Ive got an 88 Formula, stock less the throttle body coolant tubes have been removed. I got the car from my father that has passed on. He had the thermostat out of the car and we dont know why.

Im having an on going over heating issue. The car will be fine for a day or 2, maybe 50 miles then it'll over heat. We removed the TB tubes as one had a hole in it and we THOUGHT that was the source of air getting into the system and causing the issues. Ive tried both bleeding methods that are posted in various place. The first being cracking the radiator cap to bleed the system, the 2nd being bleeding the system from the rear only. Both ways have lead the car to over heat again. When I remove the rear cap to let air out, I only get coolant and not air, so no progress is made with that method.

We've checked all the tubes and havent found any leaks so Im at a loss for what to try next.

Is the over flow res cap vital to the system? Mines missing but I dont know as that can cause any problems.

Thoughts or ideas?

Welcome to the forum!

You can't find any leaks and you have coolant under the thermostat cap....so I doubt if there is any air in the system. More likely, there is blockage somewhere, and you can determine that by checking temperatures when the engine is hot. Are both stainless tubes hot? How about the radiator? Is the heater hot?

Thanks for the welcome!!

Both tube that run up the pinch welds are warm as well as the radiator and the tubes that run up the center to the heater. The first sign of it over heating is I do lose cabin heat.

The last time I drove it after the other leak was fixes was about 20mi of freeway then i parked it outside (NY weather) and whe nI drove to wrok the next day, 7mi, it had no heat and didnt make it beifer it was clearly unhappy. Maybe I didnt thoroughly burp the system before the 20mi drive and it burped up over night?

Ive got this, an 86 4cyl and 2 Zimmers now so I need to learn these cars! lol

Have you ever seen (or smelled) any coolant on the passenger side carpet? If you have a pinhole leak in the heater core, it can suck air in, and mess things up. Usually air won't stay there, but it will re-occur when you turn the car off and the coolant contracts. If you have not already done so, visit the Ogre's Cave and read the stories about radiator caps and thermostats. It's an unusual system and there are a number of ways for it to go wrong.

Welcome to the forum. I don't know if your car sat for awhile like mine but here's what happened to my car: My car would get hot sometimes when in traffic, then after awhile I saw coolant on the engine that I thought was coming from the temp sensor. It turned out that the water pump had gone bad from being parked for a long time and I could see the line on the pump from the old coolant. Now that I have changed the water pump it stays nice and cool (well as cool as these Fiero V6's can be anyway)

"Is the over flow res cap vital to the system?" Need a tank before doing any other work. But tank will work w/o the cap.

Important Note:
You don't need all of air out but only to make sure lower Tstant is covered with coolant so the Tstant and sensors/senders read coolant temp.
Bad cap or bad areas on the housing can cause even new caps to fail to seal But Good parts can fake problems because can take 1 to several heat cycles to purge air out of system.

See my Cave, Coolant Fill and rest of cooling section.
Then Read again...
coolant fill
rad caps
heater
thermostat

Weak/bad or no coolant can wreck the system from inside and still look ok otherwise.
Example, If rest of system is good can still have plugged tubes in rad and/or heater core that kills coolant flow.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

[This message has been edited by theogre (edited 03-01-2015).]

It does sound like you may have a leaking heater core. If turning the defroster on makes the windshield fog up worse that's a pretty sure sign that the heater core is leaking.

The heater is supposed to be set to hot when burping.