I have a 1990 ford bronco that is overheating when driving it down the road, if you stop at a light it will cool down and when you take off it will heat back up. I have changed the thermostat, flushed the radiator, changed the fan clutch with no help. If anyone has some suggestions I would really appreciate any help. There is no steam or smoke from the exhaust and no water in the oil.

 

Then how do you know it's heating up? The OE gauge is notoriously inaccurate, so get a dial thermometer from Wal-Mart or a parts store and see what's REALLY happening. Stab it thru the radiator fins near the upper radiator hose, but where you can see it thru the grille.

 

If it cools down while idling then that means you have sufficient are flow while not moving so it has nothing to do with the fans. You said you changed the thermostat, which is where I would have started. You are not getting enough coolant flow through the system for some reason. After the engine warms up feel the radiator to see if one section feels much cooler than the other. My guess is a plugged radiator. If the radiator is the same temp throughout, then I would have the whole system flushed to see if it is just a build up in the passages. I would look towards anything that restricts coolant flow. Good luck with it.

 

I agree. This is a copy and paste of what I wrote to TD on his AC thread.

As far as overheating, are you overheating because of your coolant leaks, and the coolant coming out and the truck overheating? If so, find your leaks. If not because of leakage, possible causes are (in order of likelihood) clogged radiator, bad t-stat, bad fan clutch (overheating at idle only), loose belt, bad head gasket, cracked or warped head.

 

Your radiator cap could also be bad and causing the coolant to reach boiling point.

 

Yes. Add "bad radiator cap" to my list! Are your hoses pressurizing when the truck gets hot? Squeeze your radiator hoses when the truck is at operating temperature. They should be pressurized.

 

ok i bought a new cap,last night and i flushed the system and i am now running a corosion remover in it , the raditor is ok not stoped or restricted, yes the hoses are very tight when the truck reaches temp, NEW CLUTCH FAN,NEW CAP, NEW THERMSTADT,FLUSHED SYSTEM, NO LEAKS NO WATER IN OIL I DROVE IT TO WORK TODAY AND IT DONE THE SAME THING i have no clue it is going to take a real smart ford man to figure this out i dont want to sell it i like this ford but i just dont know what to do.....thanks everyone for responding any other ideals anyone

 

How do you KNOW for sure that the radiator is not clogged? Just because you flushed it does not mean that it is not clogged.

 

Here is what I done...I opened the drain **** on the bottom of the radiator and put a hose in the fill tube and the water flowed freely...please tell me other ways of checking it.

 

You basically just drained and filled the radiator. That's ok if you know that the radiator is clean and you just want to drain it and refill it with fresh coolant. But that is not enough to unclog a blocked radiator. Even if it was partially blocked, enough to overheat the engine, some water would still get through and drain out from the drain plug hole. My best advice at this point is to take your truck to a shop and have them do a professional power flush of the system. Look for a coupon, you might be able to get it done for about $39 or so, but I've seen it up to about $79. They will also be able to tell you if your radiator is blocked.

If you are on a budget, you can buy one of those flush kits that you cut into one of your heater hoses and that will do a decent flush. Put the radiator cleaner in and run it as directed, then do your flush. Somewhere on here there is a thread about which heater hose to put the flush valve on. I always thought that it didn't matter, but I think someone said NOT to put it on the hose that connects to the water pump. Also, be sure that the temp control on your dash is set to "hot" when you do any flushing, so that the heater control valve is is open. One more thing: remember that when you are flushing the radiator with cold water, it can cool the truck enough to make the thermostat shut. This can get annoying when you are trying to flush.

An old trick to flush the radiator cheap is to take off the radiator cap, warm the engine to operating temp, take off the top radiator hose at the radiator, put your garden hose in the filler neck of the radiator, and flush away. When clean watwer runs out of the hose, it should be flushed. It makes a mess though, you'll have a green stream running down your street, and remember that coolant is poisonous and for some reason dogs are attracted to it and like to drink it.

The easiest way to tell if a radiator is blocked is to have a radiator shop stick a rod down one of the holes, through the filler neck, but on my Bronco the cap is set off to the side in such a way where this can't be done. Yours is probably the same way.

 

i am running a raditor flush in it now it says to run it for 6 hours then drain also there is a product called extreme cool it cost 15.00 per gallon its suppose to make yor engine run cooler is it a waste of money

 

will a cracked exhaust manifold cause this problem because the driver side is cracked

 

One other thing i have had happen is the lower hose can collapse when it gets old and will only collapse when the engine is revving thus it cools down at a stop.

 

how could i check this or shoul i just replace it

 

If it feels extremely soft when you squeeze it (unpressurized system of course), then it should be replaced. But I believe that most lower hoses have springs in them to keep them from collapsing as they get old.

I'd get your radiator power flushed or rodded out at a radiator shop.