Temp and Heat Issues

[osteologation]

Just purchased a 94 Sport 5 Spd 196k miles. Runs great. noticed that temp wouldnt get up but price was king. So I replaced the T stat (stant) and rad cap(lev r vent stant).

Now at highway speed the temp fluctuates from below N to L. And there isn't a lot of heat. Warm air at best. And while Idling the temp stays pretty much still in the O range, still very little heat though.

I've been reading a lot of threads on here and the best I can see is either air in the system or water pump. But I haven't found the same mix of issues. Its pretty cold here and I would like to get the heat working but the fluctuating temp only at highway speeds is more disconcerting to me. I dont feel its a headgasket as it has been taking coolant from overflow and its not overheating.

I will try to get as much air out of system during the week here and maybe bypass the silly valve (a/c dont work anyway). So if I'm missing the obvious let me know. Thanks.

 

[FarmTruk]

If it's not low on, or loosing, coolant, a T-stat stuck open seems most obvious to me.

 

[osteologation]

If it's not low on, or loosing, coolant, a T-stat stuck open seems most obvious to me.

That was the problem and I replaced Tstat. The engine Temp at lowest is now on the N. Before the Guage barely registered anything no matter how long you ran it.

 

[FarmTruk]

I've gotten bad t-stats brand new right out of the box. As such, I now bench-test any new t-stat before installing. Dropping it in a pan of water, bringing it to boil and back to cool. Checking the temps when it opens/closes with a kitchen thermometer.

Perhaps the heater core is blocked?

Even at "N", the heater should pump out copious amounts of heat.


A radiator/heater core flush may bring back the cabin heat. They are bad to rust/clog up.


Keep "burping" the cooling system. Sometimes it can take a while to get all the air out of these darned things.

 

[osteologation]

I've gotten bad t-stats brand new right out of the box. As such, I now bench-test any new t-stat before installing. Dropping it in a pan of water, bringing it to boil and back to cool. Checking the temps when it opens/closes with a kitchen thermometer.

Perhaps the heater core is blocked?

Even at "N", the heater should pump out copious amounts of heat.


A radiator/heater core flush may bring back the cabin heat. They are bad to rust/clog up.


Keep "burping" the cooling system. Sometimes it can take a while to get all the air out of these darned things.

I've had 4 other 4.0 liter trucks and copius heat is the truth. it was pretty cruddy it could be locked and/or air. if it were just the temp and not the heat I would suspect the tstat or the sender. But since the heat dont work very well. It jsut too dang cold out for me to do alot of this stuff atm. Thanks for the advice.

 

[FarmTruk]

I flushed my X's cooling system this past late fall. It'd been heaven-only knows how long since I'd last done it.


After using a bottle of radiator flush cleaner, it took a LOT of water thru the system before it even began to look moderately clean. I didn't do a specific HC flush, as cabin heat is not an issue.

But based on the # of flush/fill/drain cycles I did, and the fact that it STILL wasn't crystal clear, I'm gonna flush her out again good n' clean when warmer weather returns. It was just too cold to be messing with all that water in cold weather.


Catch-up maintenance is always more work/less fun/more $ than regular maintence.

 

[osteologation]

SO today its about 20 degrees warmer than yesterday outside yay. Anyway I started it up and let it warm up good. The temp still fluctuates at any rpm above idle. I sat in the driveway and held it at 1500 rpm for quite awhile and the fluctuation seemed to be somewhat less. Its got heat but not as hot as it should be. (I just sold a 94 ranger that would make you sweat no matter outside temp.) And every once in awhile I would pop the lev r vent cap and let some pressure off.

Hoses all get very hot like they should heater hoses are both hot before and after the bypass valve. And I did verify function of the valve and the actuator behind the glovebox.

I will note that when I changed that Tstat it was very dirty inside the hose and housing. Although coolant looked very clean. I would think for as hot as the heater hoses are the heat would be much more dramatic inside.

Also this truck sat for a couple months before I bought it, if it makes any difference.

