91 5.0 running cold and hot

My 91 5.0 has been running cold this whole winter. So I replaced the
water pump because I knew it was starting to fail. (Water had to
started to leek from the weep hole a couple months early, but then
stopped and never did it again.) The water pump seemed to make no
difference. So two weeks ago I replace the thermostat with a Duralast
192 degree. Again no difference. I installed it with the copper colored
stub facing in the block. I dont think it is the temp sending unit
because my fans dont even turn on until my enigine is nice and hot,
according to the gauge. (fans have a thermostat stabbed in the
radiator.)

Does any one have any ideas? I would like to fix the problem but it is
not as big a deal anymore now that it is starting to warm up here in
Utah.

Evan

Evan opined in oups.com:

> My 91 5.0 has been running cold this whole winter. So I replaced the
> water pump because I knew it was starting to fail. (Water had to
> started to leek from the weep hole a couple months early, but then
> stopped and never did it again.) The water pump seemed to make no
> difference. So two weeks ago I replace the thermostat with a Duralast
> 192 degree. Again no difference. I installed it with the copper colored
> stub facing in the block. I dont think it is the temp sending unit
> because my fans dont even turn on until my enigine is nice and hot,
> according to the gauge. (fans have a thermostat stabbed in the
> radiator.)
>
> Does any one have any ideas? I would like to fix the problem but it is
> not as big a deal anymore now that it is starting to warm up here in
> Utah.
>
> Evan
>
>

Whaddaya mean "cold and hot"? are you referring to the temp gauge?

Or is this coupled with heater performance/output?

And "HOW HOT"? some people get alarmed when the gauge goes from "O" to "M"
or v-v, depending on orientation of label..

--
- Yes, I'm a crusty old geezer curmudgeon.. deal with it! -

Backyard Mechanic opined

>
> Whaddaya mean "cold and hot"? are you referring to the temp gauge?
>
> Or is this coupled with heater performance/output?
>
> And "HOW HOT"? some people get alarmed when the gauge goes from "O" to
> "M" or v-v, depending on orientation of label..
>

And look closely at the 2 other Regulator driven gauges (not alt volt) if
they fluctuate at the same time, look for a ground problem near the cluster.

Also look at the block to firewall ground strap

--
- Yes, I'm a crusty old geezer curmudgeon.. deal with it! -

Yes I am refferring to the temp gauge. I am concerned becuase drving
down the freeway at 80 the temp gauge still says the the engine is not
warmed up. And the needle will actualy start to move back to the cold
side. Then when I come to a stop the needle starts to rise, fans turn
on and the needle slowly creeps to the hot side. All other gauges work
fine.

The 5.0 has been put into a 66 and prior to this winter has not
problems with running cold or hot, in either winter or summer.

Evan

Yes I am refferring to the temp gauge. I am concerned becuase drving
down the freeway at 80 the temp gauge still says the the engine is not
warmed up. And the needle will actualy start to move back to the cold
side. Then when I come to a stop the needle starts to rise, fans turn
on and the needle slowly creeps to the hot side. All other gauges work
fine.

The 5.0 has been put into a 66 and prior to this winter has not
problems with running cold or hot, in either winter or summer.

Evan

Yes I am refferring to the temp gauge. I am concerned becuase drving
down the freeway at 80 the temp gauge still says the the engine is not
warmed up. And the needle will actualy start to move back to the cold
side. Then when I come to a stop the needle starts to rise, fans turn
on and the needle slowly creeps to the hot side. All other gauges work
fine.

The 5.0 has been put into a 66 and prior to this winter has not
problems with running cold or hot, in either winter or summer.

Evan

Evan opined in ups.com:

> Yes I am refferring to the temp gauge. I am concerned becuase drving
> down the freeway at 80 the temp gauge still says the the engine is not
> warmed up. And the needle will actualy start to move back to the cold
> side. Then when I come to a stop the needle starts to rise, fans turn
> on and the needle slowly creeps to the hot side. All other gauges work
> fine.
>
> The 5.0 has been put into a 66 and prior to this winter has not
> problems with running cold or hot, in either winter or summer.
>
> Evan
>
>

Sounds like an air bubble... you have coolant recovery bottle, right?

That's why newer cars have them. the pressure side of the system should have
little to no air in it.

Any change in the heater output?

--
- Yes, I'm a crusty old geezer curmudgeon.. deal with it! -

Sorry about posting 3 times in a row, the computer frooze.

No I dont have a colant coolant recovery bottle.

The heater works about a 1/3 of the time. It blows cold when stopped,
warms up when I am acclerating, and goes cold when the car is traveling
at steady speed, and then randomly back to warm or cold.

It has only gotten hot once, when I was driving the car hard, but it
still went cold too. Other than that is just warm.

Yestermorning I let my car idle 5-10s to defrost the windshield, came
back and the temp gauge reading normal {needle straight down, fans on,
but the heater was blowing cold air. It caused frost on the inside of
my windows.

Evan

Evan opined in ups.com:

> Sorry about posting 3 times in a row, the computer frooze.
>
> No I dont have a colant coolant recovery bottle.
>
> The heater works about a 1/3 of the time. It blows cold when stopped,
> warms up when I am acclerating, and goes cold when the car is traveling
> at steady speed, and then randomly back to warm or cold.
>
> It has only gotten hot once, when I was driving the car hard, but it
> still went cold too. Other than that is just warm.
>
> Yestermorning I let my car idle 5-10s to defrost the windshield, came
> back and the temp gauge reading normal {needle straight down, fans on,
> but the heater was blowing cold air. It caused frost on the inside of
> my windows.
>
> Evan
>
>

That's a bubble, in both your engine and heater.

I have found you have to run the coolant into the heater bottom nipple and
hook the top to the Water pump nipple. If you feed the opposite, the air
gets into the core and just stays there.

Also get a coolant recovery bottle unless you have a separate expansion tank
on your rad which is higher than your thermostat housing.... or even then.

--
- Yes, I'm a crusty old geezer curmudgeon.. deal with it! -

ok I will try that thanks

-Evan