1997 Ford Ranger still over-heating

[JayGeePee]

Hey fellas,

I'm sure this has been answered on this forum before but I cant find it on here. My truck just recently started over-heating and I've done some trouble shooting. So far I did my thermostat, radiator cap and fan clutch. I flushed the radiator also. That pretty much leaves my pump or even worse my radiator.

My symptoms go as follows:

When I'm driving the truck down the road it does fine, but when I stop in traffic or at anytime it starts to over-heat. I noticed that when I rev it up to 1500 or more rpms it starts to cool back down. Or if I'm driving slow I can keep my rpms by driving in a lower gear it keeps it cool.

My question is, does this sound like the pump or the radiator to anyone?

 

[RonD]

The rad should take the full flow of the water pump, so with that in mind, you can test the flow by feeling the pressure in the upper and lower rad hoses.

With engine warmed up, t-stat open, raise engine RPM to about 2,500rpm.
The Water pump pushes coolant out of the engine via the upper hose and sucks it back in via the lower hose.
Squeeze upper hose and then squeeze lower hose, if lower hose has much less pressure than upper then some rad tubes are probably blocked.
Lower hose will have slightly less pressure, that is normal, but if its easy to squeeze then rad it not passing coolant freely.

Another test is to warm up engine, and rad, shut off engine, then move fan cowl out of the way and feel the rad tubes, there should be nice even heat across the tubes, any "cool spots" are tubes that are blocked.
Sediment being heavier than coolant tends to block lower tubes more than upper.


Water pump is harder to check, they do wear out, but usually it's the bearing seal and it starts to leak.
I have seen pictures of impeller blades that were eaten away by electrolysis, this of course lowers the flow, but these were from cooling systems running straight tap water or old, old coolant.

You could pull the lower rad hose off the pump and use one of those "snake" cameras to see the impeller, you can rent them for $25, but if rad checks out OK I would just replace the water pump, unless you know it is a newer pump, because it will fail eventually, bearing seal.


I had two odd over heating issues in my '94 4.0l
First one was, I was losing a little coolant with no visible leak, pressure test showed no leak, yet I was getting an air lock every few days.........arrrrgh
It was the overflow hose, had a small crack where it ran over the top of the rad, coolant would leak out on the hot rad so no sign of a leak, but the bad part was when the engine was off and cooling it would suck AIR and coolant back in.
So after a few heat and cool cycles I was getting an air bubble.

On the '94 4.0l the heater core is the by-pass for the water pump, so coolant needs to flow thru the core all the time, there is no heat control valve on the core hoses.
My core got partial blocked, old, so I got random spikes on the temp gauge, wasn't related to load or RPM, temp would just go up and then come back down.
Changed a few parts before I found a thread on this forum IDing this problem.

 

[88_Eddie]

the impellars on the inside of the pump could be worn down so much so that at idle, it's not moving enough coolant through quick enough. at higher RPM's, it's moving it quick enough to cool it down. i'd start with the pump and then go from there if it were me.

try testing it out like ron d said first though