1995 Explorer overheats

[Dean1947]

I have a 1995 Explorer that overheats when driving at hiway speeds. Doesn't overheat at idle or in city driving. Changed the thermostat, but still doing it.

 

[pbnj22]

are you low on coolant? see any leaks?

 

[koda2000]

when's the last time the cooling system was flushed? how old is the radiator? what % antifreeze mix are you using?

 

[radman]

How do you know it is over heating, are you only going by the dash gauge or do you have a temperature gun? Water temperature sensors can fail and give erroneous readings on the dash gauge.

Is it boiling over or pushing large amounts of coolant into the recovery tank?

Have you tested your radiator cap? It should hold 13psi pressure to prevent boiling.

The fact that it is good at idle proves the fan, fan clutch, fan shroud are doing their job and rules out an externally clogged radiator core, as plenty of air flow is coming through the core when stopped.

The only other issue would be a worn out or slipping water pump impeller and or a slipping drive belt.
Mike

 

[Dean1947]

Not losing any fluid and system is full of 50/50. Going by the temp gauge and engine performance, but will have it checked with a temp gun.

 

[Dean1947]

I wonder if a radiator hose might be collapsing when the engine is under load.

 

[koda2000]

I wonder if a radiator hose might be collapsing when the engine is under load.

I had this thought as well. are they soft? how old are they? these are fairly inexpensive parts and are easy enough to change. might be worth changing if they're more than 5 yrs old.

 

[my98nnj]

System hot, ~13psi of pressure, no hose is going to collapse.
A hose collapse usually happens when a radiator cap goes bad and cannot over come vacuum (cold engine) and pull coolant back from the reservoir.

Thermostats, if installed correctly are designed to run cold, open early when they fail.
The thermal spring gets weak over time allowing it to open early with the flow of coolant.

Do check the radiator cap, make sure it's allowing the system to push and pull from the reservoir. Are you seeing excess air escaping from the system? Little bubbling in the reservoir? Is so, you may have a slight leak in a head gasket and under load you're getting exhaust gases pushed into the cooling system.

 

[koda2000]

System hot, ~13psi of pressure, no hose is going to collapse.
A hose collapse usually happens when a radiator cap goes bad and cannot over come vacuum (cold engine) and pull coolant back from the reservoir.

Thermostats, if installed correctly are designed to run cold, open early when they fail.
The thermal spring gets weak over time allowing it to open early with the flow of coolant.

Do check the radiator cap, make sure it's allowing the system to push and pull from the reservoir. Are you seeing excess air escaping from the system? Little bubbling in the reservoir? Is so, you may have a slight leak in a head gasket and under load you're getting exhaust gases pushed into the cooling system.

1. a soft lower hose can collapse under higher rpm and restrict coolant flow. you don't have 13 psi in the lower hose (the w/p suction side) at higher rpm. some radiator hoses have a metal spring inside them to prevent collapse.
2. a fail-safe thermostat is designed to fail in the open position. a regular thermostat can most certainly fail in the closed position. and I've even seen fail-safe thermostats fail in the closed position.

an automotive thermostat is a thermal-mechanical device. as such it has moving parts, which will wear over time and will eventually fail (either in the open or closed position). they work by having a sealed vessel containing wax and copper filings, the wax melts at a specified temperature and expands, opening the thermostat. as the coolant cools, the wax re-solidifies and contracts, allowing a spring to close the thermostat again.

OP - check to make sure your overflow hose is not plugged (by blowing in it) and make sure it has a tight fit on the radiator side. this hose has been known to become clogged and not allow coolant flow and can cause overheating. if you remove your radiator cap first-thing in the morning, the radiator should appear 100% full. if not and there's still coolant in the overflow tank, something's wrong.

 

[Dean1947]

Thanks everyone for your input. I feel kinda silly. We installed an after-market temp gauge and problem is solved.