I have a 2000 Ford Ranger. Today it did something weird. The temp gauge started going up getting alarmingly close to that red H. I pulled off the road , popped the hood and then cranked the engine. It is not leaking anti freeze. I wait about 10 mins then drove the rest of the way home about a mile and a half. By the time I got home the temp gauge had started going up again. I checked for leaking anti freeze, what else should I check?

 

Wait until engine is cold and remove the radiator cap
See if coolant is at the very top, it should be.

Then check overflow tank on fender, should be about 1/2 full.

If radiator is a little low add some water to it, coolant if you have some but a little water is fine.
Leave radiator cap off
While engine is cold try to spin fan blades, should be hard to spin.
Start engine
If coolant starts to overflow out of radiator you may have a bad head gasket, bummer

If coolant stays in radiator after 30 seconds shut off engine
Spin fan blade again, it should spin easily
If it spun like this before starting engine then fan clutch is bad.

 

That all sounds like really complicated stuff to fix. I was hoping for an easier answer. But there may not be one.
Thanks for the information.

 

It's really not all that complicated. Something else to check for; look for debris (like leaves or bags) stuck to the radiator itself; or anything that shouldn't be there and is impeding airflow.

Also note the color of your coolant. It should be green, like a traffic light. If it's a mucky brown or any other color, flush it out and put new coolant in.

Although unlikely, there's one other part that comes to mind that could make the engine overheat. The thermostat.

When the engine is cold, the thermostat is closed, and not very much coolant is circulating in the block at this point. This allows the engine to come up to operating temperature. Once at operating temperature, the thermostat opens up and allows full flow of the coolant, going through the radiator (and cooling down) then back to the engine to take more heat away.

When a thermostat goes bad, it can either fail in the open or closed position. If it's in the open position, then the engine would therefor take a very very long time to warm up. If it is stuck in the closed position, then the block has no way to cool off other than by air around it; which is not effective at all.

If RonD's tests come back O.K., bring the truck up to operating temperature. Once it's there, park and raise the hood. Caution, you can burn yourself doing this next test, so be careful. The upper radiator hose is coming out of the top of the engine (about 1.5 inches in diameter) and goes over the alternator and then to the radiator itself. Touch this hose and see how hot it is. If it's not very warm (IE, cold) then the thermostat is your problem. If it's hot (IE, can't hold it for very long) then the thermostat is OK.


In short, overheating problems are generally simple stuff. It's a simple system with simple components that anyone can work on. Best of luck to you.

 

Those were tests to see why there was overheating, no fix until you find out why it was over heating.

If you are low on coolant then thats why it was over heating, but why was it low on coolant?
You say it wasn't leaking when you looked after it over heated, but that could be because it was low on coolant so no more to leak out by that time.

So it was leaking out and that's why it was over heating.

So first thing on the list......................cold engine remove rad cap, coolant low? then there is a leak

 

Ok stuff I have done. Checked the radiator, it's full. As is the over flow tank at the correct level. There is no contaminate in the anti freeze, it's green. Nor is there antifreeze in the oil. I will have time this evening to check the fan clutch. And the radiator test that Ron suggested. And will check the radiator hose, too. Stuff stuck in the radiator, hadn't thought of that will look. Thanks for all your helpful advice.

 

There is one other thing that can cause heating up, the heater hoses are used for circulation thru the engine.
To prevent this heat from going into the cab there is a by pass valve, it will have 4 hoses connected.
two hoses to the engine and two hoses to the firewall/heater core in the cab.

When you select "heat" this valve opens and hot coolant flows thru the heater core.
When you select "cold" then valve closes and sends hot coolant back to engine.
If this valve or actuator F's up then coolant can't circulate thru the engine like it should, so it will start to overheat.

Try turning heat up all the way if engine starts to overheat, and make sure heater is blowing hot air at that time, heaters can get "air blocks", air gets in hoses and blocks coolant flow.

Engine temp should go down with heat on, that is normal, but if it still starts to overheat then by-pass is probably not the issue.

Failing Fan clutch only effects slower speed driving and when you are stopped.
The fan is used to pull air thru the radiator cooling the coolant flowing thru it.
When you are driving at over 30mph then air flow thru rad is good, fan really isn't needed.
But when driving slowly or stopped fan needs to be working well to pull enough air thru rad for cooling.

So engine temp OK at highway speed and only climbing up when stopped or driving slow, is usually bad fan clutch.

 

Well with the headgasket not being the issue, that should be a relief. That type of job is very labor intensive and very expensive if you pay someone to do it. Gaskets are cheap, taking engines apart isn't.
While it can be done at home, this involves taking the head off the block as well as just about everything else in the process so the head will actually come off and allow you to gain access to other fasteners/parts in the way.

But I digress. Now that it's known the head gasket is good, we know it isn't something on that expensive scale. So, breathe a sigh of relief. I would, lol.

 

Thanks for all the advice guys. I did all the test which were suggested and discovered that the problem was the radiator cap. Had no idea that it could be the source of the leak. So thanks again. I learned a lot doing this.

 

Oh yes, the radiator cap can certainly be a problem. That's the very reason why mine had to be swapped out. I don't remember if I already mentioned it, but if this type of thing interests you, check out a channel called 'ericthecarguy' over on youtube. Very informative videos and entertaining, too. It's amazing what you can retain just by watching someone.