88 Ranger Running hot after new sensors

petemaresco · Nov 16, 2012

So last night I put a new MAP sensor, both upper and lower coolant temp sensors and the fuel pressure regulator. Also a new thermostat. I did all this because I'm moving to Austin on Sunday and I'm driving the truck there.

Before all this was done, the gauge needle was always below the center line. Usually on the "A" of "Normal". After doing all this work, it is much higher. usually between the O and the R, but at lowest its just at or slightly above center. It also warms up super fast, within 3 minutes.

Today, it did something ive never seen before. The outlet hose from the heater core and the upper radiator hose, both of which go to the thermostat housing, were sucked of all air and coolant and looked like you took a straw, plugged one end and then sucked the air out of it. They eventually went back to normal, but everything was still super hot. the radiator, hoses, everything. I put a second new thermostat in just to eliminate a bad thermo. It doesnt seem to be doing it now, but with the temp running as high as it is, i can't help but think its related.

I'm leaving in 36 hours and I desperately need to figure this out before I drive 1200 miles.

i took a photo and its seen as a thumbnail below, if that doesnt work, hopefully this thing i did below gives and idea.

-------
N
O________________this is where it is now, after the work.
R___
M________________this is where it was before
A
L
---------

Mark_88 · Nov 17, 2012

Sounds like you need a new rad cap...the system is trying to suck in fluid from the overflow but the cap is not sealing properly...

You can also get hoses with springs inside to stop them from collapsing, but then you wouldn't know that there is a problem...

I'd try starting with a new cap and make sure you burp the air out of the system before capping it...

petemaresco · Nov 17, 2012

Cap and radiator are all brand new. Hoses, Heater core, sensors, all new and in perfect operating order

adsm08 · Nov 17, 2012

That is right where my gauge always ran. It is not running hotter than before, the sensor is just sending a cleaner signal. Normal is normal.

Mark_88 · Nov 17, 2012

petemaresco said:
Cap and radiator are all brand new. Hoses, Heater core, sensors, all new and in perfect operating order

Are the hoses still getting sucked flat? That is a symptom of the rad cap not working or sealing properly...

petemaresco · Nov 17, 2012

i get what you're saying about the sensors sending a proper signal now, but its definitely running hotter than it should. Also for some reason, after I turn the car off, let it sit for a minute, then turn it back on, the needle shoots up to the "O" then back down between the R and the M. I took a Thermal Sensor to it and the temp reads about 190-200 at both the upper and lower sensors, and around 240 at the thermostat.

RonD · Nov 17, 2012

The t-stat should be a 192deg maybe the old one was a 180deg, this could cause the 2.3l to run below it's best temp range.
Switching from a 180 to a 192 t-stat would cause the engine to heat up faster, which is the point of the 192 t-stat, you get better mileage and lubrication when engine temp is above 200deg, so the faster you get there the better.
Oil viscosity is measured at 212deg operating temp.

I don't see the "MAP sensor, both upper and lower coolant temp sensors and the fuel pressure regulator" changes effecting the actual temp, but a loose ground can effect their signal output.
Teflon tape is a no-no on sensors that use their threads as grounds, i.e. 1 wire sensors.

On my '94 ranger I had a loose ground strap between engine and firewall, it caused my oil pressure and temp gauge to run slightly high.

The hottest reading should be at the T-stat and upper rad hose.
Normal operating temps are 200-220deg so it does seem slightly high at 240, did the new T-stat have a "jiggle valve"(hole in the t-stat plate) and did you mount it at the 12:00 position?

Might be worth a try to put back in the "old" gauge sender and see if it gives the "old" reading.

petemaresco · Nov 17, 2012

I don't recall a jiggle valve, tho the thermostat is mounted horizontally in the 3-9 position as opposed to vertically in the 12-6. The Haynes book showed it taut way which is why I did it.

The lower sensor came with tape on the threads right out of the box, and I think the old one had it too, though I can't find it. I would put the old sensor back in, but I can't find it, and its an insane mess and pain that I don't want to get Into unless absolutely necessary. As soon as the sensor comes out, it dumps coolant all over me and drains almost completely. So, if that's avoidable then I like to avoid it....

But, what do u think?

RonD · Nov 17, 2012

Leave sensor in place if old one is not available.
Yes, new sensors often have sealer on the threads, but the lower threads are always left bare

If the t-stat is mounted flat then air would clear when it opened, that's what the "jiggle valve" is for to allow air to escape.

I would load up the truck(extra weight) and take for a long drive, an hour at least, carry extra water just in case, and see if the "new" temp reading is steady, so your new "normal".

Mark_88 · Nov 17, 2012

My temp gauge hasn't worked properly since I put in the new T-stat (fail safe 192*)...or when it over heated...it always shows just above or around the L...but the heater blows good hot air and the hoses are not (too) hot...so I just figured something fried in the last over heat...

petemaresco · Nov 17, 2012

After flushing, quadruple testing everything, checking temps with a thermal laser, getting slightly above normal temps, adding water wetter and tons of other crap with no improvement, I finally drained the system, cleaned up the old lower sensor, switch, whatever it is, and the gauge went back to normal. Right below the center line...all that a work and it was the new sensor...so, I'm more comfortable driving 1200 miles like this than before.

RonD · Nov 17, 2012

Glad to read you found the problem.

"New doesn't mean it works, new means it has never been tested"

Mikel89us · Nov 20, 2012

RonD said:
Switching from a 180 to a 192 t-stat would cause the engine to heat up faster, which is the point of the 192 t-stat, you get better mileage and lubrication when engine temp is above 200deg, so the faster you get there the better.

I dont want to sound like the "know-it-all" but this isnt true, the higher temp thermostat will not heat the engine up faster, it will only run it higher temps. The only difference is the temperature the system lets water flow at. The laws of physics confirm it, iit takes the same amount of energy in two identical systems to heat up to the same temperature.

RonD · Nov 20, 2012

Mikel89us said:
I dont want to sound like the "know-it-all" but this isnt true, the higher temp thermostat will not heat the engine up faster, it will only run it higher temps. The only difference is the temperature the system lets water flow at. The laws of physics confirm it, iit takes the same amount of energy in two identical systems to heat up to the same temperature.

Yes, same energy but not the same time frame for the engine, you are forgetting about the volume of the system being separated, which is one of the points of the t-stat, the other is to maintain high engine temp in very cold weather.

Say a cooling system holds 2 gallons, 1 gallon in engine, 1 gallon in rad.
Engine heats 1 gallon in engine to 192degs in 5 minutes, then t-stat opens and it heats the other gallon to 192deg+ in 3 more minutes but never dropping below 192deg(or t-stat would close again), to get to 200deg steady temp.

With 180deg t-stat the engine gets to 180deg in 3 minutes then starts heating up the other gallon until temp gets to 200deg steady in 5 minutes, so engine gets less mileage and lubrication for a longer time, not much but not nothing.

So while both take 8 minutes to get to 200degs the 192 equipped engine would be at a higher temp earlier.

The faster the engine warms up the better.
And if was extremely cold out the 180 t-stat could allow engine to run at just above 180deg instead of just above 192deg as the 192 t-stat would.

Mikel89us · Nov 21, 2012

It does not make a big enough difference between 180 and 200 degrees to even measure the mileage change. Its so miniscule that its pointless to worry about the few minutes at a 15 degree difference. If you were talking 130 and 210, it would be a little more significant but its still such a small change in mileage that you probably couldnt measure it in a full single digit on one tank.

88 Ranger Running hot after new sensors

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