Need help! 97 2.3 4x2 basic model. So coolant was horrible, hubs removed radiator (many a moons ago worked at rad shop so not new to this just this problem) and thermostat. Someone must have run water for an extended time in this. Brown horrible crap, flushed rad while out until clear, took off thermostat and flushed in block and put on new thermostat, flushed directly into heater core until clear, cleaned off the sensors put everything back together -ran fine while cold, temp guage moved and had heat. Next day went to drive it, while cold idle was crap, no heat no guag movement. Once upper hose was warm, and engine warm idle was better but no heat or guag movement. Ran diagnostic (don't have codes at the moment), checked the sensor that is inline just after thermostat before hoses going to heater core- no fluid on it. Like it made it to thermostat and it opened when warmed like it should but no fluid past that. Pulled the hose from heater core sure enough no fluid, ran it until fluid was coming and going hooked it back up. Shut it down started it, guage works, heat, and fine at low idle. Now it's back again, something is stopping fluid from moving beyond thermostat through to heater core (like it keeps getting air in system- all hoses and what not good no cracks or anything). Coincidence or not??? Also when this happens it runs like complete crap!! Until we do the procedure then it runs ok then starts all over again.

 

Welcome to the forum

Does your '97 have a heater by-pass valve, 4 hoses?


Have you checked the overflow systems hose from rad cap to tank.
Radiator caps have 2 Valves inside
When coolant heats up it expands in volume, that's what pressurizes the radiator/engine system.
When pressure reaches Cap Rating, say 14psi, the larger valve in rad cap is pushed open and warm coolant flows out thru the overflow hose to the BOTTOM of the overflow tank.

After engine is shut off the coolant cools down and SHRINKS back to its normal cold volume so pressure in the system goes down until it gets to -1psi, this Pulls open the smaller valve in the Rad Cap, and sucks coolant from the BOTTOM of the overflow tank back into the radiator thru the overflow hose, so the same amount of coolant that went out when hot comes back in when cold, rad stays full to the top.
(Overflow tank must be kept clean, or debris can block hole at the bottom, coolant can come in, but can't be sucked back out)

This is a simple and good setup when working right, since any air in the engine system will tend to collect in the top of the radiator after the engine warms up, then when the Rad Cap opens the air will be purged/pushed out thru the overflow hose and bubble up from the BOTTOM of overflow tank.
When engine cools down COOLANT is sucked back in not the air, so self purging system.

BUT..................
If overflow hose has a crack then air is sucked back in on cool down because air is easier to pull in than coolant.

Or if there is a small leak in radiator/engine cooling system then air will be sucked back in instead of coolant.

Simple test is to top up radiator so you know it is full, then drive vehicle normally for a day.
Next morning open rad cap and see if it is still full to the top, if not then you have a leak, for sure, could be overflow hose or engine system, but there is a leak.

And if any air gets in a heater hose(high point) it will cause an air dam, blocking flow thru the heater core.

Just FYI, the heater hoses on water pump and intake/thermostat housing are needed as a By-pass so coolant can circulate thru the engine when thermostat is closed.
On my '94 the heater core always has coolant flowing thru it, there is no shut off, when my heater core got clogged up a bit the temp gauge would go up above 1/2 then drop just below 1/2(normal), it would do this randomly, had to replace the core, but very easy to do on a '94



Long shot
Head gasket leak
This pumps "air" into the cooling system
Simple free test for this is the Glove test

Cold engine
Remove rad cap, if coolant is at the top drain it down 1/2 to 1 inch
Remove overflow hose from rad, plug this hole, vacuum cap, gum, putty or ??
Unplug coil pack wires, you want a No Start

Put latex glove over rad cap opening and seal it to rad with rubber band, you can also use a balloon or even a condom, lol, instead of the glove

Crank engine and watch the glove
If it pulses up and down you have a head gasket or cracked head issue

If it just lays there no pulsing then you are good to check other issues.

If it pulses you can find the leaking cylinder by removing 1 spark plug at a time and cranking engine, glove will stop pulsing when that cylinders spark plug is removed.
Reinstall spark plug to confirm.

Cooling system pressure is 14-16psi, rad cap pressure rating.
This pressure comes from the engine heating up the coolant and the coolant expands in volume.

Cylinder pressure is 160+psi when starter motor is turning engine, that's the pulsing you see if there is a leak, after starting, cylinder is 900+psi when firing.
Cylinders are surrounded by coolant, that's the point of the cooling system, so any head gasket issue will always show up in cooling system first.
Coolant in the oil can happen but it was more common on pre-1980's engines.

 

We'll top again today and check again. I was reading that if there is problem there that the infor sent via the sensor can affect the air fuel and what not - could this be affecting the running? or maybe a coincidental?

 

Yes, Fuel Injected engines can't use a Choke Plate because there are no Jets, but a cold engine still needs to be "choked"(rich fuel mix, high idle, advanced spark) so computer needs to know the engine temp.
An ECT(engine coolant temp) sensor is used for this, only the computer uses this.
The dash Temp gauge uses a SENDER, not a sensor, fine line but NOT invisible, lol.
Sensors are always 2 wire
Senders are usually 1 wire but new ones can be 2 wire
And they are different in the way they work, so not interchangeable.

So, if your ECT sensor is not reading true coolant temp, because there is air in the system, so showing cooler temp, then computer could be choking the warmed up engine causing it to run Rich.
Or if the ECT sensor is broken and always showing warmed up engine temps then engine wouldn't run well until it did warm up.