Hey guys,

This is my second post on here. The 1st post, you dudes helped so much that this is my "go to" for solutions. So....

I've replaced my thermostat 3 times with a 192° thermostat. After installing the engine temp goes to operating temp and work perfectly.....for about a day. Then it runs like the thermostat is stuck open. It doesn't matter how long I run the truck, she stays cold. Even the heater is luke warm; not hot like it should be.

Once I take the housing off the thermostat is closed. I dropped it into a pot of boiling water and watched it open up and close; so I know it works.

I'm tired of buying a gallon of 50/50 and a new thermostat every week trying to fix this issue.

Any insight would help a ton! Thanks!!!!

 

Sounds like ya may have an air bubble, is your t stat at a high point in the system?

 

First you should tell us that you're in Arizona.

How many cores on your radiator?

Do you run a fan shroud?

Do you know what temperature it is or are you referring to the stock gauge which is notoriously inaccurate and only provides a relative temperature from what may be considered "normal"?

Btw, why not drain the coolant in a bucket and filter it before pouring back in??? Some sort of aversion to doing that???

Only a gallon? Do you completely drain the system or drain to just below the thermostat level? Is the system actually full? Is the heater valve open with confirmation that coolant is flowing through the heater core?

192° thermostat eh? Hmmm..

Try this to test.... block off the grill opening and see if it "heats up". Alternatively, remove the cooling fan belt and let it idle till it is hot. You'll have to be careful in not overheating so beware.

Maybe change to a different thermostat brand?

 

Definitely get something more reliable for measuring engine temp than the stupid gauge.

That being said, I was also thinking air in the system, a lot of people forget to bleed the air out...but I'm not sure why it would work for a day before quitting.

How bad is the fluid that you're taking out?

 

I'm going to try and tackle this one. There a lot of good things here.

According to the heat out of the vents, the gauge is pretty spot on. I only get good warm air when the temp gauge is at normal operating temp. After 45 min of stop and go driving the temp is still at the C mark and the air from the heater confirms that. Cold.

It's basically running identical to as if there is no thermostat at all.

I should recirc the fluid back in to save some cash. I drain it to the thermostat level and keep as much coolant in there as I can. 100% of the coolant is brand new 50/50.



I'm not sure how many cores in the radiator. It doesn't look like a desert tank or anything big. Looks stock sized (plastic) so someone replaced it right before I bought it (3 months ago).

The tuck runs like *** in between the cold start and normal operating temp. Once at operating temp the engine runs amazing! Buts an absolute rarity to get this engine at normal temp. I can let it idle for 30 minutes and it will be at operating temp but once I get air through the radiator while driving down the road, she goes cold again.

What's the best way to eliminate air bubbles?

The theronstat is located about 6 inches below the radiator. The top of the radiator and cap is the highest point in the system.

 

Any idea how old the heater core is ? Is it plugged ?
I would get a short piece of 5/8" RV type clear tubing, a short piece of copper or plastic pipe; clamp both hoses going to the heater core with 2 pr. of vice grips (so you don't loose coolant), remove one hose from the heater core, install the clear tubing, connect to the heater core, unclamp hoses, refill radiator, let it bubble out, run the engine and check for coolant flow thru the heater core. If you have flow thru the heater core, one hose should be hotter than the other.

 

Take rad cap off. Top off rad. Start engine while leaving rad cap off. Wait until bubbles subside. It will spill a minimal amount of coolant while bubbling.

 

Sorry.. I couldn't get this outta my head so here it is.

"Running Cold"

Got a '73, it's a pickup truck, I'm out of money -and out of luck.
I've got no help to call on my own, pump the gas, and here I go.

It's running cold yeah, It's running cold.
It's running cold yeah, Oh it's running cold.

'Spent the day in a cold garage, and listened to the engine.. loud!
It ain't got a thing on me, It's running cold - my 390FE

It's running cold yeah, It's running cold.
It's running cold yeah, Oh my god yeah it's running cold.

Got a church key here, to pop the top of my tasty adult pop,
Now all the boys are helping me cuz I ask lots of questions on F.T.E.

It's running cold yeah, It's running cold.
It's running cold yeah, Oh it's running cold.

_____________

Thanks..... now back to our regular programming.

 

Is there any chance the T stat is in at an angle or something and getting hung up?

It acts like the stat is open... the whole radiator should be mildly warm after driving for a while with stat open. Does it feel warm?

 

That is spot on what I'm thinking, Blue and White. It has nothing to do with the heater. But.... After driving for an hour at 60mph and the gauge is still around the cold mark; I'll turn the heater in to see if my gauge is reading inaccurately. Low and behold it's barely warm air. If and when I do a lot of stop and go and she does heat up the heater will blow warm like it should. I get up to 60 mph and the temp drops down again.

It's like there is no thermostat at all. Or like it's backwards. 1.) there is a 195° t-stat. 2.) it is most definitely not backwards. Brand new. I've gone through 2 or 3 t-stats thinking they were faulty.

I hate sending my truck in for something that would relatively seem so simple. Because it's running so cold it stays at the 2nd stage in the choke. 1st is cold start. It will stay there and idle high for 30 seconds or so. 2nd is while it's warming up. And 3rd is when she's fully warm. But she never gets at normal operating temp so the choke never bumps down to the 3rd lobe.

 

Choke has nothing to do with coolant temp, it runs off exhaust gas heat or electric. If it's not bumping down to the 3rd setting it needs adjusted.

When you buy the new t-stats are you testing them? They've got a habit of being DOA. As a temporary solution you could use some cardboard to block off some of the radiator.

 

When i test a thermostat i hang it from a piece of wire in one of my spouses best cooking pots, when shes not home . i don't let it touch the sides or the pan bottom , just suspend it in the water. Then i get her best cooking thermometer and hang it on the wire not touching any thing . Heat the water up on her stove and watch what temp. it opens at . If it's off i just buy a new one and test it the same way . Then i clean the pan and thermometer up and put them away the very same place i found them. JIM

 

I knew I missed a step in this process....

 

At this point you have two issues. Buy a decent aftermarket coolant gauge. Next make sure your heater core is not plugged up internally and externally. Mice love to make nests in the heater boxes, leaves also find a way in there. A plugged up core either way is going to run cold.

 

It looks like I might need to take her in. Power valve blew out, throttle shafts are worn, choke is out of whack. So out of whack that your regular idle screw on the drivers side (motocraft 2150) isn't even touching anything.

I have the confidence and know how to get it done but I need it fixed, ASAP. Sooner than what it would take me to do it. I'll have the guy throw on a better t-stat housing and better t-stat than an oreilly's stocker.

I definitely want a better temp gauge and a tach as well. I seriously hate being stumped like this.