Let me start with saying I have researched this forum on the issue and found a few threads that were similar, but none with the same symptoms as I have.

97 F350 Crew Cab 4x4, 460, E4OD (brand new reman), SRW, 160,000 miles.

The truck cools fine at highway speeds UNLOADED. The only time I have any problems with overheating is in stop/go traffic, idling, and towing. I have new 4 row radiator, 180 degree thermostat, new fan clutch, all new hoses (with the support springs inside). I noticed when I refilled the coolant system after changing the radiator and hoses that it held almost 6 quarts shy of what the manual said it should. I double checked the radiator with the supplier and yes, it is the same capacity as the old one.

I have not yet replaced the water pump or heater core. Another anomoly is I hear coolant rushing through the heater core inside the truck right after I start it and when I take off after stopping or idling.

I have checked my temp gauge, which is working properly. When towing, the temp stays right on 180 degrees until I start pulling a hill, and then it jumps up to around 230-240, then will rapidly drop back down to 180 again. It jumps around a lot when towing, but slowly and steadily rises when idling. I notice a drop in performance when the temperature goes up. As long as the motor is having to work, the temp stays up. I have noticed some very slight knock/ping under load, but usually only when the temp is higher.

I tow a 34' RV that weighs about 6500 pounds with the truck. Back in March I towed that RV about 550 miles and the temp stayed rock solid at 180. Now, with the outside temp higher, I have the overheating problem.

I have tested the coolant system for hydrocarbons...which was completely negative, so probably not head gaskets. I NEVER have had any coolant loss nor any oil in coolant or coolant in oil. The motor has not used a drop of oil in the 15,000 miles I have owned the truck.

Any ideas or suggestions would be greatly appreciated.

 

With that many miles, I would say that your motor needs the cooling sysytem flushed. Sometimes I am amazed at the growth in the water passages I see when I pull the heads on high mileage motors. You replaced the radiator but sounds like the block needs flushing.

 

In addition to flushing the block, I would check the thermostat again, in a pan of water. The irregular temperatures seem to indicate a bad thermostat.
Another possibility of the fluctuating temps is the temperature sender is bad.

As for the rushing flow of coolant in the heater core, the location of the hoses is important.
The core should fill from the bottom up, not the top down. It will hardly if never fill if it flows from the top down, and will sound like it is gurgling.
Try switching the heater hoses around on either the block or the firewall (but not both) and see if that solves the problem.

Good luck, and post back. I would like to know if this helps!

 

Just a thought there are 4 row radiator and then there are 4 row radiator. I think the problem goes back to capacity in the cooling system. Has this truck always done this? Have you run the truck with out the radiator cap in place to see if the coolant level drops when the thermostat opens? I am thinking it might not be pulling coolant back in from the overflow tank.

I think the factory may have put the wrong radiator in and you have replaced it with a matching one. I know that sounds wacko but 6 quarts would make a big difference when the weather is warmer as you say it cools ok when it is cooler.

By the way what Banjopicker66 said about the heater hoses soundes good. pushing the water down through the core would cause this kind of simptom.
Has the computer shone aney falt codes?
Good luck<O</O

Bill

 

Thanks a million for your responses. I appreciate you guys taking the time to help out!

Computer shows no codes (no small feat $!$). I did in fact cross reference the radiator with the OEM as well as having my local Ford dealership do some research for me. I have the right radiator. I read some posts that talked about drilling 1/8" holes in the thermostat housing, any merit to this?

I am fairly certain my temp sending unit is good. I have no problem telling the motor is running hotter than it should just by opening the hood and feeling the heat roll...plus checking the coolant temp by sticking a candy thermometer into the radiator...it's right on.

When I filled the cooling system after replacing the new radiator, I let the truck idle for about 45 minutes after I filled it with the cap off. I never noticed the big rush of coolant I expected to see when the thermostat opened up. (Then again, it was February and about 35 degrees when I replaced the radiator and I didn't think that much about it at the time.) I did notice the small feeder line that shoots coolant into the radiator just below the cap did flow fine. The truck has NEVER run any coolant into the overflow tank.

My opinion, at this point, is that I have a coolant passage in the block restricted or plugged. I will get a shop with a high pressure flush system to flush the block and see where I wind up. I will also try switching the coolant hoses on the heater core...thanks for the tip on that one...as well as putting in another new thermostat. I am also going to check the timing again just to make sure it's not running too far advanced.

Thanks again for all your input!

 

Ford vacuum fills the system at the factory eliminating air pockets. I install bleeders in certian places to releasse trapped air. The water pump is one of these areas. It wwill only fill half way because of air being trapped.

