Right off the bat I have to apologize for any forum taboos I might make. (I'm brand new to this site)

I drive a 1984 7.5 liter f250 (460)

Okay, so the problem: two weeks ago I was halfway to work when I smelled the sweet smell of coolant drifting into my cab. Within minutes I had coolant pouring all over my passenger floor boards. Busted heater core. I replaced the heater core that evening and the leaking stopped. Yay.

BUT... Now, my radiator is full of coolant but the overfill coolant chamber keeps draining unexplainably... There is no visible leaking and puddling. Also, every now and then I'll can smell the coolant but as I said, no leaking. I'm also confused as to why my NEW...ish thermostat is now saying that my engine temp is VERY cold despite the fact that I can see, smell, and feel that it's running hot. The thermostat was working perfectly before I replaced the heater core.

Did I do something wrong during my installation of the heater core or is this an unrelated cooling system issue?

Sorry if this was confusing. I'm a novice.

 

howdy and welcome to FTE

for the coolant overflow reservoir, it is normal for it to rest around the halfway point, as the remaining space is taken up by the expansion of coolant as it heats up, overflows, and returns to its happy resting place.

for the temp gage readings, it appears you're mixing up words a little bit. the thermostat is a temperature-operated water valve that regulates water flow to the radiator, and thus engine temp. the temp gage is simply a thermometer to give you a ballpark of where its at.
if i'm understanding you right, your temp gage is reading cold, while it seems to be quite hot. some thermostats are designed so that if you overheat once (as may have happened when the heater core leaked all your coolant while driving), the thermostat will stick open.
other times the thermostat will get a piece of loose gunk stuck in it and get stuck closed as a result of running low on coolant.

in any case, it sounds as though something is up with your thermostat, so a new one would be helpful, and maybe also an aftermarket temp gage so you have a better idea of where its at - the stock gages aren't known for accuracy

 

I wonder if you got all the air out of the cooling system when you refilled it. If not, it would remove coolant from the overflow during heating and cooling cycles. If the temp sensor is in an air bubble it might read low. Have you added coolant to the overflow several times?

You might smell coolant for a while after the heater core spilled it in the interior.

 

I can never seem to keep coolant in my reservoir.
But the Rad stays full and my temp gauge seems to work right.
Try grounding the sensor wire, and then leaving it disconnected.
Does the gauge peg on both sides of the scale?
If so, I would just replace the sensor.

Did you flush the cooling system when you changed out the heater core?
How did the antifreeze look?

 

Thanks for the replies. And yes, I meant temp. gauge not thermostat (sorry haha)

I have added coolant to the overflow resovoir several times since replacing the heater core.

Some good news, this morning before leaving for work I noticed the level of coolant in the resovoir had not changed. Just now leaving work and getting home, it's held level. My radiator is full as well. Any possible chance the new heater core I bought has a different capacity than the old broken one I removed? If so that would explain why it might have been thirsty for coolant(?) Just a wild guess. Either way, I'm happy it's holding level now.

 

I'm glad to hear the situation seems to have stabilized.
Is the gauge reading correctly now too?

 

Yeah at least now thats behind me... but no, the gauge is still tellin' me it's cool. And I can't hear or feel any coolant in the upper radiator hose. Which doesn't seem like a good thing.

 

The upper hose should be HOT and pressurized when the system is up to temperature.

Is your radiator pressure cap functioning correctly?

 

Yes the cap is brand new. I'm just overly concerned with every little thing because I just bought the truck and I'm still feeling my way through the basics. Thank you for your answers and your patience.

I guess my last tedious question the night is this: with a faulty reading from my thermostat to my temp gauge, would a 170 mile drive be safe? I was looking to make a trip for the weekend.

 

if you're sure that your actual engine temp is staying where it belongs, you should be ok making the drive. if you don't think your temp is staying where it belongs, then i would be hesitant to take it far from home

 

Can you borrow an infra-red thermometer?

It would let you know exactly what was happening, & where........until you get other gauges.

 

It sounds like when you replaced the heater core you didn't get the system full, which is hard to do as air gets trapped in places - like the heater core. And it will take several drives, with fill ups in between, to get all the air out.

Now that you seem to have it full you need to make sure it is working properly. As Jim said, the upper hose should be hot and pressurized when up to temp, which can take 10 minutes of driving in some cases. Or, check it with an infrared thermometer as Ken suggested. You should also determine if the gauge is working by grounding the wire as Jim suggested.

You said you are overly concerned, but you don't seem to be following the recommendations of the guys that really know. I wouldn't go on a long trip without following all of their suggestions.

 

I wasn't able to get my hands on an infrared thermometer but I did the ground the gauge from the "sending unit"(?). After a little trial and error with grounding and connecting the wires, I was able to get the gauge to respond. (Hot when connected, cold when disconnected).

I appreciate (and used) all of the advice I was capable of utilizing, with the exception of infrared therm. I was concerned that's why I asked about it. Would've had to have been a fool to ask a question and not heed the advice given... Made the trip this evening and it went off without hitch. Thanks for the advice.

 

I'm glad all went well on the trip. And, I'm sorry for questioning your ability or willingness to take advice. But, to paraphrase a famous Okie, all we know is what we read in the posts, and you weren't saying anything about following the advice. We've been burned in the recent past helping someone that would take some of the advice and then change things without telling us. We went round and round for seemingly weeks on that one.

But, you don't have to take the advice. Just tell us what you do and don't do so we know what the situation is.