How hot is a 4.9 supposed to run for our era?
I'm seeing temps of 200-210 and vapor locking after sitting in traffic or driving around parking lots for any length of time.
Temps are just fine when at regular speeds.

I just finished flushing the radiator and replacing coolant. it has the original copper radiator. Trace amounts of rust came out with the flush.
After adding the new coolant I let it reach full temp while I was purging air from the system, and it stayed at 195 until I started driving. As soon as I came up on traffic, it started reaching 200+ again.
There was no oil in the coolant and no coolant in the oil.

I replaced the fan clutch this year because the old one was locked up. It never got this hot with the old one because it acted like a fixed fan. The new clutch never feels too viscous, but I have a van with the same engine and its fan clutch feels the same, so I suspect the new fan clutch is fine.

I don't suspect the water pump because it seems to cool fine if I go over 20 or so.

I replaced the thermostat 3 years ago and it is for 195 degrees.

Is it normal for it to reach these temperatures with a 195 thermostat?

 

This sounds like an airflow problem through the radiator core, as you mentioned all is good when moving.

Does the radiator have a shroud? One will make a big difference.

At idle, test for adequate airflow by placing a rag or sheet of paper in front of the radiator. It should be held tightly in place.

Was there more than one option for the fan clutch? I wonder if the parts store sold you a light duty version.

Do you ever hear the clutch kick in? On my truck (351W) it unmistakable. It sounds like a hovercraft under the hood and will rapidly bring down the coolant temperature. I wonder if your new clutch is defective. Considering all was good with the old one, I'd be willing to gamble your money on a new fan clutch.

Some people knock the design, but I think the fan clutch is an amazing device. Mine works wonderfully. One caveat, though. The rest of the cooling system has to be in good working order. The fan clutch operates by sensing the temperature of airflow leaving the radiator. If not enough heat is transferred to the air (scale inside the radiator acting as an insulator, for one example), the fan clutch never senses it should kick in. So just be aware the poor fan clutch often gets wrongly blamed when the root problem is something else limiting heat transfer.

 

Thx for the advice.

I have a very small stock fan shroud. It seems like it serves little purpose other than to support the coolant recovery hose and provide a "caution fan" warning. Did Ford put a bigger shroud on later models?

There were several options for a fan clutch, but this is just an F-150 so I figured there wasn't much lighter duty than this application.
I've never noticed any noise kicking in when it heats up. The old stuck clutch always howled and it was easy to notice the difference when I changed it.
I had the new clutch sitting in a box for 1.5 years before I installed it, but I'd be surprised if that caused any problems. It more than likely sat in a box in the warehouse for some time before I ordered it.

Last time I vapor locked and was waiting for things to cool down, I spun the fan blades by hand and it didn't feel any more engaged than usual. I know a good fan clutch is supposed to tighten up, but that's a subjective thing to measure by hand.
For comparison, I spun the blades on my van after sitting in a drive-thru, and its fan clutch felt just as loose. I don't have a numerical temp gauge on that vehicle yet, but it has the same fuel setup and carb and it never vapor locks.

 

Don’t get too sidetracked comparing your truck to your van down by the river. Lots of variables, such as maybe your van has a bigger radiator or a full shroud or who knows what.

I still suggest thinking back to the configuration when your truck behaved, with the noisy locked up fan clutch. Since you never hear the present clutch ever kick in, I’d say that’s where your problem lies.

Resist the temptation to replace the fan clutch with a rigid spacer. A properly operating fan clutch is a thing of beauty. I’d be willing to gamble some of your hard-earned money on a heavier duty fan clutch and see what happens.

If you insist the present one can’t be bad because it is new, I shall move into your guest room until you repent of your ways. I will send you a list of my dietary needs. 7:30-9:00 PM is quiet time because I need silence during my accordion practice.

 

Understood and agreed.
As the fan clutch is the only variable to visibly change in correlation with the overheating, it's reasonable to suspect it as the culprit.
I should be able to afford a heavy duty fan clutch and will also invest in some kind of useful fan shroud given the opportunity.

I just wish those clutches were a bit easier to remove... Nobody has a tool for these anymore. My prybars bent the fan last time.

 

210 degrees is not hot and overheating. When you hit 230, start to be concerned. The vapor locking is related to the poor fuel they sell now, so you need to go to extra measures to make sure the fuel lines do not get too hot.

 

Dave, watch out cuz “vapor lock” is more of a broad catch-all term for heat-related fuel problems. “Fix” one aspect but it may not help much if some other aspect is the true problem.

I think true “vapor lock” refers to a mechanical pump sucking hot fuel and it turns to vapor under the partial vacuum between the tank and pump. This is where it really helps to insulate the fuel lines and add a boost pump back by the tank.

But in other cases, the fuel sitting in the carb gets too hot, such as when overheated by the exhaust manifold. Hot fuel bubbles up and gets foamy, and won’t pass properly through the various internal passages. In situations like that, you’ve got to limit heat exposure to the carb, such as with a phenolic spacer, etc.

I went through this on my 351W and tackled both sides of the equation. All is good now. But watch out, because it’s very important to get a handle on the root cause.

 

It doesn't matter, the fuel they sell now is a poor performer in any situation.

The situation you are talking about in the carb is known as "fuel percolation". It works just like a coffee percolator, the fuel boils in the carb, the bubbles of fuel rise and they push the fuel in front of them through the primary fuel system and make the main venturi drip. This happens when the engine is turned off.

 

I see somethings that dont add up from what I have seen posted.
You say your truck has a clutch fan.
Then you say the "shroud" is the little finger guard at just the top.

I thought the clutch fans were used with factory AC trucks?
The finger guard was used on non-AC trucks.
Full shrouds were used on factory AC trucks.
If above is true dose your truck have AC?

Dave ----

 

Dave, my truck's non-AC and manual trans (no trans cooler). I didn't think any trucks had a fixed fan of our era, but I'm not an expert.

As for the vapor lock, I need to figure that out on its own. I have yet to try a return line, carb spacer, or an electric fuel pump, and that will happen later. Regardless of how easily it reaches vapor lock conditions, I want to tackle the overheating first.

 

My 1980 had the super cooling option and it had a 302 with a fixed fan with lots of blades on it. It had just a solid spacer on it.

 

Here in Houston in heavy stop and go traffic, my I6 gets pretty warm (top of the normal arc). The best solution I have found is to turn off the a/c and put it in neutral at the lights (more revs, better air flow, and less load). Also, I put insulation around the fuel line. In 100 degrees, she still gets to loping, but not as bad. Drop the temp 10 degrees, and it isn't an issue. I did find after a good, long day towing about 4200 lbs at highway speeds helped clean her out and she has had much less loping since. Also note I have blocked off the heater core, so cooling isn't as good. one thing you might try is turning on the heat and see if there is a difference.