroud, and may have to modify it. Thanks!
-- Gid

 

Gid, I'd bet you one of those shiney state quarters that if you get a shroud back on, you will see a noticable difference. I remember having that problem with a van several years ago. The new shroud stopped the overheating problem, because it's design pulls air all across the radiator.


John
jowilker

66 F100s
In the still cool hours of the night, you can hear chevys rusting away.

 

You need to build yourself a full shroud to enclose the fan blades; it needs to extend to the mid-point of the fan blade (ie, don't enclose the entire fan). My neighbor still needed more cooling so he added two pusher electric fans out in front for his 400 4x4. I would stick with a 180 thermostat as a 160 just opens earlier than a 180 but engine wear increases significantly; don't run without a thermostat or this engine won't last. Make sure you have that 4 core radiator. Water wetter does work for race cars that are only allowed to run pure water; I am not sure about a 50-50 mixture which you are using, right?

Lee
1965 F100 short box styleside