1993 problems

Hey guys my 93 blew the head gasket... didn't have time to fix it so I had the shop change the headgasket and re machine the heads and do a valve job, before it blew I changed out the thermostat, radiator and radiator cap, now I have the truck back and my coolant gauge goes from the middle of normal to in between normal and hot, the engine doesn't feel hot the top of the engine is cool enough to touch! I wanted to hear some opinions! My thoughts are fan clutch but I think that's okay because it doesn't rise at idle it just fluctuates while driving.... is this the temp sender messing up!? It has never done this before


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I would check the sending unit first and head temp with a temp gun. Also could be air pockets too.

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Temp gauge should run just below 1/2 after full warm up and will go above 1/2 when climbing up a long hill, or pulling a heavier trailer.

If temp gauge is steadily running above 1/2 after warm up then yes, first thing to do is to change the temp SENDER near the thermostat housing, it could have been damaged by overheating.

There are TWO temp devices located above the thermostat housing on lower intake.
ETC sensor, used only by the computer
Temperature Sender, used only by the dash board gauge

Sender is usually 1 wire
Sensor is always 2 wire

If temp gauge is going above 1/2 and then dropping back to 1/2 randomly then you have a partially blocked heater core.
The heater core in these years is the coolant by-pass for the water pump, coolant is always flowing thru the core.
If core gets blocked then temp gauge will go up and down, randomly.


Fan clutch
The fan is used to maintain air flow thru the radiator when stopped or driving slowly.
When you are above 30MPH then air flow thru rad is enough to cool it down.
Symptom of failing fan clutch is when temp gauge starts to go up when you stop, then goes back down when you are moving again.
Same symptom can also be failing water pump, circulating less coolant at lower RPMs

RonD said:

Temp gauge should run just below 1/2 after full warm up and will go above 1/2 when climbing up a long hill, or pulling a heavier trailer.

If temp gauge is steadily running above 1/2 after warm up then yes, first thing to do is to change the temp SENDER near the thermostat housing, it could have been damaged by overheating.

There are TWO temp devices located above the thermostat housing on lower intake.
ETC sensor, used only by the computer
Temperature Sender, used only by the dash board gauge

Sender is usually 1 wire
Sensor is always 2 wire

If temp gauge is going above 1/2 and then dropping back to 1/2 randomly then you have a partially blocked heater core.
The heater core in these years is the coolant by-pass for the water pump, coolant is always flowing thru the core.
If core gets blocked then temp gauge will go up and down, randomly.


Fan clutch
The fan is used to maintain air flow thru the radiator when stopped or driving slowly.
When you are above 30MPH then air flow thru rad is enough to cool it down.
Symptom of failing fan clutch is when temp gauge starts to go up when you stop, then goes back down when you are moving again.
Same symptom can also be failing water pump, circulating less coolant at lower RPMs

Click to expand...

The temp doesn't move when it is at idle!! It more or less temp randomly goes from middle of Normal to in between the normal and hot then drops back down over and over! Fan clutch had good tension, I let it cycle with the radiator cap off and the heater on and got some bubbles and then the radiator would start overflowing, seems like a heater core blockage!?


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No, that reads like cracked head or head gasket issue.

May have not got a good seal in one of the cylinders.

Just to take head gasket or cracked head off the table do the Glove Test, its free

Cold engine
Rad cap off and coolant down about 1" or more from the top
Overflow hose off rad and that port plugged with vacuum cap or gum, or putty or..........

Unplug Coil Packs 4 wire connector, you want a No Start
Put Latex glove over rad cap opening and seal it with rubber band, or use a balloon or even a condom will work.

Cooling system has no internal pressure when cold, heating up of the coolant is what creates the pressure and that only happens after engine has been running for 10 minutes or so

Cooling system is now sealed with the Glove
Crank engine with starter motor and watch the Glove

If Glove starts to bounce then you do have a head gasket or cracked head issue
Compression pressure(160psi) from a cylinder is being forced into cooling system

If Glove just lays there then all is well for head gasket and heads

If Glove does bounce pull out 1 spark plug at a time and crank engine
When glove stops bouncing last spark plug removed was from the leaking cylinder, put spark plug back in to confirm.

Hopefully all is well with Glove test, but bubbles in the rad and overflowing while cold is a sign that a cylinder is pumping "air" into the cooling system, displacing the coolant in the heads(overflowing at rad)

This also causes random over heating issues, in the beginning, as the "air" pumped into in the cooling system circulates which blocks and releases flowing coolant randomly.
It gets worse over time as the leak gets bigger

Got her all good now! Checked everything and hat it came down to was air bubbles still trapped I burped the system some more and now the gauge stays in normal now!


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Good work

Hope it lasts, beginning of head gasket/cracked head issue starts off just like that, air trapped in system

You can easily get a FALSE gauge reading of High temperature if the ground path is iffy...


First place I'd check is BOTH ENDS of the grounding strap that runs between the rear of the Driver's side cylinder head and one of the mounting bolts for the Wiper motor...