 

Interesting thought about the heater hoses. But it brings to mind that you would never hear the coolant flowing through the heater core unless it has air in it. I usually feel the theory of air trapped in the system is a little dubious but in this case it seems the symptoms suggest it.

Most of the time, overheating in traffic or at low speeds is an airflow problem so you might test the performance of the 'new' fan clutch. (New means new, not good.)

Another possibility is water pump cavitation, which would explain the heating while towing when you tackle a hill. (Load increases, trans kicks down, engine speeds up, pump cavitates, coolant doesn't flow, engine gets hot.)

You describe two situations when the heating occurs that don't necessarily relate which makes me think you are dealing with two problem.

Six quarts less than spec is a hell of a discrepancy, so I would think that either you didn't have the system drained well or there is still a lot of air still in there.

 

Sometimes water pumps with that kind of mileage can show vanes that are severely corroded or even missing, another thought is by the time you hear knocking it is severe. Knocking can be present without you hearing it and contributes to overheating. Maybe higher octane might help?

 

Two points: One is that yes, a small hole in the t-stat can help purge air out of the system. As you did when you did the install, from cold let it idle for an extended period with the cap off.

(Put coolant in the overflow tank up to the normal level. When it cools down it will draw in air without it.)

Two is, you can expect to hear pinging from an overheated engine.

Probably the last thing you want to hear right now, but you should really be running a 195* thermostat. The engine should operate between 195-210 degrees F.

 

Keep us posted The onley think that I can think of is you might try a electric fan on the front of the radiator to help air flow.
Good luck
Bill

 

UPDATE: I switched the heater hoses at the heater core connection. That was an INSTANT FIX for the rushing water sound. Thanks "banjopicker 66"!!! Fixed that annoying problem, but I don't believe it did a thing for my overheating issue.

I have not had the chance to do much of anything else with the truck yet. I could use some help on just what composes a "cooling system flush"...I have spoke with several different shops and a Ford Dealership...at best I am being pitched a flush which involves more of a chemical wash than a pressurized flush. What exactly is it I need more, the chemical or the high pressure flush? I haven't found a shop yet that has any equipment to flush the block with any kind of pressure system.

Additionally, could not having any coolant in the overflow tank cause/create air in the cooling system? This evening I filled the overflow tank for the first time, drove the truck pretty hard for 10-15 minutes, then let it idle for 30 minutes. The temp rose slightly, but then again the outdoor temp had cooled off to about 80-85 degrees by the time I got back and let it idle.

Thanks again for everyone's help and input!!!

 

"could not having any coolant in the overflow tank cause/create air in the cooling system?" The short anser is yes.
The overflow tank does at least 2 thinges it alowes you to run a "full" radiator because it gives the coolent some place to go besides on the ground and it will pull that or some of it back in the systom when it cools. and yes if the coolent level is to low you can end up with air back in the system. I would fill the tank to the full line and see if it dropes after you drive it and and it cooles off.
Bill

 

Also, air in the system tends to rise to the top of the radiator, so as the coolant expands it pushes the air (gas) into the overflow bottle but then siphons back in coolant when it cools. This is why it is sometimes called a "degas" bottle. Not named after the Spanish painter, but a de-gassing function.

 

The old radiators were designed to have an inch or so of air in the top when cool. At operating temperatures the colant expands, and the air would be forced out. It would be inspired back in when the engine cooled.
Your radiator does not have that capability to handle the expansion, it must use an expansion tank. It is a closed system, instead of one open to the atmosphere. Coolant is expired out into the tank at operating temperatures,and inspired back in when it cools.

 

HOW MUCH COOLANT SHOULD JUST THE RADIATOR HOLD FOR MY TRUCK??? I think my whole problem is I was sold the wrong radiator that is way too small.

What should the total coolant capacity be for my truck? The manual I have says 19.8 quarts, or just shy of 5 gallons. I have pulled the water pump...which has been replaced now along with everything else that touches antifreeze. I flushed the block until you could drink the water out of it. After refilling the cooling system 3 times now, I think I may have identified my problem. After I flush the block and reinstall/reconnect everything, I fill the radiator through the cap. Three times now I have filled it and all three times it has only held 9 quarts (or just over 2 gallons). I know there is no way the remaining 2.5-3 gallons is tied up in the block. I think I may have, after all this, the wrong radiator that is way too small for the 460.

I have yet to be able to talk to the auto parts store that sold me the radiator, but the radiator being the wrong size is all that's left. If anyone could tell me how much coolant just the correct sized radiator should hold, it would be greatly appreciated.