 

[osteologation]

So I swapped out another thermostat making sure to keep the vent at 12 oclock position.

Temp still fluctuates from below N to L on the guage. Has heat but not a ton, slightly warmer sitting and idling after getting up to temp. guage doesnt fluctuate if idling and takes quite a while to build up temp driving or idling. Could it be a water pump, not flowing well?

 

[FarmTruk]

A water pump is a very simple mechanical device. The impeller is connected directly to the pulley via a shaft. If the pulley turns, the impeller circulates the coolant.

In my experience, I've never had one that failed to circulate the water. Only those that leaked around the bearing.

I suppose the bearing could sieze, but then you'd know it, as the belt would fail in short order.

 

[waskly]

head gaskets clogged?

water pump has no veins.

flush the coolant, really really well. dont add stuff like stop leaks etc.

also think you have a heater control valve, on the heater hoses, did you check that for interior heat, it blocks coolant from going into the heater box.

some where on the pass side of the engine. on the lines should be a valve.

 

[osteologation]

head gaskets clogged?

water pump has no veins.

flush the coolant, really really well. dont add stuff like stop leaks etc.

also think you have a heater control valve, on the heater hoses, did you check that for interior heat, it blocks coolant from going into the heater box.

some where on the pass side of the engine. on the lines should be a valve.

It has bright coolant in it and it had been sitting for awhile.
I have read things on here that may suggest water pump.
The valve is functional. Water pumps are cheap and it has skirts miles so I will replace it to be sure. Heater hoses get very hit both sides of valve so I assume valve works.

 

[osteologation]

It has bright coolant in it and it had been sitting for awhile.
I have read things on here that may suggest water pump.
The valve is functional. Water pumps are cheap and it has skirts miles so I will replace it to be sure. Heater hoses get very hit both sides of valve so I assume valve works.

Sorry autocorrect on iPhone lol

 

[FarmTruk]

hahahaha...

You ain't the only one with cooling issues now. My radiator is due for a r&r. Noticed this evening it's leaking at the tank/core seal.

awesomesauce.

 

[waskly]

It has bright coolant in it and it had been sitting for awhile.
I have read things on here that may suggest water pump.
The valve is functional. Water pumps are cheap and it has skirts miles so I will replace it to be sure. Heater hoses get very hit both sides of valve so I assume valve works.

the heater lines theres 2 are they both the same temp? not before or after the hose but the inlet outlet from the heater core.

 

[mr cribb]

I have your solution I'm pretty sure

So I swapped out another thermostat making sure to keep the vent at 12 oclock position.

Temp still fluctuates from below N to L on the guage. Has heat but not a ton, slightly warmer sitting and idling after getting up to temp. guage doesnt fluctuate if idling and takes quite a while to build up temp driving or idling. Could it be a water pump, not flowing well?

I got my 92 w/ about same mileage, same problem... I smelled antifreeze and got the car lot to change the water pump for me.... I too had a fluctuating temp gauge and jack for heat... Here is the solution that was overlooked.... HEATER CORE.... It's $23 four screws behind glove box and two hose clamps and takes 20 min to change.... This fixed my NO heat/ fluctuating temp gauge.

When I say behind glove box I mean it's six inches above passenger floorboard. There's four 8mm screws that you remove to access heater core. I cheated and didn't drain my system cause I just had brand new coolant put in the previous day from car lot changing water pump. The heater core pretty much hangs in place. Pop it down from the firewall and reinstall. Some say to change the heater hoses, but I had just enough cash to get the heater core itself, and my hoses seemed to be in good shape.

I hope this is your permanent fix like it was for me.

Edit: changing the WP didn't fix my fluctuating temp gauge/ no heat problem.... Replacing the HC did.

 

[osteologation]

It was the heater core. i bought a new one and it was cheap (25$ autozone) and easy to change. Old one does not leak but black goo came out when I dumped it out. Hardly any coolant. Temp stays pretty still now even when doing some wheeling. I will flush the whole system when the weather gets better.