My 93 f150 5.0 is running hot...temp guage never used to go over N, now it is at A when driving. I was checking the engine while it was idling and the top radiator hose is hotter than heck...the bottom one is virtually lukewarm???? Does this sound like the radiator is plugged? or is this normal? Tranny fluid is steaming hot too... top hose is real hard as in under pressure while the bottom one isn't. the passengers side of the radiator is very very hot and the drivers side is not real hot.

 

In a crossflow radiator which I believe that one is the tank that the upper hose connects to will be hotter than the opposite side tank since cooling is taking place between the tanks. Upper hose is transferring heated coolant from the engine to the radiator. Same is true with the lower hose being cooler than the upper one since cooling has taken place between the upper and lower hose with the lower one returning cooled coolant to the engine through the water pump. Now if the overall temperature of the cooling system is warmer than what is considered normal based on the readings you are getting on your gauge there can be a number of reasons for this some being normal, higher ambient temps and higher humidity. Otherwise, I would start looking for possible causes of the higher temps, fan clutch not working or not working properly, dirty radiator and/or AC condensor causing poor airflow, mineral buildup on the cooling tubes in the radiator causing poor heat transfer, possible bad head gasket leaking combustion gas into the coolant, etc. When was the radiator last flushed and cleaned? Is the cooling system losing coolant on a regular basis in that you are having to top off the overflow container and/or radiator more often? Your transmission cooler is located in the return tank of the radiator which is where tranny fluid transmits its heat to the engine coolant through the plate cooler. Hotter coolant means less cooling of the tranny fluid. Anything change in the cooling system lately like a new thermostat, hoses, etc.? What is the condition of the engine? Mileage? Has the timing been checked lately?

John

 

new fan clutch didn't help. Timing is right on. Tstat is working I think and was replaced last fall. The radiator was really hot by the upper hose compared to the other side. Whole system was flushed about 1.5 years ago. The Rad is probably the original, and I'm not losing any coolant. I'm thinking I have a restriction in the rad. When I flushed it I changed to the prestone orange 5 year stuff, don't know if that was a good idea. Truck has 120K on it, but has been running well (and still runs good now...just real hot and the tranny fluid boiled over and is stinkin hot).

If I pull off the uppper and lower hose, should I be able to blow through the rad easy? or does it not work that way?

 

Is the water pump pumping?

 

Are you sure the thermostat is installed in the right direction? Make sure there is a spring in the lower hose to keep it from collapsing when the water pump is pulloing in coolant. You might want to change that thermostat again if you don't find anything. Wouldn't be the first time to get a faulty one.

John

 

I would say the water pump is pumping because the heater core is hot...these pumps seem to have very little to go wrong other than the bearings.

The tstat is in right because it worked fine for over a year, and I don't think its bad because the top hose and that side of the radiator is REALLY hot, so it is getting through...plus the engine would overheat instead of run real hot and the tranny wouldn't overheat probably. The bottom hose has a spring in it to keep from collapsing.

 

dbuck50,

Even if water or air moves through the radiator that won't tell if you have a blockage or not since you have multiple rows of tubes that are tied together by the end tanks, not one continuous run. Used to be on the all metal radiators you could take the radiator out, lay it flat, plug either the outlet or inlet and fill with muriatic acid and let it set for a few minutes and then flush clean with water. With the new ones using plastic tanks can't do this without removing the tanks. How does the inside rows look? Are they covered with carbonate or do they look clean? If you have the plastic tanks you can remove them and then just soak the core but reinstalling the tanks can be a pain to get them not to leak.

No question that a partially plugged radiator can cause the problems you are describing. With the efficiency of the radiator reduced, the overall coolant temperature gtoes up and the ability to cool the tranny fluid effectively goes down. Everything runs hotter.

John

 

Great info...thanks. Just wondering though, if the tstat failed, would I be having similar symptoms? or would it just overheat and not make the radiator super hot on one side but lukewarm on the other? And would that explain the tranny overheating? thanks again!!

 

Your point earlier about the thermostat working got me thinking that there is the remote possibility that the thermostat is not opening completely which would reduce flow but not enough to cause radiator overheating but definitely could cause the water around the tranny plate cooler to be hot enough to cause insufficient tranny cooling. Again, the side of the hose from the engine should be hotter than the side of the return hose to the water pump because of the radiator cooling. Before doing anything to the radiator except maybe flushing it again I would get another thermostat and see what that does. Seems to me the thermostat replacement is minimal cost and labor on your part as opposed to pulling and cleaning and/or replacing the radiator.

John

 

Good idea, I will try that and test the tstat in some hot water with thermometer to verify what is going on. Thanks and I will post back my results after I do it on Sunday.

 

try running your truck w/out the tstat for a day or 2 just to see what happens..cant hurt and then you'll know........

 

You could try that idea (taking thermostat out)

Have a similar problem with my 82 E100 overheating. Put bars leak in (have a couple of small holes) and it still overheated. Checked the Thermostat and turns out it did not have one. Whomever had it before me took it out. So will have to take the radiator off and flush/clean/repair it until I get a new one. But mine is original metal and you can do this.

 

tried replacing the tstat and it still runs hot. I am convinced the radiator is plugged. will flush the system tomorrow and replace.

 

I dont know about newer radiators but the older ones, like mine, could have the top and bottom taken off so the core could be "rodded" out. Basically, gently scraping the scale buildup with a long thin rod/brush and solder any holes. The replaced top/bottom was resoldered back and then flushed and put back on. My husband had to do this with my 79 Cordoba, a few years ago, after it started to overheat from being plugged up. Something he learned from his father who used to work on radiators when not being mechanic for 65 years. When money is short, a good technique to know.

Cant do this with aluminum ones, for example. But even with brass/steel ones either people dont know or dont care. Like alot of things, the plugged ones are just thrown away and new ones installed. A waste.

 

Check the space between your radiator and A/C condenser. Sometimes it can get filled up with leaves and other junk and restrict the air flow across the radiator.