Help! 2.5 stays cold and no heat!

[TremblantRanger]

I've gone through a lot of threads and still can't find a clear solution... Problem started yesterday; left school, engine started to warm up, then stop at a gas station. When I started it and left, the temp gauge was a bit under normal, but as I drove, all of a sudden the gauge dropped dead and the heater started to blow cold. When I got home, I checked the rad hoses and the upper one was barely warm, and with my scantool hooked up, the engine read under 100 degrees at idle, went up barely past 100 when I gave it gas. Changed the thermostat today (bought a 192 degrees) and the old one completely fell appart as soon as I took off the housing. Not a drop of coolant came out as I opened the radiator's petcock, put plenty came out as I unbolted the thermostat housing, and the overflow thank was halfway full. With the new t-stat, same problem although the scantool now registers in the 120-ish degrees range, upper hose is now warm (could keep my hand there all day) but the temps gauge is still dead unless I shut off the truck and restart like 5 minutes later. In that case, the needle is barely up to the C, but as the engine runs or if I start the heater, I get a puff of warm air, then the needle drops off to its resting place and the air gets cold. Engine acts as if in cold mode; RPM drop slowly when I let off the gas, and after a 20 minute drive, I shut it down for a minute, and wouldn't start after. I eventually got it started by holding the gas to the floor, just like a flooded engine... Otherwise the truck still pulls strong, although fuel economy is down since this all started... I'm going to test the fan tomorrow, but exactly how freely is it supposed to move if the clutch isn't locked??? Please help a freezing bodywork student out hahaha!!!! Thanks for your advice!!!

 

[RonD]

Couple of things to check

First, with engine cold, remove 1 heater hose from firewall connection.
Coolant should flow out, if not top up coolant, you have an "air lock" in heater hoses, reattach hose after.
When refilling radiator you should always unhook 1 heater hose, when coolant start to come out of it, reattach it.

Cold start engine and feel upper rad hose at radiator end, will be cold of course.
Let engine idle for 3 to 4 minutes and feel upper hose again, should still be stone cold as before, that means new thermostat is seated and working.
If upper hose is heating up with the engine then thermostat is not seated or open, so bad.

The radiator is for extra heat generated by the engine, in very cold weather it may never get even warm to the touch, that is good and normal.
heater hoses should get hot to the touch, 190degF hot, thats the thermostat working as it should.

After you test upper hose warmth, shut of engine and spin the fan, since rad is cold and engine has been running more than 1 minute the fan should easily spin.
i.e. if you spin the fin blade it will spin a bit farther after you let go, not full circle but won't stop when you let go.

Fan clutch works off radiator heat, on the front of the fan clutch is a bi-metal spring, as the center of the radiator heats that spring up, it slow engages the fan to spin at water pump RPMs, so grabs more air for cooling.
When fan clutch is warmed up you can't spin the fan blade, you can move it but it won't spin.

Engaged fan clutch also make more fan noise
When you cold start most engine you will hear fan noise for 5-10 seconds or so until clutch release fan and the noise goes away.
That noise going away means fan clutch is good.


Engine running Rich will run cooler, 1998 doesn't have fuel Pressure regulator but does have Pulse Damper on the end of the fuel rail, it will have a vacuum hose attached to it, check that hose for fuel, or fuel smell, if damper is leaking then enginbe will run Rich and MPG will drop.

But MPG will also drop if engine is running cold in general.

 

[Doofy]

Up North, we use a winter cover that blocks most of the grill. This limits the cold air thru the radiator and increases the engine temp and heater output temp. I have also frozen portions of the radiator but the engine was warm enough not to freeze (heater put out cold air too). Normally, the engine would overheat due to no flow but it was to cold to overheat. -55F

Make sure your anti-freeze is mixed properly and get the air out of the system. Make sure the heater core is not plugged (as per RonD). Also, make sure the heater control valve is operating properly. Good Luck! No fun being cold!

 

[TremblantRanger]

@Doofy: Thing is yesterday and today was pretty warm compared to the last couple of weeks; around 0 to 3 degrees celsius, but this engine still ran stone cold :S

@RonD: Thanks a lot! I didn't disconnect a heater hose to bleed the air while filling, before starting. Will try that! Thing is, I once worked at a Toyota dealership, and after a cooling system flush, we only had to fill it up, run it at around 2000-2500 RPM and burp it until the fans kicked in, so that's how I proceeded on my Ranger... Didn't know they were so prone to air pockets! I also watched a few of eric the car guy videos, and will also check the heater core inlet and outlet hoses for temperature. I'll keep you guys posted, and thanks again!

 

[RonD]

Yes, the Toyotas I have worked on had heater hoses lower on firewall so not a high spot to trap air like on other vehicles, Rangers for one.

 

[TremblantRanger]

Update: I checked the fan, and it's good. I took a few minutes this morning to check the truck as it warmed up, and the upper rad hose stayed cool for a good while, and after maybe 10 minutes, got pretty hot, and still was after my 50 minutes drive to school, so the new t-stat seem to do its job. I filled the overflow yesterday and it's now halfway full, so it looks like the engine itself is bled. On the other hand, the heater core inlet hose was hot, but the outlet is stone cold, so the core is either blocked or has air. The temp gauge still won't move. My therory is, on the thermostat housing, there is a t-stat bypass, where the temp sensor and sender are mounted, which then go to the core inlet hose. If the core is blocked, the coolant stays still and never gets hot, just warm, which may explain the low temp readings from my scantool and why the needle doen't move; the low readings come only from convection instead of hot coolant passing by. And I guess this is why the ECU keeps the engine in warm-up mode, giving poor mileage and ample backfires... @RonD: Should I try bleeding with heater hose disconected first, or should I go straight to a backflush of the core?

 

[RonD]

I would back flush the core, that will also tell you if it is clogged up.
When you remove hoses raise them up so you don't loose too much coolant.


Can't do it now, but for future use, a heater core has no direction, so IN and OUT hoses can go on either way.
I swap the hoses every 2 to 3 years when I change the coolant, kinds like an on going back flush


If core is clogged you probably need to replace it, but you can try CLR in hot water, pour it into the core and let it sit for 20min. then flush it out, repeat as much as you want.

 

[TremblantRanger]

Finally fixed! Did a backflush, and some dark gunk came out... Rinsed till the water was clear the did it the other way around. I was a bit worried because the temp gauge kept going up and down, but went for a drive and gave it the beans a couple of times and it finally stabilized and I started to have some REAL heat! Thanks alot for the help, you have all my gratitude!!!

 

[RonD]

Good work

Heat for the Holidays.......gotta like that

 

[Doofy]

Yes, Great Job! Troubleshooting often takes lots of time and is usually frustrating. Glad you made the effort and didn't give up.