1992 No heat, gauge stays cold

[bootstrapper]

My 92 2.3L came from a barn, and many of the sensors were corroded to sh*t and have been failing one at a time. I'm trying to get the heat to work now, and I'm confused.

The gauge stays cold. It does move a little, but just barely, after the truck's real hot. The heat blows lukewarm air (blower works, hot/cold gate works).

The one heater hose gets hot, the other one warmish.

I already replaced both temp sensors. I replaced the thermostat today (tested it first), but it didn't solve the problem either.

Could it be a blocked heater core? What else besides the core?

Thanks in advance!

 

[adsm08]

Sounds like your lack of heat is due to a blocked heater core.

Pop the hoses off and run a garden hose through it, switching directions periodically, until it flows free and clear in both directions.

A bad rad cap can also cause warm-up and heater issues, but at the moment I think your immediate problem is a blocked heater core. Even with the fan going full speed there should be very little temp drop across the heater core.

 

[bootstrapper]

Is there a point to try flushing the old one if a new one is $20 at pepboys?

PS the rad cap is new too.

 

[ChiroNeek]

I had a similar issue on my Ranger and flushing was less labor intensive than doing a core replacement. Cost for the core is fairly cheap.... comes down to how much time you have on your hands, I suppose. I had lukewarm heat too... ended up changing out the t-stat and that didn't work... although my heat gauge became more responsive (moves up and down a little more) but that's probably cuz the moving parts on the tstat fatigue over time. Eventually I flushed the core... even used a diluted radiator cleaner product and some compressed air to follow...a lot of crud came out. In the end... TOASTY WARM heat.... almost gets too hot now! Lemme know how it turns out.

 

[RonD]

Yes replace core, and pick up some 3/8" self adhesive weather strip, it is used on the core to seal it in the box, not a big deal but if you want it, it will save you a trip back to the store.
Also get some coolant to refill system

In my '94 you just needed to pull off the cover under the glove box(if it has a cover), then remove 4 screws(all face down) to remove the heater box cover.
Remove hose clamps, I recommend to blow a bit of coolant out of the core, just with short hose and your mouth if possible, or put a towel down in the passenger footwell.
To get the core out you pull it towards the back of the truck then tilt it and it slides down and out, the tilt part spills coolant out.

Took me all of about 20min. the first time.


The 1 wire temp sender on the engine is for the dash board gauge, 2 wire ECT sensor is for the computer.
The 1 wire sender is a resistance type sender, and because it is 1 wire the threads need to be metal to metal to complete the circuit.
So if you use sealing tape leave the lower threads bare, if you used tape then remove it and redo it, that's why gauge reads low.

To test the gauge and wire, turn the key on, remove wire from sender, needle on gauge should go all the way down, now ground that 1 wire, to engine block or use another wire to "-" on battery, needle should go all the way up to maximum.
If this happens then wire and gauge are good.
If needle only goes up 1/2 way then there could be some corrosion on the wire somewhere, increasing resistance so gauge is not accurate, or it could be the gauge itself.

Gauge could do the opposite of above, i.e. all the way up when disconnected and all the way down when grounded, this is fine, but it means you need the specified sender for that year and engine, not a "universal" sender.

 

[kimcrwbr1]

Since your working out the bugs it probably wouldnt hurt to change the water pump now just to eliminate a variable. Alot of guys having issues with the impeller being rusted away and not circulating water properly.

 

[bootstrapper]

Thanks for the awesome info. I bought a new core, and then when I pulled the old one I thought what the heck and flushed it. I got out a whole bunch of nasty mud water out, and then put the same one back in. It looked spotless on the outside. Then I flushed the bejeezus out of the whole system with my hose when everything was disconnected, until it all ran clear.

When I drove it the core got nice and hot for the first time ever. Hooray! But the gauge stayed low. Hmmm.... Thanks RonD for the great suggestion. I don't know how you knew I taped those threads but that's the next thing I'm gonna try.

Last question: about the water pump. If the temp gauge stays low or returns to the normal/middle, can I stop worrying about the water pump? Would there be any other symptoms besides overheating?