i have a '99 XLT with a 3.0, its been running a little on the cooler side since i bought it roughly 6mo ago. i haven't had any issues other than the vacuum system for the 4WD.

about two months ago i cracked my radiator, but never over heated. I replaced the radiator, thermo, gasket, and was back on the road. but my belts have been a little squeaky ever since.

the other day i was on my way to work and i noticed my temp gauge rising, so i pulled over. but, i got a decent squeal from one of the belts and the temp gauge went right back to where its supposed to be. not only that but i used a 1/4 of a tank cruising around for about 20miles or so, which is horrible fuel milage.
on my way to work this morning and had the same temp rising symptom except this time i turned the heater off instead of pulling over, which dropped the temp right back to where its supposed to be. however i pulled into a gas station to find i was leaking a some coolant from the over flow reservoir, which was plum full.

any ideas on what could be going on.?

 

Welcome to the forum

"leaking a some coolant from the over flow reservoir, which was plum full"

Reads like a blown head gasket or cracked head
This injects "air"(exhaust) into the cooling system, which then exceeds the 15psi Rad Cap pressure and causes coolant to be pushed out of the radiator into the overflow tank filling it up and overflows it

You can do a Block Test, uses a chemical to detect "exhaust" in the coolant
Or the free Glove Test

Do this FIRST to take it off the table

 

Harbor Freight has the most inexpensive block tester on the market. Here is the kit. If there is a HF in your area, grab it there. Otherwise, Amazon.

Make sure you siphon off some of the coolant so that it doesn't get near the block tester. Use a turkey baster, syringe, or suck it out with some tubing.

 

i've done a little more digging and some more tinkering on the 3.0. it seems no matter what, if it gets to "running temp" and i shut the truck off i have coolant bubbling into the reservoir. the longer i had thought about it, i've heard the "bubbling" since i bought the truck.

I also put a bluetooth OBD2 reader on it the other day, it threw codes for
-purge solenoid vacuum hose
-positive crankcase vent
-MAF sensor
-intake manifold gasket
-fuel injector
along with a misfire in cyl 1(if i remember right)

i'll be looking to get a CLD kit/block tester kit as quick as i can to test the pressure in the system.
but before i go down that road, is there a possibility that i have a bad coolant temp sensor or bad radiator cap thats allowing it to pull air? or even just air trapped in my heater core?

 

NEED EXACT CODE numbers
There are no such codes for
-purge solenoid vacuum hose
-positive crankcase vent
-intake manifold gasket
-fuel injector

Code list here: https://www.therangerstation.com/tec...II_codes.shtml

What's a CLD kit?

Do the Glove test, its free, before wasting more time on non-fixes if it is a cylinder leak
Or at least do this
Cold engine
Remove rad cap
Top up coolant if its low
Start engine
You may see a "burp" of coolant out the rad cap opening thats OK
But coolant level should just stay as is after that, NO OVERFLOWING
If it starts to overflow then you have a cylinder leak, i.e. blown head gasket or cracked head

The cooling system, radiator and engine, is a closed system, air can not get in unless coolant can leak out
So if you don't have a coolant leak.........................


Coolant/water mix boiling point is 235degF, engine operating temp is 190degF, that's at about 1/2 on the dash's temp gauge
With radiator cap holding 15psi of pressure that raises the coolant boiling point to 265degF which is why a the cooling system is used, higher boiling point
The pressure in the cooling system comes from HEATING THE COOLANT UP, a liquid expands in volume when heated, thats how a pressure cooker works, so there is no pressure in a cooling system until coolant is heated above 140degF or so, which is why the above test is good to try

The "bubbles" in the overflow tank is not a sign of "boiling" coolant, engine is not hot enough by your reports
Any air that was trapped in the system when refilling will eventually make its way to the top of the radiator and stay there
At the next heat up to operating temp that air would be purged into the overflow tank and "bubble up" to the top of the tank and be gone for good
When engine cools back down, coolant is sucked back in to the radiator to replace the air that was purged out
That's why the overflow tank hose is on the BOTTOM of the overflow tank
Air bubbles OUT, coolant is sucked back in

So its possible to have air bubbles in the overflow tank ONE TIME after a refill, but not after that unless something is wrong

 

Bubbling in your coolant system means you have exhaust gas escaping in your coolant system. That can only mean head gasket rupture. The CLD kit will confirm that for sure.

Looks like you are in the same boat as me. Check my thread. FYI, getting to the lower engine on our trucks is pretty darned easy.

 

so turns out i might be missing some more brain cells than i thought. read the wrong stuff.
codes:
P0171
P0133
P0174
P0304
misfire in cyl 4, my fuel mixture is too lean in bank 1 & 2

 

Cylinder 4 is probably where the cylinder leak is, that's the front drivers side
Pull out #4 and #5 spark plugs and compare the tips

Both should have a light brown coloring on the white insulation
If #4 looks bright white then its being STEAM CLEANED by the coolant leaking in and that's also causing the misfire

"Lean" code does NOT mean the engine is running lean, people often make that mistake
The lean or rich codes mean the computer's calculated fuel mix is off by more than 15% + or -, so with lean code it means computer is adding more fuel that it thinks it should based on RPMs and engine load
This is solely based on O2 sensor feed back

O2 sensors use a chemical to detect oxygen in the exhaust, and they run out of that chemical in 100k miles or 12 years which ever comes first
And as they get low on the chemical they show "lean", a FALSE lean
And you also have P0133 02 Sensor Circuit Slow Response
So I would guess your O2 sensors are passed their EXPIRED DATE, lol

But deal with the Misfire FIRST, as that would cause Lean on drivers side O2

 

pulled spark plugs, all of them looked decent. nice light brown. changed cyl4 spark plug just to see if the check check engine light would kick off, it did. and i will be changing the rest of them, along with a new set of plug wires soon. i haven't had a chance to put the OBD2 on it again just to see if its still possibly throwing a code. i also haven't gotten a chance to get my hands on an O2 sensor yet, but will be soon.

i'm going to drop the oil this weekend too since its about due and see if theres any thing in there that shouldn't be. which hopefully there isn't. haven't gotten a chance to get to the glove test, been a little busy, but i'm going to try and do it tomorrow morning. had to go to work early the other day and had the same thing happen, coolant reservoir filled and ended up in my engine bay but not as much came out this time. let everything cool off drained the reservoir into a jug till it was at the correct level. filled the radiator and tried to burp out any air i could from the upper radiator hose and got some but i don't believe i got all the air out of the system. i'm just going to leave it parked at work until i can get some more parts. also my cooling fan is quite stiff, so i believe its burnt. that will also be getting changed out.

 

Remove a heater hose at the firewall, that will let all the air out of the engine side of the thermostat as you refill